Re: function based index

>hi everyone
>
>we have a query with several max functions in it.
>The performance of the query is not so well, can i achieve better
>performance with function based index on
>max(columnname)?
>according the manuals this is not allowed because max is a group function.
>anyone with a solution for this ?
>
>vr. gr.
>g.g. kor
>rdw ict groningen
>

If columnname is indexed (plain index) and Oracle ***decides*** to do so, it can use the index to fetch the proper value (it's sorted in the index, remember). Out of memory, and if it's feasible, I'd make the column 'NOT NULL' (use a default special value such as -1 or whatever to mean 'not available'). As nullable columns are not always physically stored, and therefore may have no rowid, there is no entry for NULL values in indices and, knowing it, Oracle may behave in ways you didn't expect.

HTH Stephane Faroult
Oriole

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