Module pager 

Available on crate feature pager and Unix only.

Explicit pager for cold data. See doc/developer/design/20260504_pager.md.

Modules

file 🔒

File backend for the pager. See mz_ore::pager for the public API.

swap 🔒

Swap backend for the pager. See mz_ore::pager for the public API.

Structs

Handle

An opaque handle to data paged out via pageout. The handle’s backend variant is fixed at pageout time and is independent of any later set_backend call.

Enums

Backend

Selects which backend stores paged-out data.

HandleInner 🔒

Constants

BACKEND_FILE 🔒

BACKEND_SWAP 🔒

Statics

BACKEND 🔒

Functions

assert_ranges_disjoint 🔒

Asserts that no two ranges share any byte position. Both backends assume disjoint ranges: the file backend coalesces adjacent ranges into a single pread and writes into a contiguous slice of dst, and the swap backend likewise concatenates into dst per range. Overlapping ranges would duplicate bytes in dst silently, which is almost certainly not what the caller meant; reject upfront so misuse fails loud.

backend

Returns the currently active backend.

pageout

Scatter pageout. Logical layout = chunks concatenated in order. After return, each Vec in chunks is empty. File backend preserves capacity; swap backend moves the alloc into the handle. Empty input returns a len == 0 handle of the active backend’s variant (no I/O is performed in either backend).

pageout_with

Same as pageout, but selects the backend explicitly. Bypasses the global atomic so callers (such as the column-pager layer) can dispatch per call without racing other writers.

read_at

Reads a single range. Convenience wrapper around read_at_many.

read_at_many

Reads multiple ranges. Output appended to dst in request order (concat).

set_backend

Sets the active backend for future pageout calls. Existing handles are unaffected.

set_scratch_dir

Configures the scratch directory for the file backend.

take

Consumes handle, writing the entire payload into dst (cleared first), then reclaims storage. Swap fast path: single-chunk handle into empty dst swaps in place, no copy.

try_pageout

Fallible counterpart to pageout. Returns the underlying I/O error instead of panicking. The swap backend cannot fail at I/O, so this is equivalent to Ok(pageout(chunks)) when backend is Backend::Swap.

try_pageout_with

Fallible counterpart to pageout_with.

try_read_at

Fallible counterpart to read_at.

try_read_at_many

Fallible counterpart to read_at_many. Caller-side preconditions (out-of-bounds, overlapping ranges) still panic; I/O failures return Err.

try_take

Fallible counterpart to take. On I/O error the handle is consumed and dst may hold partial data; the scratch file is unlinked on inner drop.