Re: Adding LEFT JOIN to a query has increased execution time 10 times

Hi Andrew -

On Mon, Jan 7, 2019 at 12:00 AM Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>
wrote:

> >>>>> "Alexander" == Alexander Farber <alexander(dot)farber(at)gmail(dot)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