feat: semantic chunking + pgvector hybrid (BM25+vector) retriever (#2553)

tests/vectorstore/test_pgvector.py

@@ -131,6 +131,61 @@ class TestPGVectorStoreSearch:
         assert len(results) == 2
 
 
+@pytest.mark.unit
+class TestPGVectorStoreKeywordSearch:
+    def test_keyword_search_returns_documents(self):
+        store, _, mock_cursor, mock_emb = _make_store(source_id="src1")
+        mock_cursor.fetchall.return_value = [
+            ("hello world", {"source": "a.txt"}, 0.9),
+            ("foo bar", {"source": "b.txt"}, 0.3),
+        ]
+
+        results = store.keyword_search("hello", k=5)
+
+        # Keyword search must not embed the query.
+        mock_emb.embed_query.assert_not_called()
+        assert len(results) == 2
+        assert results[0].page_content == "hello world"
+        assert results[0].metadata == {"source": "a.txt"}
+
+    def test_keyword_search_is_parameterized(self):
+        store, _, mock_cursor, _ = _make_store(source_id="src1")
+        mock_cursor.fetchall.return_value = []
+
+        store.keyword_search("DROP TABLE documents; --", k=7)
+
+        sql, params = mock_cursor.execute.call_args[0]
+        # The raw question must never be interpolated into the SQL text.
+        assert "DROP TABLE documents" not in sql
+        assert "websearch_to_tsquery('english', %s)" in sql
+        # Question is bound twice (rank + WHERE), then source_id and k.
+        assert params == ("DROP TABLE documents; --", "src1", "DROP TABLE documents; --", 7)
+
+    def test_keyword_search_handles_null_metadata(self):
+        store, _, mock_cursor, _ = _make_store()
+        mock_cursor.fetchall.return_value = [("text", None, 0.5)]
+
+        results = store.keyword_search("query")
+        assert len(results) == 1
+        assert results[0].metadata == {}
+
+    def test_keyword_search_returns_empty_on_error(self):
+        store, _, mock_cursor, _ = _make_store()
+        mock_cursor.execute.side_effect = Exception("fts failed")
+
+        assert store.keyword_search("query") == []
+
+    def test_ensure_table_exists_creates_fts_index(self):
+        store, mock_conn, mock_cursor, _ = _make_store()
+        store._ensure_table_exists()
+
+        executed = " ".join(
+            str(call.args[0]) for call in mock_cursor.execute.call_args_list
+        )
+        assert "documents_text_fts_idx" in executed
+        assert "gin(to_tsvector('english'" in executed
+
+
 @pytest.mark.unit
 class TestPGVectorStoreAddTexts:
     def test_add_texts_inserts_and_returns_ids(self):