* fix(chroma): require SQLite magic header for ChromaBackend.detect() (#1893)
Closes#1893.
ChromaBackend.detect() was returning True for a 0-byte chroma.sqlite3 file
because the check was just os.path.isfile(...). On a palace that has any
other backend marker alongside a stale 0-byte chroma.sqlite3,
resolve_backend_name then raises BackendMismatchError and the palace becomes
unopenable until the user manually rm's the empty file.
The 0-byte file appears as a side effect of any sqlite3.connect() on a
missing path — Python creates the file immediately but writes the SQLite
header only on the first statement. So any code path that touches the
chroma.sqlite3 path with bare sqlite3.connect(), including chromadb's own
PersistentClient lazy-init (see the comment at backends/chroma.py:2052),
can leave a 0-byte artifact behind.
Fix: detect() now reads the first 16 bytes and compares to the SQLite
magic prefix b"SQLite format 3\x00" instead of relying on file presence
alone. One extra open() + 16-byte read; detect() isn't a hot path.
Properties:
- Rejects 0-byte files (the symptom #1893 is about).
- Rejects non-SQLite garbage at the canonical path (partial writes, etc.).
- Doesn't false-negative on real chroma palaces: any chroma palace whose
PersistentClient has done any work has the magic header on disk
(verified — CREATE TABLE is enough to land the header).
- Doesn't couple detect() to chroma's specific schema; the magic header
is stable across chromadb releases.
Test sweep: many test files used (chroma.sqlite3).touch() or
.write_bytes(b"") as a "fake palace" shortcut, exploiting the loose
isfile() check (one such site even had the comment "# pass the isfile
guard"). After this change, those stand-ins no longer register as chroma
palaces. Introduced tests/_chroma_palace_helper.py::make_minimal_chroma_sqlite
following the existing _backend_conformance.py precedent, and updated 15
call sites across 8 test files to use it. The existing
test_chroma_detect_matches_palace_with_chroma_sqlite (which encoded the
buggy semantics with write_bytes(b"")) is renamed to
test_chroma_detect_matches_palace_with_sqlite_header and now writes a
real SQLite database via the helper. Added two new tests for the
rejection paths (empty file, non-SQLite garbage).
Full env-cleared suite: 3137 passed, 20 skipped, 0 failed. ruff check
and ruff format --check both clean.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KC5Qsknh2zFRtRvVyjXiTA
* fix(sqlite_exact): require SQLite magic header for SQLiteExactBackend.detect()
Per gemini-code-assist review on #1892 PR #1896: SQLiteExactBackend has the
same os.path.isfile() detection pattern as ChromaBackend did, with the same
0-byte-file vulnerability. Mirrors the chroma fix for repo-wide consistency.
- SQLiteExactBackend.detect() now does the same 16-byte SQLite magic-prefix
check as ChromaBackend.detect().
- _chroma_palace_helper.py: factored its body into a private
_write_minimal_sqlite_file() and gained a sibling
make_minimal_sqlite_exact_sqlite() for the sqlite_exact filename. No churn
to any existing chroma call sites.
- test_sqlite_exact_backend.py:426 (the one site that wrote b"" for
sqlite_exact.sqlite3) updated to use the new helper.
- Three new tests in test_sqlite_exact_backend.py mirror the chroma trio:
matches with valid header, rejects empty file, rejects non-SQLite garbage.
Full env-cleared suite: 3140 passed, 20 skipped, 0 failed.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KC5Qsknh2zFRtRvVyjXiTA
---------
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>
Adds a second external storage backend (Postgres/pgvector) alongside Qdrant
to prove the BaseBackend/BaseCollection contract generalizes across substrates
(SQL + JSONB containment filters + pgvector `<=>` ranking vs Qdrant's REST/dict
model), and addresses the review feedback on PR #1679.
Backend (mempalace/backends/pgvector.py):
- table-per-(namespace, palace, collection) isolation; advertises
supports_namespace_isolation
- JSONB filter pushdown for the containment subset, local-exact fallback for
$or/$contains/comparisons/where_document
- BM25 lexical search; marker-based mismatch protection
- optional psycopg dependency (lazy import), in-memory fake for CI, live test
gated on MEMPALACE_PGVECTOR_LIVE_URL
- registered in registry/__init__/pyproject entry point + [pgvector] extra;
MEMPALACE_PGVECTOR_DSN / MEMPALACE_PGVECTOR_NAMESPACE config; README docs
Isolation contract (RFC 001):
- PalaceRef/BaseBackend document the per-id MUST and the cross-namespace MUST,
gated on the new supports_namespace_isolation capability token
- runnable conformance suite (tests/_backend_conformance.py,
tests/test_backend_conformance.py); qdrant + pgvector run it via their fakes
Marker fail-loud guard:
- qdrant and pgvector now refuse get_collection when local_path is None instead
of silently opening a remote collection with no mismatch protection
Review fixes:
- palace._open_collection_or_explain handles unknown-backend KeyError as a CLI
state message instead of an escaping stack trace
- dedup.py docstring no longer claims "No API calls" unconditionally (false for
remote backends)
Prayaksh Upadhyay
Pim Messelink
Igor Lins e Silva