Pavan Deolasee <pavan.deola...@gmail.com> writes: > I first thought that analyze and vacuum can not run concurrently on the same > table since they take a conflicting lock on the table. So even if we ignore > the analyze process while calculating the OldestXmin for vacuum, we should > be fine since we know they are working on different tables. But I see > analyze also acquires sample rows from the inherited tables with a > non-conflicting lock. I probably do not understand the analyze code well, > but is that the reason why we can't ignore analyze snapshot while > determining OldestXmin for vacuum ?
The reason why we can't ignore that snapshot is that it's being set for the use of user-defined functions, which might do practically anything. They definitely could access tables other than the one under analysis. (I believe that PostGIS does such things, for example --- it wants to look at its auxiliary tables for metadata.) Also keep in mind that we allow ANALYZE to be run inside a transaction block, which might contain other operations sharing the same snapshot. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers