Re: Are there performancebenefits to reorganizing database-using export/import?

From: Robert Klemme <>
Date: Tue, 11 Nov 2008 23:09:13 +0100
Message-ID: <>

On 11.11.2008 16:59, Shakespeare wrote:

> bdbafh schreef:

>> On Nov 10, 3:52 pm, wrote:
>>> I am using Oracle on HP UNIX 11i. Since it is a production
> ------------------------------------------

>> While you are at it, you might consider key compression of
>> concatenated indexes.
>> This can reduce the space used by indexes, but you might need to re-
>> order the columns in the index in order to gain the space reduction
>> that you're after.
> I would definitely NOT advise to do so. Column order is rather important 
> in indexes!

Especially since for fast lookups you want most selective (high cardinality) columns first but for good compression you want low cardinality columns first. And then there are other considerations (i.e. column order which helps most queries) as well...

Kind regards

        robert Received on Tue Nov 11 2008 - 16:09:13 CST

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