Re: Again, sorry, caching.

From: mlw <markw(at)mohawksoft(dot)com>
To: "Mattew T(dot) O'Connor" <matthew(at)rh71(dot)postgresql(dot)org>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Again, sorry, caching.
Date: 2002-03-18 14:15:24
Message-ID: 3C95F67C.9AC1772@mohawksoft.com
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"Mattew T. O'Connor" wrote:
>
> > My big problem with putting the cache outside of the database is that it is
> > now incumbent on the applications programmer to write a cache. A database
> > should manage the data, the application should handle how the data is
> > presented. Forcing the application to implement a cache feels wrong.
>
> I believe someone suggested a possible solution that was in the pg client
> using NOTICE and triggers. The argument given against it, was that
> it would not be ACID compliant. I say, who cares. I would think that the
> "select cachable" would only be allowed for simple selects, it would not be
> used for select for update or anything else. Anytime you are given the
> result of a simple select, you are not guaranteed that the data won't change
> underneath you.

Not true, if you begin a transaction, you can be isolated of changes made to
the database.

>The primary use that you have suggested is for web sites,
> and they certainly won't mind of the cache is 0.3seconds out of date.

Again, if they don't care about accuracy, then they will use MySQL. PostgreSQL
is a far better system. Making PostgreSQL less accurate, less "correct" takes
away, IMHO, the very reasons to use it.

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