Re: partitions cardinality

From: Mauro Pagano <mauro.pagano_at_gmail.com>
Date: Sat, 18 Apr 2015 10:52:28 -0400
Message-Id: <BC30BAA2-F9CB-42E8-9908-DCB4C63DED2E_at_gmail.com>

Also depending on the version you are on there might be some new fixes (ie 18182018, there is also another one I can't find) that change the way the card is computed when scaling global stats down.

> On Apr 18, 2015, at 10:20 AM, William Robertson <william_at_williamrobertson.net> wrote:
>
> That will depend.
>
> Off the top of my head, if the partition can be determined from a
> literal (so the query is explicitly about a specific partition) then
> the partition stats will be used. If not, the optimiser will go to the
> global stats for the num_rows of the table divided by the num_distinct
> of the partition key column. There are doubtless a load more factors
> involved though (dynamic sampling, index stats, whether you have bind
> peeking disabled...) so you may need to be more specific.
>
> William Robertson
>
> On 18 Apr 2015, at 14:47, Ls Cheng <exriscer_at_gmail.com> wrote:
>
> Hi
>
> Does anyone know how cardinality is calculated in partitioned tables?
>
> TIA
> --
> http://www.freelists.org/webpage/oracle-l
>
>

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Received on Sat Apr 18 2015 - 16:52:28 CEST