1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
// Copyright Materialize, Inc. and contributors. All rights reserved.
//
// Use of this software is governed by the Business Source License
// included in the LICENSE file.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0.

//! Implementation of the storage controller trait.

use std::any::Any;
use std::cmp::Reverse;
use std::collections::{BTreeMap, BTreeSet, BinaryHeap};
use std::fmt::{Debug, Display};
use std::num::NonZeroI64;
use std::str::FromStr;
use std::sync::{Arc, Mutex};
use std::time::Duration;

use async_trait::async_trait;
use chrono::{DateTime, Utc};
use derivative::Derivative;
use differential_dataflow::lattice::Lattice;
use futures::future::BoxFuture;
use futures::stream::BoxStream;
use futures::FutureExt;
use itertools::Itertools;
use mz_build_info::BuildInfo;
use mz_cluster_client::client::ClusterReplicaLocation;
use mz_cluster_client::ReplicaId;

use mz_ore::collections::CollectionExt;
use mz_persist_client::stats::{SnapshotPartsStats, SnapshotStats};
use mz_storage_client::storage_collections::{CollectionFrontiers, StorageCollections};
use timely::progress::Timestamp as TimelyTimestamp;

use mz_ore::metrics::MetricsRegistry;
use mz_ore::now::{EpochMillis, NowFn};
use mz_ore::{assert_none, instrument};
use mz_persist_client::cache::PersistClientCache;
use mz_persist_client::cfg::USE_CRITICAL_SINCE_SNAPSHOT;
use mz_persist_client::read::ReadHandle;
use mz_persist_client::write::WriteHandle;
use mz_persist_client::{Diagnostics, PersistClient, PersistLocation, ShardId};
use mz_persist_types::codec_impls::UnitSchema;
use mz_persist_types::Codec64;
use mz_proto::RustType;
use mz_repr::adt::timestamp::CheckedTimestamp;
use mz_repr::{ColumnName, Datum, Diff, GlobalId, RelationDesc, Row, TimestampManipulation};
use mz_storage_client::client::{
    ProtoStorageCommand, ProtoStorageResponse, RunIngestionCommand, RunSinkCommand, Status,
    StatusUpdate, StorageCommand, StorageResponse, TimestamplessUpdate, Update,
};
use mz_storage_client::controller::{
    CollectionDescription, DataSource, DataSourceOther, ExportDescription, ExportState,
    IntrospectionType, MonotonicAppender, PersistEpoch, Response, SnapshotCursor,
    StorageController, StorageMetadata, StorageTxn, StorageWriteOp,
};
use mz_storage_client::metrics::StorageControllerMetrics;
use mz_storage_client::statistics::{
    SinkStatisticsUpdate, SourceStatisticsUpdate, WebhookStatistics,
};
use mz_storage_types::configuration::StorageConfiguration;
use mz_storage_types::connections::inline::InlinedConnection;
use mz_storage_types::connections::ConnectionContext;
use mz_storage_types::controller::{AlterError, CollectionMetadata, StorageError, TxnsCodecRow};
use mz_storage_types::instances::StorageInstanceId;
use mz_storage_types::parameters::StorageParameters;
use mz_storage_types::read_holds::{ReadHold, ReadHoldError};
use mz_storage_types::read_policy::ReadPolicy;
use mz_storage_types::sinks::{StorageSinkConnection, StorageSinkDesc};
use mz_storage_types::sources::{
    ExportReference, GenericSourceConnection, IngestionDescription, SourceConnection, SourceData,
    SourceDesc, SourceExport,
};
use mz_storage_types::AlterCompatible;
use mz_txn_wal::metrics::Metrics as TxnMetrics;
use mz_txn_wal::txn_read::TxnsRead;
use mz_txn_wal::txns::TxnsHandle;
use timely::order::{PartialOrder, TotalOrder};
use timely::progress::frontier::MutableAntichain;
use timely::progress::{Antichain, ChangeBatch, Timestamp};
use tokio::sync::mpsc;
use tokio::sync::watch::{channel, Sender};
use tokio::time::error::Elapsed;
use tokio_stream::StreamMap;
use tracing::{debug, info, warn};

use crate::rehydration::RehydratingStorageClient;
use crate::statistics::StatsState;
mod collection_mgmt;
mod collection_status;
mod persist_handles;
mod rehydration;
mod rtr;
mod statistics;

#[derive(Derivative)]
#[derivative(Debug)]
struct PendingCompactionCommand<T> {
    /// [`GlobalId`] of the collection we want to compact.
    id: GlobalId,
    /// [`Antichain`] representing the requested read frontier.
    read_frontier: Antichain<T>,
    /// Cluster associated with this collection, if any.
    cluster_id: Option<StorageInstanceId>,
}

/// A storage controller for a storage instance.
#[derive(Derivative)]
#[derivative(Debug)]
pub struct Controller<T: Timestamp + Lattice + Codec64 + From<EpochMillis> + TimestampManipulation>
{
    /// The build information for this process.
    build_info: &'static BuildInfo,
    /// A function that returns the current time.
    now: NowFn,
    /// The fencing token for this instance of the controller.
    envd_epoch: NonZeroI64,

    /// Whether or not this controller is in read-only mode.
    ///
    /// When in read-only mode, neither this controller nor the instances
    /// controlled by it are allowed to affect changes to external systems
    /// (largely persist).
    read_only: bool,

    /// Collections maintained by the storage controller.
    ///
    /// This collection only grows, although individual collections may be rendered unusable.
    /// This is to prevent the re-binding of identifiers to other descriptions.
    pub(crate) collections: BTreeMap<GlobalId, CollectionState<T>>,

    pub(crate) exports: BTreeMap<GlobalId, ExportState<T>>,

    /// Write handle for table shards.
    pub(crate) persist_table_worker: persist_handles::PersistTableWriteWorker<T>,
    /// Write handle for monotonic shards.
    pub(crate) persist_monotonic_worker: persist_handles::PersistMonotonicWriteWorker<T>,
    /// A shared TxnsCache running in a task and communicated with over a channel.
    txns_read: TxnsRead<T>,
    txns_metrics: Arc<TxnMetrics>,
    stashed_response: Option<StorageResponse<T>>,
    /// Compaction commands to send during the next call to
    /// `StorageController::process`.
    pending_compaction_commands: Vec<PendingCompactionCommand<T>>,
    /// Channel for sending table handle drops.
    #[derivative(Debug = "ignore")]
    pending_table_handle_drops_tx: mpsc::UnboundedSender<GlobalId>,
    /// Channel for receiving table handle drops.
    #[derivative(Debug = "ignore")]
    pending_table_handle_drops_rx: mpsc::UnboundedReceiver<GlobalId>,

    /// Interface for managed collections
    pub(crate) collection_manager: collection_mgmt::CollectionManager<T>,

    /// Facility for appending status updates for sources/sinks
    pub(crate) collection_status_manager: collection_status::CollectionStatusManager<T>,
    /// Tracks which collection is responsible for which [`IntrospectionType`].
    pub(crate) introspection_ids: Arc<Mutex<BTreeMap<IntrospectionType, GlobalId>>>,
    /// Tokens for tasks that drive updating introspection collections. Dropping
    /// this will make sure that any tasks (or other resources) will stop when
    /// needed.
    // TODO(aljoscha): Should these live somewhere else?
    introspection_tokens: BTreeMap<GlobalId, Box<dyn Any + Send + Sync>>,

    // The following two fields must always be locked in order.
    /// Consolidated metrics updates to periodically write. We do not eagerly initialize this,
    /// and its contents are entirely driven by `StorageResponse::StatisticsUpdates`'s, as well
    /// as webhook statistics.
    source_statistics: Arc<Mutex<statistics::SourceStatistics>>,
    /// Consolidated metrics updates to periodically write. We do not eagerly initialize this,
    /// and its contents are entirely driven by `StorageResponse::StatisticsUpdates`'s.
    sink_statistics: Arc<Mutex<BTreeMap<GlobalId, statistics::StatsState<SinkStatisticsUpdate>>>>,
    /// A way to update the statistics interval in the statistics tasks.
    statistics_interval_sender: Sender<Duration>,

    /// Clients for all known storage instances.
    clients: BTreeMap<StorageInstanceId, RehydratingStorageClient<T>>,
    /// For each storage instance the ID of its replica, if any.
    replicas: BTreeMap<StorageInstanceId, ReplicaId>,
    /// Set to `true` once `initialization_complete` has been called.
    initialized: bool,
    /// Storage configuration to apply to newly provisioned instances, and use during purification.
    config: StorageConfiguration,
    /// Mechanism for returning frontier advancement for tables.
    internal_response_queue: tokio::sync::mpsc::UnboundedReceiver<StorageResponse<T>>,
    /// The persist location where all storage collections are being written to
    persist_location: PersistLocation,
    /// A persist client used to write to storage collections
    persist: Arc<PersistClientCache>,
    /// Metrics of the Storage controller
    metrics: StorageControllerMetrics,
    /// Mechanism for the storage controller to send itself feedback, potentially emulating the
    /// responses we expect from clusters.
    ///
    /// Note: This is used for finalizing shards of webhook sources, once webhook sources are
    /// installed on a `clusterd` this can likely be refactored away.
    internal_response_sender: tokio::sync::mpsc::UnboundedSender<StorageResponse<T>>,

    /// `(read, write)` frontiers that have been recorded in the `Frontiers` collection, kept to be
    /// able to retract old rows.
    recorded_frontiers: BTreeMap<GlobalId, (Antichain<T>, Antichain<T>)>,
    /// Write frontiers that have been recorded in the `ReplicaFrontiers` collection, kept to be
    /// able to retract old rows.
    recorded_replica_frontiers: BTreeMap<(GlobalId, ReplicaId), Antichain<T>>,

    /// Handle to a [StorageCollections].
    storage_collections: Arc<dyn StorageCollections<Timestamp = T> + Send + Sync>,
}

#[async_trait(?Send)]
impl<'a, T> StorageController for Controller<T>
where
    T: Timestamp
        + Lattice
        + TotalOrder
        + Codec64
        + From<EpochMillis>
        + TimestampManipulation
        + Into<Datum<'a>>
        + Display,
    StorageCommand<T>: RustType<ProtoStorageCommand>,
    StorageResponse<T>: RustType<ProtoStorageResponse>,
{
    type Timestamp = T;

    fn initialization_complete(&mut self) {
        self.reconcile_dangling_statistics();
        self.initialized = true;

        for client in self.clients.values_mut() {
            client.send(StorageCommand::InitializationComplete);
        }
    }

    async fn allow_writes(&mut self, register_ts: Option<Self::Timestamp>) {
        if !self.read_only {
            // Already done!
            return;
        }

        self.read_only = false;

        let persist_client = self
            .persist
            .open(self.persist_location.clone())
            .await
            .unwrap();

        // While in read-only mode, we didn't run ingestions or write to
        // introspection collections. Start doing that now!
        let mut ingestions_to_run = Vec::new();
        let mut introspections_to_run = Vec::new();
        let mut tables_to_register = Vec::new();
        for (id, collection) in self.collections.iter() {
            match collection.data_source {
                DataSource::Ingestion(_) => {
                    ingestions_to_run.push(*id);
                }
                DataSource::IngestionExport { .. } => (),
                DataSource::Introspection(i) => {
                    introspections_to_run.push((*id, i));
                }
                DataSource::Webhook => (),
                DataSource::Other(DataSourceOther::TableWrites) => {
                    // We don't optimize allow_writes() for performance, so we
                    // don't parallelize opening these write handles, for
                    // example. For now it's meant as a tool during development
                    // of zero-downtime upgrades. If it ever becomes
                    // load-bearing, we can employ optimizations similar to what
                    // we use in create_collections.
                    let write_handle = self
                        .open_data_handles(
                            id,
                            collection.collection_metadata.data_shard,
                            collection.collection_metadata.relation_desc.clone(),
                            &persist_client,
                        )
                        .await;

                    tables_to_register.push((*id, write_handle));
                }
                DataSource::Progress | DataSource::Other(_) => {}
            };
        }

        for (id, introspection_type) in introspections_to_run {
            // Introspection collections are registered with the
            // CollectionManager when they are created. We only bring ourselves
            // up to date with collection contents or do any preparatory
            // consolidation work when we actually start writing to them!
            self.prepare_introspection_collection(id, introspection_type)
                .await
                .expect("cannot fail to prepare introspection collections now");
        }

        // We first do any cleanup/truncation work above and then allow the
        // CollectionManager to do writes. This prevents it from advancing the
        // upper while we are trying to apply truncations.
        //
        // TODO(aljoscha): We should make the truncation/cleanup work that
        // happens when we take over instead be a periodic thing, and make it
        // resilient to the upper moving concurrently.
        self.collection_manager.allow_writes();

        if !tables_to_register.is_empty() {
            let register_ts = register_ts
                .as_ref()
                .expect("must provide a register_ts")
                .clone();

            self.persist_table_worker
                .register(register_ts, tables_to_register);
        }

        for id in ingestions_to_run {
            self.run_ingestion(id)
                .expect("cannot fail to run ingestions now");
        }
    }

    fn update_parameters(&mut self, config_params: StorageParameters) {
        self.storage_collections
            .update_parameters(config_params.clone());

        // We serialize the dyncfg updates in StorageParameters, but configure
        // persist separately.
        self.persist.cfg().apply_from(&config_params.dyncfg_updates);

        for client in self.clients.values_mut() {
            client.send(StorageCommand::UpdateConfiguration(config_params.clone()));
        }
        self.config.update(config_params);
        self.statistics_interval_sender
            .send_replace(self.config.parameters.statistics_interval);
        self.collection_manager.update_user_batch_duration(
            self.config
                .parameters
                .user_storage_managed_collections_batch_duration,
        );
    }

    /// Get the current configuration
    fn config(&self) -> &StorageConfiguration {
        &self.config
    }

    fn collection_metadata(
        &self,
        id: GlobalId,
    ) -> Result<CollectionMetadata, StorageError<Self::Timestamp>> {
        self.storage_collections.collection_metadata(id)
    }

    fn collection_frontiers(
        &self,
        id: GlobalId,
    ) -> Result<
        (Antichain<Self::Timestamp>, Antichain<Self::Timestamp>),
        StorageError<Self::Timestamp>,
    > {
        Ok(match self.export(id) {
            Ok(export) => (
                export.read_hold.since().clone(),
                export.write_frontier.clone(),
            ),
            Err(_) => {
                let frontiers = self.storage_collections.collection_frontiers(id)?;
                (frontiers.implied_capability, frontiers.write_frontier)
            }
        })
    }

    fn collections_frontiers(
        &self,
        mut ids: Vec<GlobalId>,
    ) -> Result<Vec<(GlobalId, Antichain<T>, Antichain<T>)>, StorageError<Self::Timestamp>> {
        // The ids might be either normal collections or exports. Both have frontiers that might be
        // interesting to external observers.
        let mut result = vec![];
        ids.retain(|&id| match self.export(id) {
            Ok(export) => {
                result.push((
                    id,
                    export.read_hold.since().clone(),
                    export.write_frontier.clone(),
                ));
                false
            }
            Err(_) => true,
        });

        result.extend(
            self.storage_collections
                .collections_frontiers(ids)?
                .into_iter()
                .map(|frontiers| {
                    (
                        frontiers.id,
                        frontiers.implied_capability,
                        frontiers.write_frontier,
                    )
                }),
        );

        Ok(result)
    }

    fn active_collection_metadatas(&self) -> Vec<(GlobalId, CollectionMetadata)> {
        self.storage_collections.active_collection_metadatas()
    }

    fn check_exists(&self, id: GlobalId) -> Result<(), StorageError<Self::Timestamp>> {
        self.storage_collections.check_exists(id)
    }

    fn create_instance(&mut self, id: StorageInstanceId) {
        let mut client = RehydratingStorageClient::new(
            self.build_info,
            self.metrics.for_instance(id),
            self.envd_epoch,
            self.config.parameters.grpc_client.clone(),
            self.now.clone(),
        );
        if self.initialized {
            client.send(StorageCommand::InitializationComplete);
        }
        client.send(StorageCommand::UpdateConfiguration(
            self.config.parameters.clone(),
        ));
        let old_client = self.clients.insert(id, client);
        assert_none!(old_client, "storage instance {id} already exists");
    }

    fn drop_instance(&mut self, id: StorageInstanceId) {
        let client = self.clients.remove(&id);
        assert!(client.is_some(), "storage instance {id} does not exist");
    }

    fn connect_replica(
        &mut self,
        instance_id: StorageInstanceId,
        replica_id: ReplicaId,
        location: ClusterReplicaLocation,
    ) {
        let client = self
            .clients
            .get_mut(&instance_id)
            .unwrap_or_else(|| panic!("instance {instance_id} does not exist"));
        client.connect(location);

        self.replicas.insert(instance_id, replica_id);
    }

    fn drop_replica(&mut self, instance_id: StorageInstanceId, _replica_id: ReplicaId) {
        let client = self
            .clients
            .get_mut(&instance_id)
            .unwrap_or_else(|| panic!("instance {instance_id} does not exist"));
        client.reset();

        self.replicas.remove(&instance_id);
    }

    /// Create and "execute" the described collection.
    ///
    /// "Execute" is in scare quotes because what executing a collection means
    /// varies widely based on the type of collection you're creating.
    ///
    /// The general process creating a collection undergoes is:
    /// 1. Enrich the description we get from the user with the metadata only
    ///    the storage controller's metadata. This is mostly a matter of
    ///    separating concerns.
    /// 2. Generate write and read persist handles for the collection.
    /// 3. Store the collection's metadata in the appropriate field.
    /// 4. "Execte" the collection. What that means is contingent on the type of
    ///    collection. so consult the code for more details.
    ///
    // TODO(aljoscha): It would be swell if we could refactor this Leviathan of
    // a method/move individual parts to their own methods. @guswynn observes
    // that a number of these operations could be moved into fns on
    // `DataSource`.
    #[instrument(name = "storage::create_collections")]
    async fn create_collections(
        &mut self,
        storage_metadata: &StorageMetadata,
        register_ts: Option<Self::Timestamp>,
        mut collections: Vec<(GlobalId, CollectionDescription<Self::Timestamp>)>,
    ) -> Result<(), StorageError<Self::Timestamp>> {
        self.storage_collections
            .create_collections(storage_metadata, register_ts.clone(), collections.clone())
            .await?;

        // Validate first, to avoid corrupting state.
        // 1. create a dropped identifier, or
        // 2. create an existing identifier with a new description.
        // Make sure to check for errors within `ingestions` as well.
        collections.sort_by_key(|(id, _)| *id);
        collections.dedup();
        for pos in 1..collections.len() {
            if collections[pos - 1].0 == collections[pos].0 {
                return Err(StorageError::SourceIdReused(collections[pos].0));
            }
        }

        // We first enrich each collection description with some additional metadata...
        let enriched_with_metadata = collections
            .into_iter()
            .map(|(id, description)| {
                let data_shard = storage_metadata.get_collection_shard::<T>(id)?;

                let get_shard = |id| -> Result<ShardId, StorageError<T>> {
                    let shard = storage_metadata.get_collection_shard::<T>(id)?;
                    Ok(shard)
                };

                let status_shard = match description.status_collection_id {
                    Some(status_collection_id) => Some(get_shard(status_collection_id)?),
                    None => None,
                };

                let remap_shard = match &description.data_source {
                    // Only ingestions can have remap shards.
                    DataSource::Ingestion(IngestionDescription {
                        remap_collection_id,
                        ..
                    }) => {
                        // Iff ingestion has a remap collection, its metadata must
                        // exist (and be correct) by this point.
                        Some(get_shard(*remap_collection_id)?)
                    }
                    _ => None,
                };

                // If the shard is being managed by txn-wal (initially, tables), then we need to
                // pass along the shard id for the txns shard to dataflow rendering.
                let txns_shard = match description.data_source {
                    DataSource::Other(DataSourceOther::TableWrites) => {
                        Some(*self.txns_read.txns_id())
                    }
                    DataSource::Ingestion(_)
                    | DataSource::IngestionExport { .. }
                    | DataSource::Introspection(_)
                    | DataSource::Progress
                    | DataSource::Webhook
                    | DataSource::Other(DataSourceOther::Compute) => None,
                };

                let metadata = CollectionMetadata {
                    persist_location: self.persist_location.clone(),
                    remap_shard,
                    data_shard,
                    status_shard,
                    relation_desc: description.desc.clone(),
                    txns_shard,
                };

                Ok((id, description, metadata))
            })
            .collect_vec();

        // So that we can open persist handles for each collections concurrently.
        let persist_client = self
            .persist
            .open(self.persist_location.clone())
            .await
            .unwrap();
        let persist_client = &persist_client;

        // Reborrow the `&mut self` as immutable, as all the concurrent work to be processed in
        // this stream cannot all have exclusive access.
        use futures::stream::{StreamExt, TryStreamExt};
        let this = &*self;
        let mut to_register: Vec<_> = futures::stream::iter(enriched_with_metadata)
            .map(|data: Result<_, StorageError<Self::Timestamp>>| {
                async move {
                let (id, description, metadata) = data?;

                // should be replaced with real introspection (https://github.com/MaterializeInc/materialize/issues/14266)
                // but for now, it's helpful to have this mapping written down somewhere
                debug!(
                    "mapping GlobalId={} to remap shard ({:?}), data shard ({}), status shard ({:?})",
                    id, metadata.remap_shard, metadata.data_shard, metadata.status_shard
                );

                let write = this
                    .open_data_handles(
                        &id,
                        metadata.data_shard,
                        metadata.relation_desc.clone(),
                        persist_client,
                    )
                    .await;

                Ok::<_, StorageError<T>>((id, description, write, metadata))
            }})
            // Poll each future for each collection concurrently, maximum of 50 at a time.
            .buffer_unordered(50)
            // HERE BE DRAGONS:
            //
            // There are at least 2 subtleties in using `FuturesUnordered` (which
            // `buffer_unordered` uses underneath:
            // - One is captured here <https://github.com/rust-lang/futures-rs/issues/2387>
            // - And the other is deadlocking if processing an OUTPUT of a `FuturesUnordered`
            // stream attempts to obtain an async mutex that is also obtained in the futures
            // being polled.
            //
            // Both of these could potentially be issues in all usages of `buffer_unordered` in
            // this method, so we stick the standard advice: only use `try_collect` or
            // `collect`!
            .try_collect()
            .await?;

        // Reorder in dependency order.
        to_register.sort_by_key(|(id, ..)| *id);

        // The set of collections that we should render at the end of this
        // function.
        let mut to_execute = BTreeSet::new();
        // New collections that are being created; this is distinct from the set
        // of collections we plan to execute because
        // `DataSource::IngestionExport` is added as a new collection, but is
        // not executed directly.
        let mut new_collections = BTreeSet::new();
        let mut table_registers = Vec::with_capacity(to_register.len());

        // Statistics need a level of indirection so we can mutably borrow
        // `self` when registering collections and when we are inserting
        // statistics.
        let mut new_source_statistic_entries = BTreeSet::new();
        let mut new_webhook_statistic_entries = BTreeSet::new();

        for (id, mut description, write, metadata) in to_register {
            to_execute.insert(id);
            new_collections.insert(id);

            // Ensure that the ingestion has an export for its primary source.
            // This is done in an awkward spot to appease the borrow checker.
            if let DataSource::Ingestion(ingestion) = &mut description.data_source {
                ingestion.source_exports.insert(
                    id,
                    SourceExport {
                        ingestion_output: None,
                        storage_metadata: (),
                    },
                );
            }

            let write_frontier = write.upper();

            // Determine if this collection has another dependency.
            let storage_dependencies =
                self.determine_collection_dependencies(id, &description.data_source)?;

            let dependency_read_holds = self
                .storage_collections
                .acquire_read_holds(storage_dependencies)
                .expect("can acquire read holds");

            let mut dependency_since = Antichain::from_elem(T::minimum());
            for read_hold in dependency_read_holds.iter() {
                dependency_since.join_assign(read_hold.since());
            }

            // Assert some invariants.
            if !dependency_read_holds.is_empty() {
                // The dependency since cannot be in advance of the
                // dependent upper unless the collection is new. If the
                // dependency since advanced past the dependent's upper,
                // the dependent cannot read data from the dependency at
                // its upper.
                //
                // Another way of understanding that this is a problem
                // is that this means that the read hold installed on
                // the dependency was probably not been upheld––if it
                // were, the dependency's since could not have advanced
                // as far the dependent's upper.
                mz_ore::soft_assert_or_log!(
                    write_frontier.elements() == &[T::minimum()]
                        || PartialOrder::less_than(&dependency_since, write_frontier),
                    "dependency since has advanced past dependent ({id}) upper \n
                            dependent ({id}): upper {:?} \n
                            dependency since {:?}",
                    write_frontier,
                    dependency_since
                );
            }

            let mut collection_state = CollectionState {
                data_source: description.data_source.clone(),
                collection_metadata: metadata.clone(),
                extra_state: CollectionStateExtra::None,
            };

            // Install the collection state in the appropriate spot.
            match &collection_state.data_source {
                DataSource::Introspection(_) => {
                    debug!(data_source = ?collection_state.data_source, meta = ?metadata, "registering {} with persist monotonic worker", id);
                    self.persist_monotonic_worker.register(id, write);
                    self.collections.insert(id, collection_state);
                }
                DataSource::Webhook => {
                    debug!(data_source = ?collection_state.data_source, meta = ?metadata, "registering {} with persist monotonic worker", id);
                    self.persist_monotonic_worker.register(id, write);
                    self.collections.insert(id, collection_state);
                    new_source_statistic_entries.insert(id);
                    // This collection of statistics is periodically aggregated into
                    // `source_statistics`.
                    new_webhook_statistic_entries.insert(id);
                }
                DataSource::IngestionExport {
                    ingestion_id,
                    external_reference,
                } => {
                    debug!(data_source = ?collection_state.data_source, meta = ?metadata, "not registering {} with a controller persist worker", id);
                    // Adjust the source to contain this export.
                    let ingestion_state = self
                        .collections
                        .get_mut(ingestion_id)
                        .expect("known to exist");

                    let instance_id = match &mut ingestion_state.data_source {
                        DataSource::Ingestion(ingestion_desc) => {
                            ingestion_desc.source_exports.insert(
                                id,
                                SourceExport {
                                    ingestion_output: Some(ExportReference::from(
                                        external_reference.clone(),
                                    )),
                                    storage_metadata: (),
                                },
                            );

                            // Record the ingestion's cluster ID for the
                            // ingestion export. This way we always have a
                            // record of it, even if the ingestion's collection
                            // description disappears.
                            ingestion_desc.instance_id
                        }
                        _ => unreachable!(
                            "SourceExport must only refer to primary sources that already exist"
                        ),
                    };

                    // Executing the source export doesn't do anything, ensure we execute the source instead.
                    to_execute.remove(&id);
                    to_execute.insert(*ingestion_id);

                    let ingestion_state = IngestionState {
                        read_capabilities: MutableAntichain::from(dependency_since.clone()),
                        dependency_read_holds,
                        derived_since: dependency_since,
                        write_frontier: Antichain::from_elem(Self::Timestamp::minimum()),
                        hold_policy: ReadPolicy::step_back(),
                        instance_id,
                    };

                    collection_state.extra_state = CollectionStateExtra::Ingestion(ingestion_state);

                    self.collections.insert(id, collection_state);
                    new_source_statistic_entries.insert(id);
                }
                DataSource::Other(DataSourceOther::TableWrites) => {
                    debug!(data_source = ?collection_state.data_source, meta = ?metadata, "registering {} with persist table worker", id);
                    self.collections.insert(id, collection_state);
                    table_registers.push((id, write));
                }
                DataSource::Progress | DataSource::Other(DataSourceOther::Compute) => {
                    debug!(data_source = ?collection_state.data_source, meta = ?metadata, "not registering {} with a controller persist worker", id);
                    self.collections.insert(id, collection_state);
                }
                DataSource::Ingestion(ingestion_desc) => {
                    debug!(?ingestion_desc, meta = ?metadata, "not registering {} with a controller persist worker", id);

                    let mut dependency_since = Antichain::from_elem(T::minimum());
                    for read_hold in dependency_read_holds.iter() {
                        dependency_since.join_assign(read_hold.since());
                    }

                    let ingestion_state = IngestionState {
                        read_capabilities: MutableAntichain::from(dependency_since.clone()),
                        dependency_read_holds,
                        derived_since: dependency_since,
                        write_frontier: Antichain::from_elem(Self::Timestamp::minimum()),
                        hold_policy: ReadPolicy::step_back(),
                        instance_id: ingestion_desc.instance_id,
                    };

                    collection_state.extra_state = CollectionStateExtra::Ingestion(ingestion_state);

                    self.collections.insert(id, collection_state);
                    new_source_statistic_entries.insert(id);
                }
            }
        }

        {
            // Ensure all sources are associated with the statistics.
            //
            // We currently do not call `create_collections` after we have initialized the source
            // statistics scrapers, but in the interest of safety, avoid overriding existing
            // statistics values.
            let mut source_statistics = self.source_statistics.lock().expect("poisoned");

            for id in new_source_statistic_entries {
                source_statistics
                    .source_statistics
                    .entry(id)
                    .or_insert(StatsState::new(SourceStatisticsUpdate::new(id)));
            }
            for id in new_webhook_statistic_entries {
                source_statistics.webhook_statistics.entry(id).or_default();
            }
        }

        // Register the tables all in one batch.
        //
        // We cannot register tables at the table worker when in read-only mode.
        // When coming out of read-only mode (via `allow_writes()`), we will
        // register all tables that are known by that point.
        if !table_registers.is_empty() && !self.read_only {
            let register_ts = register_ts
                .expect("caller should have provided a register_ts when creating a table");
            // This register call advances the logical upper of the table. The
            // register call eventually circles that info back to the
            // controller, but some tests fail if we don't synchronously update
            // it in create_collections, so just do that now.
            self.persist_table_worker
                .register(register_ts, table_registers)
                .await
                .expect("table worker unexpectedly shut down");
        }

        self.append_shard_mappings(new_collections.into_iter(), 1)
            .await;

        // TODO(guswynn): perform the io in this final section concurrently.
        for id in to_execute {
            match &self.collection(id)?.data_source {
                DataSource::Ingestion(_) => {
                    if !self.read_only {
                        self.run_ingestion(id)?;
                    }
                }
                DataSource::IngestionExport { .. } => unreachable!(
                    "ingestion exports do not execute directly, but instead schedule their source to be re-executed"
                ),
                DataSource::Introspection(i) => {


                    // We always register the collection with the collection manager,
                    // regardless of read-only mode. The CollectionManager itself is
                    // aware of read-only mode and will not attempt to write before told
                    // to do so.
                    //
                    self.register_introspection_collection(id, *i)
                        .await?;

                }
                DataSource::Webhook => {
                    // Register the collection so our manager knows about it.
                    //
                    // NOTE: Maybe this shouldn't be in the collection manager,
                    // and collection manager should only be responsble for
                    // built-in introspection collections?
                    self.collection_manager.register_append_only_collection(id);
                }
                DataSource::Progress | DataSource::Other(_) => {}
            };
        }

        Ok(())
    }

    fn check_alter_ingestion_source_desc(
        &mut self,
        ingestion_id: GlobalId,
        source_desc: &SourceDesc,
    ) -> Result<(), StorageError<Self::Timestamp>> {
        let source_collection = self.collection(ingestion_id)?;
        let data_source = &source_collection.data_source;
        match &data_source {
            DataSource::Ingestion(cur_ingestion) => {
                cur_ingestion
                    .desc
                    .alter_compatible(ingestion_id, source_desc)?;

                let reference_resolver = cur_ingestion.desc.connection.get_reference_resolver();

                // Ensure updated `SourceDesc` contains reference to all
                // current external references.
                for export_id in cur_ingestion
                    .source_exports
                    .keys()
                    .filter(|export| **export != ingestion_id)
                {
                    let collection = self
                        .collections
                        .get(export_id)
                        .ok_or_else(|| AlterError { id: ingestion_id })?;

                    let external_reference = match &collection.data_source {
                        DataSource::IngestionExport {
                            external_reference, ..
                        } => external_reference,
                        o => {
                            tracing::warn!(
                                "{export_id:?} not DataSource::IngestionExport but {o:#?}",
                            );
                            Err(AlterError { id: ingestion_id })?
                        }
                    };

                    if reference_resolver
                        .resolve_idx(&external_reference.0)
                        .is_err()
                    {
                        tracing::warn!(
                            "subsource {export_id} of {ingestion_id} refers to \
                            {external_reference:?}, which is missing from \
                            updated SourceDesc \n{source_desc:#?}"
                        );
                        Err(AlterError { id: ingestion_id })?
                    }
                }
            }
            o => {
                tracing::info!(
                    "{ingestion_id} inalterable because its data source is {:?} and not an ingestion",
                    o
                );
                Err(AlterError { id: ingestion_id })?
            }
        }

        Ok(())
    }

    async fn alter_ingestion_source_desc(
        &mut self,
        ingestion_id: GlobalId,
        source_desc: SourceDesc,
    ) -> Result<(), StorageError<Self::Timestamp>> {
        self.check_alter_ingestion_source_desc(ingestion_id, &source_desc)?;

        // Update the `SourceDesc` and the source exports
        // simultaneously.
        let collection = self
            .collections
            .get_mut(&ingestion_id)
            .expect("validated exists");
        let curr_ingestion = match &mut collection.data_source {
            DataSource::Ingestion(curr_ingestion) => curr_ingestion,
            _ => unreachable!("verified collection refers to ingestion"),
        };

        curr_ingestion.desc = source_desc;
        tracing::debug!("altered {ingestion_id}'s SourceDesc");

        // n.b. we do not re-run updated ingestions because updating the source
        // desc is only done in preparation for adding subsources, which will
        // then run the ingestion.
        //
        // If this expectation ever changes, we will almost certainly know
        // because failing to run an altered ingestion means that whatever
        // changes you expect to occur will not be reflected in the running
        // dataflow.

        Ok(())
    }

    async fn alter_ingestion_connections(
        &mut self,
        source_connections: BTreeMap<GlobalId, GenericSourceConnection<InlinedConnection>>,
    ) -> Result<(), StorageError<Self::Timestamp>> {
        // Also have to let StorageCollections know!
        self.storage_collections
            .alter_ingestion_connections(source_connections.clone())
            .await?;

        let mut ingestions_to_run = BTreeSet::new();

        for (id, conn) in source_connections {
            let collection = self
                .collections
                .get_mut(&id)
                .ok_or_else(|| StorageError::IdentifierMissing(id))?;

            match &mut collection.data_source {
                DataSource::Ingestion(ingestion) => {
                    // If the connection hasn't changed, there's no sense in
                    // re-rendering the dataflow.
                    if ingestion.desc.connection != conn {
                        tracing::info!(from = ?ingestion.desc.connection, to = ?conn, "alter_ingestion_connections, updating");
                        ingestion.desc.connection = conn;
                        ingestions_to_run.insert(id);
                    } else {
                        tracing::warn!(
                            "update_source_connection called on {id} but the \
                            connection was the same"
                        );
                    }
                }
                o => {
                    tracing::warn!("update_source_connection called on {:?}", o);
                    Err(StorageError::IdentifierInvalid(id))?;
                }
            }
        }

        for id in ingestions_to_run {
            self.run_ingestion(id)?;
        }
        Ok(())
    }

    fn export(
        &self,
        id: GlobalId,
    ) -> Result<&ExportState<Self::Timestamp>, StorageError<Self::Timestamp>> {
        self.exports
            .get(&id)
            .ok_or(StorageError::IdentifierMissing(id))
    }

    fn export_mut(
        &mut self,
        id: GlobalId,
    ) -> Result<&mut ExportState<Self::Timestamp>, StorageError<Self::Timestamp>> {
        self.exports
            .get_mut(&id)
            .ok_or(StorageError::IdentifierMissing(id))
    }

    async fn create_exports(
        &mut self,
        exports: Vec<(GlobalId, ExportDescription<Self::Timestamp>)>,
    ) -> Result<(), StorageError<Self::Timestamp>> {
        // Validate first, to avoid corrupting state.
        let mut dedup = BTreeMap::new();
        for (id, desc) in exports.iter() {
            if dedup.insert(id, desc).is_some() {
                return Err(StorageError::SinkIdReused(*id));
            }
            if let Ok(export) = self.export(*id) {
                if &export.description != desc {
                    return Err(StorageError::SinkIdReused(*id));
                }
            }
        }

        for (id, description) in exports {
            let from_id = description.sink.from;

            // Acquire read holds at StorageCollections to ensure that the
            // sinked collection is not dropped while we're sinking it.
            let desired_read_holds = vec![from_id.clone()];
            let read_hold = self
                .storage_collections
                .acquire_read_holds(desired_read_holds)
                .expect("missing dependency")
                .into_element();

            info!(
                sink_id = id.to_string(),
                from_id = from_id.to_string(),
                acquired_read_hold = ?read_hold,
                "sink acquired read holds"
            );
            let read_policy = ReadPolicy::step_back();

            let from_storage_metadata = self.storage_collections.collection_metadata(from_id)?;

            info!(
                sink_id = id.to_string(),
                from_id = from_id.to_string(),
                as_of = ?description.sink.as_of,
                "create_exports: creating sink"
            );

            self.exports.insert(
                id,
                ExportState::new(description.clone(), read_hold, read_policy),
            );

            let status_id = if let Some(status_collection_id) = description.sink.status_id {
                Some(
                    self.storage_collections
                        .collection_metadata(status_collection_id)?
                        .data_shard,
                )
            } else {
                None
            };

            let cmd = RunSinkCommand {
                id,
                description: StorageSinkDesc {
                    from: from_id,
                    from_desc: description.sink.from_desc,
                    connection: description.sink.connection,
                    envelope: description.sink.envelope,
                    as_of: description.sink.as_of,
                    version: description.sink.version,
                    status_id,
                    from_storage_metadata,
                    with_snapshot: description.sink.with_snapshot,
                },
            };

            // Fetch the client for this exports's cluster.
            let client = self
                .clients
                .get_mut(&description.instance_id)
                .ok_or_else(|| StorageError::ExportInstanceMissing {
                    storage_instance_id: description.instance_id,
                    export_id: id,
                })?;

            // Just like with `new_source_statistic_entries`, we can probably
            // `insert` here, but in the interest of safety, never override
            // existing values.
            self.sink_statistics
                .lock()
                .expect("poisoned")
                .entry(id)
                .or_insert(StatsState::new(SinkStatisticsUpdate::new(id)));

            client.send(StorageCommand::RunSinks(vec![cmd]));
        }
        Ok(())
    }

    async fn alter_export(
        &mut self,
        id: GlobalId,
        new_description: ExportDescription<Self::Timestamp>,
    ) -> Result<(), StorageError<Self::Timestamp>> {
        let from_id = new_description.sink.from;

        // Acquire read holds at StorageCollections to ensure that the
        // sinked collection is not dropped while we're sinking it.
        let desired_read_holds = vec![from_id.clone()];
        let read_hold = self
            .storage_collections
            .acquire_read_holds(desired_read_holds)
            .expect("missing dependency")
            .into_element();
        let from_storage_metadata = self.storage_collections.collection_metadata(from_id)?;

        // Check whether the sink's write frontier is beyond the read hold we got
        let cur_export = self
            .exports
            .get_mut(&id)
            .ok_or_else(|| StorageError::IdentifierMissing(id))?;
        let input_readable = cur_export
            .write_frontier
            .iter()
            .all(|t| read_hold.since().less_than(t));
        if !input_readable {
            return Err(StorageError::ReadBeforeSince(from_id));
        }

        let new_export = ExportState {
            description: new_description.clone(),
            read_hold,
            read_policy: cur_export.read_policy.clone(),
            write_frontier: cur_export.write_frontier.clone(),
        };
        *cur_export = new_export;

        let status_id = match new_description.sink.status_id.clone() {
            Some(id) => Some(self.storage_collections.collection_metadata(id)?.data_shard),
            None => None,
        };

        let cmd = RunSinkCommand {
            id,
            description: StorageSinkDesc {
                from: from_id,
                from_desc: new_description.sink.from_desc,
                connection: new_description.sink.connection,
                envelope: new_description.sink.envelope,
                as_of: new_description.sink.as_of,
                version: new_description.sink.version,
                status_id,
                from_storage_metadata,
                with_snapshot: new_description.sink.with_snapshot,
            },
        };

        // Fetch the client for this exports's cluster.
        let client = self
            .clients
            .get_mut(&new_description.instance_id)
            .ok_or_else(|| StorageError::ExportInstanceMissing {
                storage_instance_id: new_description.instance_id,
                export_id: id,
            })?;

        client.send(StorageCommand::RunSinks(vec![cmd]));
        Ok(())
    }

    /// Create the sinks described by the `ExportDescription`.
    async fn alter_export_connections(
        &mut self,
        exports: BTreeMap<GlobalId, StorageSinkConnection>,
    ) -> Result<(), StorageError<Self::Timestamp>> {
        let mut updates_by_instance =
            BTreeMap::<StorageInstanceId, Vec<(RunSinkCommand<T>, ExportDescription<T>)>>::new();

        for (id, connection) in exports {
            // We stage changes in new_export_description and then apply all
            // updates to exports at the end.
            //
            // We don't just go ahead and clone the `ExportState` itself and
            // update that because `ExportState` is not clone, because it holds
            // a `ReadHandle` and cloning that would cause additional work for
            // whoever guarantees those read holds.
            let (mut new_export_description, as_of) = {
                let export = self.export(id).expect("export exists");
                let export_description = export.description.clone();
                let as_of = export.read_hold.since().clone();

                (export_description, as_of)
            };
            let current_sink = new_export_description.sink.clone();

            new_export_description.sink.connection = connection;

            // Ensure compatibility
            current_sink.alter_compatible(id, &new_export_description.sink)?;

            let from_storage_metadata = self
                .storage_collections
                .collection_metadata(new_export_description.sink.from)?;

            let status_id =
                if let Some(status_collection_id) = new_export_description.sink.status_id {
                    Some(
                        self.storage_collections
                            .collection_metadata(status_collection_id)?
                            .data_shard,
                    )
                } else {
                    None
                };

            let cmd = RunSinkCommand {
                id,
                description: StorageSinkDesc {
                    from: new_export_description.sink.from,
                    from_desc: new_export_description.sink.from_desc.clone(),
                    connection: new_export_description.sink.connection.clone(),
                    envelope: new_export_description.sink.envelope,
                    with_snapshot: new_export_description.sink.with_snapshot,
                    version: new_export_description.sink.version,
                    // Here we are about to send a RunSinkCommand with the current read capaibility
                    // held by this sink. However, clusters are already running a version of the
                    // sink and nothing guarantees that by the time this command arrives at the
                    // clusters they won't have made additional progress such that this read
                    // capability is invalidated.
                    // The solution to this problem is for the controller to track specific
                    // executions of dataflows such that it can track the shutdown of the current
                    // instance and the initialization of the new instance separately and ensure
                    // read holds are held for the correct amount of time.
                    // TODO(petrosagg): change the controller to explicitly track dataflow executions
                    as_of: as_of.to_owned(),
                    status_id,
                    from_storage_metadata,
                },
            };

            let update = updates_by_instance
                .entry(new_export_description.instance_id)
                .or_default();
            update.push((cmd, new_export_description));
        }

        for (instance_id, updates) in updates_by_instance {
            let mut export_updates = BTreeMap::new();
            let mut cmds = Vec::with_capacity(updates.len());

            for (cmd, export_state) in updates {
                export_updates.insert(cmd.id, export_state);
                cmds.push(cmd);
            }

            // Fetch the client for this exports's cluster.
            let client = self.clients.get_mut(&instance_id).ok_or_else(|| {
                StorageError::ExportInstanceMissing {
                    storage_instance_id: instance_id,
                    export_id: *export_updates
                        .keys()
                        .next()
                        .expect("set of exports not empty"),
                }
            })?;

            client.send(StorageCommand::RunSinks(cmds));

            // Update state only after all possible errors have occurred.
            for (id, new_export_description) in export_updates {
                let export = self.export_mut(id).expect("export known to exist");
                export.description = new_export_description;
            }
        }

        Ok(())
    }

    // Dropping a table takes roughly the following flow:
    //
    //   1. We remove the table from the persist table write worker.
    //   2. The table removal is awaited in an async task.
    //   3. A message is sent to the storage controller that the table has been removed from the
    //      table write worker.
    //   4. The controller drains all table drop messages during `process`.
    //   5. `process` calls `drop_sources` with the dropped tables.
    fn drop_tables(
        &mut self,
        identifiers: Vec<GlobalId>,
        ts: Self::Timestamp,
    ) -> Result<(), StorageError<Self::Timestamp>> {
        assert!(
            identifiers.iter().all(|id| self.collections[id].is_table()),
            "identifiers contain non-tables: {:?}",
            identifiers
                .iter()
                .filter(|id| !self.collections[id].is_table())
                .collect::<Vec<_>>()
        );
        let drop_notif = self
            .persist_table_worker
            .drop_handles(identifiers.clone(), ts);
        let tx = self.pending_table_handle_drops_tx.clone();
        mz_ore::task::spawn(|| "table-cleanup".to_string(), async move {
            drop_notif.await;
            for identifier in identifiers {
                let _ = tx.send(identifier);
            }
        });
        Ok(())
    }

    fn drop_sources(
        &mut self,
        storage_metadata: &StorageMetadata,
        identifiers: Vec<GlobalId>,
    ) -> Result<(), StorageError<Self::Timestamp>> {
        self.validate_collection_ids(identifiers.iter().cloned())?;
        self.drop_sources_unvalidated(storage_metadata, identifiers)
    }

    fn drop_sources_unvalidated(
        &mut self,
        storage_metadata: &StorageMetadata,
        ids: Vec<GlobalId>,
    ) -> Result<(), StorageError<Self::Timestamp>> {
        let mut ingestions_to_execute = BTreeSet::new();
        let mut ingestions_to_drop = BTreeSet::new();
        for id in ids.iter() {
            let metadata = storage_metadata.get_collection_shard::<T>(*id);
            mz_ore::soft_assert_or_log!(
                matches!(metadata, Err(StorageError::IdentifierMissing(_))),
                "dropping {id}, but drop was not synchronized with storage \
                controller via `synchronize_collections`"
            );

            let collection_state = self.collections.get(id);

            if let Some(collection_state) = collection_state {
                match collection_state.data_source {
                    // Webhooks and tables are dropped differently from
                    // ingestions and other collections.
                    //
                    // We can immediately compact them, because they don't
                    // interact with clusterd.
                    DataSource::Webhook | DataSource::Other(DataSourceOther::TableWrites) => {
                        let pending_compaction_command = PendingCompactionCommand {
                            id: *id,
                            read_frontier: Antichain::new(),
                            cluster_id: None,
                        };

                        tracing::debug!(?pending_compaction_command, "pushing pending compaction");

                        self.pending_compaction_commands
                            .push(pending_compaction_command);
                    }
                    DataSource::Ingestion(_) => {
                        ingestions_to_drop.insert(id);
                    }
                    DataSource::IngestionExport { ingestion_id, .. } => {
                        // If we are dropping source exports, we need to modify the
                        // ingestion that it runs on.
                        //
                        // If we remove this export, we need to stop producing data to
                        // it, so plan to re-execute the ingestion with the amended
                        // description.
                        ingestions_to_execute.insert(ingestion_id);

                        // Adjust the source to remove this export.
                        let ingestion_state = match self.collections.get_mut(&ingestion_id) {
                            Some(ingestion_collection) => ingestion_collection,
                            // Primary ingestion already dropped.
                            None => {
                                tracing::error!("primary source {ingestion_id} seemingly dropped before subsource {id}");
                                continue;
                            }
                        };

                        match &mut ingestion_state.data_source {
                            DataSource::Ingestion(ingestion_desc) => {
                                let removed = ingestion_desc.source_exports.remove(id);
                                mz_ore::soft_assert_or_log!(
                                    removed.is_some(),
                                    "dropped subsource {id} already removed from source exports"
                                );
                            }
                            _ => unreachable!("SourceExport must only refer to primary sources that already exist"),
                        };

                        // Ingestion exports also have ReadHolds that we need to
                        // downgrade, and much of their drop machinery is the
                        // same as for the "main" ingestion.
                        ingestions_to_drop.insert(id);
                    }
                    DataSource::Other(_) | DataSource::Introspection(_) | DataSource::Progress => {
                        ()
                    }
                }
            }
        }

        // Do not bother re-executing ingestions we know we plan to drop.
        ingestions_to_execute.retain(|id| !ingestions_to_drop.contains(id));
        for ingestion_id in ingestions_to_execute {
            self.run_ingestion(ingestion_id)?;
        }

        // For ingestions, we fabricate a new hold that will propagate through
        // the cluster and then back to us.

        // We don't explicitly remove read capabilities! Downgrading the
        // frontier of the source to `[]` (the empty Antichain), will propagate
        // to the storage dependencies.
        let ingestion_policies = ingestions_to_drop
            .iter()
            .map(|id| (**id, ReadPolicy::ValidFrom(Antichain::new())))
            .collect();

        tracing::debug!(
            ?ingestion_policies,
            "dropping sources by setting read hold policies"
        );
        self.set_hold_policies(ingestion_policies);

        // Also let StorageCollections know!
        self.storage_collections
            .drop_collections_unvalidated(storage_metadata, ids);

        Ok(())
    }

    /// Drops the read capability for the sinks and allows their resources to be reclaimed.
    fn drop_sinks(
        &mut self,
        identifiers: Vec<GlobalId>,
    ) -> Result<(), StorageError<Self::Timestamp>> {
        self.validate_export_ids(identifiers.iter().cloned())?;
        self.drop_sinks_unvalidated(identifiers);
        Ok(())
    }

    fn drop_sinks_unvalidated(&mut self, identifiers: Vec<GlobalId>) {
        for id in identifiers {
            // Already removed.
            if self.export(id).is_err() {
                continue;
            }

            // We don't explicitly remove read capabilities! Downgrading the
            // frontier of the sink to `[]` (the empty Antichain), will
            // propagate to the storage dependencies.

            // Remove sink by removing its write frontier and arranging for deprovisioning.
            self.update_write_frontiers(&[(id, Antichain::new())]);
        }
    }

    #[instrument(level = "debug")]
    fn append_table(
        &mut self,
        write_ts: Self::Timestamp,
        advance_to: Self::Timestamp,
        commands: Vec<(GlobalId, Vec<TimestamplessUpdate>)>,
    ) -> Result<
        tokio::sync::oneshot::Receiver<Result<(), StorageError<Self::Timestamp>>>,
        StorageError<Self::Timestamp>,
    > {
        if self.read_only {
            return Err(StorageError::ReadOnly);
        }

        // TODO(petrosagg): validate appends against the expected RelationDesc of the collection
        for (id, updates) in commands.iter() {
            if !updates.is_empty() {
                if !write_ts.less_than(&advance_to) {
                    return Err(StorageError::UpdateBeyondUpper(*id));
                }
            }
        }

        Ok(self
            .persist_table_worker
            .append(write_ts, advance_to, commands))
    }

    fn monotonic_appender(
        &self,
        id: GlobalId,
    ) -> Result<MonotonicAppender<Self::Timestamp>, StorageError<Self::Timestamp>> {
        self.collection_manager.monotonic_appender(id)
    }

    fn webhook_statistics(
        &self,
        id: GlobalId,
    ) -> Result<Arc<WebhookStatistics>, StorageError<Self::Timestamp>> {
        // Call to this method are usually cached so the lock is not in the critical path.
        let source_statistics = self.source_statistics.lock().expect("poisoned");
        source_statistics
            .webhook_statistics
            .get(&id)
            .cloned()
            .ok_or(StorageError::IdentifierMissing(id))
    }

    // TODO(petrosagg): This signature is not very useful in the context of partially ordered times
    // where the as_of frontier might have multiple elements. In the current form the mutually
    // incomparable updates will be accumulated together to a state of the collection that never
    // actually existed. We should include the original time in the updates advanced by the as_of
    // frontier in the result and let the caller decide what to do with the information.
    async fn snapshot(
        &mut self,
        id: GlobalId,
        as_of: Self::Timestamp,
    ) -> Result<Vec<(Row, Diff)>, StorageError<Self::Timestamp>> {
        let metadata = &self.storage_collections.collection_metadata(id)?;
        let contents = match metadata.txns_shard.as_ref() {
            None => {
                // We're not using txn-wal for tables, so we can take a snapshot directly.
                let mut read_handle = self.read_handle_for_snapshot(id).await?;
                read_handle
                    .snapshot_and_fetch(Antichain::from_elem(as_of))
                    .await
            }
            Some(txns_id) => {
                // We _are_ using txn-wal for tables. It advances the physical upper of the
                // shard lazily, so we need to ask it for the snapshot to ensure the read is
                // unblocked.
                //
                // Consider the following scenario:
                // - Table A is written to via txns at time 5
                // - Tables other than A are written to via txns consuming timestamps up to 10
                // - We'd like to read A at 7
                // - The application process of A's txn has advanced the upper to 5+1, but we need
                //   it to be past 7, but the txns shard knows that (5,10) is empty of writes to A
                // - This branch allows it to handle that advancing the physical upper of Table A to
                //   10 (NB but only once we see it get past the write at 5!)
                // - Then we can read it normally.
                assert_eq!(txns_id, self.txns_read.txns_id());
                self.txns_read.update_gt(as_of.clone()).await;
                let data_snapshot = self
                    .txns_read
                    .data_snapshot(metadata.data_shard, as_of.clone())
                    .await;
                let mut read_handle = self.read_handle_for_snapshot(id).await?;
                data_snapshot.snapshot_and_fetch(&mut read_handle).await
            }
        };
        match contents {
            Ok(contents) => {
                let mut snapshot = Vec::with_capacity(contents.len());
                for ((data, _), _, diff) in contents {
                    // TODO(petrosagg): We should accumulate the errors too and let the user
                    // interprret the result
                    let row = data.expect("invalid protobuf data").0?;
                    snapshot.push((row, diff));
                }
                Ok(snapshot)
            }
            Err(_) => Err(StorageError::ReadBeforeSince(id)),
        }
    }

    async fn snapshot_cursor(
        &mut self,
        id: GlobalId,
        as_of: Self::Timestamp,
    ) -> Result<SnapshotCursor<Self::Timestamp>, StorageError<Self::Timestamp>>
    where
        Self::Timestamp: Timestamp + Lattice + Codec64,
    {
        let metadata = &self.storage_collections.collection_metadata(id)?;

        // See the comments in Self::snapshot for what's going on here.
        let cursor = match metadata.txns_shard.as_ref() {
            None => {
                let mut handle = self.read_handle_for_snapshot(id).await?;
                let cursor = handle
                    .snapshot_cursor(Antichain::from_elem(as_of), |_| true)
                    .await
                    .map_err(|_| StorageError::ReadBeforeSince(id))?;
                SnapshotCursor {
                    _read_handle: handle,
                    cursor,
                }
            }
            Some(txns_id) => {
                assert_eq!(txns_id, self.txns_read.txns_id());
                self.txns_read.update_gt(as_of.clone()).await;
                let data_snapshot = self
                    .txns_read
                    .data_snapshot(metadata.data_shard, as_of.clone())
                    .await;
                let mut handle = self.read_handle_for_snapshot(id).await?;
                let cursor = data_snapshot
                    .snapshot_cursor(&mut handle, |_| true)
                    .await
                    .map_err(|_| StorageError::ReadBeforeSince(id))?;
                SnapshotCursor {
                    _read_handle: handle,
                    cursor,
                }
            }
        };

        Ok(cursor)
    }

    async fn snapshot_stats(
        &self,
        id: GlobalId,
        as_of: Antichain<Self::Timestamp>,
    ) -> Result<SnapshotStats, StorageError<Self::Timestamp>> {
        self.storage_collections.snapshot_stats(id, as_of).await
    }

    async fn snapshot_parts_stats(
        &self,
        id: GlobalId,
        as_of: Antichain<Self::Timestamp>,
    ) -> BoxFuture<'static, Result<SnapshotPartsStats, StorageError<Self::Timestamp>>> {
        self.storage_collections
            .snapshot_parts_stats(id, as_of)
            .await
    }

    #[instrument(level = "debug")]
    fn set_read_policy(&mut self, policies: Vec<(GlobalId, ReadPolicy<Self::Timestamp>)>) {
        self.storage_collections.set_read_policies(policies);
    }

    fn acquire_read_holds(
        &mut self,
        desired_holds: Vec<GlobalId>,
    ) -> Result<Vec<ReadHold<Self::Timestamp>>, ReadHoldError> {
        self.storage_collections.acquire_read_holds(desired_holds)
    }

    #[instrument(level = "debug", fields(updates))]
    fn update_read_capabilities(
        &mut self,
        updates: &mut BTreeMap<GlobalId, ChangeBatch<Self::Timestamp>>,
    ) {
        self.storage_collections.update_read_capabilities(updates);
    }

    async fn ready(&mut self) {
        if self.pending_compaction_commands.len() > 0 {
            return;
        }

        if let Ok(dropped_id) = self.pending_table_handle_drops_rx.try_recv() {
            // HACKY: We cannot check if the channel has data on the version of
            // tokio that we're using, so we do a try_recv and put it back.
            self.pending_table_handle_drops_tx
                .send(dropped_id)
                .expect("ourselves are not dropped");
            return;
        }

        let mut clients = self
            .clients
            .values_mut()
            .map(|client| client.response_stream())
            .enumerate()
            .collect::<StreamMap<_, _>>();

        use tokio_stream::StreamExt;
        let msg = tokio::select! {
            // Order matters here. We want to process internal commands
            // before processing external commands.
            biased;

            Some(m) = self.internal_response_queue.recv() => m,
            Some((_id, m)) = clients.next() => m,
        };

        self.stashed_response = Some(msg);
    }

    #[instrument(level = "debug")]
    async fn process(
        &mut self,
        storage_metadata: &StorageMetadata,
    ) -> Result<Option<Response<T>>, anyhow::Error> {
        let mut updated_frontiers = None;
        match self.stashed_response.take() {
            None => (),
            Some(StorageResponse::FrontierUppers(updates)) => {
                self.update_write_frontiers(&updates);
                updated_frontiers = Some(Response::FrontierUpdates(updates));
            }
            Some(StorageResponse::DroppedIds(ids)) => {
                for id in ids.iter() {
                    tracing::debug!("DroppedIds for collections {id}");

                    if let Some(_collection) = self.collections.remove(id) {
                        // Nothing to do, we already dropped read holds in
                        // `drop_sources_unvalidated`.
                    } else if let Some(export) = self.exports.get_mut(id) {
                        // TODO: Current main never drops export state, so we
                        // also don't do that, because it would be yet more
                        // refactoring. Instead, we downgrade to the empty
                        // frontier, which satisfies StorageCollections just as
                        // much.
                        tracing::info!("downgrading read hold of export {id} to empty frontier!");
                        export
                            .read_hold
                            .try_downgrade(Antichain::new())
                            .expect("must be possible");
                    } else {
                        panic!("DroppedIds for ID {id} but we have neither ingestion nor export under that ID");
                    }
                }
            }
            Some(StorageResponse::StatisticsUpdates(source_stats, sink_stats)) => {
                // Note we only hold the locks while moving some plain-old-data around here.
                //
                // We just write the whole object, as the update from storage represents the
                // current values.
                //
                // We don't overwrite removed objects, as we may have received a late
                // `StatisticsUpdates` while we were shutting down the storage object.
                {
                    let mut shared_stats = self.source_statistics.lock().expect("poisoned");
                    for stat in source_stats {
                        // Don't override it if its been removed.
                        shared_stats
                            .source_statistics
                            .entry(stat.id)
                            .and_modify(|current| current.stat().incorporate(stat));
                    }
                }

                {
                    let mut shared_stats = self.sink_statistics.lock().expect("poisoned");
                    for stat in sink_stats {
                        // Don't override it if its been removed.
                        shared_stats
                            .entry(stat.id)
                            .and_modify(|current| current.stat().incorporate(stat));
                    }
                }
            }
            Some(StorageResponse::StatusUpdates(updates)) => {
                self.record_status_updates(updates).await;
            }
        }

        // IDs of sources that were dropped whose statuses should be updated.
        let mut pending_source_drops = vec![];

        // IDs of all collections that were dropped whose shard mappings should be deleted.
        let mut pending_collection_drops = vec![];

        // IDs of sinks that were dropped whose statuses should be updated (and statistics
        // cleared).
        let mut pending_sink_drops = vec![];

        // IDs of sources (and subsources) whose statistics should be cleared.
        let mut source_statistics_to_drop = vec![];

        // Process dropped tables in a single batch.
        let mut dropped_table_ids = Vec::new();
        while let Ok(dropped_id) = self.pending_table_handle_drops_rx.try_recv() {
            dropped_table_ids.push(dropped_id);
        }
        if !dropped_table_ids.is_empty() {
            self.drop_sources(storage_metadata, dropped_table_ids)?;
        }

        // TODO(aljoscha): We could consolidate these before sending to
        // instances, but this seems fine for now.
        for compaction_command in self.pending_compaction_commands.drain(..) {
            let PendingCompactionCommand {
                id,
                read_frontier,
                cluster_id,
            } = compaction_command;

            // TODO(petrosagg): make this a strict check
            // TODO(aljoscha): What's up with this TODO?
            // Note that while collections are dropped, the `client` may already
            // be cleared out, before we do this post-processing!
            let client = cluster_id.and_then(|cluster_id| self.clients.get_mut(&cluster_id));

            let internal_response_sender = self.internal_response_sender.clone();
            let spawn_cleanup_task = |drop_fut| {
                mz_ore::task::spawn(|| format!("storage-table-cleanup-{id}"), async move {
                    // Wait for the relevant component to drop its resources and handles, this
                    // guarantees we won't see any more writes.
                    drop_fut.await;

                    // Notify that this ID has been dropped, which will start finalization of
                    // the shard.
                    let _ = internal_response_sender.send(StorageResponse::DroppedIds([id].into()));
                });
            };

            if read_frontier.is_empty() {
                if client.is_some() && self.collections.contains_key(&id) {
                    let collection = self.collections.get(&id).expect("known to exist");
                    match collection.extra_state {
                        CollectionStateExtra::Ingestion(_) => {
                            pending_source_drops.push(id);
                        }
                        CollectionStateExtra::None => {
                            // Nothing to do
                        }
                    }
                } else if let Some(collection) = self.collections.get(&id) {
                    match collection.data_source {
                        DataSource::Other(DataSourceOther::TableWrites) => {
                            pending_collection_drops.push(id);

                            // Hacky, return an empty future so the IDs are finalized below.
                            let drop_fut = async move {}.boxed();
                            spawn_cleanup_task(drop_fut);
                        }
                        DataSource::Webhook => {
                            pending_collection_drops.push(id);

                            // TODO(parkmycar): The Collection Manager and PersistMonotonicWriter
                            // could probably use some love and maybe get merged together?
                            let unregister_notif =
                                self.collection_manager.unregister_collection(id);
                            let monotonic_worker = self.persist_monotonic_worker.clone();
                            let drop_fut = async move {
                                // Wait for the collection manager to stop writing.
                                unregister_notif.await;
                                // Wait for the montonic worker to drop the handle.
                                monotonic_worker.drop_handle(id).await;
                            };
                            let drop_fut = drop_fut.boxed();

                            spawn_cleanup_task(drop_fut);
                        }
                        DataSource::Ingestion(_) => (),
                        DataSource::IngestionExport { .. } => (),
                        DataSource::Introspection(_) => (),
                        DataSource::Progress => (),
                        DataSource::Other(_) => (),
                    }
                } else if client.is_some() && self.exports.contains_key(&id) {
                    pending_sink_drops.push(id);
                } else if client.is_none() {
                    tracing::info!("Compaction command for id {id}, but we don't have a client.");
                } else {
                    panic!("Reference to absent collection {id}");
                };
            }

            // Sources can have subsources, which don't have associated clusters, which
            // is why this operates differently than sinks.
            if read_frontier.is_empty() {
                source_statistics_to_drop.push(id);
            }

            // Note that while collections are dropped, the `client` may already
            // be cleared out, before we do this post-processing!
            if let Some(client) = client {
                client.send(StorageCommand::AllowCompaction(vec![(
                    id,
                    read_frontier.clone(),
                )]));
            }
        }

        // Delete all collection->shard mappings, making sure to de-duplicate.
        let shards_to_update: BTreeSet<_> = pending_source_drops
            .iter()
            .chain(pending_collection_drops.iter())
            .cloned()
            .collect();
        self.append_shard_mappings(shards_to_update.into_iter(), -1)
            .await;

        // Record the drop status for all pending source and sink drops.
        //
        // We also delete the items' statistics objects.
        //
        // The locks are held for a short time, only while we do some hash map removals.

        let status_now = mz_ore::now::to_datetime((self.now)());

        let mut dropped_sources = vec![];
        for id in pending_source_drops.drain(..) {
            dropped_sources.push(StatusUpdate::new(id, status_now, Status::Dropped));
        }

        if !self.read_only {
            self.collection_status_manager
                .append_updates(dropped_sources, IntrospectionType::SourceStatusHistory)
                .await;
        }

        {
            let mut source_statistics = self.source_statistics.lock().expect("poisoned");
            for id in source_statistics_to_drop {
                source_statistics.source_statistics.remove(&id);
                source_statistics.webhook_statistics.remove(&id);
            }
        }

        // Record the drop status for all pending sink drops.
        let mut dropped_sinks = vec![];
        {
            let mut sink_statistics = self.sink_statistics.lock().expect("poisoned");
            for id in pending_sink_drops.drain(..) {
                dropped_sinks.push(StatusUpdate::new(id, status_now, Status::Dropped));
                sink_statistics.remove(&id);
            }
        }

        if !self.read_only {
            self.collection_status_manager
                .append_updates(dropped_sinks, IntrospectionType::SinkStatusHistory)
                .await;
        }

        Ok(updated_frontiers)
    }

    async fn inspect_persist_state(
        &self,
        id: GlobalId,
    ) -> Result<serde_json::Value, anyhow::Error> {
        let collection = &self.storage_collections.collection_metadata(id)?;
        let client = self
            .persist
            .open(collection.persist_location.clone())
            .await?;
        let shard_state = client
            .inspect_shard::<Self::Timestamp>(&collection.data_shard)
            .await?;
        let json_state = serde_json::to_value(shard_state)?;
        Ok(json_state)
    }

    async fn record_frontiers(
        &mut self,
        external_frontiers: BTreeMap<
            GlobalId,
            (Antichain<Self::Timestamp>, Antichain<Self::Timestamp>),
        >,
    ) {
        let mut frontiers = external_frontiers;

        // Enrich `frontiers` with storage frontiers.
        for CollectionFrontiers {
            id,
            implied_capability: since,
            write_frontier: upper,
            ..
        } in self.storage_collections.active_collection_frontiers()
        {
            frontiers.insert(id, (since, upper));
        }
        for (object_id, export) in self.active_exports() {
            // Exports cannot be read from, so their `since` is always the empty frontier.
            let since = Antichain::new();
            let upper = export.write_frontier.clone();
            frontiers.insert(object_id, (since, upper));
        }

        let mut updates = Vec::new();
        let mut push_update =
            |object_id: GlobalId,
             (since, upper): (Antichain<Self::Timestamp>, Antichain<Self::Timestamp>),
             diff: Diff| {
                let read_frontier = since.into_option().map_or(Datum::Null, |ts| ts.into());
                let write_frontier = upper.into_option().map_or(Datum::Null, |ts| ts.into());
                let row = Row::pack_slice(&[
                    Datum::String(&object_id.to_string()),
                    read_frontier,
                    write_frontier,
                ]);
                updates.push((row, diff));
            };

        let mut old_frontiers = std::mem::replace(&mut self.recorded_frontiers, frontiers);
        for (&id, new) in &self.recorded_frontiers {
            match old_frontiers.remove(&id) {
                Some(old) if &old != new => {
                    push_update(id, new.clone(), 1);
                    push_update(id, old, -1);
                }
                Some(_) => (),
                None => push_update(id, new.clone(), 1),
            }
        }
        for (id, old) in old_frontiers {
            push_update(id, old, -1);
        }

        let id = self.introspection_ids.lock().expect("poisoned")[&IntrospectionType::Frontiers];
        self.collection_manager
            .differential_append(id, updates)
            .await;
    }

    async fn record_replica_frontiers(
        &mut self,
        external_frontiers: BTreeMap<(GlobalId, ReplicaId), Antichain<Self::Timestamp>>,
    ) {
        let mut frontiers = external_frontiers;

        // Enrich `frontiers` with storage frontiers.
        let mut uppers: BTreeMap<GlobalId, Antichain<Self::Timestamp>> = self
            .storage_collections
            .active_collection_frontiers()
            .into_iter()
            .map(
                |CollectionFrontiers {
                     id, write_frontier, ..
                 }| (id, write_frontier),
            )
            .collect();
        for (object_id, collection_state) in self.collections.iter() {
            let ingestion_state = match &collection_state.extra_state {
                CollectionStateExtra::Ingestion(ingestion) => ingestion,
                CollectionStateExtra::None => continue,
            };

            let replica_id = self
                .replicas
                .get(&ingestion_state.instance_id)
                .and_then(|r| uppers.remove(object_id).map(|uppers| (r.clone(), uppers)));

            if let Some((replica_id, upper)) = replica_id {
                frontiers.insert((*object_id, replica_id), upper);
            }
        }
        for (object_id, export) in self.active_exports() {
            let cluster_id = export.cluster_id();
            let replica_id = self.replicas.get(&cluster_id).copied();
            if let Some(replica_id) = replica_id {
                let upper = export.write_frontier.clone();
                frontiers.insert((object_id, replica_id), upper);
            }
        }

        let mut updates = Vec::new();
        let mut push_update = |(object_id, replica_id): (GlobalId, ReplicaId),
                               upper: Antichain<Self::Timestamp>,
                               diff: Diff| {
            let write_frontier = upper.into_option().map_or(Datum::Null, |ts| ts.into());
            let row = Row::pack_slice(&[
                Datum::String(&object_id.to_string()),
                Datum::String(&replica_id.to_string()),
                write_frontier,
            ]);
            updates.push((row, diff));
        };

        let mut old_frontiers = std::mem::replace(&mut self.recorded_replica_frontiers, frontiers);
        for (&key, new) in &self.recorded_replica_frontiers {
            match old_frontiers.remove(&key) {
                Some(old) if &old != new => {
                    push_update(key, new.clone(), 1);
                    push_update(key, old, -1);
                }
                Some(_) => (),
                None => push_update(key, new.clone(), 1),
            }
        }
        for (key, old) in old_frontiers {
            push_update(key, old, -1);
        }

        let id =
            self.introspection_ids.lock().expect("poisoned")[&IntrospectionType::ReplicaFrontiers];
        self.collection_manager
            .differential_append(id, updates)
            .await;
    }

    async fn append_introspection_updates(
        &mut self,
        type_: IntrospectionType,
        updates: Vec<(Row, Diff)>,
    ) {
        let id = self.introspection_ids.lock().expect("poisoned")[&type_];
        self.collection_manager.blind_write(id, updates).await;
    }

    async fn update_introspection_collection(
        &mut self,
        type_: IntrospectionType,
        op: StorageWriteOp,
    ) {
        let id = self.introspection_ids.lock().expect("poisoned")[&type_];
        self.collection_manager.differential_write(id, op).await;
    }

    async fn initialize_state(
        &mut self,
        txn: &mut (dyn StorageTxn<T> + Send),
        init_ids: BTreeSet<GlobalId>,
        drop_ids: BTreeSet<GlobalId>,
    ) -> Result<(), StorageError<T>> {
        self.storage_collections
            .initialize_state(txn, init_ids, drop_ids)
            .await
    }

    async fn prepare_state(
        &self,
        txn: &mut (dyn StorageTxn<T> + Send),
        ids_to_add: BTreeSet<GlobalId>,
        ids_to_drop: BTreeSet<GlobalId>,
    ) -> Result<(), StorageError<T>> {
        self.storage_collections
            .prepare_state(txn, ids_to_add, ids_to_drop)
            .await
    }

    async fn real_time_recent_timestamp(
        &mut self,
        timestamp_objects: BTreeSet<GlobalId>,
        timeout: Duration,
    ) -> Result<
        BoxFuture<'static, Result<Self::Timestamp, StorageError<Self::Timestamp>>>,
        StorageError<Self::Timestamp>,
    > {
        use mz_storage_types::sources::GenericSourceConnection;

        let mut rtr_futures = BTreeMap::new();

        // Only user sources can be read from w/ RTR.
        for id in timestamp_objects.into_iter().filter(GlobalId::is_user) {
            let collection = match self.collection(id) {
                Ok(c) => c,
                // Not a storage item, which we accept.
                Err(_) => continue,
            };

            let (source_conn, remap_id) = match &collection.data_source {
                DataSource::Ingestion(IngestionDescription {
                    desc: SourceDesc { connection, .. },
                    remap_collection_id,
                    ..
                }) => match connection {
                    GenericSourceConnection::Kafka(_)
                    | GenericSourceConnection::Postgres(_)
                    | GenericSourceConnection::MySql(_) => {
                        (connection.clone(), *remap_collection_id)
                    }

                    // These internal sources do not yet (and might never)
                    // support RTR. However, erroring if they're selected from
                    // poses an annoying user experience, so instead just skip
                    // over them.
                    GenericSourceConnection::LoadGenerator(_) => continue,
                },
                // Skip over all other objects
                _ => {
                    continue;
                }
            };

            // Prepare for getting the external system's frontier.
            let config = self.config().clone();

            // Determine the remap collection we plan to read from.
            //
            // Note that the process of reading from the remap shard is the same
            // as other areas in this code that do the same thing, but we inline
            // it here because we must prove that we have not taken ownership of
            // `self` to move the stream of data from the remap shard into a
            // future.
            let read_handle = self.read_handle_for_snapshot(remap_id).await?;

            // Have to acquire a read hold to prevent the since from advancing
            // while we read.
            let remap_read_hold = self
                .storage_collections
                .acquire_read_holds(vec![remap_id])
                .map_err(|_e| StorageError::ReadBeforeSince(remap_id))?
                .expect_element(|| format!("known to be exactly one"));

            let remap_as_of = remap_read_hold
                .since()
                .to_owned()
                .into_option()
                .ok_or(StorageError::ReadBeforeSince(remap_id))?;

            rtr_futures.insert(
                id,
                tokio::time::timeout(timeout, async move {
                    use mz_storage_types::sources::SourceConnection as _;

                    // Fetch the remap shard's contents; we must do this first so
                    // that the `as_of` doesn't change.
                    let as_of = Antichain::from_elem(remap_as_of);
                    let remap_subscribe = read_handle
                        .subscribe(as_of.clone())
                        .await
                        .map_err(|_| StorageError::ReadBeforeSince(remap_id))?;

                    tracing::debug!(?id, type_ = source_conn.name(), upstream = ?source_conn.external_reference(), "fetching real time recency");

                    let result = rtr::real_time_recency_ts(source_conn, id, config, as_of, remap_subscribe)
                        .await.map_err(|e| {
                            tracing::debug!(?id, "real time recency error: {:?}", e);
                            e
                        });

                    // Drop once we have read succesfully.
                    drop(remap_read_hold);

                    result
                }),
            );
        }

        Ok(Box::pin(async move {
            let (ids, futs): (Vec<_>, Vec<_>) = rtr_futures.into_iter().unzip();
            ids.into_iter()
                .zip_eq(futures::future::join_all(futs).await)
                .try_fold(T::minimum(), |curr, (id, per_source_res)| {
                    let new =
                        per_source_res.map_err(|_e: Elapsed| StorageError::RtrTimeout(id))??;
                    Ok::<_, StorageError<Self::Timestamp>>(std::cmp::max(curr, new))
                })
        }))
    }
}

/// Seed [`StorageTxn`] with any state required to instantiate a
/// [`StorageController`].
///
/// This cannot be a member of [`StorageController`] because it cannot take a
/// `self` parameter.
///
pub fn prepare_initialization<T>(txn: &mut dyn StorageTxn<T>) -> Result<(), StorageError<T>> {
    if txn.get_txn_wal_shard().is_none() {
        let txns_id = ShardId::new();
        txn.write_txn_wal_shard(txns_id)?;
    }

    Ok(())
}

impl<T> Controller<T>
where
    T: Timestamp + Lattice + TotalOrder + Codec64 + From<EpochMillis> + TimestampManipulation,
    StorageCommand<T>: RustType<ProtoStorageCommand>,
    StorageResponse<T>: RustType<ProtoStorageResponse>,

    Self: StorageController<Timestamp = T>,
{
    /// Create a new storage controller from a client it should wrap.
    ///
    /// Note that when creating a new storage controller, you must also
    /// reconcile it with the previous state.
    ///
    /// # Panics
    /// If this function is called before [`prepare_initialization`].
    pub async fn new(
        build_info: &'static BuildInfo,
        persist_location: PersistLocation,
        persist_clients: Arc<PersistClientCache>,
        now: NowFn,
        txns_metrics: Arc<TxnMetrics>,
        envd_epoch: NonZeroI64,
        read_only: bool,
        metrics_registry: MetricsRegistry,
        connection_context: ConnectionContext,
        txn: &dyn StorageTxn<T>,
        storage_collections: Arc<dyn StorageCollections<Timestamp = T> + Send + Sync>,
    ) -> Self {
        let (tx, rx) = tokio::sync::mpsc::unbounded_channel();

        // This value must be already installed because we must ensure it's
        // durably recorded before it is used, otherwise we risk leaking persist
        // state.
        let txns_id = txn
            .get_txn_wal_shard()
            .expect("must call prepare initialization before creating storage controller");

        let txns_client = persist_clients
            .open(persist_location.clone())
            .await
            .expect("location should be valid");

        let txns = TxnsHandle::open(
            T::minimum(),
            txns_client.clone(),
            Arc::clone(&txns_metrics),
            txns_id,
            Arc::new(RelationDesc::empty()),
            Arc::new(UnitSchema),
        )
        .await;
        let persist_table_worker = persist_handles::PersistTableWriteWorker::new_txns(txns);
        let txns_read = TxnsRead::start::<TxnsCodecRow>(txns_client.clone(), txns_id).await;
        let persist_monotonic_worker = persist_handles::PersistMonotonicWriteWorker::new();
        let collection_manager_write_handle = persist_monotonic_worker.clone();

        let collection_manager = collection_mgmt::CollectionManager::new(
            read_only,
            collection_manager_write_handle,
            now.clone(),
        );

        let introspection_ids = Arc::new(Mutex::new(BTreeMap::new()));

        let collection_status_manager = crate::collection_status::CollectionStatusManager::new(
            collection_manager.clone(),
            Arc::clone(&introspection_ids),
        );

        let (statistics_interval_sender, _) =
            channel(mz_storage_types::parameters::STATISTICS_INTERVAL_DEFAULT);

        let (pending_table_handle_drops_tx, pending_table_handle_drops_rx) =
            tokio::sync::mpsc::unbounded_channel();

        Self {
            build_info,
            collections: BTreeMap::default(),
            exports: BTreeMap::default(),
            persist_table_worker,
            persist_monotonic_worker,
            txns_read,
            txns_metrics,
            stashed_response: None,
            pending_compaction_commands: vec![],
            pending_table_handle_drops_tx,
            pending_table_handle_drops_rx,
            collection_manager,
            collection_status_manager,
            introspection_ids,
            introspection_tokens: BTreeMap::new(),
            now,
            envd_epoch,
            read_only,
            source_statistics: Arc::new(Mutex::new(statistics::SourceStatistics {
                source_statistics: BTreeMap::new(),
                webhook_statistics: BTreeMap::new(),
            })),
            sink_statistics: Arc::new(Mutex::new(BTreeMap::new())),
            statistics_interval_sender,
            clients: BTreeMap::new(),
            replicas: BTreeMap::new(),
            initialized: false,
            config: StorageConfiguration::new(connection_context, mz_dyncfgs::all_dyncfgs()),
            internal_response_sender: tx,
            internal_response_queue: rx,
            persist_location,
            persist: persist_clients,
            metrics: StorageControllerMetrics::new(metrics_registry),
            recorded_frontiers: BTreeMap::new(),
            recorded_replica_frontiers: BTreeMap::new(),
            storage_collections,
        }
    }

    // This is different from `set_read_policies`, which is for external users.
    // This method is for setting the policy that the controller uses when
    // maintaining the read holds that it has for collections/exports at the
    // StorageCollections.
    //
    // This is really only used when dropping things, where we set the
    // ReadPolicy to the empty Antichain.
    #[instrument(level = "debug")]
    fn set_hold_policies(&mut self, policies: Vec<(GlobalId, ReadPolicy<T>)>) {
        let mut read_capability_changes = BTreeMap::default();

        for (id, policy) in policies.into_iter() {
            if let Some(collection) = self.collections.get_mut(&id) {
                let ingestion = match &mut collection.extra_state {
                    CollectionStateExtra::Ingestion(ingestion) => ingestion,
                    CollectionStateExtra::None => {
                        unreachable!("set_hold_policies is only called for ingestions");
                    }
                };
                let mut new_derived_since = policy.frontier(ingestion.write_frontier.borrow());

                if PartialOrder::less_equal(&ingestion.derived_since, &new_derived_since) {
                    let mut update = ChangeBatch::new();
                    update.extend(new_derived_since.iter().map(|time| (time.clone(), 1)));
                    std::mem::swap(&mut ingestion.derived_since, &mut new_derived_since);
                    update.extend(new_derived_since.iter().map(|time| (time.clone(), -1)));

                    if !update.is_empty() {
                        read_capability_changes.insert(id, update);
                    }
                }

                ingestion.hold_policy = policy;
            } else if let Some(_export) = self.exports.get_mut(&id) {
                unreachable!("set_hold_policies is only called for ingestions");
            }
        }

        if !read_capability_changes.is_empty() {
            self.update_hold_capabilities(&mut read_capability_changes);
        }
    }

    #[instrument(level = "debug", fields(updates))]
    fn update_write_frontiers(&mut self, updates: &[(GlobalId, Antichain<T>)]) {
        let mut read_capability_changes = BTreeMap::default();

        for (id, new_upper) in updates.iter() {
            if let Some(collection) = self.collections.get_mut(id) {
                let ingestion = match &mut collection.extra_state {
                    CollectionStateExtra::Ingestion(ingestion) => ingestion,
                    CollectionStateExtra::None => {
                        if matches!(collection.data_source, DataSource::Progress) {
                            // We do get these, but can't do anything with it!
                        } else {
                            tracing::error!(
                                ?collection,
                                ?new_upper,
                                "updated write frontier for collection which is not an ingestion"
                            );
                        }
                        continue;
                    }
                };

                if PartialOrder::less_than(&ingestion.write_frontier, new_upper) {
                    ingestion.write_frontier.clone_from(new_upper);
                }

                debug!(%id, ?ingestion, ?new_upper, "upper update for ingestion!");

                let mut new_derived_since = ingestion
                    .hold_policy
                    .frontier(ingestion.write_frontier.borrow());

                if PartialOrder::less_equal(&ingestion.derived_since, &new_derived_since) {
                    let mut update = ChangeBatch::new();
                    update.extend(new_derived_since.iter().map(|time| (time.clone(), 1)));
                    std::mem::swap(&mut ingestion.derived_since, &mut new_derived_since);
                    update.extend(new_derived_since.iter().map(|time| (time.clone(), -1)));

                    if !update.is_empty() {
                        read_capability_changes.insert(*id, update);
                    }
                }
            } else if let Ok(export) = self.export_mut(*id) {
                if PartialOrder::less_than(&export.write_frontier, new_upper) {
                    export.write_frontier.clone_from(new_upper);
                }

                // Ignore read policy for sinks whose write frontiers are closed, which identifies
                // the sink is being dropped; we need to advance the read frontier to the empty
                // chain to signal to the dataflow machinery that they should deprovision this
                // object.
                let new_read_capability = if export.write_frontier.is_empty() {
                    export.write_frontier.clone()
                } else {
                    export.read_policy.frontier(export.write_frontier.borrow())
                };

                if PartialOrder::less_equal(export.read_hold.since(), &new_read_capability) {
                    let mut update = ChangeBatch::new();
                    update.extend(new_read_capability.iter().map(|time| (time.clone(), 1)));
                    update.extend(
                        export
                            .read_hold
                            .since()
                            .iter()
                            .map(|time| (time.clone(), -1)),
                    );

                    if !update.is_empty() {
                        read_capability_changes.insert(*id, update);
                    }
                }
            } else if self.storage_collections.check_exists(*id).is_ok() {
                // StorageCollections is handling it!
            } else {
                // TODO: This can happen because subsources report back an upper
                // but we don't store them in our `ingestions` field, _nor_ do
                // we acquire read holds for them. Also because we don't get
                // `DroppedIds` messages for them, so we wouldn't know when to
                // clean up read holds.
                info!(
                    "Reference to absent collection {id}, new_upper={:?}",
                    new_upper
                );
            }
        }

        if !read_capability_changes.is_empty() {
            self.update_hold_capabilities(&mut read_capability_changes);
        }
    }

    // This is different from `update_read_capabilities`, which is for external users.
    // This method is for maintaining the read holds that the controller has at
    // the StorageCollections, for storage dependencies.
    #[instrument(level = "debug", fields(updates))]
    fn update_hold_capabilities(&mut self, updates: &mut BTreeMap<GlobalId, ChangeBatch<T>>) {
        // Location to record consequences that we need to act on.
        let mut collections_net = BTreeMap::new();
        let mut exports_net = BTreeMap::new();

        // We must not rely on any specific relative ordering of `GlobalId`s.
        // That said, it is reasonable to assume that collections generally have
        // greater IDs than their dependencies, so starting with the largest is
        // a useful optimization.
        while let Some(key) = updates.keys().rev().next().cloned() {
            let mut update = updates.remove(&key).unwrap();

            if key.is_user() {
                debug!(id = %key, ?update, "update_hold_capability");
            }

            if let Some(collection) = self.collections.get_mut(&key) {
                let ingestion = match &mut collection.extra_state {
                    CollectionStateExtra::Ingestion(ingestion) => ingestion,
                    CollectionStateExtra::None => {
                        tracing::error!(
                            ?collection,
                            ?update,
                            "trying to update holds for collection which is not an ingestion"
                        );
                        // WIP: See if this ever panics in ci.
                        panic!(
                            "trying to update holds for collection {:?} which is not an ingestion: {:?}", collection, update
                        );
                    }
                };

                let changes = ingestion.read_capabilities.update_iter(update.drain());
                update.extend(changes);

                let (changes, frontier, _cluster_id) =
                    collections_net.entry(key).or_insert_with(|| {
                        (ChangeBatch::new(), Antichain::new(), ingestion.instance_id)
                    });

                changes.extend(update.drain());
                *frontier = ingestion.read_capabilities.frontier().to_owned();
            } else if let Ok(export) = self.export_mut(key) {
                // Seed with our current read hold, then apply changes, to
                // derive how we need to change our read hold.
                let mut staged_read_hold = MutableAntichain::new();
                staged_read_hold
                    .update_iter(export.read_hold.since().iter().map(|t| (t.clone(), 1)));
                let changes = staged_read_hold.update_iter(update.drain());
                update.extend(changes);

                // Make sure we also send `AllowCompaction` commands for sinks,
                // which drives updating the sink's `as_of`, among other things.
                let (changes, frontier, _cluster_id) = exports_net
                    .entry(key)
                    .or_insert_with(|| (ChangeBatch::new(), Antichain::new(), export.cluster_id()));

                changes.extend(update.drain());
                *frontier = staged_read_hold.frontier().to_owned();
            } else {
                // This is confusing and we should probably error.
                tracing::warn!(id = ?key, ?update, "update_hold_capabilities for unknown object");
            }
        }

        // Translate our net compute actions into `AllowCompaction` commands and
        // downgrade persist sinces. The actual downgrades are performed by a Tokio
        // task asynchorously.
        //
        // N.B. We only downgrade persist sinces for collections because
        // exports/sinks don't have an associated collection. We still _do_ want
        // to sent `AllowCompaction` commands to workers for them, though.
        let mut worker_compaction_commands = BTreeMap::default();

        for (key, (mut changes, frontier, cluster_id)) in collections_net {
            if !changes.is_empty() {
                if key.is_user() {
                    debug!(id = %key, ?frontier, "downgrading ingestion read holds!");
                }

                let collection = self
                    .collections
                    .get_mut(&key)
                    .expect("missing collection state");

                let ingestion = match &mut collection.extra_state {
                    CollectionStateExtra::Ingestion(ingestion) => ingestion,
                    CollectionStateExtra::None => {
                        panic!("trying to downgrade read holds for collection which is not an ingestion: {:?}", collection);
                    }
                };

                for read_hold in ingestion.dependency_read_holds.iter_mut() {
                    read_hold
                        .try_downgrade(frontier.clone())
                        .expect("we only advance the frontier");
                }

                worker_compaction_commands.insert(key, (frontier.clone(), cluster_id));
            }
        }
        for (key, (mut changes, frontier, cluster_id)) in exports_net {
            if !changes.is_empty() {
                let export_state = self.exports.get_mut(&key).expect("missing export state");

                export_state
                    .read_hold
                    .try_downgrade(frontier.clone())
                    .expect("we only advance the frontier");

                worker_compaction_commands.insert(key, (frontier, cluster_id));
            }
        }

        for (id, (read_frontier, cluster_id)) in worker_compaction_commands {
            // Acquiring a client for a storage instance requires await, so we
            // instead stash these for later and process when we can.
            self.pending_compaction_commands
                .push(PendingCompactionCommand {
                    id,
                    read_frontier,
                    cluster_id: Some(cluster_id),
                });
        }
    }

    /// Validate that a collection exists for all identifiers, and error if any do not.
    fn validate_collection_ids(
        &self,
        ids: impl Iterator<Item = GlobalId>,
    ) -> Result<(), StorageError<T>> {
        for id in ids {
            self.storage_collections.check_exists(id)?;
        }
        Ok(())
    }

    /// Validate that a collection exists for all identifiers, and error if any do not.
    fn validate_export_ids(
        &self,
        ids: impl Iterator<Item = GlobalId>,
    ) -> Result<(), StorageError<T>> {
        for id in ids {
            self.export(id)?;
        }
        Ok(())
    }

    /// Iterate over exports that have not been dropped.
    fn active_exports(&self) -> impl Iterator<Item = (GlobalId, &ExportState<T>)> {
        self.exports
            .iter()
            .filter(|(_id, e)| !e.is_dropped())
            .map(|(id, e)| (*id, e))
    }

    /// Opens a write and critical since handles for the given `shard`.
    ///
    /// `since` is an optional `since` that the read handle will be forwarded to if it is less than
    /// its current since.
    ///
    /// This will `halt!` the process if we cannot successfully acquire a critical handle with our
    /// current epoch.
    async fn open_data_handles(
        &self,
        id: &GlobalId,
        shard: ShardId,
        relation_desc: RelationDesc,
        persist_client: &PersistClient,
    ) -> WriteHandle<SourceData, (), T, Diff> {
        let diagnostics = Diagnostics {
            shard_name: id.to_string(),
            handle_purpose: format!("controller data for {}", id),
        };

        let mut write = persist_client
            .open_writer(
                shard,
                Arc::new(relation_desc),
                Arc::new(UnitSchema),
                diagnostics.clone(),
            )
            .await
            .expect("invalid persist usage");

        // N.B.
        // Fetch the most recent upper for the write handle. Otherwise, this may be behind
        // the since of the since handle. Its vital this happens AFTER we create
        // the since handle as it needs to be linearized with that operation. It may be true
        // that creating the write handle after the since handle already ensures this, but we
        // do this out of an abundance of caution.
        //
        // Note that this returns the upper, but also sets it on the handle to be fetched later.
        write.fetch_recent_upper().await;

        write
    }

    /// Registers the given introspection collection and does any preparatory
    /// work that we have to to do before we start writing to it. This
    /// preparatory work will include partial truncation or other cleanup
    /// schemes, depending on introspection type.
    async fn register_introspection_collection(
        &mut self,
        id: GlobalId,
        introspection_type: IntrospectionType,
    ) -> Result<(), StorageError<T>> {
        tracing::info!(%id, ?introspection_type, "registering introspection collection");

        let prev = self
            .introspection_ids
            .lock()
            .expect("poisoned lock")
            .insert(introspection_type, id);
        assert!(
            prev.is_none(),
            "cannot have multiple IDs for introspection type"
        );

        let metadata = self.storage_collections.collection_metadata(id)?.clone();
        let persist_client = self
            .persist
            .open(metadata.persist_location.clone())
            .await
            .unwrap();

        let read_handle_fn = move || {
            let persist_client = persist_client.clone();
            let metadata = metadata.clone();

            let fut = async move {
                let read_handle = persist_client
                    .open_leased_reader::<SourceData, (), T, Diff>(
                        metadata.data_shard,
                        Arc::new(metadata.relation_desc.clone()),
                        Arc::new(UnitSchema),
                        Diagnostics {
                            shard_name: id.to_string(),
                            handle_purpose: format!("snapshot {}", id),
                        },
                        USE_CRITICAL_SINCE_SNAPSHOT.get(persist_client.dyncfgs()),
                    )
                    .await
                    .expect("invalid persist usage");
                read_handle
            };

            fut.boxed()
        };

        // Types of storage-managed/introspection collections:
        //
        // Append-only: Only accepts blind writes, writes that can
        // be applied at any timestamp and don’t depend on current
        // collection contents.
        //
        // Pseudo append-only: We treat them largely as append-only
        // collections but periodically (currently on bootstrap)
        // retract old updates from them.
        //
        // Differential: at any given time `t` , collection contents
        // mirrors some (small cardinality) state. The cardinality
        // of the collection stays constant if the thing that is
        // mirrored doesn’t change in cardinality. At steady state,
        // updates always come in pairs of retractions/additions.

        match introspection_type {
            // For these, we first register the collection and then prepare it,
            // because the code that prepares differential collection expects to
            // be able to update desired state via the collection manager
            // already.
            IntrospectionType::ShardMapping
            | IntrospectionType::Frontiers
            | IntrospectionType::ReplicaFrontiers
            | IntrospectionType::StorageSourceStatistics
            | IntrospectionType::StorageSinkStatistics => {
                self.collection_manager
                    .register_differential_collection(id, read_handle_fn);

                if !self.read_only {
                    self.prepare_introspection_collection(id, introspection_type)
                        .await?;
                }
            }

            // For these, we first have to prepare and then register with
            // collection manager, because the preparation logic wants to read
            // the shard's contents and then do uncontested writes.
            //
            // TODO(aljoscha): We should make the truncation/cleanup work that
            // happens when we take over instead be a periodic thing, and make
            // it resilient to the upper moving concurrently.
            IntrospectionType::SourceStatusHistory
            | IntrospectionType::SinkStatusHistory
            | IntrospectionType::PrivatelinkConnectionStatusHistory => {
                if !self.read_only {
                    self.prepare_introspection_collection(id, introspection_type)
                        .await?;
                }

                self.collection_manager.register_append_only_collection(id);
            }

            // Same as our other differential collections, but for these the
            // preparation logic currently doesn't do anything.
            IntrospectionType::ComputeDependencies
            | IntrospectionType::ComputeOperatorHydrationStatus
            | IntrospectionType::ComputeMaterializedViewRefreshes
            | IntrospectionType::ComputeErrorCounts
            | IntrospectionType::ComputeHydrationTimes => {
                self.collection_manager
                    .register_differential_collection(id, read_handle_fn);

                if !self.read_only {
                    self.prepare_introspection_collection(id, introspection_type)
                        .await?;
                }
            }

            // Note [btv] - we don't truncate these, because that uses
            // a huge amount of memory on environmentd startup.
            IntrospectionType::PreparedStatementHistory
            | IntrospectionType::StatementExecutionHistory
            | IntrospectionType::SessionHistory
            | IntrospectionType::StatementLifecycleHistory
            | IntrospectionType::SqlText => {
                if !self.read_only {
                    self.prepare_introspection_collection(id, introspection_type)
                        .await?;
                }

                self.collection_manager.register_append_only_collection(id);
            }
        }

        Ok(())
    }

    /// Does any work that is required before this controller instance starts
    /// writing to the given introspection collection.
    ///
    /// This migh include consolidation, deleting older entries or seeding
    /// in-memory state of, say, scrapers, with current collection contents.
    async fn prepare_introspection_collection(
        &mut self,
        id: GlobalId,
        introspection_type: IntrospectionType,
    ) -> Result<(), StorageError<T>> {
        tracing::info!(%id, ?introspection_type, "preparing introspection collection for writes");

        match introspection_type {
            IntrospectionType::ShardMapping => {
                self.initialize_shard_mapping().await;
            }
            IntrospectionType::Frontiers | IntrospectionType::ReplicaFrontiers => {
                // Differential collections start with an empty
                // desired state. No need to manually reset.
            }
            IntrospectionType::StorageSourceStatistics => {
                let prev = self.snapshot_statistics(id).await;

                let scraper_token = statistics::spawn_statistics_scraper::<
                    statistics::SourceStatistics,
                    SourceStatisticsUpdate,
                    _,
                >(
                    id.clone(),
                    // These do a shallow copy.
                    self.collection_manager.clone(),
                    Arc::clone(&self.source_statistics),
                    prev,
                    self.config.parameters.statistics_interval,
                    self.statistics_interval_sender.subscribe(),
                    self.metrics.clone(),
                );
                let web_token = statistics::spawn_webhook_statistics_scraper(
                    Arc::clone(&self.source_statistics),
                    self.config.parameters.statistics_interval,
                    self.statistics_interval_sender.subscribe(),
                );

                // Make sure these are dropped when the controller is
                // dropped, so that the internal task will stop.
                self.introspection_tokens
                    .insert(id, Box::new((scraper_token, web_token)));
            }
            IntrospectionType::StorageSinkStatistics => {
                let prev = self.snapshot_statistics(id).await;

                let scraper_token =
                    statistics::spawn_statistics_scraper::<_, SinkStatisticsUpdate, _>(
                        id.clone(),
                        // These do a shallow copy.
                        self.collection_manager.clone(),
                        Arc::clone(&self.sink_statistics),
                        prev,
                        self.config.parameters.statistics_interval,
                        self.statistics_interval_sender.subscribe(),
                        self.metrics.clone(),
                    );

                // Make sure this is dropped when the controller is
                // dropped, so that the internal task will stop.
                self.introspection_tokens.insert(id, scraper_token);
            }
            IntrospectionType::SourceStatusHistory => {
                let last_status_per_id = self
                    .partially_truncate_status_history(IntrospectionType::SourceStatusHistory)
                    .await;

                let status_col = collection_status::MZ_SOURCE_STATUS_HISTORY_DESC
                    .get_by_name(&ColumnName::from("status"))
                    .expect("schema has not changed")
                    .0;

                self.collection_status_manager.extend_previous_statuses(
                    last_status_per_id.into_iter().map(|(id, row)| {
                        (
                            id,
                            Status::from_str(
                                row.iter()
                                    .nth(status_col)
                                    .expect("schema has not changed")
                                    .unwrap_str(),
                            )
                            .expect("statuses must be uncorrupted"),
                        )
                    }),
                )
            }
            IntrospectionType::SinkStatusHistory => {
                let last_status_per_id = self
                    .partially_truncate_status_history(IntrospectionType::SinkStatusHistory)
                    .await;

                let status_col = collection_status::MZ_SINK_STATUS_HISTORY_DESC
                    .get_by_name(&ColumnName::from("status"))
                    .expect("schema has not changed")
                    .0;

                self.collection_status_manager.extend_previous_statuses(
                    last_status_per_id.into_iter().map(|(id, row)| {
                        (
                            id,
                            Status::from_str(
                                row.iter()
                                    .nth(status_col)
                                    .expect("schema has not changed")
                                    .unwrap_str(),
                            )
                            .expect("statuses must be uncorrupted"),
                        )
                    }),
                )
            }
            IntrospectionType::PrivatelinkConnectionStatusHistory => {
                self.partially_truncate_status_history(
                    IntrospectionType::PrivatelinkConnectionStatusHistory,
                )
                .await;
            }

            // Truncate compute-maintained collections.
            IntrospectionType::ComputeDependencies
            | IntrospectionType::ComputeOperatorHydrationStatus
            | IntrospectionType::ComputeMaterializedViewRefreshes
            | IntrospectionType::ComputeErrorCounts
            | IntrospectionType::ComputeHydrationTimes => {
                // Differential collections start with an empty
                // desired state. No need to manually reset.
            }

            // Note [btv] - we don't truncate these, because that uses
            // a huge amount of memory on environmentd startup.
            IntrospectionType::PreparedStatementHistory
            | IntrospectionType::StatementExecutionHistory
            | IntrospectionType::SessionHistory
            | IntrospectionType::StatementLifecycleHistory
            | IntrospectionType::SqlText => {
                // NOTE(aljoscha): We never remove from these
                // collections. Someone, at some point needs to
                // think about that! Issue:
                // https://github.com/MaterializeInc/materialize/issues/25696
            }
        }

        Ok(())
    }

    /// Get the current rows in the given statistics table. This is used to bootstrap
    /// the statistics tasks.
    ///
    // TODO(guswynn): we need to be more careful about the update time we get here:
    // <https://github.com/MaterializeInc/materialize/issues/25349>
    async fn snapshot_statistics(&mut self, id: GlobalId) -> Vec<Row> {
        let upper = self
            .persist_monotonic_worker
            .recent_upper(id)
            .await
            .expect("missing collection")
            .expect("missing collection");

        match upper.as_option() {
            Some(f) if f > &T::minimum() => {
                let as_of = f.step_back().unwrap();

                let snapshot = self.snapshot(id, as_of).await.unwrap();
                snapshot
                    .into_iter()
                    .map(|(row, diff)| {
                        assert!(diff == 1);
                        row
                    })
                    .collect()
            }
            // If collection is closed or the frontier is the minimum, we cannot
            // or don't need to truncate (respectively).
            _ => Vec::new(),
        }
    }

    /// Remove statistics for sources/sinks that were dropped but still have statistics rows
    /// hanging around.
    fn reconcile_dangling_statistics(&mut self) {
        self.source_statistics
            .lock()
            .expect("poisoned")
            .source_statistics
            // collections should also contain subsources.
            .retain(|k, _| self.storage_collections.check_exists(*k).is_ok());
        self.sink_statistics
            .lock()
            .expect("poisoned")
            .retain(|k, _| self.exports.contains_key(k));
    }

    /// Initializes the data expressing which global IDs correspond to which
    /// shards. Necessary because we cannot write any of these mappings that we
    /// discover before the shard mapping collection exists.
    ///
    /// # Panics
    /// - If `IntrospectionType::ShardMapping` is not associated with a
    /// `GlobalId` in `self.introspection_ids`.
    /// - If `IntrospectionType::ShardMapping`'s `GlobalId` is not registered as
    ///   a managed collection.
    async fn initialize_shard_mapping(&mut self) {
        let id =
            self.introspection_ids.lock().expect("poisoned lock")[&IntrospectionType::ShardMapping];

        let mut row_buf = Row::default();
        let collection_metadatas = self.storage_collections.active_collection_metadatas();
        let mut updates = Vec::with_capacity(collection_metadatas.len());
        for (global_id, CollectionMetadata { data_shard, .. }) in collection_metadatas {
            let mut packer = row_buf.packer();
            packer.push(Datum::from(global_id.to_string().as_str()));
            packer.push(Datum::from(data_shard.to_string().as_str()));
            updates.push((row_buf.clone(), 1));
        }

        self.collection_manager
            .differential_append(id, updates)
            .await;
    }

    /// Effectively truncates the status history shard except for the most
    /// recent updates from each ID.
    ///
    /// NOTE: The history collections are really append-only collections, but
    /// every-now-and-then we want to retract old updates so that the collection
    /// does not grow unboundedly. Crucially, these are _not_ incremental
    /// collections, they are not derived from a state at some time `t` and we
    /// cannot maintain a desired state for them.
    ///
    /// Returns a map with latest unpacked row per id.
    async fn partially_truncate_status_history(
        &mut self,
        collection: IntrospectionType,
    ) -> BTreeMap<GlobalId, Row> {
        let (keep_n, occurred_at_col, id_col) = match collection {
            IntrospectionType::SourceStatusHistory => (
                self.config.parameters.keep_n_source_status_history_entries,
                collection_status::MZ_SOURCE_STATUS_HISTORY_DESC
                    .get_by_name(&ColumnName::from("occurred_at"))
                    .expect("schema has not changed")
                    .0,
                collection_status::MZ_SOURCE_STATUS_HISTORY_DESC
                    .get_by_name(&ColumnName::from("source_id"))
                    .expect("schema has not changed")
                    .0,
            ),
            IntrospectionType::SinkStatusHistory => (
                self.config.parameters.keep_n_sink_status_history_entries,
                collection_status::MZ_SINK_STATUS_HISTORY_DESC
                    .get_by_name(&ColumnName::from("occurred_at"))
                    .expect("schema has not changed")
                    .0,
                collection_status::MZ_SINK_STATUS_HISTORY_DESC
                    .get_by_name(&ColumnName::from("sink_id"))
                    .expect("schema has not changed")
                    .0,
            ),
            IntrospectionType::PrivatelinkConnectionStatusHistory => (
                self.config
                    .parameters
                    .keep_n_privatelink_status_history_entries,
                collection_status::MZ_AWS_PRIVATELINK_CONNECTION_STATUS_HISTORY_DESC
                    .get_by_name(&ColumnName::from("occurred_at"))
                    .expect("schema has not changed")
                    .0,
                collection_status::MZ_AWS_PRIVATELINK_CONNECTION_STATUS_HISTORY_DESC
                    .get_by_name(&ColumnName::from("connection_id"))
                    .expect("schema has not changed")
                    .0,
            ),
            _ => unreachable!(),
        };

        let id = self.introspection_ids.lock().expect("poisoned")[&collection];

        let upper = self
            .persist_monotonic_worker
            .recent_upper(id)
            .await
            .expect("missing collection")
            .expect("missing collection");

        let mut rows = match upper.as_option() {
            Some(f) if f > &T::minimum() => {
                let as_of = f.step_back().unwrap();

                self.snapshot(id, as_of).await.expect("snapshot succeeds")
            }
            // If collection is closed or the frontier is the minimum, we cannot
            // or don't need to truncate (respectively).
            _ => return BTreeMap::new(),
        };

        // BTreeMap<Id, MinHeap<(OccurredAt, Row)>>, to track the
        // earliest events for each id.
        let mut last_n_entries_per_id: BTreeMap<Datum, BinaryHeap<Reverse<(Datum, Vec<Datum>)>>> =
            BTreeMap::new();

        // BTreeMap to keep track of the row with the latest timestamp for each id
        let mut latest_row_per_id: BTreeMap<Datum, (CheckedTimestamp<DateTime<Utc>>, Vec<Datum>)> =
            BTreeMap::new();

        // Consolidate the snapshot, so we can process it correctly below.
        differential_dataflow::consolidation::consolidate(&mut rows);

        let mut deletions = vec![];

        for (row, diff) in rows.iter() {
            let status_row = row.unpack();
            let id = status_row[id_col];
            let occurred_at = status_row[occurred_at_col];

            // Duplicate rows ARE possible if many status changes happen in VERY quick succession,
            // so we go ahead and handle them.
            assert!(
                *diff > 0,
                "only know how to operate over consolidated data with diffs > 0, \
                found diff {} for object {} in {:?}",
                diff,
                id,
                collection
            );

            // Keep track of the timestamp of the latest row per id
            let timestamp = occurred_at.unwrap_timestamptz();
            match latest_row_per_id.get(&id) {
                Some(existing) if &existing.0 > &timestamp => {}
                _ => {
                    latest_row_per_id.insert(id, (timestamp, status_row.clone()));
                }
            }

            // Consider duplicated rows separately.
            for _ in 0..*diff {
                let entries = last_n_entries_per_id.entry(id).or_default();

                // We CAN have multiple statuses (most likely Starting and Running) at the exact same
                // millisecond, depending on how the `health_operator` is scheduled.
                //
                // Note that these will be arbitrarily ordered, so a Starting event might
                // survive and a Running one won't. The next restart will remove the other,
                // so we don't bother being careful about it.
                //
                // TODO(guswynn): unpack these into health-status objects and use
                // their `Ord1 impl.
                entries.push(Reverse((occurred_at, status_row.clone())));

                // Retain some number of entries, using pop to mark the oldest entries for
                // deletion.
                while entries.len() > keep_n {
                    if let Some(Reverse((_, r))) = entries.pop() {
                        deletions.push(r);
                    }
                }
            }
        }

        // It is very important that we append our retractions at the timestamp
        // right after the timestamp at which we got our snapshot. Otherwise,
        // it's possible for someone else to sneak in retractions or other
        // unexpected changes.
        let expected_upper = upper.into_option().expect("checked above");
        let new_upper = TimestampManipulation::step_forward(&expected_upper);

        let mut row_buf = Row::default();
        // Updates are only deletes because everything else is already in the shard.
        let updates = deletions
            .into_iter()
            .map(|unpacked_row| {
                // Re-pack all rows
                let mut packer = row_buf.packer();
                packer.extend(unpacked_row.into_iter());

                let update = Update {
                    row: row_buf.clone(),
                    timestamp: expected_upper.clone(),
                    diff: -1,
                };

                update
            })
            .collect();

        let command = (id, updates, expected_upper.clone(), new_upper);

        let res = self
            .persist_monotonic_worker
            .compare_and_append(vec![command])
            .await
            .expect("command must succeed");

        match res {
            Ok(_) => {
                // All good, yay!
            }
            Err(storage_err) => {
                match storage_err {
                    StorageError::InvalidUppers(failed_ids) => {
                        assert_eq!(
                            failed_ids.len(),
                            1,
                            "received errors for more than one collection"
                        );
                        assert_eq!(
                            failed_ids[0].id, id,
                            "received errors for a different collection"
                        );

                        // This is fine, it just means the upper moved because
                        // of continual upper advancement or because seomeone
                        // already appended some more retractions/updates.
                        //
                        // NOTE: We might want to attempt these partial
                        // retractions on an interval, instead of only when
                        // starting up!
                        info!(%id, ?expected_upper, current_upper = ?failed_ids[0].current_upper, "failed to append partial truncation");
                    }
                    // Uh-oh, something else went wrong!
                    other => {
                        panic!("Unhandled error while appending to managed collection {id:?}: {other:?}")
                    }
                }
            }
        }

        latest_row_per_id
            .into_iter()
            .filter_map(|(key, (_, row_vec))| {
                match GlobalId::from_str(key.unwrap_str()) {
                    Ok(id) => {
                        let mut packer = row_buf.packer();
                        packer.extend(row_vec.into_iter());
                        Some((id, row_buf.clone()))
                    }
                    // Ignore any rows that can't be unwrapped correctly
                    Err(_) => None,
                }
            })
            .collect()
    }

    /// Appends a new global ID, shard ID pair to the appropriate collection.
    /// Use a `diff` of 1 to append a new entry; -1 to retract an existing
    /// entry.
    ///
    /// However, data is written iff we know of the `GlobalId` of the
    /// `IntrospectionType::ShardMapping` collection; in other cases, data is
    /// dropped on the floor. In these cases, the data is later written by
    /// [`Self::initialize_shard_mapping`].
    ///
    /// # Panics
    /// - If `self.collections` does not have an entry for `global_id`.
    /// - If `IntrospectionType::ShardMapping`'s `GlobalId` is not registered as
    ///   a managed collection.
    /// - If diff is any value other than `1` or `-1`.
    #[instrument(level = "debug")]
    async fn append_shard_mappings<I>(&self, global_ids: I, diff: i64)
    where
        I: Iterator<Item = GlobalId>,
    {
        mz_ore::soft_assert_or_log!(diff == -1 || diff == 1, "use 1 for insert or -1 for delete");

        let id = match self
            .introspection_ids
            .lock()
            .expect("poisoned")
            .get(&IntrospectionType::ShardMapping)
        {
            Some(id) => *id,
            _ => return,
        };

        let mut updates = vec![];
        // Pack updates into rows
        let mut row_buf = Row::default();

        for global_id in global_ids {
            let shard_id = if let Some(collection) = self.collections.get(&global_id) {
                collection.collection_metadata.data_shard.clone()
            } else {
                panic!("unknown global id: {}", global_id);
            };

            let mut packer = row_buf.packer();
            packer.push(Datum::from(global_id.to_string().as_str()));
            packer.push(Datum::from(shard_id.to_string().as_str()));
            updates.push((row_buf.clone(), diff));
        }

        self.collection_manager
            .differential_append(id, updates)
            .await;
    }

    /// Determines and returns this collection's dependencies, if any.
    fn determine_collection_dependencies(
        &self,
        self_id: GlobalId,
        data_source: &DataSource,
    ) -> Result<Vec<GlobalId>, StorageError<T>> {
        let dependency = match &data_source {
            DataSource::Introspection(_)
            | DataSource::Webhook
            | DataSource::Other(DataSourceOther::TableWrites)
            | DataSource::Progress
            | DataSource::Other(DataSourceOther::Compute) => vec![],
            DataSource::IngestionExport { ingestion_id, .. } => {
                // Ingestion exports depend on their primary source's remap
                // collection.
                let source_collection = self.collection(*ingestion_id)?;
                let ingestion_remap_collection_id = match &source_collection.data_source {
                    DataSource::Ingestion(ingestion) => ingestion.remap_collection_id,
                    _ => unreachable!(
                        "SourceExport must only refer to primary sources that already exist"
                    ),
                };

                // Ingestion exports (aka. subsources) must make sure that 1)
                // their own collection's since stays one step behind the upper,
                // and, 2) that the remap shard's since stays one step behind
                // their upper. Hence they track themselves and the remap shard
                // as dependencies.
                vec![self_id, ingestion_remap_collection_id]
            }
            // Ingestions depend on their remap collection.
            DataSource::Ingestion(ingestion) => {
                // Ingestions must make sure that 1) their own collection's
                // since stays one step behind the upper, and, 2) that the remap
                // shard's since stays one step behind their upper. Hence they
                // track themselves and the remap shard as dependencies.
                vec![self_id, ingestion.remap_collection_id]
            }
        };

        Ok(dependency)
    }

    async fn read_handle_for_snapshot(
        &self,
        id: GlobalId,
    ) -> Result<ReadHandle<SourceData, (), T, Diff>, StorageError<T>> {
        let metadata = &self.storage_collections.collection_metadata(id)?;

        let persist_client = self
            .persist
            .open(metadata.persist_location.clone())
            .await
            .unwrap();

        // We create a new read handle every time someone requests a snapshot and then immediately
        // expire it instead of keeping a read handle permanently in our state to avoid having it
        // heartbeat continously. The assumption is that calls to snapshot are rare and therefore
        // worth it to always create a new handle.
        let read_handle = persist_client
            .open_leased_reader::<SourceData, (), _, _>(
                metadata.data_shard,
                Arc::new(metadata.relation_desc.clone()),
                Arc::new(UnitSchema),
                Diagnostics {
                    shard_name: id.to_string(),
                    handle_purpose: format!("snapshot {}", id),
                },
                USE_CRITICAL_SINCE_SNAPSHOT.get(persist_client.dyncfgs()),
            )
            .await
            .expect("invalid persist usage");
        Ok(read_handle)
    }

    // TODO: This appears to have become unused at some point. Figure out if the
    // caller is coming back or if we should delete it.
    #[allow(dead_code)]
    async fn snapshot_and_stream(
        &self,
        id: GlobalId,
        as_of: T,
    ) -> Result<BoxStream<(SourceData, T, Diff)>, StorageError<T>> {
        use futures::stream::StreamExt;

        let metadata = &self.storage_collections.collection_metadata(id)?;

        // See the comments in Self::snapshot for what's going on here.
        match metadata.txns_shard.as_ref() {
            None => {
                let as_of = Antichain::from_elem(as_of);
                let mut read_handle = self.read_handle_for_snapshot(id).await?;
                let contents = read_handle.snapshot_and_stream(as_of).await;
                match contents {
                    Ok(contents) => {
                        Ok(Box::pin(contents.map(|((result_k, result_v), t, diff)| {
                            let () = result_v.expect("invalid empty value");
                            let data = result_k.expect("invalid key data");
                            (data, t, diff)
                        })))
                    }
                    Err(_) => Err(StorageError::ReadBeforeSince(id)),
                }
            }
            Some(txns_id) => {
                assert_eq!(txns_id, self.txns_read.txns_id());
                self.txns_read.update_gt(as_of.clone()).await;
                let data_snapshot = self
                    .txns_read
                    .data_snapshot(metadata.data_shard, as_of.clone())
                    .await;
                let mut handle = self.read_handle_for_snapshot(id).await?;
                let contents = data_snapshot.snapshot_and_stream(&mut handle).await;
                match contents {
                    Ok(contents) => {
                        Ok(Box::pin(contents.map(|((result_k, result_v), t, diff)| {
                            let () = result_v.expect("invalid empty value");
                            let data = result_k.expect("invalid key data");
                            (data, t, diff)
                        })))
                    }
                    Err(_) => Err(StorageError::ReadBeforeSince(id)),
                }
            }
        }
    }

    /// Handles writing of status updates for sources/sinks to the appropriate
    /// status relation
    async fn record_status_updates(&mut self, updates: Vec<StatusUpdate>) {
        if self.read_only {
            return;
        }

        let mut sink_status_updates = vec![];
        let mut source_status_updates = vec![];

        for update in updates {
            let id = update.id;
            if self.exports.contains_key(&id) {
                sink_status_updates.push(update);
            } else if self.storage_collections.check_exists(id).is_ok() {
                source_status_updates.push(update);
            }
        }

        self.collection_status_manager
            .append_updates(
                source_status_updates,
                IntrospectionType::SourceStatusHistory,
            )
            .await;
        self.collection_status_manager
            .append_updates(sink_status_updates, IntrospectionType::SinkStatusHistory)
            .await;
    }

    fn collection(&self, id: GlobalId) -> Result<&CollectionState<T>, StorageError<T>> {
        self.collections
            .get(&id)
            .ok_or(StorageError::IdentifierMissing(id))
    }

    /// Runs the identified ingestion using the current definition of the
    /// ingestion in-memory.
    fn run_ingestion(&mut self, id: GlobalId) -> Result<(), StorageError<T>> {
        tracing::info!(%id, "starting ingestion");

        let collection = self.collection(id)?;
        let ingestion_description = match &collection.data_source {
            DataSource::Ingestion(i) => i.clone(),
            _ => {
                tracing::warn!("run_ingestion called on non-ingestion ID {}", id);
                Err(StorageError::IdentifierInvalid(id))?
            }
        };

        // Enrich all of the exports with their metadata
        let mut source_exports = BTreeMap::new();
        for (
            export_id,
            SourceExport {
                ingestion_output,
                storage_metadata: (),
            },
        ) in ingestion_description.source_exports
        {
            let export_storage_metadata = self.collection(export_id)?.collection_metadata.clone();
            source_exports.insert(
                export_id,
                SourceExport {
                    ingestion_output,
                    storage_metadata: export_storage_metadata,
                },
            );
        }

        let description = IngestionDescription::<CollectionMetadata> {
            source_exports,
            // The ingestion metadata is simply the collection metadata of the collection with
            // the associated ingestion
            ingestion_metadata: collection.collection_metadata.clone(),
            // The rest of the fields are identical
            desc: ingestion_description.desc,
            instance_id: ingestion_description.instance_id,
            remap_collection_id: ingestion_description.remap_collection_id,
        };

        let storage_instance_id = description.instance_id;
        // Fetch the client for this ingestion's instance.
        let client = self.clients.get_mut(&storage_instance_id).ok_or_else(|| {
            StorageError::IngestionInstanceMissing {
                storage_instance_id,
                ingestion_id: id,
            }
        })?;

        let augmented_ingestion = RunIngestionCommand { id, description };
        client.send(StorageCommand::RunIngestions(vec![augmented_ingestion]));

        Ok(())
    }
}

/// State maintained about individual collections.
#[derive(Debug)]
struct CollectionState<T: TimelyTimestamp> {
    /// The source of this collection's data.
    pub data_source: DataSource,

    pub collection_metadata: CollectionMetadata,

    pub extra_state: CollectionStateExtra<T>,
}

impl<T: TimelyTimestamp> CollectionState<T> {
    /// Returns true if `self` is a table, false otherwise.
    pub fn is_table(&self) -> bool {
        matches!(
            self.data_source,
            DataSource::Other(DataSourceOther::TableWrites)
        )
    }
}

/// Additional state that the controller maintains for select collection types.
#[derive(Debug)]
enum CollectionStateExtra<T: TimelyTimestamp> {
    Ingestion(IngestionState<T>),
    None,
}

/// State maintained about ingestions and ingestion exports
#[derive(Debug)]
struct IngestionState<T: TimelyTimestamp> {
    /// Really only for keeping track of changes to the `derived_since`.
    pub read_capabilities: MutableAntichain<T>,

    /// The current since frontier, derived from `write_frontier` using
    /// `hold_policy`.
    pub derived_since: Antichain<T>,

    /// Holds that this ingestion (or ingestion export) has on its dependencies.
    pub dependency_read_holds: Vec<ReadHold<T>>,

    /// Reported write frontier.
    pub write_frontier: Antichain<T>,

    /// The policy that drives how we downgrade our read hold. That is how we
    /// derive our since from our upper.
    ///
    /// This is a _storage-controller-internal_ policy used to derive its
    /// personal read hold on the collection. It should not be confused with any
    /// read policies that the adapter might install at [StorageCollections].
    pub hold_policy: ReadPolicy<T>,

    /// The ID of the instance in which the ingestion is running.
    pub instance_id: StorageInstanceId,
}