On Sat, 2010-03-27 at 19:15 +0000, Greg Stark wrote: > On Sat, Mar 27, 2010 at 10:10 AM, Simon Riggs <si...@2ndquadrant.com> wrote: > > It appears that in practice many of the index items point to heap items > > that are LP_DEAD. So for the purposes of accessing a heap tuple's xmin, > > then we're both right. To the current purpose the tuple has been > > removed, though you are also right: its stub remains. > > If we're pruning an index entry to a heap tuple that has been HOT > pruned wouldn't the HOT pruning record have already conflicted with > any queries that could see it?
Quite probably, but a query that started after that record arrived might slip through. We have to treat each WAL record separately. Do you agree with the conjecture? That LP_DEAD items can be ignored because their xid would have been earlier than the latest LP_NORMAL tuple we find? (on any page). Or is a slightly less strong condition true: we can ignore LP_DEAD items on a page that is also referenced by an LP_NORMAL item. -- Simon Riggs www.2ndQuadrant.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
