The BLOB-seq_id migration shim (PR #664) ran int.from_bytes(..., 'big')
over every BLOB in max_seq_id, including chromadb 1.5.x's own native
format (b'\x11\x11' + 6 ASCII digits). That conversion yields a ~1.23e18
integer that silently suppresses every subsequent embeddings_queue write
for the affected segment (queue filter is seq_id > start), causing
silent drawer-write drops after a 1.5.x upgrade.
Two-part fix:
1. Shim narrowing (mempalace/backends/chroma.py)
- Drop max_seq_id from the shim loop. chromadb owns that column's
format; we don't reinterpret it.
- Defense-in-depth: skip rows in embeddings whose seq_id BLOB has the
sysdb-10 b'\x11\x11' prefix rather than misconvert.
2. Recovery command (mempalace/repair.py, mempalace/cli.py)
- mempalace repair --mode max-seq-id [--segment <uuid>]
[--from-sidecar <path>] [--dry-run] [--yes] [--no-backup]
- Detects poisoned rows via threshold (seq_id > 2**53).
- Default heuristic: MAX(embeddings.seq_id) over the collection owning
the poisoned segment. Matches METADATA max exactly; VECTOR segments
get a few seq_ids ahead (queue skips an already-indexed window — an
acceptable loss vs. resetting to 0 and re-processing everything).
- --from-sidecar copies clean values from a pre-corruption sqlite db.
- Backs up chroma.sqlite3, closes chroma handles, atomic UPDATEs,
post-repair verification that raises MaxSeqIdVerificationError if
any row is still above threshold.
Tests: 8 new in tests/test_repair.py (detection, heuristic, sidecar,
dry-run, segment filter, no-op, backup, rollback-on-verify-failure).
3 new in tests/test_backends.py (max_seq_id untouched by shim,
sysdb-10 prefix skipped in embeddings, legacy big-endian u64 BLOBs
still convert). Full suite: 1103 passed.
The user-reported case in #1208: a palace with 67,580 drawers had its
HNSW files manually quarantined to recover from corruption. ``mempalace
repair`` then ran cleanly and reported "Drawers found: 10000 ... Repair
complete. 10000 drawers rebuilt." Backup was the v3.3.3 chroma.sqlite3
that did contain the full 67,580 — but the rebuilt collection only had
the first 10K. 85% data loss, no warning.
Root cause: ChromaDB's collection-layer get() silently caps at
``CHROMADB_DEFAULT_GET_LIMIT = 10_000`` rows when reading from a
collection whose segment metadata is stale (typical post-quarantine
state). col.count() returns the same capped value, so neither the
loop bound nor the extraction count flagged the truncation.
Fix is defense-in-depth, not a recovery mechanism. Repair now:
1. After extraction, queries chroma.sqlite3 directly via a read-only
sqlite3 connection: COUNT(*) FROM embeddings JOIN segments JOIN
collections WHERE name='mempalace_drawers'. If that count exceeds
the extracted count, abort with a clear message before any
destructive operation.
2. Falls back to a weaker check when the SQLite query can't run
(chromadb schema drift, locked file): if extracted exactly equals
CHROMADB_DEFAULT_GET_LIMIT, that's a strong-enough cap signal to
refuse without explicit acknowledgement.
3. Adds ``--confirm-truncation-ok`` (CLI) and ``confirm_truncation_ok``
(rebuild_index kwarg) to override after independent verification.
Useful for the rare case of a palace genuinely sized at exactly
10,000 drawers.
The guard logic lives in ``repair.check_extraction_safety()`` so the
two extraction paths (CLI ``cmd_repair`` and the lower-level
``rebuild_index``) share a single implementation. Raises
``TruncationDetected`` carrying the printable message.
Tests: 9 new cases covering the safe path (counts match, SQLite
unreadable but well under cap), both abort paths (SQLite higher than
extracted, unreadable + at cap), the override flag, and end-to-end
behavior of ``rebuild_index`` with the guard wired in. Plus two
``sqlite_drawer_count`` tests for the missing-file and bad-schema
cases.
What's NOT in this PR: actually recovering the missing 57,580
drawers from the user's case. The on-disk SQLite still holds them;
recovery is a separate flow (direct-extract from chroma.sqlite3,
bypass the chromadb collection layer entirely). This PR's job is
to stop repair from making it worse.
Refs #1208.
Prerequisite for RFC 001 (plugin spec, #743). Removes every direct
`import chromadb` outside the ChromaDB backend itself so the core
modules depend only on the backend abstraction layer.
Extends ChromaBackend with make_client, get_or_create_collection,
delete_collection, create_collection, and backend_version. Adds
update() to the BaseCollection contract. Non-backend callers
(mcp_server, dedup, repair, migrate, cli) now go through the
abstraction; tests patch ChromaBackend instead of chromadb.
With this landed, the RFC 001 spec can be enforced and PalaceStore
(#643) can ship as a plugin without touching core modules.
eblander