On 2015-08-18 20:36:13 -0400, Tom Lane wrote: > I wrote: > > Just thinking about this ... I wonder why we need to call > > TransactionIdIsInProgress() at all rather than believing the answer from > > the snapshot? Under what circumstances could TransactionIdIsInProgress() > > return true where XidInMVCCSnapshot() had not? > > I experimented with the attached patch, which replaces > HeapTupleSatisfiesMVCC's calls of TransactionIdIsInProgress with > XidInMVCCSnapshot, and then as a cross-check has all the "return false" > exits from XidInMVCCSnapshot assert !TransactionIdIsInProgress().
I'm not sure about it, but it might be worthwhile to add a TransactionIdIsKnownCompleted() check before the more expensive parts of XidInMVCCSnapshot(). Neither the array search nor, much more so, the subtrans lookups are free. - Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
