Source

File: wp-includes/wp-db.php

private function _do_query( $query ) {
		if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES ) {
			$this->timer_start();
		}

		if ( ! empty( $this->dbh ) && $this->use_mysqli ) {
			$this->result = mysqli_query( $this->dbh, $query );
		} elseif ( ! empty( $this->dbh ) ) {
			$this->result = mysql_query( $query, $this->dbh );
		}
		$this->num_queries++;

		if ( defined( 'SAVEQUERIES' ) && SAVEQUERIES ) {
			$this->log_query(
				$query,
				$this->timer_stop(),
				$this->get_caller(),
				$this->time_start,
				array()
			);
		}
	}