feat: optimize SQLite PRAGMAs (WAL, mmap 256MB, cache 32MB, temp_store) and add compound indexes

app/database.py

@@ -7,9 +7,11 @@ from app import config
 def get_db_connection() -> sqlite3.Connection:
     conn = sqlite3.connect(config.DB_PATH, timeout=15.0)
     conn.row_factory = sqlite3.Row
-    conn.execute("PRAGMA journal_mode=WAL;")
-    conn.execute("PRAGMA synchronous=NORMAL;")
-    conn.execute("PRAGMA foreign_keys=ON;")
+    conn.execute("PRAGMA synchronous = NORMAL;")
+    conn.execute("PRAGMA mmap_size = 268435456;")  # 256MB memory-mapped I/O
+    conn.execute("PRAGMA cache_size = -32000;")     # 32MB RAM page cache
+    conn.execute("PRAGMA temp_store = MEMORY;")     # In-memory temporary tables & sorts
+    conn.execute("PRAGMA foreign_keys = ON;")
     return conn
 
 
@@ -27,7 +29,9 @@ def get_db() -> Generator[sqlite3.Connection, None, None]:
 
 
 def _migrate(conn: sqlite3.Connection):
-    """Safe schema migrations: add new columns/tables without touching existing data."""
+    """Safe schema migrations: add new columns/tables/indexes without touching existing data."""
+    conn.execute("PRAGMA journal_mode=WAL;")
+
     # --- vocabulary_cards new columns ---
     existing_cols = {
         row[1] for row in conn.execute("PRAGMA table_info(vocabulary_cards)").fetchall()
@@ -61,9 +65,6 @@ def _migrate(conn: sqlite3.Connection):
     );
     """)
 
-    conn.execute("CREATE INDEX IF NOT EXISTS idx_srs_user ON srs_logs(user_id);")
-    conn.execute("CREATE INDEX IF NOT EXISTS idx_srs_reviewed ON srs_logs(user_id, reviewed_at);")
-
     # Ensure books table exists
     conn.execute("""
     CREATE TABLE IF NOT EXISTS books (
@@ -81,7 +82,6 @@ def _migrate(conn: sqlite3.Connection):
         FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
     );
     """)
-    conn.execute("CREATE INDEX IF NOT EXISTS idx_books_user ON books(user_id);")
 
     # --- Deduplicate vocabulary_cards (case-insensitive) and enforce UNIQUE index ---
     dup_rows = conn.execute("""
@@ -148,14 +148,37 @@ def _migrate(conn: sqlite3.Connection):
             ),
         )
 
+    # Composite and single column indexes for high-speed queries
     conn.execute(
         "CREATE UNIQUE INDEX IF NOT EXISTS idx_vocab_user_term_nocase ON vocabulary_cards(user_id, term COLLATE NOCASE);"
     )
+    conn.execute(
+        "CREATE INDEX IF NOT EXISTS idx_vocab_user_created ON vocabulary_cards(user_id, created_at DESC);"
+    )
+    conn.execute(
+        "CREATE INDEX IF NOT EXISTS idx_vocab_user_srs_state ON vocabulary_cards(user_id, srs_state, srs_next_review);"
+    )
+    conn.execute(
+        "CREATE INDEX IF NOT EXISTS idx_vocab_user_srs_created ON vocabulary_cards(user_id, srs_state, created_at DESC);"
+    )
+    conn.execute(
+        "CREATE INDEX IF NOT EXISTS idx_vocab_collection ON vocabulary_cards(user_id, collection);"
+    )
+
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_srs_user ON srs_logs(user_id);")
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_srs_reviewed ON srs_logs(user_id, reviewed_at);")
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_srs_card ON srs_logs(card_id);")
+
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_books_user ON books(user_id);")
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_books_user_updated ON books(user_id, updated_at DESC);")
+
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_sessions_user ON sessions(user_id);")
 
 
 def init_db():
     config.DB_PATH.parent.mkdir(parents=True, exist_ok=True)
     with get_db() as conn:
+        conn.execute("PRAGMA journal_mode=WAL;")
         conn.executescript("""
         CREATE TABLE IF NOT EXISTS users (
             id INTEGER PRIMARY KEY AUTOINCREMENT,
@@ -174,6 +197,7 @@ def init_db():
             ip TEXT,
             FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
         );
+        CREATE INDEX IF NOT EXISTS idx_sessions_user ON sessions(user_id);
 
         CREATE TABLE IF NOT EXISTS vocabulary_cards (
             id INTEGER PRIMARY KEY AUTOINCREMENT,
@@ -202,9 +226,12 @@ def init_db():
 
         CREATE INDEX IF NOT EXISTS idx_vocab_user ON vocabulary_cards(user_id);
         CREATE INDEX IF NOT EXISTS idx_vocab_term ON vocabulary_cards(term);
-        CREATE INDEX IF NOT EXISTS idx_vocab_created ON vocabulary_cards(created_at DESC);
+        CREATE INDEX IF NOT EXISTS idx_vocab_user_created ON vocabulary_cards(user_id, created_at DESC);
         CREATE INDEX IF NOT EXISTS idx_vocab_collection ON vocabulary_cards(user_id, collection);
         CREATE INDEX IF NOT EXISTS idx_vocab_srs_queue ON vocabulary_cards(user_id, srs_next_review, srs_state);
+        CREATE INDEX IF NOT EXISTS idx_vocab_user_srs_state ON vocabulary_cards(user_id, srs_state, srs_next_review);
+        CREATE INDEX IF NOT EXISTS idx_vocab_user_srs_created ON vocabulary_cards(user_id, srs_state, created_at DESC);
+        CREATE UNIQUE INDEX IF NOT EXISTS idx_vocab_user_term_nocase ON vocabulary_cards(user_id, term COLLATE NOCASE);
 
         CREATE TABLE IF NOT EXISTS srs_logs (
             id INTEGER PRIMARY KEY AUTOINCREMENT,
@@ -220,6 +247,7 @@ def init_db():
 
         CREATE INDEX IF NOT EXISTS idx_srs_user ON srs_logs(user_id);
         CREATE INDEX IF NOT EXISTS idx_srs_reviewed ON srs_logs(user_id, reviewed_at);
+        CREATE INDEX IF NOT EXISTS idx_srs_card ON srs_logs(card_id);
 
         CREATE TABLE IF NOT EXISTS dictionary_cache (
             query TEXT PRIMARY KEY COLLATE NOCASE,
@@ -232,7 +260,7 @@ def init_db():
             user_id INTEGER NOT NULL,
             title TEXT NOT NULL,
             author TEXT DEFAULT '',
-            source_type TEXT NOT NULL, -- 'epub', 'txt', 'md', 'text'
+            source_type TEXT NOT NULL, -- 'epub', 'txt', 'md', 'text', 'pdf'
             chapters_json TEXT NOT NULL, -- JSON array: [{"title": "Chapter 1", "content": "..."}]
             current_chapter INTEGER DEFAULT 0,
             current_position REAL DEFAULT 0,
@@ -242,6 +270,7 @@ def init_db():
             FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
         );
         CREATE INDEX IF NOT EXISTS idx_books_user ON books(user_id);
+        CREATE INDEX IF NOT EXISTS idx_books_user_updated ON books(user_id, updated_at DESC);
         """)
         # Apply migrations for pre-existing databases
         _migrate(conn)