Re: performance drop after upgrade (9.6 > 10)

2017-10-11 13:06 GMT+02:00 johannes graën <johannes(at)selfnet(dot)de>:

> Hi,
>
> I wrote a query that joins several tables usually returning less than
> 1000 rows, groups them and generates a JSON object of the result. In
> 9.6 is was a question of milliseconds for that query to return the
> requested data. Now, after upgrading to 10, the query never returns -
> at least it hasn't returned in the last hour.
>
> To see what happens, I requested the query plan [1]. It looks complex
> and shows a lot of parallelization. I don't have the query plan from
> 9.6, but I remember it being considerably simpler.
>
> Can anyone have a guess what altered the performance here so
> dramatically? Is there a way to disable new parallelization features
> just for this query to see if it makes any difference?
>
>

have you fresh statistics? After upgrade is necessary to run ANALYZE command

Regards

Pavel

Best
> Johannes
>
>
> [1] https://explain.depesz.com/s/xsPP
>
>
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