Re: Support Parallel Query Execution in Executor

I am working with Solaris on SPARC almost exclusively and I believe Josh said that Sun was the one who found the bursty
behaviorwith scans.  Has it been confirmed that this is the case on all/most platforms?
 

Myron Scott
-----Original Message-----

From:  Tom Lane <tgl@sss.pgh.pa.us>
Subj:  Re: [HACKERS] Support Parallel Query Execution in Executor
Date:  Sun Apr 9, 2006 11:48 am
Size:  1K
To:  Gregory Maxwell <gmaxwell@gmail.com>
cc:  pgsql-hackers@postgresql.org

"Gregory Maxwell" <gmaxwell@gmail.com> writes:
> On 4/9/06, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> So before we go inventing complicated bits of code with lots of added
>> overhead, we should first find out exactly why the system doesn't
>> already work the way it's supposed to.

> But is that really the behavior we should expect?

Certainly.  If the OS has readahead logic at all, it ought to think that
a seqscan of a large table qualifies.  Your arguments seem to question
whether readahead is useful at all --- but they would apply *just as
well* to an app doing its own readahead, which is what is really
getting proposed in this thread.

Before we go replacing a standard OS-level facility with our own
version, we need to have a much clearer idea of why the OS isn't getting
the job done for us.  Otherwise we're likely to write a large amount of
code and find out that it doesn't work very well either.
        regards, tom lane

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