Re: Slow running query - Mailing list pgsql-admin

From Tom Lane
Subject Re: Slow running query
Date
Msg-id 14517.1576078369@sss.pgh.pa.us
Whole thread Raw
In response to Slow running query  (Shrikant Bhende <shrikantpostgresql@gmail.com>)
Responses Re: Slow running query  (Shrikant Bhende <shrikantpostgresql@gmail.com>)
List pgsql-admin
Shrikant Bhende <shrikantpostgresql@gmail.com> writes:
> Below is the query which is running very slow, can anyone suggest any
> improvement for the same to make it faster.

Not when you haven't given us any supporting data :-(.  There's some
advice about how to ask useful performance questions here:

https://wiki.postgresql.org/wiki/Slow_Query_Questions

However, just scanning your EXPLAIN output, it seems that the bulk
of the time is being spent inside two user-defined functions:

>                                              ->  Function Scan on get_num_connections f  (cost=0.25..10.25 rows=1000
width=24)(actual time=22331.461..22331.479 rows=263 loops=1) 
...
>                                              ->  Function Scan on get_num_proprietary f_1  (cost=0.25..10.25
rows=1000width=24) (actual time=4052.081..4052.085 rows=26 loops=1) 
...
>  Planning time: 18.362 ms
>  Execution time: 33944.679 ms

ie, 26 of the 34 seconds are being spent there.  You're not going to be
able to move the needle very far unless you can make those a lot cheaper.

I notice that the first thing the plan does with these is FULL JOIN them
to each other, which seems suspiciously like a performance anti-pattern.

            regards, tom lane



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