[TYPO3-core] RFC: Bug #13508: Use exec_TRUNCATETABLEquery() instead of DELETE FROM throughout the core

[Christian Kuhn]

This is an SVN patch request.

Type: Bugfix / Performance improvement

BT: http://bugs.typo3.org/view.php?id=13508

Branch: trunk

Problem:
Thanks to #13504 we now have a dbal compatible way of truncating tables. 
mysql handles this much more efficiently than delete from.

Solution:
Use this new API method core wide where DELETE FROM with an empty WHERE 
is called.

Notes:
- There is a nice performance improvement for the clearing of cache 
tables (if not using caching framework, which already did a direct 
TRUNCATE), especially if they are filled with hundreds of thousands of 
records on a system under load. mysql "truncate" is way faster than 
"delete from", especially on innodb where concurrent queries where 
usually stuck because of innodb's transaction capabilities.

- Warning: In comparison to delete, truncate does (!) reset the 
auto_increment value to zero. Because of this I'm currently not 100% 
sure about the two hunks in 
typo3/sysext/extbase/Classes/Utility/Cache.php and the second hunk in 
typo3/sysext/install/mod/class.tx_install.php. Please review carefully.

Thanks
Christian
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