Re: Support Parallel Query Execution in Executor

"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