Re: anti-join chosen even when slower than old plan

On 11/10/2010 5:43 PM, Kevin Grittner wrote:
> The only half-sane answer I've thought of is to apply a different
> cost to full-table or full-index scans based on the ratio with
> effective cache size.

The "effective_cache_size" is, in my humble opinion, a wrong method. It
would be much easier to have a parameter, let's call it
"optimizer_index_caching", which would give the assumption of the
percentage of an index that is cached. In other words, if
"optimizer_index_caching" was set to 80, the optimizer would assume that
80% of any index is cached and would apply different cost estimate. It's
not exact but it's simple and modifiable. It would also be a great tool
in the hands of the DBA which has to manage OLTP database or DW database
and would be able to create a definitive bias toward one type of the
execution plan.
I have to confess that the idea about such parameter is not entirely
mine:*http://tinyurl.com/33gu4f6*

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Mladen Gogala
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