Re: count * performance issue
| От | Shoaib Mir |
|---|---|
| Тема | Re: count * performance issue |
| Дата | |
| Msg-id | bf54be870803052215y5bb56235k5ea05ada1d701022@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: count * performance issue ("A. Kretschmer" <andreas.kretschmer@schollglas.com>) |
| Ответы |
Re: count * performance issue
Re: count * performance issue |
| Список | pgsql-performance |
On Thu, Mar 6, 2008 at 5:08 PM, A. Kretschmer <andreas.kretschmer@schollglas.com> wrote:>
Or do something like:
ANALYZE tablename;
select reltuple from pg_class where relname = 'tablename';
That will also return the total number of rows in a table and I guess might be much faster then doing a count(*) but yes if trigger can be an option that can be the easiest way to do it and fastest too.
--
Shoaib Mir
Fujitsu Australia Software Technology
shoaibm[@]fast.fujitsu.com.au
> am having a table with nearly 50 lakh records,
>
> it has more than 15 columns, i want to count how many records are there, it is
> taking nearly 17 seconds to do that...
>
> i know that to get a approximate count we can use
> SELECT reltuples FROM pg_class where relname = TABLENAME;
>
> but this give approximate count, and i require exact count...
There aren't a general solution. If you realy need the exact count of
tuples than you can play with a TRIGGER and increase/decrease the
tuple-count for this table in an extra table.
Or do something like:
ANALYZE tablename;
select reltuple from pg_class where relname = 'tablename';
That will also return the total number of rows in a table and I guess might be much faster then doing a count(*) but yes if trigger can be an option that can be the easiest way to do it and fastest too.
--
Shoaib Mir
Fujitsu Australia Software Technology
shoaibm[@]fast.fujitsu.com.au
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