kami
98 lines
3.5 KiB
Go
98 lines
3.5 KiB
Go
package store
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import (
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"context"
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"database/sql"
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"errors"
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"fmt"
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)
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// metaKeyEmbedderID names the embedder that wrote the stored vectors.
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//
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// Why one value for the whole DB and not a column on every vector row: the
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// vectors are only ever rewritten all at once (one backfill re-embeds every
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// note and fact together), so a per-row marker would hold the same string in
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// every row and cost a column on two tables for nothing.
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const metaKeyEmbedderID = "embedder_id"
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// Meta reads a single value from the meta table. Missing key ⇒ empty string.
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func (s *Store) Meta(ctx context.Context, key string) (string, error) {
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var v string
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err := s.db.QueryRowContext(ctx, `SELECT value FROM meta WHERE key = ?`, key).Scan(&v)
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if errors.Is(err, sql.ErrNoRows) {
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return "", nil
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}
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if err != nil {
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return "", fmt.Errorf("read meta %s: %w", key, err)
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}
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return v, nil
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}
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// SetMeta writes (or overwrites) a single meta value.
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func (s *Store) SetMeta(ctx context.Context, key, value string) error {
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_, err := s.db.ExecContext(ctx,
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`INSERT INTO meta (key, value) VALUES (?,?)
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ON CONFLICT(key) DO UPDATE SET value = excluded.value`, key, value)
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if err != nil {
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return fmt.Errorf("write meta %s: %w", key, err)
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}
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return nil
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}
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// EmbedderUnknown is the stored id reported for a DB that already holds
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// vectors but never recorded who wrote them.
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const EmbedderUnknown = "unknown (written before this marker existed)"
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// CheckEmbedder compares the embedder now configured against the one that
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// wrote the stored vectors. Returns the stored id and whether it differs.
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//
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// Vectors from two different models live in different spaces, so cosine
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// between them is noise rather than a low score — and both of our models are
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// 384-dimensional, so nothing else catches it.
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//
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// Three cases, and the middle one is the one that actually matters:
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//
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// - marker present ⇒ compare the two ids.
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// - marker absent but vectors already stored ⇒ this is a DB from before the
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// marker, so we cannot know who wrote them. Report a mismatch. This is the
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// real case on the deployed box: those vectors came from the old embedder,
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// and claiming them for the current one would hide the exact problem the
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// marker was added to catch.
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// - marker absent and no vectors ⇒ fresh DB, claim it, nothing to fix.
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//
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// TODO(#378): on a mismatch, run the one-shot backfill here — re-embed every
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// stored note and fact text with the current embedder (EmbedPassage side),
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// write the vectors back, then SetMeta the current id.
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func (s *Store) CheckEmbedder(ctx context.Context, currentID string) (stored string, mismatch bool, err error) {
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stored, err = s.Meta(ctx, metaKeyEmbedderID)
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if err != nil {
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return "", false, err
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}
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if stored != "" {
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return stored, stored != currentID, nil
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}
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n, err := s.countVectors(ctx)
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if err != nil {
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return "", false, err
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}
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if n > 0 {
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return EmbedderUnknown, true, nil
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}
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return currentID, false, s.SetMeta(ctx, metaKeyEmbedderID, currentID)
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}
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// countVectors — how many stored rows carry an embedding. Used only to tell a
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// fresh DB apart from one that predates the marker.
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func (s *Store) countVectors(ctx context.Context) (int, error) {
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var notes, vecs int
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if err := s.db.QueryRowContext(ctx,
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`SELECT count(*) FROM notes WHERE embedding IS NOT NULL`).Scan(¬es); err != nil {
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return 0, fmt.Errorf("count note vectors: %w", err)
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}
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if err := s.db.QueryRowContext(ctx,
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`SELECT count(*) FROM memory_vectors`).Scan(&vecs); err != nil {
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return 0, fmt.Errorf("count memory vectors: %w", err)
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}
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return notes + vecs, nil
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}
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