Implement ALTER TABLE ... DROP FOREIGN KEY

Author: JanJakes

tests/WP_SQLite_Driver_Metadata_Tests.php

@@ -108,7 +108,12 @@ public function testUseStatement() {
 	}
 
 	private function assertQuery( $sql ) {
-		$retval = $this->engine->query( $sql );
+		try {
+			$retval = $this->engine->query( $sql );
+		} catch ( Exception $e ) {
+			var_dump( $this->engine->get_last_sqlite_queries() );
+			throw $e;
+		}
 		$this->assertNotFalse( $retval );
 		return $retval;
 	}
@@ -1567,4 +1572,56 @@ public function testInformationSchemaAlterTableAddForeignKeys(): void {
 			$result
 		);
 	}
+
+	public function testInformationSchemaAlterTableDropForeignKeys(): void {
+		$this->assertQuery( 'CREATE TABLE t1 (id INT PRIMARY KEY, name VARCHAR(255))' );
+		$this->assertQuery(
+			'CREATE TABLE t2 (
+				id INT,
+				t1_id INT REFERENCES t1 (id),
+				FOREIGN KEY (t1_id) REFERENCES t1 (id),
+				CONSTRAINT fk1 FOREIGN KEY (t1_id) REFERENCES t1 (id) ON DELETE CASCADE
+			)'
+		);
+
+		// INFORMATION_SCHEMA.TABLE_CONSTRAINTS
+		$result = $this->assertQuery( "SELECT * FROM information_schema.table_constraints WHERE table_name = 't2'" );
+		$this->assertCount( 3, $result );
+
+		// INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS
+		$result = $this->assertQuery( "SELECT * FROM information_schema.referential_constraints WHERE table_name = 't2'" );
+		$this->assertCount( 3, $result );
+
+		// INFORMATION_SCHEMA.KEY_COLUMN_USAGE
+		$result = $this->assertQuery( "SELECT * FROM information_schema.key_column_usage WHERE table_name = 't2'" );
+		$this->assertCount( 3, $result );
+
+		// SHOW CREATE TABLE
+		$result = $this->assertQuery( 'SHOW CREATE TABLE t2' );
+		$this->assertEquals(
+			array(
+				(object) array(
+					'Create Table' => implode(
+						"\n",
+						array(
+							'CREATE TABLE `t2` (',
+							'  `id` int DEFAULT NULL,',
+							'  `t1_id` int DEFAULT NULL,',
+							'  CONSTRAINT `fk1` FOREIGN KEY (`t1_id`) REFERENCES `t1` (`id`) ON DELETE CASCADE,',
+							'  CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`t1_id`) REFERENCES `t1` (`id`),',
+							'  CONSTRAINT `t2_ibfk_2` FOREIGN KEY (`t1_id`) REFERENCES `t1` (`id`)',
+							') ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci',
+						)
+					),
+				),
+			),
+			$result
+		);
+
+		// DROP FOREIGN KEY
+		$this->assertQuery( 'ALTER TABLE t2 DROP FOREIGN KEY fk1' );
+
+		$result = $this->assertQuery( "SELECT * FROM information_schema.table_constraints WHERE table_name = 't2'" );
+		$this->assertCount( 2, $result );
+	}
 }

wp-includes/sqlite-ast/class-wp-sqlite-information-schema-builder.php

@@ -640,6 +640,15 @@ public function record_alter_table( WP_Parser_Node $node ): void {
 
 			// DROP
 			if ( WP_MySQL_Lexer::DROP_SYMBOL === $first_token->id ) {
+				// DROP FOREIGN KEY
+				if ( $action->has_child_token( WP_MySQL_Lexer::FOREIGN_SYMBOL ) ) {
+					$field_identifier = $action->get_first_child_node( 'fieldIdentifier' );
+					$identifiers      = $field_identifier->get_descendant_nodes( 'identifier' );
+					$name             = $this->get_value( end( $identifiers ) );
+					$this->record_drop_foreign_key( $table_is_temporary, $table_name, $name );
+					continue;
+				}
+
 				// DROP [COLUMN]
 				$column_ref = $action->get_first_child_node( 'fieldIdentifier' );
 				if ( null !== $column_ref ) {
@@ -1209,6 +1218,46 @@ private function record_add_constraint(
 		}
 	}
 
+	/**
+	 * Analyze DROP FOREIGN KEY statement and record data in the information schema.
+	 *
+	 * @param bool   $table_is_temporary Whether the table is temporary.
+	 * @param string $table_name         The table name.
+	 * @param string $name               The foreign key name.
+	 */
+	private function record_drop_foreign_key(
+		bool $table_is_temporary,
+		string $table_name,
+		string $name
+	): void {
+		$this->delete_values(
+			$this->get_table_name( $table_is_temporary, 'table_constraints' ),
+			array(
+				'TABLE_SCHEMA' => $this->db_name,
+				'TABLE_NAME'   => $table_name,
+				'CONSTRAINT_NAME' => $name,
+			)
+		);
+
+		$this->delete_values(
+			$this->get_table_name( $table_is_temporary, 'referential_constraints' ),
+			array(
+				'CONSTRAINT_SCHEMA' => $this->db_name,
+				'TABLE_NAME'        => $table_name,
+				'CONSTRAINT_NAME'   => $name,
+			)
+		);
+
+		$this->delete_values(
+			$this->get_table_name( $table_is_temporary, 'key_column_usage' ),
+			array(
+				'TABLE_SCHEMA'    => $this->db_name,
+				'TABLE_NAME'      => $table_name,
+				'CONSTRAINT_NAME' => $name,
+			)
+		);
+	}
+
 	/**
 	 * Analyze "columnDefinition" or "fieldDefinition" AST node and extract column data.
 	 *