For the query above, the following recommendations will be helpful as part of the SQL tuning process. You'll find 3 sections below:
Description of the steps you can take to speed up the query.
The optimal indexes for this query, which you can copy and create in your database.
An automatically re-written query you can copy and execute in your database.
The optimization process and recommendations:
Avoid Selecting Unnecessary Columns (query line: 2): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
Avoid Selecting Unnecessary Columns (query line: 6): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.
Prefer Inner Join Over Left Join (modified query below): We identified that one or more left joined entities (e.g. `wp_terms`) are used in the 'where' clause, in a way that allows to replace it with an optimized inner join. Inner joins can be fully optimized by the database, while Left joins apply limitations on the database's optimizer.
Sort and Limit Before Joining (modified query below): In cases where the joins aren't filtering any rows, it's possible to sort and limit the amount of rows using a subquery in the FROM clause, before applying the joins to all other tables.
Optimal indexes for this query:
ALTER TABLE `wp_posts` ADD INDEX `wp_posts_idx_post_date` (`post_date`);
ALTER TABLE `wp_term_relationships` ADD INDEX `wp_relationships_idx_term_id` (`term_taxonomy_id`);
ALTER TABLE `wp_term_taxonomy` ADD INDEX `wp_taxonomy_idx_term_id` (`term_id`);
ALTER TABLE `wp_terms` ADD INDEX `wp_terms_idx_term_id` (`term_id`);
The optimized query:
p.ID AS p_ID
p.post_date DESC LIMIT 10) p
ON rel.object_id = p.p_ID
ON tax.term_taxonomy_id = rel.term_taxonomy_id
ON t.term_id = tax.term_id
t.term_id = 6 LIMIT 10