Hi, On 2025-07-11 14:03:42 +0300, Nikita Malakhov wrote: > It's a pity I missed this thread when you developed the patch. > I've developed a feature recently and discovered that SeqScan > does not make use of scan keys, and there is a Tom Lane's > comment regarding this: > * Note that unlike IndexScan, SeqScan never use keys in heap_beginscan > * (and this is very bad) - so, here we do not check are keys ok or not. > > Have you considered passing scan keys like it is done in IndexScan?
You can't easily do that without causing issues: 1) ScanKeys are evaluated while holding a buffer lock, we shouldn't do that with arbitrary functions (since they could recurse and acquire other locks in a non-correct order) 2) ScanKeys are rather restrictive in what they can express, but not restrictive enough to make 1) not a problem. That means that you can't just evaluate the whole predicate using ScanKeys. 3) ScanKey evaluation is actually sometimes *more* expensive than expression evaluation, because the columns are deformed one-by-one. Greetings, Andres Freund
