Re: Deleting takes days, should I add some index?

čt 25. 2. 2021 v 22:02 odesílatel Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
napsal:

> Hi
>
> čt 25. 2. 2021 v 19:39 odesílatel Alexander Farber <
> alexander(dot)farber(at)gmail(dot)com> napsal:
>
>> Pavel, thank you for asking!
>>
>> I have put the anonymized dump of my database at:
>>
>> http://wordsbyfarber.com/words_dev.sql.gz (beware, it is a 1.3 GB
>> download)
>>
>> The question is why does the command take days (when I tried last time):
>>
>> delete from words_games where created < now() - interval '12 month';
>>
>>
> I tried to remove just only one row
>
> postgres=# explain analyze delete from words_games where gid = 44877;
>
> ┌────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
> │ QUERY PLAN
> │
>
> ╞════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════╡
> │ Delete on words_games (cost=0.42..8.44 rows=0 width=0) (actual
> time=0.268..0.270 rows=0 loops=1) │
> │ -> Index Scan using words_games_pkey on words_games (cost=0.42..8.44
> rows=1 width=6) (actual time=0.205..0.209 rows=1 loops=1) │
> │ Index Cond: (gid = 44877)
> │
> │ Planning Time: 0.328 ms
> │
> │ Trigger for constraint words_chat_gid_fkey on words_games: time=0.215
> calls=1 │
> │ Trigger for constraint words_moves_gid_fkey on words_games: time=0.240
> calls=1 │
> │ Trigger for constraint words_scores_gid_fkey on words_games: time=0.103
> calls=1 │
> │ Trigger for constraint words_puzzles_mid_fkey on words_moves:
> time=56.099 calls=4 │
> │ Trigger for constraint words_scores_mid_fkey on words_moves:
> time=22536.280 calls=4 │
> │ Execution Time: 22593.293 ms
> │
>
> └────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
> (10 rows)
>
> looks so you miss index
>
> create index on words_scores(mid);
>

postgres=# explain analyze delete from words_games where gid = 183154;
┌────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ QUERY PLAN
│
╞════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════╡
│ Delete on words_games (cost=0.42..8.44 rows=0 width=0) (actual
time=0.369..0.371 rows=0 loops=1) │
│ -> Index Scan using words_games_pkey on words_games (cost=0.42..8.44
rows=1 width=6) (actual time=0.283..0.288 rows=1 loops=1) │
│ Index Cond: (gid = 183154)
│
│ Planning Time: 0.230 ms
│
│ Trigger for constraint words_chat_gid_fkey on words_games: time=0.131
calls=1 │
│ Trigger for constraint words_moves_gid_fkey on words_games: time=1.329
calls=1 │
│ Trigger for constraint words_scores_gid_fkey on words_games: time=1.704
calls=1 │
│ Trigger for constraint words_puzzles_mid_fkey on words_moves: time=4.068
calls=51 │
│ Trigger for constraint words_scores_mid_fkey on words_moves: time=5.304
calls=51 │
│ Execution Time: 13.037 ms
│
└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
(10 rows)

Regards

Pavel

> Regards
>
> Pavel
>
>