Question

I have a project where the admin needs to create multiple newsletters with some crawled posts from the web.

I insert the posts in posts table after crawling has completed and assign them a feed_id to identify the source. this is the structure of posts table (truncated):

CREATE TABLE `posts` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `feed_id` int(11) NOT NULL,
  `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `updated_at` timestamp NULL DEFAULT NULL,
  `identifier` varchar(255) DEFAULT NULL,
  `published` timestamp NULL DEFAULT NULL,
  `content` longtext,
  ...
  ...
  `is_unread` int(1) NOT NULL DEFAULT '1',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Every admin (user) has access to one or more “feeds”. So in Newsletter creation page I want to show them a list of posts from the feeds they are allowed to see and also, I show a button to put the posts in specifict categories of that newsletter, if the user previously selected that post, I should show him that and let him remove it from the category. So I have some other tables too: newsletters, categories, newsletter_post, category_post. Here is their structures:

newsletters:

CREATE TABLE `newsletters` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `updated_at` timestamp NULL DEFAULT NULL,
  `sent_at` timestamp NULL DEFAULT NULL,
  `title` varchar(255) DEFAULT NULL,
  `date` date DEFAULT NULL,
  `topic_id` int(11) NOT NULL,
  `user_id` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

categories:

CREATE TABLE `categories` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `topic_id` int(11) NOT NULL,
  `title` varchar(255) DEFAULT NULL,
  `slug` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

newsletter_post:

CREATE TABLE `newsletter_post` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `updated_at` timestamp NULL DEFAULT NULL,
  `newsletter_id` int(11) NOT NULL,
  `post_id` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

category_post:

CREATE TABLE `category_post` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `updated_at` timestamp NULL DEFAULT NULL,
  `category_id` int(11) NOT NULL,
  `post_id` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

So I’m using this query to find posts for the allowed feeds and check the status if a post is in a specific category of this specific newsletter:

SELECT DISTINCT `posts`.`id`, `published`, `posts`.`title`, `posts`.`content`, `source_name`, `category_id`, `newsletter_id`, `link_href`, categories.title as category_title
FROM `posts`
LEFT JOIN `category_post` ON `posts`.`id` = `category_post`.`post_id`
LEFT JOIN `categories` ON `categories`.`id` = `category_post`.`category_id`
LEFT JOIN `newsletter_post` ON `posts`.`id` = `newsletter_post`.`post_id`
LEFT JOIN `newsletters` ON `newsletters`.`id` = `newsletter_post`.`newsletter_id`
WHERE `feed_id` IN (6, 7) ORDER BY `posts`.`published` DESC LIMIT 40 OFFSET 0

but the problem is this is horrible and not optimized. My posts table contains up to 50,000 rows each month, and each row with 3~10kbs of data in avg., so sometimes when I try to run the query (which is frequently run by the admin to make the newsletter, pagination etc) mysql shows this error: too much rows to join, etc. and most of the times its really slow.

and the reason I’m doing all this in one query is because I want the result to be in one json response so I can show them the user quickly without doing additional requests.

I wanna know if there is a better way to do this query or use indexes or something else.
Thanks you in advance for your help.

Answer 1

index your posts table on

( feed_id, published )

so the data is already optimized for your WHERE clause, and pre-sorted to help your ORDER BY.