Re: [v9.5] Custom Plan API

On 8 May 2014 04:33, Kouhei Kaigai <kaigai@ak.jp.nec.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