Re: performance degredation after upgrade from 9.6 to 12

[John Felix <johnfelix@xxxxxxxxxxxxx>]

Op 24-11-2019 om 19:05 schreef Mariel Cherkassky:

Hey Jeff,

This example was only used to show that pg96  had better perfomance than pg12 in a very simple case.

 In all the tests that I run most of the queries took less time on 9.6`s version.  I dont know why, but as you can see after disabling the parameter the simple test that I did showed different results.  I intend to test this theory tomorrow. I'm going to disable the parameter and run the same application flows that I have on both machines (9.6 vs 12 with zero value for the param).

I didnt send this mail after doing just one simple test, I have more than 100 queries that work better on 9.6 . If u have any explanation I will be happy to hear.

I'll update tomorrow once I'll have the results..

I've had the same experience with parallel query. By default parallel query is disabled in 9.6. When we upgraded from 9.6 to 10 is was significant slower till I disabled parallel query.

We have a very small database (40 tables and all together max 4GB) and we have no long running queries (the largest queries run max 2 to 3 seconds). That's when parallel query gives a performance degrade in my opinion.

Best regards,

John Felix