Re: Boom filters for hash joins (was: A design for amcheck heapam verification)

On 09/19/2017 06:03 PM, Peter Geoghegan wrote:
> On Tue, Sep 19, 2017 at 6:28 AM, Tomas Vondra
> <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>> The patch is fairly simple, and did not try to push the bloom filters to
>> scan nodes or anything like that. It might be a meaningful first step,
>> though, particularly for selective joins (where only small number of
>> rows from the outer relation has a match in the hash table).
>
> I believe that parallelism makes the use of Bloom filter a lot more
> compelling, too. Obviously this is something that wasn't taken into
> consideration in 2015.
>

I haven't thought about it from that point of view. Can you elaborate
why that would be the case? Sorry if this was explained earlier in this
thread (I don't see it in the history, though).

I can't quite remember why I haven't pursued the patch in 2015, but it
was probably clear it wouldn't get in in the last CF, and I never got
back to it.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
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