Re: bloom filter not used after 19C upgrade

On Wed, 2024-05-08 at 23:16 +0200, Lothar Flatz wrote:
> Hi,
>
> You could try hinting the bloom filter and see what happens.
> If I get the message right decision is made at runtime. (Not sure).
> In such case it can make a difference how well the table is cached.
> Need more facts, e.g. both plans.
>
> Thanks
>
> Lothar

Hi Lothar, 
I may be mistaken, but if the decision is made at runtime, then it is not possible to know in advance whether Bloom filters will be used or not. The only places where it's possible to see it is V$SQL_PLAN and V$SQL_JOIN and not explain plan.
Other than that, Bloom filters were invented by Mr. Bloom, of the Bialystock & Bloom fame, from the movie "The Producers". That is what it's so hard to catch them. BTW, if you decide to watch the movie, a smart decision by any standard, I'd recommend the Gene Wilder version, rather than the modern one with Will Ferrell.
Regards

-- 
Mladen Gogala
Database SME
https://dbwhisperer.wordpress.com


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