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Re: CBO when one table has no stats

From: Telemachus <telemachus_at_ulysseswillreturn.net>
Date: Tue, 1 Apr 2003 10:36:13 +0100
Message-ID: <i4dia.6198$pK2.6162@news.indigo.ie>


But it doesn't have to be completely out of date to be effective - once you get a plan you're happy with then why change it. Get your 'happy stats' plan.
"NetComrade" <andreyNSPAM_at_bookexchange.net> wrote in message news:3e8864d4.3020609386_at_nyc.news.speakeasy.net...
> we are going to add dbms_stats.gather_table_stats to the proc that
> populates the table.
>
> We might consider populating stats manually, but the size of the table
> changes slightly every day, and that's not something that's easy to
> calculate.
>
> On Mon, 31 Mar 2003 17:47:01 +0800, Connor McDonald
> <connor_mcdonald_at_yahoo.com> wrote:
>
> >NetComrade wrote:
> >>
> >> For whatever reason i thought that CBO will be used if ALL tables have
> >> statistics collected for them, but it seems it's the other way around,
> >> if at least ONE table in the query has statistics for it it would be
> >> the other way around, could somebody confirm?
> >>
> >> We have some tables that stay empty, and get filled very quickly and
> >> get used right away, and i hoped to avoid FTS by deleting statistics
> >> for those, and relying on RBO, now i need to come up with a better
> >> strategy.
> >> .......
> >> We use Oracle 8.1.7.4 on Solaris 2.7 boxes
> >> remove NSPAM to email
> >
> >The cbo makes assumptions when stats are missing. They are documented
> >in (I think) the performance manual, but things like average row size
> >100 bytes etc are used. On later versions of Oracle, the optimizer can
> >dynamically sample the rows to make a better estimate
> >
> >hth
> >connor
> >--
> >=========================
> >Connor McDonald
> >http://www.oracledba.co.uk
> >
> >"Some days you're the pigeon, some days you're the statue"
>
> .......
> We use Oracle 8.1.7.4 on Solaris 2.7 boxes
> remove NSPAM to email
Received on Tue Apr 01 2003 - 03:36:13 CST

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