Howto shrink large piwik_archive_blob_####_## tables

My piwik_archive_blob_####_## tables are usually about 100 to 150 Mb in size.
I recently noticed that the piwik_archive_blob_2011_01 and piwik_archive_blob_2011_04 tables were unusually large, one about 800 Mb and the other about 900 Mb.

I was able to shrink them to a size of 150 Mb and 270 Mb using the MySql Command “optimize table piwik_archive_blob_####_##”

Thanks for that pointer. Even after deleting and recreating the blob and archive tables yesterday I was able to shrink some of them to half of their sizes.

Does this command have any negative side effects? What about including it into archive.sh script?

It should already be the case via scheduled tasks, see http://dev.piwik.org/trac/browser/tags/1.4/plugins/CoreAdminHome/CoreAdminHome.php#L39

I have auto archiving set up but the first and actual month archives still have a great potential for optimisation after the cron job ran. See attached screenshots. When is the scheduled optimisation supposed to run?