Excerpts from Bruce Momjian's message of jue ago 16 11:24:55 -0400 2012: > On Mon, Oct 17, 2011 at 08:38:18PM +0100, Simon Riggs wrote: > > On Mon, Oct 17, 2011 at 8:03 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > > > Alvaro Herrera <alvhe...@alvh.no-ip.org> writes: > > >> I just noticed that HeapTupleHeaderAdvanceLatestRemovedXid is comparing > > >> Xmax as a TransactionId without verifying whether it is a multixact or > > >> not. Since they advance separately, this could lead to bogus answers. > > >> This probably needs to be fixed. I didn't look into past releases to > > >> see if there's a live released bug here or not. > > > > > >> I think the fix is simply to ignore the Xmax if the HEAP_XMAX_IS_MULTI > > >> bit is set. > > > > > >> Additionally I think it should check HEAP_XMAX_INVALID before reading > > >> the Xmax at all. > > > > > > If it's failing to even check XMAX_INVALID, surely it's completely > > > broken? Perhaps it assumes its caller has checked all this? > > > > HeapTupleHeaderAdvanceLatestRemovedXid() is only ever called when > > HeapTupleSatisfiesVacuum() returns HEAPTUPLE_DEAD, which only happens > > when HEAP_XMAX_IS_MULTI is not set. > > > > I'll add an assert to check this and a comment to explain. > > Was this completed?
As far as I recall, there are changes related to this in my fklocks patch. I am hoping to have some review happen on it during the upcoming commitfest (which presumably means I need to do a merge to newer sources.) -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
