A blast from the past is forwarded below.


Begin forwarded message:

From: Tom Lane <[EMAIL PROTECTED]>
Date: August 23, 2005 3:23:43 PM EDT
To: Donald Courtney <[EMAIL PROTECTED]>
Cc: pgsql-performance@postgresql.org, Frank Wiles <[EMAIL PROTECTED]>, gokulnathbabu manoharan <[EMAIL PROTECTED]>
Subject: Re: [PERFORM] Caching by Postgres

Donald Courtney <[EMAIL PROTECTED]> writes:
I am not alone in having the *expectation* that a database should have
some cache size parameter and the option to skip the file system. If
I use oracle, sybase, mysql and maxdb they all have the ability to
size a data cache and move to 64 bits.

And you're not alone in holding that opinion despite having no shred
of evidence that it's worthwhile expanding the cache that far.

However, since we've gotten tired of hearing this FUD over and over,
8.1 will have the ability to set shared_buffers as high as you want.
I expect next we'll be hearing from people complaining that they
set shared_buffers to use all of RAM and performance went into the
tank ...

regards, tom lane

On Oct 4, 2005, at 11:06 PM, Ron Peacetree wrote:

Unfortunately, no matter what I say or do, I'm not going to please
or convince anyone who has already have made their minds up
to the extent that they post comments like Mr Trainor's below.
His response style pretty much proves my earlier point that this
is presently a religious issue within the pg community.

The absolute best proof would be to build a version of pg that does
what Oracle and DB2 have done and implement it's own DB
specific memory manager and then compare the performance
between the two versions on the same HW, OS, and schema.

The second best proof would be to set up either DB2 or Oracle so
that they _don't_ use their memory managers and compare their
performance to a set up that _does_ use said memory managers
on the same HW, OS, and schema.

I don't currently have the resources for either experiment.

Some might even argue that IBM (where Codd and Date worked)
and Oracle just _might_ have had justification for the huge effort
they put into developing such infrastructure.

Then there's the large library of research on caching strategies
in just about every HW and SW domain, including DB theory,
that points put that the more context dependent, ie application
or domain specific awareness, caching strategies are the better
they are.

Maybe after we do all we can about physical IO and sorting
performance I'll take on the religious fanatics on this one.

One problem set at a time.

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