Re: WIP: bloom filter in Hash Joins with batches
| От | David Rowley |
|---|---|
| Тема | Re: WIP: bloom filter in Hash Joins with batches |
| Дата | |
| Msg-id | CAKJS1f9hCxfYrvxpEWROahi8jhmg47nFO0jdbd=aAupLkQ2JoQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: WIP: bloom filter in Hash Joins with batches (Tomas Vondra <tomas.vondra@2ndquadrant.com>) |
| Список | pgsql-hackers |
On 11 January 2016 at 09:30, Tomas Vondra <tomas.vondra@2ndquadrant.com> wrote:
-- Hi,
On 01/10/2016 04:03 AM, Peter Geoghegan wrote:On Sat, Jan 9, 2016 at 4:08 PM, Peter Geoghegan <pg@heroku.com> wrote:Also, are you aware of this?
http://www.nus.edu.sg/nurop/2010/Proceedings/SoC/NUROP_Congress_Cheng%20Bin.pdf
It talks about bloom filters for hash joins in PostgreSQL
specifically. Interestingly, they talk about specific TPC-H queries.
Interesting. The way that paper uses bloom filters is very different from what I do in the patch. They build the bloom filters and then propagate them into the scan nodes to eliminate the tuples early.
That does sound interesting, but unless I'm somehow mistaken, I guess to do that you'd have to abandon the more efficient hashing of the hash value that you're doing in the current patch, and hash the complete value in the scan node, then hash them again if they make it into the hash join node. That does not sound like it would be a win if hashing longer varlana values.
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