Re: BUG #5652: Optimizer does wrong thing with partitioned tables

Euler Taveira de Oliveira wrote:
> Mladen Gogala escreveu:
>
>> Optimizer chooses to scan each partitioned table sequentially, instead of
>> using the available index:
>>
>>
> This is not a bug. How would the optimizer know that the maximum value is in
> that specific partition? There is neither a global index for a partitioned
> table nor an optimizer artifact to know aggregate information before scanning
> all of the partitions. Maybe when we have a better support for table
> partitioning such optimizer artifact would be implemented but don't hold your
> breath.
>
>
>
Euler, optimizer is selecting a wrong path, which is a bug by
definition. I am not asking the optimizer to know what is the maximum, I
am asking it to select the right path, something that it isn't doing. As
is visible from the original bug report, the optimizer is choosing
sequential scan instead of the index scan. When only a single partition
is involved, the index scan is selected, while for the entire table,
sequential scan is selected for every partition.

--

Mladen Gogala
Sr. Oracle DBA
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