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
