Re: Query performance issue

Greg Sabino Mullane <htamfids@gmail.com>

From: Greg Sabino Mullane <htamfids@gmail.com>
To: yudhi s <learnerdatabase99@gmail.com>
Cc: pgsql-general@lists.postgresql.org, hjp-pgsql@hjp.at
Date: 2024-10-22T19:01:55Z
Lists: pgsql-general
To be frank, there is so much wrong with this query that it is hard to know
where to start. But a few top items:

* Make sure all of the tables involved have been analyzed. You might want
to bump default_statistics_target up and see if that helps.

* As mentioned already, increase work_mem, as you have things spilling to
disk (e.g. external merge Disk: 36280kB)

* Don't use the "FROM table1, table2, table3" syntax but use "FROM table1
JOIN table2 ON (...) JOIN table3 ON (...)

* Try not to use subselects. Things like WHERE x IN (SELECT ...) are
expensive and hard to optimize.

* You have useless GROUP BY clauses in there. Remove to simplify the query

* There is no LIMIT. Does the client really need all 135,214 rows?

Cheers,
Greg