| From: | Herouth Maoz <herouth(at)oumail(dot)openu(dot)ac(dot)il> |
|---|---|
| To: | Chris Bitmead <chris(dot)bitmead(at)bigfoot(dot)com>, General <pgsql-general(at)postgreSQL(dot)org> |
| Subject: | Re: [GENERAL] Re: Data warehousing |
| Date: | 1999-06-29 09:38:00 |
| Message-ID: | l03130301b39e42f3d784@[147.233.159.109] |
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| Lists: | pgsql-general |
At 16:00 +0300 on 28/06/1999, Chris Bitmead wrote:
> Why do multi-field indexes? Umm. How about to avoid doing a sequential
> scan? If your query depends on multiple fields then once you've found
> the set based on the first index you would have to sequential scan that
> subset based on the second condition, unless you have a multi-field
> index.
Well, I may be wrong, but I seem to recall reading in one of these mailing
lists once that there is no real difference performance-wise between
multiple-field indices and single-field indices on same columns. There was
a bit of overhead. I think Vadim should know the answer to this question.
Herouth
--
Herouth Maoz, Internet developer.
Open University of Israel - Telem project
http://telem.openu.ac.il/~herutma
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