Need to clean up wp_postmeta database table WordPress

fuscata answers:

Do you have a lot of revisions?

SELECT COUNT(*) FROM `wp_posts` WHERE `post_type` = 'revision';

If so, you can <strong>back up your database</strong>, then delete them. See [[LINK href="http://www.ambrosite.com/blog/clean-up-wordpress-revisions-using-a-mysql-multi-table-delete"]]http://www.ambrosite.com/blog/clean-up-wordpress-revisions-using-a-mysql-multi-table-delete[[/LINK]]

If that doesn't work, you may need a better hosting plan, caching and/or to tweak MySQL settings. The "gone away" error is usually caused by MySQL hitting its connection limit.

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Navjot Singh answers:

You can use this query to delete postmeta values which are not attached to any posts:

<blockquote>DELETE pm
FROM wp_postmeta pm
LEFT JOIN wp_posts wp ON wp.ID = pm.post_id
WHERE wp.ID IS NULL</blockquote>

If you know of any custom key which was used by a plugin which you no longer use, you can run this query to remove it from table completely:

<blockquote>DELETE FROM wp_postmeta WHERE meta_key = 'your-meta-key';</blockquote>

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