perf: optimize SQLite PRAGMAs for WAL mode

Author: Algorithm5838

backend/open_webui/internal/db.py

@@ -95,7 +95,17 @@ def create_sqlcipher_connection():
         import sqlcipher3
 
         conn = sqlcipher3.connect(db_path, check_same_thread=False)
+        # PRAGMA key must be set before any other statements
         conn.execute(f"PRAGMA key = '{database_password}'")
+        if DATABASE_ENABLE_SQLITE_WAL:
+            conn.execute('PRAGMA journal_mode=WAL')
+            conn.execute('PRAGMA synchronous=NORMAL')
+        else:
+            conn.execute('PRAGMA journal_mode=DELETE')
+            # leave synchronous=FULL (default) for durability without WAL
+        conn.execute('PRAGMA cache_size=-32000')
+        conn.execute('PRAGMA temp_store=MEMORY')
+        conn.execute('PRAGMA busy_timeout=5000')
         return conn
 
     # The dummy "sqlite://" URL would cause SQLAlchemy to auto-select
@@ -132,8 +142,13 @@ def on_connect(dbapi_connection, connection_record):
         cursor = dbapi_connection.cursor()
         if DATABASE_ENABLE_SQLITE_WAL:
             cursor.execute('PRAGMA journal_mode=WAL')
+            cursor.execute('PRAGMA synchronous=NORMAL')
         else:
             cursor.execute('PRAGMA journal_mode=DELETE')
+            # leave synchronous=FULL (default) for durability without WAL
+        cursor.execute('PRAGMA cache_size=-32000')
+        cursor.execute('PRAGMA temp_store=MEMORY')
+        cursor.execute('PRAGMA busy_timeout=5000')
         cursor.close()
 
     event.listen(engine, 'connect', on_connect)