Re: count * performance issue

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buy every time i need to put ANALYZE...
this takes the same time as count(*) takes, what is the use ??

On Thu, Mar 6, 2008 at 11:45 AM, Shoaib Mir <shoaibmir@[EMAIL PROTECTED]
> wrote:

> On Thu, Mar 6, 2008 at 5:08 PM, A. Kretschmer <
> andreas.kretschmer@[EMAIL PROTECTED]
> wrote:>
>
> > > 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[@[EMAIL PROTECTED]
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buy every time i need to put ANALYZE...<br>this takes the same time as
count(*) takes, what is the use ??<br><br><div class="gmail_quote">On Thu,
Mar 6, 2008 at 11:45 AM, Shoaib Mir &lt;<a
href="mailto:shoaibmir@[EMAIL PROTECTED]
">shoaibmir@[EMAIL PROTECTED]
>&gt; wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204,
204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div
class="Ih2E3d">On Thu, Mar 6, 2008 at 5:08 PM, A. Kretschmer &lt;<a
href="mailto:andreas.kretschmer@[EMAIL PROTECTED]
"
target="_blank">andreas.kretschmer@[EMAIL PROTECTED]
>&gt; wrote:&gt;<br>
<div class="gmail_quote"><blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt
0.8ex; padding-left: 1ex;">

&gt; am having a table with nearly 50 lakh records,<br>
&gt;<br>
&gt; it has more than 15 columns, i want to count how many records are
there, it is<br>
&gt; taking nearly 17 seconds to do that...<br>
&gt;<br>
&gt; i know that to get a approximate count we can use<br>
&gt; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;SELECT reltuples FROM pg_class
where relname = TABLENAME;<br>
&gt;<br>
&gt; but this give approximate count, and i require exact count...<br>
<br>
There aren&#39;t a general solution. If you realy need the exact count
of<br>
tuples than you can play with a TRIGGER and increase/decrease the<br>
tuple-count for this table in an extra table.<br>
<br>
<br></blockquote></div><br></div>Or do something like:<br><br>ANALYZE
tablename;<br>select reltuple from pg_class where relname =
&#39;tablename&#39;;<br><br>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.<br clear="all">
<font color="#888888">
<br>-- <br>Shoaib Mir<br>Fujitsu Australia Software
Technology<br>shoaibm[@[EMAIL PROTECTED]
></blockquote></div><br>

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