wikimedia / mediawiki

		return $this->relationExists( $sequence, 'S', $schema );

	}

	public function triggerExists( $table, $trigger ) {

		$q = <<<SQL

	SELECT 1 FROM pg_class, pg_namespace, pg_trigger

		WHERE relnamespace=pg_namespace.oid AND relkind='r'

			  AND tgrelid=pg_class.oid

			  AND nspname=%s AND relname=%s AND tgname=%s

SQL;

		$res = $this->query(

			sprintf(

				$q,

				$this->addQuotes( $this->getCoreSchema() ),

				$this->addQuotes( $table ),

				$this->addQuotes( $trigger )

			)

		);

		if ( !$res ) {

			return null;

		}

		$rows = $res->numRows();

		return $rows;

	}

	public function ruleExists( $table, $rule ) {

		$exists = $this->selectField( 'pg_rules', 'rulename',

		return $exists === $rule;

	}

	public function constraintExists( $table, $constraint ) {

		$sql = sprintf( "SELECT 1 FROM information_schema.table_constraints " .

			"WHERE constraint_schema = %s AND table_name = %s AND constraint_name = %s",

			$this->addQuotes( $this->getCoreSchema() ),

			$this->addQuotes( $table ),

			$this->addQuotes( $constraint )

		);

		$res = $this->query( $sql );

		if ( !$res ) {

			return null;

		}

		$rows = $res->numRows();

		return $rows;

	}

	/**

	 * Query whether a given schema exists. Returns true if it does, false if it doesn't.