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feat(store): ADR 0003 G2 content-defined chunking (X6 winner K1) - #85
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…dup rule, decision) ADR 0003 section 6.4 X6 for step G2 (#45): chunker definition, seven chunked candidates plus the no-chunking control, the four AIEN repository histories at pinned commits, the measurements, the deduplication rule G2 is accepted against, and the decision criterion. Committed before any run. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Blobs above the chunk threshold are cut by a FastCDC-style gear chunker with normalized chunking (the chunker fixed in evidence/g2-content-defined-chunking/x6/ RULE.md) and stored as chunks inside the segments, one copy per ChunkDigest. The blob identity stays its BlobDigest over the whole content; reads reassemble the chunks (contiguous runs in one read) and verify the BlobDigest. - chunk.rs: ChunkDigest, gear table, cut rule, ChunkParams (StoreLimits.chunking, refused at open when invalid), manifests. - WAL v2 chunked frames (flag 0x02): manifests, chunk table, chunk bytes; payload digest over the prefix, every chunk verified against its digest on recovery. - Commit drops chunks already indexed and manifests of blobs already stored, counting records accepted earlier in the same batch (X6 rule section 5). - Chunk index and manifests rebuilt by replay and persisted in the checkpoint segment index (version 2 only when it holds chunks; version 1 otherwise). - Old stores stay readable: A1 fixtures and an A2 segment-store fixture written by the A2 code (generator under evidence/.../fixture-generator). - Tests g2_*: round trip, dedup between revisions, inside a record and a batch, parameter changes, damage refusals, crash after batch sync, index v2 decoder. - Red/green: red against A2 (behaviour probe and compile), 8 mutations each caught (evidence/g2-content-defined-chunking/red-green/). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
…mmitted) `synapse-bench x6` reads the four corpus histories from bare clones (first-parent commits, added or modified regular files, blob bytes provided the first time they appear), runs the eight configurations three times with the order rotated per repetition, and records raw per-change and per-read times, log and content bytes, and one aien_spbm energy window per phase. `x6-report` applies the RULE.md section 6 criterion (unit-tested on constructed runs). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
…sults X6 (RULE.md sha256 dd4ed8f9..., unchanged) ran on real AIEN histories: K1 (T 16 KiB, avg 4 KiB) is the only eligible candidate (20.7 % fewer log bytes, 1.095x seconds per change, 1.068x per read). ChunkParams::X6_DEFAULT is K1. Adds raw.json, report.json, RESULTS.md, manifest and checksums, and docs/G2_CONTENT_DEFINED_CHUNKING.md. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Co-authored-by: Drake Stapleton <drake@aienos.com>
…lobs) Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Co-authored-by: Drake Stapleton <drake@aienos.com>
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Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Co-authored-by: Drake Stapleton <drake@aienos.com>
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What changed
ADR 0003 step G2 (content-defined chunking, after experiment X6). Blobs above a threshold are cut into chunks by an in-house FastCDC-style gear chunker (no new crates) and stored in the segments once per
ChunkDigest; the blob's identity stays itsBlobDigestover the whole content. Chunked WAL v2 frames (flag 0x02), a chunk index and manifests rebuilt by replay and persisted in the checkpoint segment index (version 2 only when chunks exist), commit-time dedup against the chunk index and earlier records of the same batch, reads that reassemble chunks and verify theBlobDigest.StoreLimits.chunkingholds the parameters; old whole-blob stores (A1 files, A2 segments) stay readable.Base: main with A2 (#77) and B1 (#81) merged. Revision records (B1) still store their blobs whole (inline, never chunked).
Why
X6 fixed the rule before its runs (
evidence/g2-content-defined-chunking/x6/RULE.md, commit ab9ccc0, sha256 dd4ed8f9...). Result (host-observed, shared host, one agent, 1,037 changes / 24,093 revisions / 433.8 MB of real AIEN history, 3 reps): K1 (T 16 KiB, avg 4 KiB) is the only eligible candidate: 20.7 % fewer log bytes than no chunking, 1.095x seconds per accepted change (limit 1.10, thin margin), 1.068x seconds per read. Seconds per accepted change 2.133 ms vs the 1.006 ms A2 flush bound (0.471 of bound at one agent; no chunking 0.516). Joules (SoC package meter only) are inside noise above idle.ChunkParams::X6_DEFAULTis K1. Seex6/RESULTS.mdanddocs/G2_CONTENT_DEFINED_CHUNKING.md.How verified
g2_every_blob_round_trips_byte_for_byte_with_unchanged_blob_digest,g2_dedup_between_two_revisions_follows_the_x6_rule(plus batch, parameter, damage, crash, index v2 and old-store tests incrates/synapse-store/src/g2_tests.rs).evidence/g2-content-defined-chunking/red-green/).cargo fmt --all --check && cargo clippy --locked --workspace --all-targets -- -D warnings && cargo test --locked --workspaceall pass.tests/fixtures/g2-a2).Deviations and limits
ChunkDigestlives insynapse-store, notsynapse-core(avoids the parallel B1 envelope work). No format marker bump: pre-G2 builds fail closed on chunked frames and indexes. UNVERIFIED: K1 vs the ingest limit on a quiet host (margin is within noise), cold reads, multi-agent ingest with chunking, power loss. Tested again after rebasing onto main (342 workspace tests pass). NOT_RUN:crumb compile(synapse has nocrumb.lockpin, and its root.crumbis already UNCOMPILED on the A2 baseline).Fixes #45
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