From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
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To: | Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, PgHacker <pgsql-hackers(at)postgresql(dot)org>, Stephen Frost <sfrost(at)snowman(dot)net>, Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com>, Jim Mlodgenski <jimmy76(at)gmail(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Kohei KaiGai <kaigai(at)kaigai(dot)gr(dot)jp> |
Subject: | Re: [v9.5] Custom Plan API |
Date: | 2014-05-08 09:51:17 |
Message-ID: | CA+U5nM+5W3xwqQsaJV=Q25RtdPu3LcBuJp_1B7riUF9==TPVcQ@mail.gmail.com |
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On 8 May 2014 04:33, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> wrote:
>> From your description, my understanding is that you would like to stream
>> data from 2 standard tables to the GPU, then perform a join on the GPU itself.
>>
>> I have been told that is not likely to be useful because of the data transfer
>> overheads.
>>
> Here are two solutions. One is currently I'm working; in case when number
> of rows in left- and right- tables are not balanced well, we can keep a hash
> table in the GPU DRAM, then we transfer the data stream chunk-by-chunk from
> the other side. Kernel execution and data transfer can be run asynchronously,
> so it allows to hide data transfer cost as long as we have enough number of
> chunks, like processor pipelining.
Makes sense to me, thanks for explaining.
The hardware-enhanced hash join sounds like a great idea.
My understanding is we would need
* a custom cost-model
* a custom execution node
The main question seems to be whether doing that would be allowable,
cos its certainly doable.
I'm still looking for a way to avoid adding planning time for all
queries though.
> Other solution is "integrated" GPU that kills necessity of data transfer,
> like Intel's Haswell, AMD's Kaveri or Nvidia's Tegra K1; all majors are
> moving to same direction.
Sounds useful, but very non-specific, as yet.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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