[support] info about caching

[Larry Garfield]

On Wednesday 24 September 2008 2:12:18 pm Simone Dal Maso wrote:
> Hi,
> I've a problem.
> I changed my server and I backup and restore my drupal site. The only
> problem I have is that new contents for anonymous users are not presented
> in homepage. If I login with the admin account I can see it normally. I
> disabled chaching of pages but the problem remains.
> Do you think that I should drop the cache tables? There are some tables
> llike cache, cacheviews etc, can I remove them without problems? thanks in
> advance.

Dropping a table means removing it from the system.  Don't do that.  Things 
will break.  A lot. :-)

Under normal circumstances Drupal should be fairly smart about clearing the 
cache when it needs to.  When restoring from a backup, however, you're not 
dealing with normal circumstances.

If you're on Drupal 6, then on the admin/settings/performance page is a big 
button that says "clear all caches".  Put it to good use.  If you're on 
Drupal 5, then the devel module provides a block with a link that will do 
that for you.

In either case, it should always be safe to TRUNCATE (not DROP) the cache 
tables, that is, any table that begins with "cache".  The query "TRUNCATE 
cache" will delete all records in the cache table.  That should always be 
safe to do to any cache table unless some module has done something 
incredibly stupid.  One caveat, don't remove just part of the table this way.  
Some cache systems will only regenerate themselves if the entire table is 
empty, but will regenerate.  So just go ahead and clear the whole table.

-- 
Larry Garfield
larry at garfieldtech.com