Re: Adding LEFT JOIN to a query has increased execution time 10 times
| От | Alexander Farber |
|---|---|
| Тема | Re: Adding LEFT JOIN to a query has increased execution time 10 times |
| Дата | |
| Msg-id | CAADeyWjw2UASz-FM3UZxsViTTeLVU4RJVqRJFP+8pdOWTdK2-g@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Adding LEFT JOIN to a query has increased execution time 10 times (Andrew Gierth <andrew@tao11.riddles.org.uk>) |
| Список | pgsql-general |
Hi Andrew -
On Mon, Jan 7, 2019 at 12:00 AM Andrew Gierth <andrew@tao11.riddles.org.uk> wrote:
>>>>> "Alexander" == Alexander Farber <alexander.farber@gmail.com> writes:
Alexander> With the further help of the IRC folks the query has been
Alexander> optimized (7-10 seconds -> 0.3 second)
0.3 MILLIseconds, actually.
(You chanced not to catch me around on IRC, but I see that didn't
matter.)
it is amazing to see how the query I got used to be so slow in the past months is suddenly returning so quickly.
Yes, I figured I have missed you on the IRC yesterday, but the advice to go there (haven't used it for 20 years) has been very helpful anyway.
Alexander> CREATE INDEX ON words_moves (gid, played DESC);
Alexander> CREATE INDEX ON words_social (uid, stamp DESC);
I'm not a big fan of using DESC on indexes; it's almost never needed,
because any btree index can be scanned in reverse. (You only actually
need it if you're mixing ASC/DESC orderings in an ORDER BY and want an
index that matches it.)
Ok good to know, I will remove the DESC from the indices.
Regards
Alex
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