| From: | Mario Weilguni <mweilguni(at)sime(dot)com> |
|---|---|
| To: | pgsql-performance(at)postgresql(dot)org |
| Cc: | ismo(dot)tuononen(at)solenovo(dot)fi, Albert Cervera Areny <albert(at)sedifa(dot)com> |
| Subject: | Re: Performance of count(*) |
| Date: | 2007-03-22 13:26:51 |
| Message-ID: | 200703221426.51948.mweilguni@sime.com |
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| Lists: | pgsql-performance |
Am Donnerstag, 22. März 2007 12:30 schrieb ismo(dot)tuononen(at)solenovo(dot)fi:
> approximated count?????
>
> why? who would need it? where you can use it?
>
> calculating costs and desiding how to execute query needs
> approximated count, but it's totally worthless information for any user
> IMO.
No, it is not useless. Try:
http://www.google.com/search?hl=de&q=test&btnG=Google-Suche&meta=
Do you really think google counted each of those individual 895 million
results? It doesn't. In fact, the estimate of google can be off by an order
of magnitude, and still nobody complains...
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