On Fri, Nov 6, 2020 at 4:54 PM Thomas Munro <thomas.mu...@gmail.com> wrote:
> On Fri, Nov 6, 2020 at 9:48 PM Andy Fan <zhihui.fan1...@gmail.com> wrote: > > I have 2 ideas about this. One is in the Read Committed level, we can > advance xmin > > aggressively. suppose it started at t1, and complete a query at t2. the > xmin should > > be t1 currently. Can we advance the xmin to t2 since it is read > committed level, > > The data older than t2 will never be used? Another one is can we force > to clean > > up the old tuples which are older than xxx? If users want to access > that, > > we can just raise errors. Oracle uses this strategy and the error code > is > > ORA-01555. > > Hi Andy, > > For the second idea, we have old_snapshot_threshold which does exactly > that since 9.6. There have been some questions about whether it works > correctly, though: see https://commitfest.postgresql.org/30/2682/ if > you would like to help look into that :-) > Hi Tomas: This is exactly what I want and I have big interest with that. Thanks for the information! -- Best Regards Andy Fan
