Re: Slow counting on v9.3

Kai Sellgren <kaisellgren 'at' gmail.com> writes:

> Hi,
>
> I'm experiecing slow count performance:
>
> SELECT COUNT(*) AS "count"
> FROM "NewsArticle"
>
> Takes 210 ms. I've run analyze and vacuum. I'm on 9.3. Here're the stats http:/
> /d.pr/i/6YoB
>
> I don't understand why is it that slow. It returns 1 integer, and counts
> without filters.

You might actually have a lot more dead tuples than reported in
statistic. Last vacuum is old according to your screenshot. Try
"VACUUM FULL ANALYZE" on your table, then try again counting.

> This performs quickly:
>
> SELECT reltuples AS count
> FROM pg_class
> WHERE relname = 'NewsArticle';

This is not the same. This one uses precomputed statistics, and
doesn't scan the actual table data.

> But I'd like to add conditions so I don't like the last method.
>
>
> --
> Yours sincerely,
> Kai Sellgren

--
Guillaume Cottenceau