Hints and RBO?

From: Bill Buchan <wbuchan_at_uk.noha-systems.com>
Date: Fri, 13 Oct 2000 16:46:36 GMT
Message-ID: <39e73af8.52266@nntp.edi.noha-systems.com>

I'm confused. Please help me resolve the flaw in my logic (I have RTFM but I'm missing the bit I want to understand!):

I have set the optimizer mode to CHOOSE but have not gathered any statistics. Therefore the optimizer will default to RULE based?

However if I put HINTs in my SQL the EXPLAIN PLAN changes; therefore the optimizer is responding to the hints.

I thought that you could only use hints with CBO?

Where have I gone wrong?

Also, I presume that if the COST column in PLAN_TABLE is not null, then statistics are being used by the CBO. My problem is that I deleted all the statistics (ANALYZE all indexs,tables DELETE STATISTICS) and there are still values appearing in this column when I do a new EXPLAIN.

Many thanks for any enlightenment (PS. v.8.0.6 on Solaris) - Bill. Received on Fri Oct 13 2000 - 11:46:36 CDT