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WordPress assorted database clean up SQL queries.

WordPress database clean up queries

Orphan rows

Since WordPress uses MyISAM for it's storage engine, we don't get foreign keys relationships as offered by InnoDB/etc. - thus orphan rows can show themselves over time.

wp_posts -> wp_posts (parent/child)

SELECT * FROM wp_posts
LEFT JOIN wp_posts child ON (wp_posts.post_parent = child.ID)
WHERE (wp_posts.post_parent <> 0) AND (child.ID IS NULL)

DELETE wp_posts FROM wp_posts
LEFT JOIN wp_posts child ON (wp_posts.post_parent = child.ID)
WHERE (wp_posts.post_parent <> 0) AND (child.ID IS NULL)

wp_postmeta -> wp_posts

SELECT * FROM wp_postmeta
LEFT JOIN wp_posts ON (wp_postmeta.post_id = wp_posts.ID)
WHERE (wp_posts.ID IS NULL)

DELETE wp_postmeta FROM wp_postmeta
LEFT JOIN wp_posts ON (wp_postmeta.post_id = wp_posts.ID)
WHERE (wp_posts.ID IS NULL)

wp_term_taxonomy -> wp_terms

SELECT * FROM wp_term_taxonomy
LEFT JOIN wp_terms ON (wp_term_taxonomy.term_id = wp_terms.term_id)
WHERE (wp_terms.term_id IS NULL)

DELETE wp_term_taxonomy FROM wp_term_taxonomy
LEFT JOIN wp_terms ON (wp_term_taxonomy.term_id = wp_terms.term_id)
WHERE (wp_terms.term_id IS NULL)

wp_term_relationships -> wp_term_taxonomy

SELECT * FROM wp_term_relationships
LEFT JOIN wp_term_taxonomy
	ON (wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id)
WHERE (wp_term_taxonomy.term_taxonomy_id IS NULL)

DELETE wp_term_relationships FROM wp_term_relationships
LEFT JOIN wp_term_taxonomy
	ON (wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id)
WHERE (wp_term_taxonomy.term_taxonomy_id IS NULL)

wp_usermeta -> wp_users

SELECT * FROM wp_usermeta
LEFT JOIN wp_users ON (wp_usermeta.user_id = wp_users.ID)
WHERE (wp_users.ID IS NULL)

DELETE wp_usermeta FROM wp_usermeta
LEFT JOIN wp_users ON (wp_usermeta.user_id = wp_users.ID)
WHERE (wp_users.ID IS NULL)

wp_posts -> wp_users

SELECT * FROM wp_posts
LEFT JOIN wp_users ON (wp_posts.post_author = wp_users.ID)
WHERE (wp_users.ID IS NULL)

DELETE wp_posts FROM wp_posts
LEFT JOIN wp_users ON (wp_posts.post_author = wp_users.ID)
WHERE (wp_users.ID IS NULL)

Other

wp_postmeta dupes

Checking for dupe _wp_attached_file / _wp_attachment_metadata keys (should only ever be one each per attachment post type).

SELECT post_id,meta_key,meta_value
FROM wp_postmeta
WHERE (meta_key IN('_wp_attached_file','_wp_attachment_metadata'))
GROUP BY post_id,meta_key
HAVING (COUNT(post_id) > 1)

wp_postmeta dupes #2

Where an identical meta_key exists for the same post more than once.

SELECT *,COUNT(*) AS keycount
FROM wp_postmeta
GROUP BY post_id,meta_key
HAVING (COUNT(*) > 1)

DELETE FROM wp_postmeta
WHERE (meta_id IN (
	SELECT * FROM (
		SELECT meta_id
		FROM wp_postmeta tmp
		GROUP BY post_id,meta_key
		HAVING (COUNT(*) > 1)
	) AS tmp
))

wp_postmeta missing

Checking for missing _wp_attached_file / _wp_attachment_metadata keys on wp_posts.post_type = 'attachment' rows.

SELECT * FROM wp_posts
LEFT JOIN wp_postmeta ON (
	(wp_posts.ID = wp_postmeta.post_id) AND
	(wp_postmeta.meta_key = '_wp_attached_file')
)
WHERE (wp_posts.post_type = 'attachment') AND (wp_postmeta.meta_id IS NULL)

SELECT * FROM wp_posts
LEFT JOIN wp_postmeta ON (
	(wp_posts.ID = wp_postmeta.post_id) AND
	(wp_postmeta.meta_key = '_wp_attachment_metadata')
)
WHERE (wp_posts.post_type = 'attachment') AND (wp_postmeta.meta_id IS NULL)

wp_postmeta '_edit_lock' and '_edit_last' rows

Rows created against a post when edited by a WordPress admin user. They can be safely removed.

SELECT * FROM wp_postmeta
WHERE meta_key IN ('_edit_lock','_edit_last')

DELETE FROM wp_postmeta
WHERE meta_key IN ('_edit_lock','_edit_last')

wp_options 'transient' rows

A transient value is one stored by WordPress and/or a plugin generated from a complex query - basically a cache. More information can be found in this answer on Stack Overflow.

SELECT * FROM wp_options
WHERE option_name LIKE '%\_transient\_%'

DELETE FROM wp_options
WHERE option_name LIKE '%\_transient\_%'

wp_posts revisions

Every save of a WordPress post will create a new revision (and related wp_postmeta rows). To clear out all revisions older than 15 days:

SELECT * FROM wp_posts
WHERE
	(post_type = 'revision') AND
	(post_modified_gmt < DATE_SUB(NOW(),INTERVAL 15 DAY))
ORDER BY post_modified_gmt DESC

DELETE FROM wp_posts
WHERE
	(post_type = 'revision') AND
	(post_modified_gmt < DATE_SUB(NOW(),INTERVAL 15 DAY))

You may need to run the wp_postmeta -> wp_posts orphans query after cleaning up revisions.

@markjaquith

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markjaquith commented Sep 17, 2018

These are incredibly useful. Thank you!

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