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Bug #89997

closed

Unnecessary fetching of duplicate records in Typo3DatabaseBackend

Added by Markus Klösges almost 5 years ago. Updated over 4 years ago.

Status:
Closed
Priority:
Should have
Assignee:
-
Category:
-
Target version:
-
Start date:
2019-12-19
Due date:
% Done:

100%

Estimated time:
TYPO3 Version:
10
PHP Version:
Tags:
Complexity:
Is Regression:
Sprint Focus:

Description

A (possible) bug in EXT:staticfilecache (reported at https://github.com/lochmueller/staticfilecache/issues/233) generates massive amounts of duplicated identifier entries in tables managed by the caching framework.

This revealed that the Typo3DatabaseBackend will fetch each and every identifier in there, just to deduplicate them in php-space afterwards.
That may lead to OutOfMemory-situations, where a massive amount of rows is fetched, to be thrown away again.

The DBMS is able to do that more efficiently using a DISTINCT/Group By. Note that most other functions in Typo3DatabaseBackend already use this method.

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