On Fri, 16 Dec 2016, 12:10 a.m. Sameer Kumar, <sameer.ku...@ashnik.com> wrote:
> Hi, > > I was wondering if there is some change in the way > max_standby_streaming_delay and hot_standby_feedback work in v9.5. > > Below is a scenario which I had built to test out something but the > behavior confused me. I would like to check if there is something/some > parameter which I am missing or if my understanding is wrong. > > I have a Standby Server with hot_standby_feedback set to off. > > My max_standby_streaming_delay is set to 30s. > > I started a transaction on standby with repeatable read isolation level. I > fired a select > > select count(*) from table_a; > > This gave me result 60000; > > I deleted a huge chunk of rows on Primary for table_a. > > I can see that autovaccum lauched an autovacuum and autoanalyze (going by > the timestamp in pg_stat_user_tables for table_a) after these deletes. For > a short period of time I also saw that pg_class.reltuples was reduced to a > smaller number (I think because of deletions). > > But when I checked again, pg_stat_user_tables on master revealed that > autovacuum has triggered a few times since the deletion for table_a. I also > noted that on master pg_class.reltuples are back to roughly 60000 (which > was the case before deletion). > > I thought if my hot_standby_feedback is off, I might face an issue with > rows being removed by vacuum. But that did not happen. Can someone help me > to understand how MVCC, autovacuum work with Streaming replication. > > I am running Postgresql 9.5.1 on CentOS 7.2 64bit. Pls let me know if I have missed any relevant imp detail. > > Regards > Sameer > -- > > -- > > Best Regards, > > *Sameer Kumar | DB Solution Architect* > > *ASHNIK PTE. LTD.* > > 101 Cecil Street, #11-11 Tong Eng Building, Singapore 069533 > > T: +65 6438 3504 | www.ashnik.com > > Skype: sameer.ashnik | T: +65 8110 0350 > > > [image: www.ashnik.com] <http://www.ashnik.com/> > -- -- Best Regards, *Sameer Kumar | DB Solution Architect* *ASHNIK PTE. LTD.* 101 Cecil Street, #11-11 Tong Eng Building, Singapore 069533 T: +65 6438 3504 | www.ashnik.com Skype: sameer.ashnik | T: +65 8110 0350 [image: www.ashnik.com] <http://www.ashnik.com/>
