Re: Performance Issue after upgrade from 9 to 11

On 1/29/20 1:58 PM, Perumal Raj wrote:
> Hi Tom /Adrian,
> 
> Issue is not specific to a table or particular Query. Also there is no 
> change in DB parameter after upgrade.

You obviously are seeing some difference, so pick a query and do an 
EXPLAIN ANALYZE on it. Without some actual performance data this issue 
is not going to be solved.

> 
> That the only way i can make it most of the the query to run as like 
> before upgrade.
> 
> Note:
> Some web reference says , Engine will take some time to adjust until it 
> runs autovacuum .

The above assumes you have not done a manual ANALYZE on the database, as 
ANALYZE is done as part of autovacuum.

> 
> 
> 
> 
> On Wed, Jan 29, 2020 at 10:22 AM Tom Lane <tgl@sss.pgh.pa.us 
> <mailto:tgl@sss.pgh.pa.us>> wrote:
> 
>     Perumal Raj <perucinci@gmail.com <mailto:perucinci@gmail.com>> writes:
>      > We have recently upgraded postgres from 9.2 to 11.6 and started
>     seeing
>      > performance issue immediately and  able to fix the performance
>     issue after
>      > disabling parameter: enable_seqscan.
>      > Question :
>      > Should i keep the above parameter always disabled ? If not why
>     the behavior
>      > changed in Higher version ?
> 
>     This is unanswerable with the amount of information you've given.
>     Yes, turning off enable_seqscan is a bad idea in general, but why
>     you got a worse plan without that requires details.
> 
>     https://wiki.postgresql.org/wiki/Slow_Query_Questions
> 
>                              regards, tom lane
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com