TYPO3 Core

A problem arises, if MM relations are changed by a TCE-form (handled by class.t3lib_tcemain.php) and the resulting count of relations stays the same (eg change of sorting or removing n relations and adding n relations).

If the count stays the same, the field counting the number of relations (for example a TCA selectbox with MM relations) will not be updated since the values are considered to be the same - and they are indeed, but there might have been a change in the MM table which isn't considered when checking if updatedb should be performed and consequently caches are cleared.

Without more drastic chances in mind, I'd suggest to not perform the so called "similarity" check in class.t3lib_tcemain.php for TCA fields being configured as foreign_table with MM; therefore those fields will always get updated.

This certainly isn't the most efficient way to solve this but at least removes potential erratic behaviour which is quite hard to track down... just changing the sorting within such fields eg won't affect any cache clearing.

Patch against class.t3lib_tcemain.php of 4.1.0RC2

(issue imported from #M5184)