| From: | "Trevor Talbot" <quension(at)gmail(dot)com> |
|---|---|
| To: | "PgSQL General ML" <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Yet Another COUNT(*)...WHERE...question |
| Date: | 2007-08-16 16:01:03 |
| Message-ID: | 90bce5730708160901t5e0519cbt60b5769ab9b510af@mail.gmail.com |
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| Lists: | pgsql-general |
On 8/16/07, Rainer Bauer <usenet(at)munnin(dot)com> wrote:
> My point is that whatever search criterias are involved and how many items are found eBay always returns the *accurate* number of items found.
>
> Before this drifts off:
> * I do know *why* count(*) is slow using Postgres.
> * I *think* that count(*) is fast on eBay because count is cheaper using Oracle (which eBay does: <http://www.sun.com/customers/index.xml?c=ebay.xml>).
> * I realize that pagination for multi-million tuple results does not make sense.
You got me curious, so I went hunting for more hints on what eBay
actually does, and found these slides from a presentation given by two
eBay engineers last year:
http://www.addsimplicity.com/downloads/eBaySDForum2006-11-29.pdf
It's, er, a whole different ballgame there. Database behavior is
barely involved in their searching; they do joins and RI across
database clusters within the _application_. I knew eBay was big, but
wow...
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