[TYPO3-core] RFC: Bug #11903: Use separate tables for tags in the caching framework

[Oliver Hader]

Hi Masi,

Martin Kutschker schrieb:
> For the SQL Server (and Oracle) I haven't found a way to get the job done in a single (nested)
> statement. So have to use two statements:
> 
> DELETE FROM table2
>  WHERE id IN
>   (SELECT table1.id
>    FROM table1 JOIN table2 ON (table1.id=table2.id)
>    WHERE table1.column1=value)
> DELETE FROM table1
>  WHERE table1.column1=value
> 
> But after writing this I wonder if the JOIN is really needed. What exactly is it that the caching
> framework is trying to do?

The tags are stored in the table "[cache]_tags" and select from that
table that has an identifier that is equal in the table "[cache]". The
caching framework tries to remove from both tables at once - thus,
clearing the tag references and the cached content.

Since there it seems that there is no common way to create these queries
it would be fine to use two DELETE queries with accordant subqueries.
It's important that selects are fast (using separate tags instead of
full table scan with LIKE "%tag%"), deletes could be a bit slower...

Then we would have something like this:

$TYPO3_DB->exec_DELETEquery(
  'cache',
  'identifier IN (' .
      $TYPO3_DB->SELECTquery(
        'identifier',
        'cache_tags',
        'tag = ' . $tag
      ) .
    ')'
);
$TYPO3_DB->exec_DELETEquery(
  'cache_tags',
  'tag = ' . $tag
);

What do you think?

olly
-- 
Oliver Hader
TYPO3 Release Manager 4.3