PHP SQL query slow? - php

Question

Here is my function which i am using to un-follow users.It first DELETE the relationship between users and all the notifications that are related to this relationship.Then it INSERT a new notification for user which we are going to un-follow and then UPDATE his followers count (as one follower has left).I am using multi_query and this query seems to be bit slower on large database and i want to know whether it's a good practice or not or is there is any more complex form of query to get the job done.
PHP Function
// 'By' is the array that hold logged user and 'followed' is the user id which we are going to unfollow
function unFollowUser($followed,$by) {
$following = $this->getUserByID($followed);// Return fetch_assoc of user row
if(!empty($following['idu'])) { // if user exists
// return user followers as number of rows
$followers = $this->db->real_escape_string($this->numberFollowers($following['idu'])) - 1;
$followed_esc = $this->db->real_escape_string($following['idu']);
$by_user_esc = $this->db->real_escape_string($by['idu']);
// delete relationship
$query = "DELETE FROM `relationships` WHERE `relationships`.`user2` = '$followed_esc' AND `relationships`.`user1` = '$by_user_esc' ;" ;
// delete notification (user started following you )
$query.= "DELETE FROM `notifications` WHERE `notifications`.`not_from` = '$by_user_esc' AND `notifications`.`not_to` = '$followed_esc' ;" ;
// Insert a new notification( user has unfollowed you)
$query.= "INSERT INTO `notifications`(`id`, `not_from`, `not_to`, `not_content_id`,`not_content`,`not_type`,`not_read`, `not_time`) VALUES (NULL, '$by_user_esc', '$followed_esc', '0','0','5','0', CURRENT_TIMESTAMP) ;" ;
// update user followers (-1)
$query .= "UPDATE `users` SET `followers` = '$followers' WHERE `users`.`idu` = '$followed_esc' ;" ;
if($this->db->multi_query($query) === TRUE) {
return 1;
} else {
return 0;
}
} else {
return 0;
}
}
Table structures
--
-- Table structure for table `notifications`
--
CREATE TABLE IF NOT EXISTS `notifications` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`not_from` int(11) NOT NULL,
`not_to` int(11) NOT NULL,
`not_content_id` int(11) NOT NULL,
`not_content` int(11) NOT NULL,
`not_type` int(11) NOT NULL,
`not_read` int(11) NOT NULL,
`not_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (`id`),
UNIQUE KEY `id` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
--
-- Table structure for table `relationships`
--
CREATE TABLE IF NOT EXISTS `relationships` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`user1` int(11) NOT NULL,
`user2` int(11) NOT NULL,
`status` int(11) NOT NULL,
`time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
--
-- Table structure for table `users`
--
CREATE TABLE IF NOT EXISTS `users` (
`idu` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(32) NOT NULL,
`password` varchar(256) NOT NULL,
`email` varchar(256) NOT NULL,
`first_name` varchar(32) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
`last_name` varchar(32) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
`verified` int(11) NOT NULL,
`posts` text CHARACTER SET utf32 NOT NULL,
`photos` text CHARACTER SET utf32 NOT NULL,
`followers` text CHARACTER SET utf32 NOT NULL,
UNIQUE KEY `id` (`idu`),
UNIQUE KEY `idu` (`idu`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Answer 1

In my testing, multi_query has been the fastest way to execute multiple different queries. Why do you feel it's running slow? Compared to what?
Anyway, improvements could come from adding indexes to some of the columns you search frequently:
relationships.users2
relationships.users1
notifications.not_from
notifications.not_to
users.idu
Adding indexes makes searching faster, but it has at least two downsides:
Makes the DB a lot more resource hungry, which could affect your server performance
Makes writing operations take longer
I don't see any problem with your current queries. Really consider whether the slow performance you're seeing comes from the DB queries themselves, or from the rest of your PHP process. Try measuring the script time with the queries, then skipping the queries and taking another measurement (you could hardcode query results). It will give you an idea of whether the slowness is attributable to something else.
Either way, benchmark.

Answer 2

Try creating index on user where deletes are running , this may speed up query