Re: PostgreSQL, MySQL, etc., was Re: PostgreSQL is much

Christopher Browne wrote:

> A long time ago, in a galaxy far, far away, Randolf Richardson <rr@8x.ca> wrote:
>> [sNip]
>>>> the difference is that with mysql, nothing pushes the table out of
>>>> memory; it always stays in memory.  in postgresql, a big query on
>>>> another tables, or perhaps a vacuum, or other highly active
>>>> applications on the same server can cause the small tables to be
>>>> pushed out of memory.  both approches have positives and
>>>> negatives, and in many cases you would probably notice no
>>>> differance
>>>
>>> If this is a small heavily used table, 7.5 with the new ARC buffer
>>> management policy should do much better.  Even better, the table
>>> does not actually need to be small: the heavily used portion will
>>> stay in memory where it can be very fast, and the rest will be just
>>> wait its turn on disk.
>>
>>         Is this a configurable option by any chance?  If not, then
>> perhaps it should be on a per-table, per-index (etc.) basis.
>
> It is a MUCH BETTER thing to have policies that don't require
> configuration effort.
>
> One of the characteristic problems with Oracle is that you have
> immense numbers of "knobs" to tune.  You can get it to work "just
> right" if you throw a large enough horde of DBAs at it.
>
> In the case of the ARC policy, what Jan is trying to do is to come up
> with a strategy that is an improvement irrespective of the
> characteristics of the table.  If that works out as hoped for, there
> will be no need to "configure" anything in order to take advantage of
> it.

The stuff is in CVS HEAD. Randolf, look at the README file in
src/backend/storage/buffer for some explanations.


Jan

>
> You'd find your applications running faster simply by installing a 7.5
> server; no need to configure anything.  It's like getting Pentium chip
> with improved execution strategies; you don't have to recompile
> anything (the way IA-64 mandates it); you just install the app on the
> new box and watch it speed up.


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