On Thu, Jul 17, 2025 at 7:27 PM Mihail Nikalayeu <mihailnikala...@gmail.com> wrote: > > FWIW _hash_readpage has a comment about a stashed LSN, so it seems as > > if this was barely missed by the work on hash indexes around 2017: > > I think commit 22c5e735 [0] (Remove lsn from HashScanPosData) is the > thing you are looking for in relation to hash.
Oh yeah, good catch. I wonder if this is already correct. It definitely *looks* wrong, because _hash_kill_items() is prepared to re-pin and then LP_DEAD-mark a page, without the LSN check that would make that safe. But it seems possible that that never actually happens -- maybe the HashScanPosIsPinned() check will invariably find that the page is already pinned (in which case commit 22c5e735 merely neglected to remove some dead code from _hash_kill_items, but was otherwise correct). Do you happen to recall anything about this, Robert and Amit? FWIW, I'm asking about this now because I want to switch index AMs that use amgettuple over to a new amgetbatch interface that enables index prefetching, with prefetch windows that can span multiple leaf pages. This involves moving management of buffer pins out of affected index AMs, and into a new layer that will decide when to release each index page buffer pin (and call _hash_kill_items-like routines) based on its own criteria. -- Peter Geoghegan
