The table that really growing is “wp_ commentmeta”. It contains mostly “akismet_result”, “akismet_history” & “akismet_as_submitted” meta key. These entries are created by akismet plugins in relation to spam comments. The entries will not get deleted even after all spam comments deleted permanently. There is a annoying bug in this plugin.
You can remove all Akismet’s CommentMeta data. However, remember to backup your database prior to removing these entries, so you can restore it if anything goes wrong.
Step1: Open PhpMyAdmin.
Step2: Checkout all Akismet data using select query
[code] SELECT * FROM wp_commentmeta WHERE meta_key
Step3: If you are fine with this data execute delete query.
[code] DELETE FROM wp_commentmeta WHERE meta_key