Find IVF cells through an index that a rename renames

sqlite-vec-ivf.c

@@ -466,29 +466,25 @@ static int ivf_create_shadow_tables(vec0_vtab *p, int col_idx) {
   if (rc != SQLITE_OK || sqlite3_step(stmt) != SQLITE_DONE) { sqlite3_finalize(stmt); return SQLITE_ERROR; }
   sqlite3_finalize(stmt);
 
-  // cell_id is rowid (auto-increment), centroid_id is indexed
+  // cell_id is the rowid. A centroid's cells are found through the index of
+  // the UNIQUE constraint, which ALTER TABLE RENAME renames with its table; an
+  // index from CREATE INDEX would keep the old table's name, and xRename
+  // cannot drop it ("database table is locked").
   zSql = sqlite3_mprintf(
       "CREATE TABLE " VEC0_SHADOW_IVF_CELLS_NAME
-      " (centroid_id INTEGER NOT NULL,"
+      " (cell_id INTEGER PRIMARY KEY,"
+      "  centroid_id INTEGER NOT NULL,"
       "  n_vectors INTEGER NOT NULL DEFAULT 0,"
       "  validity BLOB NOT NULL,"
       "  rowids BLOB NOT NULL,"
-      "  vectors BLOB NOT NULL)",
+      "  vectors BLOB NOT NULL,"
+      "  UNIQUE (centroid_id, cell_id))",
       p->schemaName, p->tableName, col_idx);
   if (!zSql) return SQLITE_NOMEM;
   rc = sqlite3_prepare_v2(p->db, zSql, -1, &stmt, NULL); sqlite3_free(zSql);
   if (rc != SQLITE_OK || sqlite3_step(stmt) != SQLITE_DONE) { sqlite3_finalize(stmt); return SQLITE_ERROR; }
   sqlite3_finalize(stmt);
 
-  // Index on centroid_id for cell lookup
-  zSql = sqlite3_mprintf(
-      "CREATE INDEX \"%w_ivf_cells%02d_centroid\" ON \"%w_ivf_cells%02d\" (centroid_id)",
-      p->tableName, col_idx, p->tableName, col_idx);
-  if (!zSql) return SQLITE_NOMEM;
-  rc = sqlite3_prepare_v2(p->db, zSql, -1, &stmt, NULL); sqlite3_free(zSql);
-  if (rc != SQLITE_OK || sqlite3_step(stmt) != SQLITE_DONE) { sqlite3_finalize(stmt); return SQLITE_ERROR; }
-  sqlite3_finalize(stmt);
-
   zSql = sqlite3_mprintf(
       "CREATE TABLE " VEC0_SHADOW_IVF_ROWID_MAP_NAME
       " (rowid INTEGER PRIMARY KEY, cell_id INTEGER NOT NULL, slot INTEGER NOT NULL)",

tests/test-ivf-rename.py

@@ -96,3 +96,29 @@ def test_rename_ivf_drop_after(db):
 
     assert _shadow_tables(db, "v") == []
     assert _shadow_tables(db, "v2") == []
+
+
+def test_rename_ivf_then_create_under_old_name(db):
+    """A rename leaves no index named for the old table, so a new IVF table
+    can take the old name."""
+    create = """
+        CREATE VIRTUAL TABLE v USING vec0(
+            a float[4] indexed by ivf(nlist=2)
+        )
+    """
+    db.execute(create)
+    db.execute("insert into v(rowid, a) values (1, ?)", [_f32([0.1] * 4)])
+    db.execute("ALTER TABLE v RENAME TO v2")
+
+    indexes = [
+        row[0] for row in db.execute(
+            r"select name from sqlite_master where type='index' and tbl_name like 'v2\_%' escape '\'"
+        ).fetchall()
+    ]
+    assert indexes
+    assert not any(name.startswith("v_") for name in indexes)
+
+    db.execute(create)
+    db.execute("insert into v(rowid, a) values (1, ?)", [_f32([0.9] * 4)])
+    assert db.execute("select a from v where rowid = 1").fetchone()[0] == _f32([0.9] * 4)
+    assert db.execute("select a from v2 where rowid = 1").fetchone()[0] == _f32([0.1] * 4)