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// 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.
//! Fetching batches of data from persist's backing store
use std::fmt::Debug;
use std::marker::PhantomData;
use std::sync::Arc;
use std::time::Instant;
use anyhow::anyhow;
use differential_dataflow::difference::Semigroup;
use differential_dataflow::lattice::Lattice;
use differential_dataflow::trace::Description;
use mz_ore::bytes::SegmentedBytes;
use mz_ore::cast::CastFrom;
use mz_persist::indexed::encoding::BlobTraceBatchPart;
use mz_persist::location::{Blob, SeqNo};
use mz_persist_types::stats::PartStats;
use mz_persist_types::{Codec, Codec64};
use mz_proto::{IntoRustIfSome, ProtoType, RustType, TryFromProtoError};
use serde::{Deserialize, Serialize};
use timely::progress::frontier::AntichainRef;
use timely::progress::{Antichain, Timestamp};
use timely::PartialOrder;
use tracing::{debug_span, trace_span, Instrument};
use crate::batch::{
proto_fetch_batch_filter, ProtoFetchBatchFilter, ProtoFetchBatchFilterListen, ProtoLease,
ProtoLeasedBatchPart,
};
use crate::error::InvalidUsage;
use crate::internal::encoding::{LazyInlineBatchPart, LazyPartStats, LazyProto, Schemas};
use crate::internal::machine::retry_external;
use crate::internal::metrics::{Metrics, ReadMetrics, ShardMetrics};
use crate::internal::paths::BlobKey;
use crate::internal::state::{BatchPart, HollowBatchPart};
use crate::read::LeasedReaderId;
use crate::ShardId;
/// Capable of fetching [`LeasedBatchPart`] while not holding any capabilities.
#[derive(Debug)]
pub struct BatchFetcher<K, V, T, D>
where
T: Timestamp + Lattice + Codec64,
// These are only here so we can use them in the auto-expiring `Drop` impl.
K: Debug + Codec,
V: Debug + Codec,
D: Semigroup + Codec64 + Send + Sync,
{
pub(crate) blob: Arc<dyn Blob + Send + Sync>,
pub(crate) metrics: Arc<Metrics>,
pub(crate) shard_metrics: Arc<ShardMetrics>,
pub(crate) shard_id: ShardId,
pub(crate) schemas: Schemas<K, V>,
// Ensures that `BatchFetcher` is of the same type as the `ReadHandle` it's
// derived from.
pub(crate) _phantom: PhantomData<(K, V, T, D)>,
}
impl<K, V, T, D> BatchFetcher<K, V, T, D>
where
K: Debug + Codec,
V: Debug + Codec,
T: Timestamp + Lattice + Codec64,
D: Semigroup + Codec64 + Send + Sync,
{
/// Takes a [`SerdeLeasedBatchPart`] into a [`LeasedBatchPart`].
pub fn leased_part_from_exchangeable(&self, x: SerdeLeasedBatchPart) -> LeasedBatchPart<T> {
x.decode(Arc::clone(&self.metrics))
}
/// Trade in an exchange-able [LeasedBatchPart] for the data it represents.
///
/// Note to check the `LeasedBatchPart` documentation for how to handle the
/// returned value.
pub async fn fetch_leased_part(
&self,
part: &LeasedBatchPart<T>,
) -> Result<FetchedBlob<K, V, T, D>, InvalidUsage<T>> {
if &part.shard_id != &self.shard_id {
let batch_shard = part.shard_id.clone();
return Err(InvalidUsage::BatchNotFromThisShard {
batch_shard,
handle_shard: self.shard_id.clone(),
});
}
let buf = match &part.part {
BatchPart::Hollow(x) => {
let buf = fetch_batch_part_blob(
&part.shard_id,
self.blob.as_ref(),
&self.metrics,
&self.shard_metrics,
&self.metrics.read.batch_fetcher,
x,
)
.await
.unwrap_or_else(|blob_key| {
// Ideally, readers should never encounter a missing blob. They place a seqno
// hold as they consume their snapshot/listen, preventing any blobs they need
// from being deleted by garbage collection, and all blob implementations are
// linearizable so there should be no possibility of stale reads.
//
// If we do have a bug and a reader does encounter a missing blob, the state
// cannot be recovered, and our best option is to panic and retry the whole
// process.
panic!("batch fetcher could not fetch batch part: {}", blob_key)
});
FetchedBlobBuf::Hollow {
buf,
part: x.clone(),
}
}
BatchPart::Inline {
updates,
ts_rewrite,
} => FetchedBlobBuf::Inline {
desc: part.desc.clone(),
updates: updates.clone(),
ts_rewrite: ts_rewrite.clone(),
},
};
let fetched_blob = FetchedBlob {
metrics: Arc::clone(&self.metrics),
read_metrics: self.metrics.read.batch_fetcher.clone(),
buf,
registered_desc: part.desc.clone(),
schemas: self.schemas.clone(),
filter: part.filter.clone(),
filter_pushdown_audit: part.filter_pushdown_audit,
_phantom: PhantomData,
};
Ok(fetched_blob)
}
}
#[derive(Debug, Clone)]
pub(crate) enum FetchBatchFilter<T> {
Snapshot {
as_of: Antichain<T>,
},
Listen {
as_of: Antichain<T>,
lower: Antichain<T>,
},
Compaction {
since: Antichain<T>,
},
}
impl<T: Timestamp + Lattice> FetchBatchFilter<T> {
pub(crate) fn filter_ts(&self, t: &mut T) -> bool {
match self {
FetchBatchFilter::Snapshot { as_of } => {
// This time is covered by a listen
if as_of.less_than(t) {
return false;
}
t.advance_by(as_of.borrow());
true
}
FetchBatchFilter::Listen { as_of, lower } => {
// This time is covered by a snapshot
if !as_of.less_than(t) {
return false;
}
// Because of compaction, the next batch we get might also
// contain updates we've already emitted. For example, we
// emitted `[1, 2)` and then compaction combined that batch with
// a `[2, 3)` batch into a new `[1, 3)` batch. If this happens,
// we just need to filter out anything < the frontier. This
// frontier was the upper of the last batch (and thus exclusive)
// so for the == case, we still emit.
if !lower.less_equal(t) {
return false;
}
true
}
FetchBatchFilter::Compaction { since } => {
t.advance_by(since.borrow());
true
}
}
}
}
impl<T: Timestamp + Codec64> RustType<ProtoFetchBatchFilter> for FetchBatchFilter<T> {
fn into_proto(&self) -> ProtoFetchBatchFilter {
let kind = match self {
FetchBatchFilter::Snapshot { as_of } => {
proto_fetch_batch_filter::Kind::Snapshot(as_of.into_proto())
}
FetchBatchFilter::Listen { as_of, lower } => {
proto_fetch_batch_filter::Kind::Listen(ProtoFetchBatchFilterListen {
as_of: Some(as_of.into_proto()),
lower: Some(lower.into_proto()),
})
}
FetchBatchFilter::Compaction { .. } => unreachable!("not serialized"),
};
ProtoFetchBatchFilter { kind: Some(kind) }
}
fn from_proto(proto: ProtoFetchBatchFilter) -> Result<Self, TryFromProtoError> {
let kind = proto
.kind
.ok_or_else(|| TryFromProtoError::missing_field("ProtoFetchBatchFilter::kind"))?;
match kind {
proto_fetch_batch_filter::Kind::Snapshot(as_of) => Ok(FetchBatchFilter::Snapshot {
as_of: as_of.into_rust()?,
}),
proto_fetch_batch_filter::Kind::Listen(ProtoFetchBatchFilterListen {
as_of,
lower,
}) => Ok(FetchBatchFilter::Listen {
as_of: as_of.into_rust_if_some("ProtoFetchBatchFilterListen::as_of")?,
lower: lower.into_rust_if_some("ProtoFetchBatchFilterListen::lower")?,
}),
}
}
}
/// Trade in an exchange-able [LeasedBatchPart] for the data it represents.
///
/// Note to check the `LeasedBatchPart` documentation for how to handle the
/// returned value.
pub(crate) async fn fetch_leased_part<K, V, T, D>(
part: &LeasedBatchPart<T>,
blob: &(dyn Blob + Send + Sync),
metrics: Arc<Metrics>,
read_metrics: &ReadMetrics,
shard_metrics: &ShardMetrics,
reader_id: &LeasedReaderId,
schemas: Schemas<K, V>,
) -> FetchedPart<K, V, T, D>
where
K: Debug + Codec,
V: Debug + Codec,
T: Timestamp + Lattice + Codec64,
D: Semigroup + Codec64 + Send + Sync,
{
let encoded_part = EncodedPart::fetch(
&part.shard_id,
blob,
&metrics,
shard_metrics,
read_metrics,
&part.desc,
&part.part,
)
.await
.unwrap_or_else(|blob_key| {
// Ideally, readers should never encounter a missing blob. They place a seqno
// hold as they consume their snapshot/listen, preventing any blobs they need
// from being deleted by garbage collection, and all blob implementations are
// linearizable so there should be no possibility of stale reads.
//
// If we do have a bug and a reader does encounter a missing blob, the state
// cannot be recovered, and our best option is to panic and retry the whole
// process.
panic!("{} could not fetch batch part: {}", reader_id, blob_key)
});
FetchedPart::new(
metrics,
encoded_part,
schemas,
part.filter.clone(),
part.filter_pushdown_audit,
part.part.stats(),
)
}
pub(crate) async fn fetch_batch_part_blob<T>(
shard_id: &ShardId,
blob: &(dyn Blob + Send + Sync),
metrics: &Metrics,
shard_metrics: &ShardMetrics,
read_metrics: &ReadMetrics,
part: &HollowBatchPart<T>,
) -> Result<SegmentedBytes, BlobKey> {
let now = Instant::now();
let get_span = debug_span!("fetch_batch::get");
let blob_key = part.key.complete(shard_id);
let value = retry_external(&metrics.retries.external.fetch_batch_get, || async {
shard_metrics.blob_gets.inc();
blob.get(&blob_key).await
})
.instrument(get_span.clone())
.await
.ok_or(blob_key)?;
drop(get_span);
read_metrics.part_count.inc();
read_metrics.part_bytes.inc_by(u64::cast_from(value.len()));
read_metrics.seconds.inc_by(now.elapsed().as_secs_f64());
Ok(value)
}
pub(crate) fn decode_batch_part_blob<T>(
metrics: &Metrics,
read_metrics: &ReadMetrics,
registered_desc: Description<T>,
part: &HollowBatchPart<T>,
buf: &SegmentedBytes,
) -> EncodedPart<T>
where
T: Timestamp + Lattice + Codec64,
{
trace_span!("fetch_batch::decode").in_scope(|| {
let parsed = metrics
.codecs
.batch
.decode(|| BlobTraceBatchPart::decode(buf, &metrics.columnar))
.map_err(|err| anyhow!("couldn't decode batch at key {}: {}", part.key, err))
// We received a State that we couldn't decode. This could happen if
// persist messes up backward/forward compatibility, if the durable
// data was corrupted, or if operations messes up deployment. In any
// case, fail loudly.
.expect("internal error: invalid encoded state");
read_metrics.part_goodbytes.inc_by(u64::cast_from(
parsed.updates.iter().map(|x| x.goodbytes()).sum::<usize>(),
));
EncodedPart::from_hollow(read_metrics.clone(), registered_desc, part, parsed)
})
}
pub(crate) async fn fetch_batch_part<T>(
shard_id: &ShardId,
blob: &(dyn Blob + Send + Sync),
metrics: &Metrics,
shard_metrics: &ShardMetrics,
read_metrics: &ReadMetrics,
registered_desc: &Description<T>,
part: &HollowBatchPart<T>,
) -> Result<EncodedPart<T>, BlobKey>
where
T: Timestamp + Lattice + Codec64,
{
let buf =
fetch_batch_part_blob(shard_id, blob, metrics, shard_metrics, read_metrics, part).await?;
let part = decode_batch_part_blob(metrics, read_metrics, registered_desc.clone(), part, &buf);
Ok(part)
}
/// A token representing one fetch-able batch part.
///
/// It is tradeable via `crate::fetch::fetch_batch` for the resulting data
/// stored in the part.
///
/// # Exchange
///
/// You can exchange `LeasedBatchPart`:
/// - If `leased_seqno.is_none()`
/// - By converting it to [`SerdeLeasedBatchPart`] through
/// [`Self::into_exchangeable_part`]. [`SerdeLeasedBatchPart`] is exchangeable,
/// including over the network.
///
/// n.b. `Self::into_exchangeable_part` is known to be equivalent to
/// `SerdeLeasedBatchPart::from(self)`, but we want the additional warning message to
/// be visible and sufficiently scary.
///
/// # Panics
/// `LeasedBatchPart` panics when dropped unless a very strict set of invariants are
/// held:
///
/// `LeasedBatchPart` may only be dropped if it:
/// - Does not have a leased `SeqNo (i.e. `self.leased_seqno.is_none()`)
///
/// In any other circumstance, dropping `LeasedBatchPart` panics.
#[derive(Debug)]
pub struct LeasedBatchPart<T> {
pub(crate) metrics: Arc<Metrics>,
pub(crate) shard_id: ShardId,
pub(crate) reader_id: LeasedReaderId,
pub(crate) filter: FetchBatchFilter<T>,
pub(crate) desc: Description<T>,
pub(crate) part: BatchPart<T>,
/// The `SeqNo` from which this part originated; we track this value as
/// long as necessary to ensure the `SeqNo` isn't garbage collected while a
/// read still depends on it.
pub(crate) leased_seqno: Option<SeqNo>,
pub(crate) filter_pushdown_audit: bool,
}
impl<T> LeasedBatchPart<T>
where
T: Timestamp + Codec64,
{
/// Takes `self` into a [`SerdeLeasedBatchPart`], which allows `self` to be
/// exchanged (potentially across the network).
///
/// !!!WARNING!!!
///
/// This semantically transfers the lease to the returned
/// SerdeLeasedBatchPart. If `self` has a `leased_seqno`, failing to take
/// the returned `SerdeLeasedBatchPart` back into a `LeasedBatchPart` will
/// leak `SeqNo`s and prevent persist GC.
pub fn into_exchangeable_part(mut self) -> SerdeLeasedBatchPart {
let (proto, _metrics) = self.into_proto();
// If `x` has a lease, we've effectively transferred it to `r`.
let _ = self.leased_seqno.take();
SerdeLeasedBatchPart {
encoded_size_bytes: self.part.encoded_size_bytes(),
proto: LazyProto::from(&proto),
}
}
/// Because sources get dropped without notice, we need to permit another
/// operator to safely expire leases.
///
/// The part's `reader_id` is intentionally inaccessible, and should
/// be obtained from the issuing [`crate::ReadHandle`], or one of its derived
/// structures, e.g. [`crate::read::Subscribe`].
///
/// # Panics
/// - If `reader_id` is different than the [`LeasedReaderId`] from
/// the part issuer.
pub(crate) fn return_lease(&mut self, reader_id: &LeasedReaderId) -> Option<SeqNo> {
assert!(
&self.reader_id == reader_id,
"only issuing reader can authorize lease expiration"
);
self.leased_seqno.take()
}
/// The encoded size of this part in bytes
pub fn encoded_size_bytes(&self) -> usize {
self.part.encoded_size_bytes()
}
/// The filter has indicated we don't need this part, we can verify the
/// ongoing end-to-end correctness of corner cases via "audit". This means
/// we fetch the part like normal and if the MFP keeps anything from it,
/// then something has gone horribly wrong.
pub fn request_filter_pushdown_audit(&mut self) {
self.filter_pushdown_audit = true;
}
/// Returns the pushdown stats for this part.
pub fn stats(&self) -> Option<PartStats> {
self.part.stats().map(|x| x.decode())
}
}
impl<T> Drop for LeasedBatchPart<T> {
/// For details, see [`LeasedBatchPart`].
fn drop(&mut self) {
self.metrics.lease.dropped_part.inc()
}
}
/// A [Blob] object that has been fetched, but not at all decoded.
///
/// In contrast to [FetchedPart], this representation hasn't yet done parquet
/// decoding.
#[derive(Debug)]
pub struct FetchedBlob<K: Codec, V: Codec, T, D> {
metrics: Arc<Metrics>,
read_metrics: ReadMetrics,
buf: FetchedBlobBuf<T>,
registered_desc: Description<T>,
schemas: Schemas<K, V>,
filter: FetchBatchFilter<T>,
filter_pushdown_audit: bool,
_phantom: PhantomData<fn() -> D>,
}
#[derive(Debug, Clone)]
enum FetchedBlobBuf<T> {
Hollow {
buf: SegmentedBytes,
part: HollowBatchPart<T>,
},
Inline {
desc: Description<T>,
updates: LazyInlineBatchPart,
ts_rewrite: Option<Antichain<T>>,
},
}
impl<K: Codec, V: Codec, T: Clone, D> Clone for FetchedBlob<K, V, T, D> {
fn clone(&self) -> Self {
Self {
metrics: Arc::clone(&self.metrics),
read_metrics: self.read_metrics.clone(),
buf: self.buf.clone(),
registered_desc: self.registered_desc.clone(),
schemas: self.schemas.clone(),
filter: self.filter.clone(),
filter_pushdown_audit: self.filter_pushdown_audit.clone(),
_phantom: self._phantom.clone(),
}
}
}
impl<K: Codec, V: Codec, T: Timestamp + Lattice + Codec64, D> FetchedBlob<K, V, T, D> {
/// Partially decodes this blob into a [FetchedPart].
pub fn parse(&self) -> FetchedPart<K, V, T, D> {
let (part, stats) = match &self.buf {
FetchedBlobBuf::Hollow { buf, part } => {
let parsed = decode_batch_part_blob(
&self.metrics,
&self.read_metrics,
self.registered_desc.clone(),
part,
buf,
);
(parsed, part.stats.as_ref())
}
FetchedBlobBuf::Inline {
desc,
updates,
ts_rewrite,
} => {
let parsed = EncodedPart::from_inline(
&self.metrics,
self.read_metrics.clone(),
desc.clone(),
updates,
ts_rewrite.as_ref(),
);
(parsed, None)
}
};
FetchedPart::new(
Arc::clone(&self.metrics),
part,
self.schemas.clone(),
self.filter.clone(),
self.filter_pushdown_audit,
stats,
)
}
}
/// A [Blob] object that has been fetched, but not yet fully decoded.
///
/// In contrast to [FetchedBlob], this representation has already done parquet
/// decoding.
#[derive(Debug)]
pub struct FetchedPart<K: Codec, V: Codec, T, D> {
metrics: Arc<Metrics>,
ts_filter: FetchBatchFilter<T>,
part: EncodedPart<T>,
schemas: Schemas<K, V>,
filter_pushdown_audit: Option<LazyPartStats>,
part_cursor: Cursor,
key_storage: Option<K::Storage>,
val_storage: Option<V::Storage>,
_phantom: PhantomData<fn() -> D>,
}
impl<K: Codec, V: Codec, T: Clone, D> Clone for FetchedPart<K, V, T, D> {
fn clone(&self) -> Self {
Self {
metrics: Arc::clone(&self.metrics),
ts_filter: self.ts_filter.clone(),
part: self.part.clone(),
schemas: self.schemas.clone(),
filter_pushdown_audit: self.filter_pushdown_audit.clone(),
part_cursor: self.part_cursor.clone(),
key_storage: None,
val_storage: None,
_phantom: self._phantom.clone(),
}
}
}
impl<K: Codec, V: Codec, T: Timestamp + Lattice + Codec64, D> FetchedPart<K, V, T, D> {
fn new(
metrics: Arc<Metrics>,
part: EncodedPart<T>,
schemas: Schemas<K, V>,
ts_filter: FetchBatchFilter<T>,
filter_pushdown_audit: bool,
stats: Option<&LazyPartStats>,
) -> Self {
let filter_pushdown_audit = if filter_pushdown_audit {
stats.cloned()
} else {
None
};
FetchedPart {
metrics,
ts_filter,
part,
schemas,
filter_pushdown_audit,
part_cursor: Cursor::default(),
key_storage: None,
val_storage: None,
_phantom: PhantomData,
}
}
/// Returns Some if this part was only fetched as part of a filter pushdown
/// audit. See [LeasedBatchPart::request_filter_pushdown_audit].
///
/// If set, the value in the Option is for debugging and should be included
/// in any error messages.
pub fn is_filter_pushdown_audit(&self) -> Option<impl std::fmt::Debug> {
self.filter_pushdown_audit.clone()
}
}
/// A [Blob] object that has been fetched, but has no associated decoding
/// logic.
#[derive(Debug, Clone)]
pub(crate) struct EncodedPart<T> {
metrics: ReadMetrics,
registered_desc: Description<T>,
part: Arc<BlobTraceBatchPart<T>>,
needs_truncation: bool,
ts_rewrite: Option<Antichain<T>>,
}
impl<K, V, T, D> FetchedPart<K, V, T, D>
where
K: Debug + Codec + Default,
V: Debug + Codec + Default,
T: Timestamp + Lattice + Codec64,
D: Semigroup + Codec64 + Send + Sync,
{
/// [Self::next] but optionally providing a `K` and `V` for alloc reuse.
pub fn next_with_storage(
&mut self,
key: &mut Option<K>,
val: &mut Option<V>,
) -> Option<((Result<K, String>, Result<V, String>), T, D)> {
while let Some((k, v, mut t, d)) = self.part_cursor.pop(&self.part) {
if !self.ts_filter.filter_ts(&mut t) {
continue;
}
let mut d = D::decode(d);
// If `filter_ts` advances our timestamp, we may end up with the same K, V, T in successive
// records. If so, opportunistically consolidate those out.
while let Some((k_next, v_next, mut t_next, d_next)) = self.part_cursor.peek(&self.part)
{
if (k, v) != (k_next, v_next) {
break;
}
if !self.ts_filter.filter_ts(&mut t_next) {
break;
}
if t != t_next {
break;
}
// All equal... consolidate!
self.part_cursor.idx += 1;
d.plus_equals(&D::decode(d_next));
}
// If multiple updates consolidate out entirely, drop the record.
if d.is_zero() {
continue;
}
let k = self.metrics.codecs.key.decode(|| match key.take() {
Some(mut key) => match K::decode_from(&mut key, k, &mut self.key_storage) {
Ok(()) => Ok(key),
Err(err) => Err(err),
},
None => K::decode(k),
});
let v = self.metrics.codecs.val.decode(|| match val.take() {
Some(mut val) => match V::decode_from(&mut val, v, &mut self.val_storage) {
Ok(()) => Ok(val),
Err(err) => Err(err),
},
None => V::decode(v),
});
return Some(((k, v), t, d));
}
None
}
}
impl<K, V, T, D> Iterator for FetchedPart<K, V, T, D>
where
K: Debug + Codec + Default,
V: Debug + Codec + Default,
T: Timestamp + Lattice + Codec64,
D: Semigroup + Codec64 + Send + Sync,
{
type Item = ((Result<K, String>, Result<V, String>), T, D);
fn next(&mut self) -> Option<Self::Item> {
self.next_with_storage(&mut None, &mut None)
}
fn size_hint(&self) -> (usize, Option<usize>) {
// We don't know in advance how restrictive the filter will be.
let max_len = self.part.part.updates.iter().map(|x| x.len()).sum();
(0, Some(max_len))
}
}
impl<T> EncodedPart<T>
where
T: Timestamp + Lattice + Codec64,
{
pub async fn fetch(
shard_id: &ShardId,
blob: &(dyn Blob + Send + Sync),
metrics: &Metrics,
shard_metrics: &ShardMetrics,
read_metrics: &ReadMetrics,
registered_desc: &Description<T>,
part: &BatchPart<T>,
) -> Result<Self, BlobKey> {
match part {
BatchPart::Hollow(x) => {
fetch_batch_part(
shard_id,
blob,
metrics,
shard_metrics,
read_metrics,
registered_desc,
x,
)
.await
}
BatchPart::Inline {
updates,
ts_rewrite,
} => Ok(EncodedPart::from_inline(
metrics,
read_metrics.clone(),
registered_desc.clone(),
updates,
ts_rewrite.as_ref(),
)),
}
}
pub(crate) fn from_inline(
metrics: &Metrics,
read_metrics: ReadMetrics,
desc: Description<T>,
x: &LazyInlineBatchPart,
ts_rewrite: Option<&Antichain<T>>,
) -> Self {
let parsed = x.decode(&metrics.columnar).expect("valid inline part");
Self::new(read_metrics, desc, "inline", ts_rewrite, parsed)
}
pub(crate) fn from_hollow(
metrics: ReadMetrics,
registered_desc: Description<T>,
part: &HollowBatchPart<T>,
parsed: BlobTraceBatchPart<T>,
) -> Self {
Self::new(
metrics,
registered_desc,
&part.key.0,
part.ts_rewrite.as_ref(),
parsed,
)
}
pub(crate) fn new(
metrics: ReadMetrics,
registered_desc: Description<T>,
printable_name: &str,
ts_rewrite: Option<&Antichain<T>>,
parsed: BlobTraceBatchPart<T>,
) -> Self {
// There are two types of batches in persist:
// - Batches written by a persist user (either directly or indirectly
// via BatchBuilder). These always have a since of the minimum
// timestamp and may be registered in persist state with a tighter set
// of bounds than are inline in the batch (truncation). To read one of
// these batches, all data physically in the batch but outside of the
// truncated bounds must be ignored. Not every user batch is
// truncated.
// - Batches written by compaction. These always have an inline desc
// that exactly matches the one they are registered with. The since
// can be anything.
let inline_desc = &parsed.desc;
let needs_truncation = inline_desc.lower() != registered_desc.lower()
|| inline_desc.upper() != registered_desc.upper();
if needs_truncation {
assert!(
PartialOrder::less_equal(inline_desc.lower(), registered_desc.lower()),
"key={} inline={:?} registered={:?}",
printable_name,
inline_desc,
registered_desc
);
if ts_rewrite.is_none() {
// The ts rewrite feature allows us to advance the registered
// upper of a batch that's already been staged (the inline
// upper), so if it's been used, then there's no useful
// invariant that we can assert here.
assert!(
PartialOrder::less_equal(registered_desc.upper(), inline_desc.upper()),
"key={} inline={:?} registered={:?}",
printable_name,
inline_desc,
registered_desc
);
}
// As mentioned above, batches that needs truncation will always have a
// since of the minimum timestamp. Technically we could truncate any
// batch where the since is less_than the output_desc's lower, but we're
// strict here so we don't get any surprises.
assert_eq!(
inline_desc.since(),
&Antichain::from_elem(T::minimum()),
"key={} inline={:?} registered={:?}",
printable_name,
inline_desc,
registered_desc
);
} else {
assert_eq!(
inline_desc, ®istered_desc,
"key={} inline={:?} registered={:?}",
printable_name, inline_desc, registered_desc
);
}
EncodedPart {
metrics,
registered_desc,
part: Arc::new(parsed),
needs_truncation,
ts_rewrite: ts_rewrite.cloned(),
}
}
pub(crate) fn maybe_unconsolidated(&self) -> bool {
// At time of writing, only user parts may be unconsolidated, and they are always
// written with a since of [T::minimum()].
self.part.desc.since().borrow() == AntichainRef::new(&[T::minimum()])
}
}
/// A pointer into a particular encoded part, with methods for fetching an update and
/// scanning forward to the next. It is an error to use the same cursor for distinct
/// parts.
///
/// We avoid implementing copy to make it hard to accidentally duplicate a cursor. However,
/// clone is very cheap.
#[derive(Debug, Clone, Default)]
pub(crate) struct Cursor {
part_idx: usize,
idx: usize,
}
impl Cursor {
/// A cursor points to a particular update in the backing part data.
/// If the update it points to is not valid, advance it to the next valid update
/// if there is one, and return the pointed-to data.
pub fn peek<'a, T: Timestamp + Lattice + Codec64>(
&mut self,
encoded: &'a EncodedPart<T>,
) -> Option<(&'a [u8], &'a [u8], T, [u8; 8])> {
while let Some(part) = encoded.part.updates.get(self.part_idx) {
let ((k, v), t, d) = match part.get(self.idx) {
Some(x) => x,
None => {
self.part_idx += 1;
self.idx = 0;
continue;
}
};
let mut t = T::decode(t);
// We assert on the write side that at most one of rewrite or
// truncation is used, so it shouldn't matter which is run first.
//
// That said, my (Dan's) intuition here is that rewrite goes first,
// though I don't particularly have a justification for it.
if let Some(ts_rewrite) = encoded.ts_rewrite.as_ref() {
t.advance_by(ts_rewrite.borrow());
encoded.metrics.ts_rewrite.inc();
}
// This filtering is really subtle, see the comment above for
// what's going on here.
let truncated_t = encoded.needs_truncation && {
!encoded.registered_desc.lower().less_equal(&t)
|| encoded.registered_desc.upper().less_equal(&t)
};
if truncated_t {
self.idx += 1;
continue;
}
return Some((k, v, t, d));
}
None
}
/// Similar to peek, but advance the cursor just past the end of the most recent update.
pub fn pop<'a, T: Timestamp + Lattice + Codec64>(
&mut self,
part: &'a EncodedPart<T>,
) -> Option<(&'a [u8], &'a [u8], T, [u8; 8])> {
let update = self.peek(part);
if update.is_some() {
self.idx += 1;
}
update
}
/// Advance the cursor just past the end of the most recent update, if there is one.
pub fn advance<'a, T: Timestamp + Codec64>(&mut self, part: &'a EncodedPart<T>) {
if self.part_idx < part.part.updates.len() {
self.idx += 1;
}
}
}
/// This represents the serde encoding for [`LeasedBatchPart`]. We expose the struct
/// itself (unlike other encodable structs) to attempt to provide stricter drop
/// semantics on `LeasedBatchPart`, i.e. `SerdeLeasedBatchPart` is exchangeable
/// (including over the network), where `LeasedBatchPart` is not.
///
/// For more details see documentation and comments on:
/// - [`LeasedBatchPart`]
/// - `From<SerdeLeasedBatchPart>` for `LeasedBatchPart<T>`
#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct SerdeLeasedBatchPart {
// Duplicated with the one serialized in the proto for use in backpressure.
encoded_size_bytes: usize,
// We wrap this in a LazyProto because it guarantees that we use the proto
// encoding for the serde impls.
proto: LazyProto<ProtoLeasedBatchPart>,
}
impl SerdeLeasedBatchPart {
/// Returns the encoded size of the given part.
pub fn encoded_size_bytes(&self) -> usize {
self.encoded_size_bytes
}
pub(crate) fn decode<T: Timestamp + Codec64>(
&self,
metrics: Arc<Metrics>,
) -> LeasedBatchPart<T> {
let proto = self.proto.decode().expect("valid leased batch part");
(proto, metrics)
.into_rust()
.expect("valid leased batch part")
}
}
// TODO: The way we're smuggling the metrics through here is a bit odd. Perhaps
// we could refactor `LeasedBatchPart` into some proto-able struct plus the
// metrics for the Drop bit?
impl<T: Timestamp + Codec64> RustType<(ProtoLeasedBatchPart, Arc<Metrics>)> for LeasedBatchPart<T> {
fn into_proto(&self) -> (ProtoLeasedBatchPart, Arc<Metrics>) {
let proto = ProtoLeasedBatchPart {
shard_id: self.shard_id.into_proto(),
filter: Some(self.filter.into_proto()),
desc: Some(self.desc.into_proto()),
part: Some(self.part.into_proto()),
lease: Some(ProtoLease {
reader_id: self.reader_id.into_proto(),
seqno: self.leased_seqno.map(|x| x.into_proto()),
}),
filter_pushdown_audit: self.filter_pushdown_audit,
};
(proto, Arc::clone(&self.metrics))
}
fn from_proto(proto: (ProtoLeasedBatchPart, Arc<Metrics>)) -> Result<Self, TryFromProtoError> {
let (proto, metrics) = proto;
let lease = proto
.lease
.ok_or_else(|| TryFromProtoError::missing_field("ProtoLeasedBatchPart::lease"))?;
Ok(LeasedBatchPart {
metrics,
shard_id: proto.shard_id.into_rust()?,
filter: proto
.filter
.into_rust_if_some("ProtoLeasedBatchPart::filter")?,
desc: proto.desc.into_rust_if_some("ProtoLeasedBatchPart::desc")?,
part: proto.part.into_rust_if_some("ProtoLeasedBatchPart::part")?,
reader_id: lease.reader_id.into_rust()?,
leased_seqno: lease.seqno.map(|x| x.into_rust()).transpose()?,
filter_pushdown_audit: proto.filter_pushdown_audit,
})
}
}
#[mz_ore::test]
fn client_exchange_data() {
// The whole point of SerdeLeasedBatchPart is that it can be exchanged
// between timely workers, including over the network. Enforce then that it
// implements ExchangeData.
fn is_exchange_data<T: timely::ExchangeData>() {}
is_exchange_data::<SerdeLeasedBatchPart>();
is_exchange_data::<SerdeLeasedBatchPart>();
}