ITAGAKI Takahiro wrote: > Tom Lane <[EMAIL PROTECTED]> wrote: > >> ITAGAKI Takahiro <[EMAIL PROTECTED]> writes: >>> Here is a trivial fix of locking issue in pgstattuple(). >> Hmm, is this really a bug, and if so how far back does it go? >> I'm thinking that having a pin on the buffer should be enough to >> call PageGetHeapFreeSpace. > > Hmm... we might use pd_upper and pd_lower at different times, > but the error is ok for pgstattuple purpose. > (It might be dangerous for tuple insertion, though.) > Inconsistent usage of locks is confusable -- remove them, please.
No I think the original patch was right. You can indeed read inconsistent values for pd_upper and pd_lower, though the window is very small. But a bigger issue is that in 8.3 PageGetHeapFreeSpace counts the used line pointers to see if MaxHeapTuplesPerPage has been reached, and I'm not convinced you can do that safely without holding a lock. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
