[storage/metadata] Improve Delta Write Efficiency for Common Case #1189
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Pull Request Overview
This PR adds delta‐write support so that when keys and value lengths remain stable, only changed segments are written in-place rather than rewriting the entire blob.
- Tracks each key’s byte offset and length in the blob and marks modified keys
- Implements overwrite vs. full-rewrite logic in
sync(), plus metrics for overwrites and rewrites - Updates docs, tests, and benchmarks to reflect new behavior and renamed parameters
Reviewed Changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| storage/src/metadata/storage.rs | Added lengths and modified tracking, implemented in-place overwrite logic, updated metrics |
| storage/src/metadata/mod.rs | Renamed docs and tests to use sync_rewrites/sync_overwrites metrics |
| storage/src/metadata/benches/utils.rs | Renamed modified_pct→modified and updated helper function signature |
| storage/src/metadata/benches/sync.rs | Updated benchmark loops/labels to use modified count |
Comments suppressed due to low confidence (3)
storage/src/metadata/storage.rs:53
- [nitpick] The field name
key_order_changedis a bit ambiguous; consider renaming it to something likelast_rewrite_versionorlast_key_order_change_versionfor greater clarity.
key_order_changed: u64,
storage/src/metadata/benches/utils.rs:38
- [nitpick] The comment is unclear: consider rephrasing to
Modify the first <count> keys and emit a new set of key-value pairsor update toModifymodifiedkeysto match the parameter name.
/// Modify `modified` of keys and emit a new set of keys.
storage/src/metadata/storage.rs:184
- [nitpick] Since
KimplementsArrayand may have a fixed size, consider usingK::SIZEdirectly instead ofencode_size()to avoid potential runtime overhead.
cursor += key.encode_size();
Codecov ReportAttention: Patch coverage is
@@ Coverage Diff @@
## main #1189 +/- ##
==========================================
+ Coverage 91.22% 91.28% +0.05%
==========================================
Files 216 216
Lines 57982 58364 +382
==========================================
+ Hits 52896 53278 +382
Misses 5086 5086
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Modifying 1 key on a 100, 1000, and 10000 key store takes ~roughly the same time (and modifies the same amount of data on disk):