flutter_gemma_rag_sqlite

First-class SQLite vector store for flutter_gemma. KNN runs inside SQLite via sqlite-vec (vec0 virtual table) — no Dart brute-force, no in-memory index.

Opt-in package implementing VectorStoreRepository:

• Native (Android/iOS/macOS/Linux/Windows): SqliteVectorStore — package:sqlite3 (dart:ffi) + the per-platform vec0 loadable extension.
• Web: WebSqliteVectorStore — package:sqlite3/wasm.dart driving a custom sqlite3.wasm with sqlite-vec/vec0 statically linked.

Both arms speak the same vec0 SQL dialect, so KNN and Filter behave identically across all six platforms. A vec0 table declares an id TEXT PRIMARY KEY, so KNN returns the document id directly — no JOIN, no rowid bridge.

Usage

import 'package:flutter/foundation.dart' show kIsWeb;
import 'package:flutter_gemma/flutter_gemma.dart';
import 'package:flutter_gemma_rag_sqlite/flutter_gemma_rag_sqlite.dart';

await FlutterGemma.initialize(
  vectorStore: kIsWeb ? WebSqliteVectorStore() : SqliteVectorStore(),
);

searchSimilar returns cosine similarity (1 = identical, higher = better), sorted descending, filtered by threshold — the same contract as the qdrant store (vec0 returns distance; the store converts 1 - distance at the boundary).

Declared-column filters

vec0 filters KNN only on declared, typed metadata columns (not arbitrary JSON). Declare the filterable fields once at init via filterSchema:; the store promotes those fields out of each document's metadata JSON into real columns and translates Filter (must/should/mustNot) into a vec0 WHERE:

await FlutterGemma.initialize(
  vectorStore: kIsWeb ? WebSqliteVectorStore() : SqliteVectorStore(),
  filterSchema: const FilterSchema(fields: [
    FilterField(name: 'lang', type: FilterFieldType.string),
    FilterField(name: 'year', type: FilterFieldType.number),
    FilterField(name: 'archived', type: FilterFieldType.bool),
  ]),
);

// later, at query time:
final hits = await store.searchSimilar(
  queryEmbedding: queryVec,
  topK: 10,
  filter: const Filter(
    must:    [FieldRange(key: 'year', gte: 2000)],
    mustNot: [FieldEquals(key: 'archived', value: true)],
  ),
);

Filtering on an undeclared key is a safe no-op (never throws). With no filterSchema, the store ignores filters entirely — identical to filter: null. Supported operators: =, !=, >, >=, <, <=, BETWEEN, IN (FieldEquals, FieldRange, FieldMatchAny); max 16 declared columns.

Setup

Native needs no setup — the vec0 loadable extension is fetched per platform by this package's Native Assets hook (hook/build.dart), SHA256-verified, and loaded automatically before any database is opened.

Web ships the custom sqlite3.wasm (with sqlite-vec linked in) as the package web asset web/rag/sqlite3.wasm. Copy it into your app's web root so it sits next to index.html at rag/sqlite3.wasm — that's the URL WasmSqlite3.loadFromUrl fetches. Resolve the package directory with dart pub deps/flutter pub (the path printed by your IDE) and copy the asset:

mkdir -p web/rag
# <pkg> = the flutter_gemma_rag_sqlite directory in your pub cache / workspace
cp <pkg>/web/rag/sqlite3.wasm web/rag/sqlite3.wasm

OPFS persistence and SharedArrayBuffer require your web server to send the cross-origin isolation headers:

Cross-Origin-Opener-Policy: same-origin
Cross-Origin-Embedder-Policy: require-corp

There is no CDN <script>, no wa-sqlite worker, and no index.html wiring anymore.