Re: estimate sort_area_size

If you know roughly the size the index
will be (average(row length) * number of rows) is a guideline, and have enough memory, then

    size of index * 1.2
will be about the right amount for a complete in-memory sort, which will be the fastest. Allow plenty of spare as this is a very rough approximation.

If you don't have anything like that amount of memory free, then the next best is the 'one-pass' sort, where the data gets dumped to disc once in chunks and re-read. In this case, there is an excellent note on Steve Adams' website that describes how to calculate the amount of memory you need to achieve a one-pass sort. See

    http://www.ixora.com.au

--
Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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"zeb" <thierry.constant1.nospam_at_free.fr> wrote in message
news:3ec747cb$0$17283$626a54ce_at_news.free.fr...
> Hi,
>
> Is there a way  to estimate the sort_area_size for the creation of
index for
> a big table ?
>
> Thanks in advance
>
>