I fixed it.
Per Camponez's suggestion, I ran update.php on a test version of the site and that fixed the bloat there. So I ran update.php on production Teflpedia site also. It cleared the objectcache table, which had grown to 743 MB, back to zero which brings the database back down to expected size. The database is now 148 MB instead of 933 MB. I think I will routinely run update.php before backing up the database from now on and that should take care of it.
I suspect this bit in LocalSettings.php, which sets $wgMainCacheType to CACHE_DB, may have started this cache bloat building back in February 2012:
## Shared memory settings # Roger 21 Feb 2012 comments out original line below to try another value # so that 3rd badlogin will trigger ConfirmEdit captcha #$wgMainCacheType = CACHE_NONE; $wgMainCacheType = CACHE_DB; // yea! badlogin trigger works with this $wgMemCachedServers = array();
It appears that using the database as a chache works fine, as long as I clear the cache from time to time. Running update.php once a month as part of my backup routine will do the job I think. Unless someone points me at a better way.
Thank you everyone for your replies and tips!
Once again, Mediawiki-l shines.
Roger :-)