On 2014-06-27 08:39:13 -0600, Ryan Johnson wrote: > On 27/06/2014 3:14 AM, Andres Freund wrote: > >On 2014-06-26 22:47:47 -0600, Ryan Johnson wrote: > >>Hi, > >> > >>As part of a research project, I'm trying to change Read Committed isolation > >>to use HeapTupleSatisfiesNow rather than acquiring a new snapshot at every > >>command [1]. Things appear to have gone reasonably well so far, except > >>certain queries fail with "ERROR: non-MVCC snapshots are not supported in > >>index-only scans." > >You're aware that unless you employ additional locking you can simply > >miss individual rows or see them several times because of concurrent > >updates? > >The reason it has worked (< 9.4) for system catalogs is that updates of > >rows were only performed while objects were locked access exclusively - > >that's the reason why some places in the code use inplace updates btw...
> Yes, I was aware of the need for locking. The documentation just made it > sound that locking was already in place for non-MVCC index scans. I was > hoping I'd missed some easy way to activate it. Well, it is/was for the places (i.e. DDL) that actually use non-MVCC scans. Greetings, Andres Freund -- Andres Freund 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
