Re: delete taking long time

My bad, I assumed postgres creates indexes on foreign keys automatically.
I created indexes on all fk and on ts and OMG:

bro=# select count(ts) from connection where ts >'2016-03-10 00:00:00';

count

--------

546997

(1 row)

bro=# select now(); delete from connection where uid in (select uid from
connection where ts > '2016-03-10 00:00:00' ); select now();

now

-------------------------------

2016-03-16 14:02:43.172617+00

(1 row)

DELETE 546997

now

-------------------------------

2016-03-16 14:04:25.608695+00

(1 row)

Took less than 2 minutes. Thanks for the help.

On 16 March 2016 at 11:57, Andreas Kretschmer <akretschmer(at)spamfence(dot)net>
wrote:

> ivo liondov <ivo(dot)liondov(at)gmail(dot)com> wrote:
>
> >
> > explain (analyze) delete from connection where uid in (select uid from
> > connection where ts > '2016-03-10 01:00:00' and ts < '2016-03-10
> 01:10:00');
> >
> >
> >
> -------------------------------------------------------------------------------------------------------------------------------------------------
> >
> > Delete on connection (cost=0.43..174184.31 rows=7756 width=12) (actual
> time=
> > 529.739..529.739 rows=0 loops=1)
> >
> > -> Nested Loop (cost=0.43..174184.31 rows=7756 width=12) (actual
> time=
> > 0.036..526.295 rows=2156 loops=1)
> >
> > -> Seq Scan on connection connection_1 (cost=0.00..115684.55
> rows=
> > 7756 width=24) (actual time=0.020..505.012 rows=2156 loops=1)
> >
> > Filter: ((ts > '2016-03-10 01:00:00'::timestamp without
> time
> > zone) AND (ts < '2016-03-10 01:10:00'::timestamp without time zone))
>
>
> there is no index on the ts-column.
>
>
>
>
>
>
>
>
> >
> > Rows Removed by Filter: 3108811
> >
> > -> Index Scan using connection_pkey on connection
> (cost=0.43..7.53
> > rows=1 width=24) (actual time=0.009..0.010 rows=1 loops=2156)
> >
> > Index Cond: ((uid)::text = (connection_1.uid)::text)
> >
> > Planning time: 0.220 ms
> >
> > Trigger for constraint dns_uid_fkey: time=133.046 calls=2156
> >
> > Trigger for constraint files_uid_fkey: time=39780.799 calls=2156
> >
> > Trigger for constraint http_uid_fkey: time=99300.851 calls=2156
> >
> > Trigger for constraint notice_uid_fkey: time=128.653 calls=2156
> >
> > Trigger for constraint snmp_uid_fkey: time=59.491 calls=2156
> >
> > Trigger for constraint ssl_uid_fkey: time=74.052 calls=2156
> >
> > Trigger for constraint weird_uid_fkey: time=25868.651 calls=2156
> >
> > Execution time: 165880.419 ms
>
> i guess there are no indexes for this tables and the relevant columns
>
>
> > I think you are right, fk seem to take the biggest chunk of time from
> the hole
> > delete operation. I made a test with 10.000 rows, it took 12 minutes.
> 20.000
> > rows took about 25 minutes to delete.
>
> create the missing indexes now and come back with the new duration.
>
>
> Andreas
> --
> Really, I'm not out to destroy Microsoft. That will just be a completely
> unintentional side effect. (Linus Torvalds)
> "If I was god, I would recompile penguin with --enable-fly." (unknown)
> Kaufbach, Saxony, Germany, Europe. N 51.05082°, E 13.56889°
>
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