Method searchNodesFTS

src/db/queries.ts:1377–1440

* FTS5 search with prefix matching

(query: string, options: SearchOptions)

   * FTS5 search with prefix matching
   */
  private searchNodesFTS(query: string, options: SearchOptions): SearchResult[] {
    const { kinds, languages, limit = 100, offset = 0 } = options;

    // Add prefix wildcard for better matching (e.g., "auth" matches "AuthService", "authenticate")
    // Escape special FTS5 characters and add prefix wildcard.
    //
    // `::` is a qualifier separator in Rust/C++/Ruby, not a token char,
    // so treat it as whitespace before the strip step. Otherwise queries
    // like `stage_apply::run` collapse to `stage_applyrun` (the colons
    // are stripped without splitting) and find nothing. See #173.
    const ftsQuery = query
      .replace(/::/g, ' ') // Rust/C++/Ruby qualifier separator
      .replace(/['"*():^]/g, '') // Remove FTS5 special chars
      .split(/\s+/)
      .filter(term => term.length > 0)
      // Strip FTS5 boolean operators to prevent query manipulation
      .filter(term => !/^(AND|OR|NOT|NEAR)$/i.test(term))
      .map(term => `"${term}"*`) // Prefix match each term
      .join(' OR ');

    if (!ftsQuery) {
      return [];
    }

    // BM25 column weights: id=0, name=20, qualified_name=5, docstring=1, signature=2
    // Heavy name weight ensures exact/prefix name matches rank above incidental
    // mentions in long docstrings or qualified names of nested symbols.
    // Fetch 5x requested limit so post-hoc rescoring (kindBonus, pathRelevance,
    // nameMatchBonus) can promote results that BM25 alone undervalues.
    const ftsLimit = Math.max(limit * 5, 100);

    let sql = `
      SELECT nodes.*, bm25(nodes_fts, 0, 20, 5, 1, 2) as score
      FROM nodes_fts
      JOIN nodes ON nodes_fts.id = nodes.id
      WHERE nodes_fts MATCH ?
    `;

    const params: (string | number)[] = [ftsQuery];

    if (kinds && kinds.length > 0) {
      sql += ` AND nodes.kind IN (${kinds.map(() => '?').join(',')})`;
      params.push(...kinds);
    }

    if (languages && languages.length > 0) {
      sql += ` AND nodes.language IN (${languages.map(() => '?').join(',')})`;
      params.push(...languages);
    }

    sql += ' ORDER BY score LIMIT ? OFFSET ?';
    params.push(ftsLimit, offset);

    try {
      const rows = this.db.prepare(sql).all(...params) as (NodeRow & { score: number })[];
      return rows.map((row) => ({
        node: rowToNode(row),
        score: Math.abs(row.score), // bm25 returns negative scores