TYPO3 Core

Yeah. That's a limitation of DB engines, I think the magic number for mysql/maria is somewhere around 1000 placeholders.

The core stumbled upon this at various places already, and the solution was usually, to either split into multiple queries, or to not use placeholders in those cases.

In case you are walking into this with a query generated by core, this should probably be considered a core bug and should be fixed. Please point out the scenario where this is going wrong, if so.

In case that's a query generated by some of your extensions, or a third party extension, this should be changed in the affected extension (it's not a core issue, and this issue should be closed). As a kickstart, the core methods QueryBuilder->quoteArrayBasedValueListToIntegerList() and QueryBuilder->quoteArrayBasedValueListToStringList() can help in this area. Blaming the history of these methods and looking for usages should give some examples on how core solves the scenario. Be careful to get this right, though: If things are messed up, you're risking sql injection security issues.