Question

Just curious if it’s possible to make this query any faster? or if there is any other similar queries that would work better?

SELECT id,source FROM posts
WHERE id = ANY(SELECT image_id FROM `post_tags` WHERE tag_id = (SELECT id FROM `tags` WHERE tag = _utf8 '$TAG' collate utf8_bin))
  AND posts.exists = 'n'
ORDER BY posts.ratecount DESC
LIMIT 0,100

Without using the:

  AND posts.exists = 'n'
ORDER BY posts.ratecount
DESC LIMIT 0,100

It speeds up to query to usable levels, but somewhat need this for what I’m doing.

• Tags table has unique index for both ‘tag’ and ‘id’.
• Tags has 83K rows.
• Post_tags has unique index for ‘image_id’, ‘tag_id’. Also normal index for each.
• Post_tags has 471K rows.
• Posts has unique index for ‘id’. Also normal index for ‘exists’ and ‘ratecount’.
• Posts table has about 1.1M rows.

Answer 1

Managed to get it working using a JOIN as someone suggested.

SELECT * FROM posts
LEFT JOIN post_tags ON post_tags.image_id = posts.id
JOIN tags ON post_tags.tag_id = tags.id
WHERE tags.tag = _utf8 '$tag' collate utf8_bin
  AND posts.exists = 'n'
ORDER BY posts.ratecount DESC
LIMIT 0,100

Reduced time taken from 22s > 0.26s.