Re: SQL code tuning

Niall,

>> I on the other hand have seen query time go from 10 secs to
>> 35 minutes just by adding 13 rows to a table when using CBO.
>> There are advantages and disadvantages to both.

 Was that an accident or pure poor choosing of a path by CBO? I am puzzled how CBO could be "dumb" sometimes? Even if you have /*+ordered*/ on, won't CBO find the *best* path from the information it gathers from data dictionary. I bet what CBO does is Traverse down the B*Tree of all possible path and pick the right one. What will CBO do when your /*+ ordered */ contradict with what is possibly best out there? So, I still can't see how adding 13 rows to a table will raise the issue. Enlighten me.

Allan W. Tham
DBA Received on Thu Nov 01 2001 - 20:21:19 CST