db-derby-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Bergquist, Brett" <BBergqu...@canoga.com>
Subject Should the optimizer ever have a cost of "0.0"?
Date Tue, 27 Aug 2013 15:18:38 GMT
I am just wondering if while the optimizer is producing a plan if a cost of "0.0" should ever
be seen.  Thinking naively, it seems to me that all join plans and all access paths have some
sort of cost which should be greater than "0.0".   From my testing over the last few days,
when a plan comes up with a join such as "join T1 with T2" and the T1 cost is "0.0", then
this dominates the plan cost and even if T2's access path is going to be a table scan of millions
of rows, this plan might be chosen.   This just does not seem right to me.

View raw message