[loop-cycle-951] refactor: break up _migrate_schema() (#552) (#558)

src/timmy/memory_system.py

@@ -98,29 +98,8 @@ def _get_table_columns(conn: sqlite3.Connection, table_name: str) -> set[str]:
     return {row[1] for row in cursor.fetchall()}
 
 
-def _migrate_schema(conn: sqlite3.Connection) -> None:
-    """Migrate from old three-table schema to unified memories table.
-
-    Migration paths:
-    - episodes table -> memories (context_type -> memory_type)
-    - chunks table -> memories with memory_type='vault_chunk'
-    - facts table -> dropped (unused, 0 rows expected)
-    """
-    cursor = conn.execute("SELECT name FROM sqlite_master WHERE type='table'")
-    tables = {row[0] for row in cursor.fetchall()}
-
-    has_memories = "memories" in tables
-    has_episodes = "episodes" in tables
-    has_chunks = "chunks" in tables
-    has_facts = "facts" in tables
-
-    # Check if we need to migrate (old schema exists)
-    if not has_memories and (has_episodes or has_chunks or has_facts):
-        logger.info("Migration: Creating unified memories table")
-        # Schema will be created by _ensure_schema above
-
-    # Migrate episodes -> memories
-    if has_episodes and has_memories:
+def _migrate_episodes(conn: sqlite3.Connection) -> None:
+    """Migrate episodes table rows into the unified memories table."""
     logger.info("Migration: Converting episodes table to memories")
     try:
         cols = _get_table_columns(conn, "episodes")
@@ -146,8 +125,9 @@ def _migrate_schema(conn: sqlite3.Connection) -> None:
     except sqlite3.Error as exc:
         logger.warning("Migration: Failed to migrate episodes: %s", exc)
 
-    # Migrate chunks -> memories as vault_chunk
-    if has_chunks and has_memories:
+
+def _migrate_chunks(conn: sqlite3.Connection) -> None:
+    """Migrate chunks table rows into the unified memories table."""
     logger.info("Migration: Converting chunks table to memories")
     try:
         cols = _get_table_columns(conn, "chunks")
@@ -175,13 +155,38 @@ def _migrate_schema(conn: sqlite3.Connection) -> None:
     except sqlite3.Error as exc:
         logger.warning("Migration: Failed to migrate chunks: %s", exc)
 
-    # Drop old tables
-    if has_facts:
+
+def _drop_legacy_table(conn: sqlite3.Connection, table: str) -> None:
+    """Drop a legacy table if it exists."""
     try:
-            conn.execute("DROP TABLE facts")
-            logger.info("Migration: Dropped old facts table")
+        conn.execute(f"DROP TABLE {table}")  # noqa: S608
+        logger.info("Migration: Dropped old %s table", table)
     except sqlite3.Error as exc:
-            logger.warning("Migration: Failed to drop facts: %s", exc)
+        logger.warning("Migration: Failed to drop %s: %s", table, exc)
+
+
+def _migrate_schema(conn: sqlite3.Connection) -> None:
+    """Migrate from old three-table schema to unified memories table.
+
+    Migration paths:
+    - episodes table -> memories (context_type -> memory_type)
+    - chunks table -> memories with memory_type='vault_chunk'
+    - facts table -> dropped (unused, 0 rows expected)
+    """
+    cursor = conn.execute("SELECT name FROM sqlite_master WHERE type='table'")
+    tables = {row[0] for row in cursor.fetchall()}
+
+    has_memories = "memories" in tables
+
+    if not has_memories and (tables & {"episodes", "chunks", "facts"}):
+        logger.info("Migration: Creating unified memories table")
+
+    if "episodes" in tables and has_memories:
+        _migrate_episodes(conn)
+    if "chunks" in tables and has_memories:
+        _migrate_chunks(conn)
+    if "facts" in tables:
+        _drop_legacy_table(conn, "facts")
 
     conn.commit()