Question

I’m trying to optimise the following query in wordpress, as it takes nearly a minute and a half to return a result. The table relationships are expressed in the following diagram:

SELECT SQL_CALC_FOUND_ROWS wp_posts . *
    FROM wp_posts
       INNER JOIN wp_term_relationships 
        ON (wp_posts.ID = wp_term_relationships.object_id)
       INNER JOIN wp_term_relationships AS tt1 
        ON (wp_posts.ID = tt1.object_id)
       INNER JOIN wp_term_relationships AS tt2 
        ON (wp_posts.ID = tt2.object_id)
       INNER JOIN wp_term_relationships AS tt3 
        ON (wp_posts.ID = tt3.object_id)
       INNER JOIN wp_term_relationships AS tt4 
        ON (wp_posts.ID = tt4.object_id)
    WHERE 1 = 1
        AND (
            wp_term_relationships.term_taxonomy_id IN (25) 
            OR tt1.term_taxonomy_id IN (26) 
            OR tt2.term_taxonomy_id IN (16) 
            OR tt3.term_taxonomy_id IN (17) 
            OR tt4.term_taxonomy_id IN (18)
        ) 
        AND wp_posts.post_type IN ('product') 
        AND (wp_posts.post_status = 'publish')
    GROUP BY wp_posts.ID
    ORDER BY wp_posts.post_title ASC
    LIMIT 0 , 15

Answer 1

I don’t understand the point of all the inner joins on the wp_term_relationships table when all it appears you’re doing is looking for a series of values. Wouldn’t the following perform the same and execute much faster?

SELECT SQL_CALC_FOUND_ROWS wp_posts . *
    FROM wp_posts
       INNER JOIN wp_term_relationships 
        ON (wp_posts.ID = wp_term_relationships.object_id)
    WHERE wp_term_relationships.term_taxonomy_id IN (25, 26, 16, 17, 18) 
        AND wp_posts.post_type = 'product' 
        AND wp_posts.post_status = 'publish'
    GROUP BY wp_posts.ID
    ORDER BY wp_posts.post_title ASC
    LIMIT 0 , 15