fix(vector_store): make VectorManager methods work on persistent backends (#855)

[yunaremaia]

Closes #855

Problem

VectorManager.maintain_store() and VectorManager.collect_statistics() reached into VectorStore internals (store.vectors / store.metadata), which are only initialized for the inmemory backend. Any persistent backend (FAISS, Qdrant, Pinecone, Milvus, ...) never sets them, so both methods crashed immediately with AttributeError — they were unusable outside the inmemory backend.

Fix

• New public VectorStore.count() accessor (backend-agnostic), following the get_vector()/get_metadata() precedent from AttributeError in VectorStore.get_vector() and get_metadata() when using persistent backends #843 and the NotImplementedError-on-unsupported-capability precedent from AttributeError: 'VectorStore' object has no attribute 'vectors' in build_decision_context() and explain_decision() #848's _filter_by_metadata() fix:
  • inmemory → counts its local dict
  • persistent backend with a count() → delegates
  • persistent backend without one → raises NotImplementedError with a clear message (so callers can tell "no vectors" from "counting not supported")
• VectorManager.maintain_store() and collect_statistics() now go through store.count() instead of poking internals.
  • maintain_store() keeps the exact inmemory semantics (separate vector/metadata dict counts, so a desync still reports healthy: false) and reports a 1:1 metadata_count for persistent backends, where metadata is stored alongside each vector.

Tests

10 hermetic unit tests (no external services): inmemory count, empty store, delegation to a backend count(), NotImplementedError path, and both VectorManager methods against inmemory, counting and non-counting persistent-style stores — including a regression assertion that the failure mode is NotImplementedError, not AttributeError.

Core vector_store suite: 40 passed. (Pre-existing environment failures in test_kg_integration.py / test_decision_embedding_pipeline.py are unrelated — they fail identically on main without this change.)

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PR Summary by Qodo

Fix VectorManager health/stats on persistent vector stores via VectorStore.count()

🐞 Bug fix 🧪 Tests ✨ Enhancement 🕐 20-40 Minutes

AI Description

• Add backend-agnostic VectorStore.count() with clear NotImplementedError on unsupported backends
• Update VectorManager health/stats to use count() instead of inmemory-only internals
• Add regression tests covering inmemory, delegating backends, and missing-count behavior

Diagram

graph TD
  VM["VectorManager"] --> VS["VectorStore.count()"] --> D1{"Backend inmemory?"}
  D1 -->|"yes"| IM["Inmemory dicts"] --> RC["Return count"]
  D1 -->|"no"| BS["Persistent backend store"] --> D2{"count() supported?"}
  D2 -->|"yes"| RC
  D2 -->|"no"| NIE["NotImplementedError"]

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High-Level Assessment

The following are alternative approaches to this PR:

1. Require count() across all persistent backend adapters

• ➕ Uniform capability across backends; fewer conditional branches at call sites
• ➕ Avoids NotImplementedError behavior differences between backends
• ➖ Higher scope: requires touching every backend integration (and potentially external service calls)
• ➖ Harder to keep tests hermetic; may force expensive remote count operations

2. Move health/stats logic into VectorStore (single abstraction boundary)

• ➕ VectorManager stays thin; VectorStore owns backend-specific semantics
• ➕ Easier to maintain invariants around metadata/vector counting behavior
• ➖ Shifts responsibilities and could expand VectorStore’s surface area beyond storage concerns
• ➖ Still needs a count-like capability; doesn’t eliminate the underlying feature gap

3. Introduce a formal backend capability interface (Protocol/ABC)

• ➕ Makes supported operations explicit (count/filter/etc.)
• ➕ Improves type safety and discoverability for backend implementers
• ➖ More architectural change than needed for VectorManager.maintain_store() and collect_statistics() crash with AttributeError on persistent VectorStore backends #855
• ➖ Requires updating multiple backends and tests; larger migration cost

Recommendation: The PR’s approach—adding a backend-agnostic VectorStore.count() with explicit NotImplementedError when unsupported—is the best tradeoff for #855. It fixes the immediate crash, preserves inmemory semantics in maintain_store(), and provides a clear capability signal for persistent backends without forcing a broad backend-interface refactor.

Files changed (2) +158 / -4

Bug fix (1) +34 / -4

vector_store.pyAdd VectorStore.count() and use it in VectorManager health/stats +34/-4

Add VectorStore.count() and use it in VectorManager health/stats

• Introduces a public VectorStore.count() accessor that counts inmemory vectors, delegates to persistent backend stores that implement count(), and raises NotImplementedError when counting isn’t supported. Updates VectorManager.maintain_store() and collect_statistics() to use count() instead of accessing inmemory-only .vectors/.metadata internals, preserving separate metadata counting for inmemory while using 1:1 counts for persistent stores.

semantica/vector_store/vector_store.py

Tests (1) +124 / -0

test_vector_manager_persistent.pyRegression tests for persistent-backend VectorManager counting (#855) +124/-0

Regression tests for persistent-backend VectorManager counting (#855)

• Adds hermetic unit tests for VectorStore.count() across inmemory, delegating persistent-style backends, and the unsupported-count NotImplementedError path. Adds regression coverage ensuring VectorManager.collect_statistics() and maintain_store() work for persistent-style stores and fail with NotImplementedError (not AttributeError) when counting isn’t available.

tests/vector_store/test_vector_manager_persistent.py

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Code Review by Qodo

🐞 Bugs (0) 📘 Rule violations (0) 📎 Requirement gaps (0) 🎨 UX issues (0) 🔗 Cross-repo conflicts (0) 📜 Skill insights (0)

1. Silent zero count ✓ Resolved 🐞 Bug ≡ Correctness

Description

VectorStore.count() returns 0 when backend != "inmemory" and _backend_store is None, which makes
VectorManager.collect_statistics()/maintain_store() report an empty, healthy store instead of
surfacing that the persistent backend isn’t initialized. This is inconsistent with
get_vector()/get_metadata(), which raise NotImplementedError when a non-inmemory backend can’t
fulfill the request.

Code

semantica/vector_store/vector_store.py[R845-848]

+                "implement count. Vector counting is only supported for the "
+                "inmemory backend."
+            )
+        return 0

Evidence

The new count() implementation explicitly returns 0 when _backend_store is missing, while other
backend-agnostic accessors raise when a non-inmemory backend cannot serve the request; VectorManager
now depends on count() for integrity/stats, so this can mask backend initialization problems.

semantica/vector_store/vector_store.py[809-826]
semantica/vector_store/vector_store.py[827-849]
semantica/vector_store/vector_store.py[1484-1511]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
`VectorStore.count()` falls through to `return 0` when `self.backend != "inmemory"` and `self._backend_store is None`. This can cause `VectorManager.collect_statistics()` and `VectorManager.maintain_store()` to silently misreport a non-inmemory store as empty/healthy when the backend store is actually missing/uninitialized.
### Issue Context
Other public accessors (`get_vector()`, `get_metadata()`) do not silently succeed in this situation; they raise `NotImplementedError`. `count()` should follow the same capability/initialization semantics.
### Fix Focus Areas
- semantica/vector_store/vector_store.py[827-849]
- semantica/vector_store/vector_store.py[809-826]
- semantica/vector_store/vector_store.py[1484-1511]
### Suggested change
- Replace the final `return 0` with an exception for non-inmemory backends when `_backend_store` is missing (e.g., `raise NotImplementedError("Backend store is not initialized; cannot count vectors")` or `RuntimeError`).
- Optionally, keep returning 0 only when `backend == "inmemory"` (already handled) or if you have an explicit, documented meaning for `_backend_store is None`.

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---

2. Unvalidated count callability ✓ Resolved 🐞 Bug ☼ Reliability

Description

VectorStore.count() checks only hasattr(_backend_store, "count") and then calls it; if a backend
adapter exposes a non-callable count attribute/property, this will raise TypeError at runtime.
Defensive validation would make the failure mode a clearer NotImplementedError.

Code

semantica/vector_store/vector_store.py[R840-842]

+        elif self._backend_store is not None:
+            if hasattr(self._backend_store, "count"):
+                return self._backend_store.count()

Evidence

The added code uses hasattr() and immediately invokes .count(), which assumes the attribute is
callable.

semantica/vector_store/vector_store.py[827-847]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
`VectorStore.count()` invokes `_backend_store.count()` after only `hasattr()` checking. If `count` exists but isn’t callable (mis-shaped adapter), this becomes a runtime `TypeError`.
### Issue Context
The documented contract is a `count()` method, so this is a low-likelihood defensive improvement; adding a `callable()` check yields a cleaner, capability-style error.
### Fix Focus Areas
- semantica/vector_store/vector_store.py[840-847]
### Suggested change
- Replace the current check with:
- `count_attr = getattr(self._backend_store, "count", None)`
- `if callable(count_attr): return count_attr()`
- otherwise raise `NotImplementedError(...)`

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---

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[Sameer6305]

@yunaremaia can you fix the qodo reviews, before we review it.

[yunaremaia]

Fixed both Qodo findings in cd972c9:

1. Silent zero count — VectorStore.count() no longer returns 0 when a persistent backend has no wrapped store. It now raises NotImplementedError, consistent with get_vector()/get_metadata(), so a missing backend initialization can't masquerade as an empty, healthy store.
2. Unvalidated count callability — the hasattr check was replaced with a getattr + callable() capability check, so a mis-shaped adapter exposes a clean NotImplementedError instead of a runtime TypeError.

Regression tests added for both cases (12/12 passing in the persistent-backend suite). Ready for review.

[Sameer6305]

Fixed both Qodo findings in cd972c9:

1. Silent zero count — VectorStore.count() no longer returns 0 when a persistent backend has no wrapped store. It now raises NotImplementedError, consistent with get_vector()/get_metadata(), so a missing backend initialization can't masquerade as an empty, healthy store.
2. Unvalidated count callability — the hasattr check was replaced with a getattr + callable() capability check, so a mis-shaped adapter exposes a clean NotImplementedError instead of a runtime TypeError.

Regression tests added for both cases (12/12 passing in the persistent-backend suite). Ready for review.

Thanks @yunaremaia will review it.

[yunaremaia]

Rebased onto the latest main (was behind) — no conflicts, the 12 persistent-backend tests still pass. Ready for your review whenever convenient.

[yunaremaia]

Thanks for assigning #914 to me — I'll take it to merge. Current state: rebased onto latest main (082da9a, no conflicts), the 12 persistent-backend tests pass (VectorManager on FAISS/Qdrant/Pinecone/Milvus + inmemory delegation + NotImplementedError contract), and both Qodo findings are addressed in the earlier commits. Standing by for your review — happy to iterate on anything that comes up.

[Sameer6305]

Thanks @yunaremaia for the solid work on this fix and for addressing the persistent-backend compatibility issue.

I reviewed the implementation against the existing VectorStore/VectorManager abstractions, backend behavior, edge cases, and the added tests.

During review, I found that the initial count() abstraction still left the shipped persistent backends without an actual count implementation, and maintain_store() was treating metadata_count == vector_count as a guaranteed invariant for persistent stores. So corrected this by:

• Adding count() implementations for FAISS, SQLiteVec, and PgVector where reliable counts are available.
• Keeping NotImplementedError for backends where a reliable count cannot currently be guaranteed.
• Updating maintain_store() so persistent backends report metadata_count=None rather than manufacturing a 1:1 metadata invariant.
• Improving the unsupported-count error message.
• Expanding the regression tests to cover the new backend behavior and persistent/in-memory semantics.

These fixes are included in commit df02fa88 (fix(vector_store): implement count() on FAISS/SQLite/PgVector backends (#914)).

The focused validation passed (25/25 targeted tests; SQLite-specific tests are skipped when sqlite-vec is unavailable), and the working tree/diff checks are clean.

@KaifAhmad1 From my side, this is approved and ready for your final review/verdict before merge.

[KaifAhmad1]

Approving — thanks both.

@yunaremaia, nice fix for #855: the backend-agnostic VectorStore.count() is the right shape (following the get_vector()/get_metadata() precedent from #843), and you were quick to close out both Qodo findings.

@Sameer6305, good catch that the initial version didn't actually ship a count() on any real backend, and that maintain_store() was manufacturing a vacuous metadata_count == vector_count for persistent stores — the metadata_count: None fix is the honest answer there.

Independently reviewed the diff against the actual FAISSStore/PgVectorStore/SQLiteVecStore internals (not just the description) — confirmed FAISS really has no delete path so len(index.vector_ids) is safe, confirmed FAISS's count() correctly avoids the get_stats() "no_index" dict (which lacks a vector_count key, unlike Pg/SQLite's), and checked there are no other callers in the repo that depend on metadata_count being a non-None int. Added a changelog entry (859690c) documenting the fix. No blockers — ready to merge.

[yunaremaia]

Thank you @KaifAhmad1! The backend-agnostic count() shape was the goal — glad it matches the repo's precedent. Standing by for the CI to finish.