[AST] Support MySQL locking clauses (FOR UPDATE, SKIP LOCKED, etc.)

tests/WP_SQLite_Driver_Tests.php

@@ -7380,6 +7380,22 @@ public function testUpdateWithJoinComplexQuery(): void {
 		);
 	}
 
+	public function testLockingClauses() {
+		$this->engine->query( "INSERT INTO _options (option_name, option_value) VALUES ('test_lock', '1')" );
+
+		// Test FOR UPDATE
+		$res = $this->engine->query( "SELECT option_value FROM _options WHERE option_name = 'test_lock' FOR UPDATE" );
+		$this->assertEquals( '1', $res[0]->option_value );
+
+		// Test LOCK IN SHARE MODE
+		$res = $this->engine->query( "SELECT option_value FROM _options WHERE option_name = 'test_lock' LOCK IN SHARE MODE" );
+		$this->assertEquals( '1', $res[0]->option_value );
+
+		// Test multiple clauses
+		$res = $this->engine->query( "SELECT option_value FROM _options WHERE option_name = 'test_lock' FOR UPDATE SKIP LOCKED" );
+		$this->assertEquals( '1', $res[0]->option_value );
+	}
+
 	public function testBinaryLiterals(): void {
 		$result = $this->assertQuery( 'SELECT 0b0100000101111010' );
 		$this->assertEquals( array( (object) array( '0b0100000101111010' => 'Az' ) ), $result );

wp-includes/sqlite-ast/class-wp-pdo-mysql-on-sqlite.php

@@ -3808,8 +3808,10 @@ private function translate( $node ): ?string {
 			case 'indexHintList':
 				return null;
 			case 'lockingClause':
-				// SQLite doesn't support locking clauses (SELECT ... FOR UPDATE).
-				// They are not needed in SQLite due to the database file locking.
+				// MySQL locking clauses (e.g., SELECT ... FOR UPDATE) are not supported in SQLite.
+				// We omit them for syntax compatibility. While this doesn't preserve row-level
+				// locking semantics, SQLite's database-level locking is sufficient for
+				// typical WordPress workloads.
 				return null;
 			default:
 				return $this->translate_sequence( $node->get_children() );