Re: How many PARTITIONS for a hash partitioned table would be a REASONABLE number?

nilendu_at_nilendu.com wrote in message news:<1112827711.132343.194100_at_g14g2000cwa.googlegroups.com>...
> Another thing that we considered is the cardinality of each values.
>
> In other words, you may want to find out -
>
> select a3, count(*) num_a3 from A
> group by a3
> order by 2 desc;
>
> Are the num_a3 s closely spaced?

No, they are not aligned at all. We have very distinct values for num_a3.

> Hash partitioning will work the best when number of appearance for each
> num_a3 is close to each other.

For me Oracle manages eliminating unneeded partitions wery well for queries with a3 in (LIST).

> Did you try benchmarking the query with a global index created on A3 as
> well?

Yes. The index not used of not effective at all that way. Seems that IN-LIST queries can not benefit from index. Received on Thu Apr 07 2005 - 01:45:51 CDT