Re: Bloom Filter lookup for hash joins

On 26 June 2013 07:46, Atri Sharma <atri(dot)jiit(at)gmail(dot)com> wrote:

> I have been researching bloom filters and discussed it on IRC with
> RhodiumToad and David Fetter, and they pointed me to the various
> places that could potentially have bloom filters, apart from the
> places that already have them currently.
>
> I have been reading the current implementation of hash joins, and in
> ExecScanHashBucket, which I understand is the actual lookup function,
> we could potentially look at a bloom filter per bucket. Instead of
> actually looking up each hash value for the outer relation, we could
> just check the corresponding bloom filter for that bucket, and if we
> get a positive, then lookup the actual values i.e. continue with our
> current behaviour (since we could be looking at a false positive).
>

Exactly this was suggested by me on the NTUP_PER_BUCKET thread last week.

Probably good idea to join in there also.

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Simon Riggs http://www.2ndQuadrant.com/
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