Re: Support Parallel Query Execution in Executor

On Sun, Apr 09, 2006 at 08:23:36AM -0700, Myron Scott wrote:
> >This is the part I'm curious about - is this using the
> >shared_buffers region
> >in a circular buffer fashion to store pre-fetched pages?
>
> Yes. That is basically what the slave thread is trying to do. As
> well as weed out
> any tuples/pages that don't need to be looked at due to dead tuples.
> I did several things to try and insure that a buffer needed by the
> master thread
> would not be pulled out of the buffer pool before it was seen by the
> master.
> I wanted to do this without holding the buffer pinned, so I did the
> change to
> the buffer free list to do this.

Is this necessary? I mean, what's the chance that a page might get
thrown out early? And if so, what's the chance that page will still be
in the OS cache?

The cost of fetching a page from the OS is not really much of an
overhead, so I'd like to know how much benefit these buffer cache hacks
actually produce.

Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.