PostgresStore

A durable CacheStore backed by Postgres with the pgvector extension.

This is the "durable semantic cache as a one-dependency choice": point it at a Postgres you already run and cached answers survive a restart and are shared across processes. As with every kmemo store, the adapter reimplements no match logic — the nearest-neighbour search is pgvector's cosine-distance operator (<=>), and dev.kmemo.SemanticCache still owns threshold, guards and verification.

Schema. One table (created on first use, or provision it yourself from the shipped schema.sql): id primary key, scope, prompt, response, embedding vector, created_at, expires_at (nullable — null never expires), metadata jsonb. The embedding column is left dimension-unconstrained so mixed embedding sizes are a storage error at query time, not a schema wall. The search is an exact scan by default (correct, and matching the conformance suite); add an HNSW/IVFFlat index on embedding once your dimension is fixed to scale it.

Expiry. Every read filters on expires_at IS NULL OR expires_at > now, where now comes from the injected clock — so expiry is deterministic under a fixed clock in tests, and honest under the system clock in production. purgeExpired deletes the dead rows when you want the space back.

Parameters