On 2016-10-18 13:38:14 -0400, Tom Lane wrote: > Robert Haas <robertmh...@gmail.com> writes: > > On Tue, Oct 18, 2016 at 5:37 AM, Amit Kapila <amit.kapil...@gmail.com> > > wrote: > >> I have implemented this idea and it works for MVCC scans. However, I > >> think this might not work for non-MVCC scans. Consider a case where > >> in Process-1, hash scan has returned one row and before it could check > >> it's validity in heap, vacuum marks that tuple as dead and removed the > >> entry from heap and some new tuple has been placed at that offset in > >> heap. > > > Oops, that's bad. > > Do we care? Under what circumstances would a hash index be used for a > non-MVCC scan?
Uniqueness checks, are the most important one that comes to mind. Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
