Re: Support Parallel Query Execution in Executor

"Jonah H. Harris" <jonah(dot)harris(at)gmail(dot)com> writes:
> On 4/9/06, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I was considering a variant idea in the shower this morning:suppose
>> that we invent one or more "background reader" processes that have
>> basically the same infrastructure as the background writer, but have
>> the responsibility of causing buffer reads to happen at useful times

> This is sort of what I'm playing with. There are N-number of backends
> which are configured at startup and are available solely for parallel
> processing.

That's not remotely the same thing: a backend is a very different animal
from a bgwriter. In particular, bgwriter (and bgreaders if we had 'em)
aren't database-specific, don't need to think about permission checking
as they don't execute on behalf of particular users, don't have syscaches
to keep in-sync with everything else, etc etc.

regards, tom lane