Kevin Grittner wrote: > If you run `make installcheck` against a cluster with > default_transaction_isolation = 'repeatable read' you get one > failure:
So there's some code that's specifically intended to handle this case: /* * If using transaction-snapshot mode, it would be possible * for another transaction to insert a tuple that's not * visible to our snapshot if we have already acquired one, * when in snapshot-isolation mode; therefore, disallow this * from running in such a transaction unless a snapshot hasn't * been acquired yet. * * This code is called by VACUUM and * brin_summarize_new_values. Have the error message mention * the latter because VACUUM cannot run in a transaction and * thus cannot cause this issue. */ if (IsolationUsesXactSnapshot() && FirstSnapshotSet) ereport(ERROR, (errcode(ERRCODE_INVALID_TRANSACTION_STATE), errmsg("brin_summarize_new_values() cannot run in a transaction that has already obtained a snapshot"))); However, this comment is full of it because a snapshot is obtained even for VACUUM. So the fact that brin_summarize_new_values() is mentioned as being in trouble is just a very minor issue: fixing that would just be a matter of passing a flag down from the caller into summarize_range() to indicate whether it's vacuum or the function. The real problem is that VACUUM should be allowed to run without error. -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, 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