2006/4/14, Philippe Poelvoorde <[EMAIL PROTECTED]>:
> Hi,
>
> I have one table :
> CREATE TABLE `ressources_summary` (
> `res_type` tinyint(3) unsigned NOT NULL default '0',
> `res_id` int(10) unsigned NOT NULL default '0',
> `comment_count` smallint(5) unsigned NOT NULL default '0',
> `comment_last_timestamp` timestamp NOT NULL default '-00-00 00:00:00',
> `comment_last_user_id` int(11) NOT NULL default '0',
> PRIMARY KEY (`res_type`,`res_id`)
> ) ENGINE=MyISAM
>
> it gather summary on comments for any ressources (poll, articles,
> forums, admin). A ressource is uniquely identify by (res_type,
> res_id), the others columns are self-explanatory (I hope).
> I'm wondering about the efficiency of storing a comment_count of 0
> (and user_id=0, timestamp=0).
> There is comments on 20% of the ressources.
> What is the cost of looking for a row that does not exists in a table ?
> Would it be more efficient to only store summary for comment_count
> greater than 0 and knowing missing rows have a count of zero, or to
> store everything ?
I went for the version without all zeros. It dramatically reduce the
number of rows, and overall performances are better with this summary
table.
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