Re: CBO when one table has no stats

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 Mon Mar 31 2003 - 10:25:05 CST