[Zope] Interbase / Cacheing - A thought

[Ian Sparks]

Hannu,

Does PostgresSQL allow you to have dynamic events? By this I mean can you do
things like :

PostEvent "Update_tblUsers_Record_" + new.RecordID;

I believe that in Interbase the events are compiled into the trigger, not
interpreted at Runtime so you can't have an Interbase event alert you to a
change in a particular record, only that a change has occurred on a table.

Coming from a RDBMS background myself I'd prefer to see RDBMS integration be
tighter to Zope - properties etc being stored in the database where
appropriate. For reasons of speed you don't want to have to go to the DB
each time you want a property but having a data-aware object which knows
when to update itself would solve this problem nicely.

It should also help with load-balancing and failover where you could have a
cluster of Zope instances all working on the same monster DB, all being kept
in sync. via the event alerter mechanism.

Just my thoughts.

- Ian.


----- Original Message -----
From: "Hannu Krosing" <hannu@tm.ee>
To: "Ian Sparks" <isparks@wmute.u-net.com>
Cc: <zope@zope.org>
Sent: Thursday, June 01, 2000 11:28 AM
Subject: Re: [Zope] Interbase / Cacheing - A thought


Ian Sparks wrote:
>
> Had a thought that I wanted to share.
>
> Interbase has a feature known as "event alerts". In a trigger you can post
> "events" which are just fixed data strings e.g. "DataAdded" or
> "Insert_tblUsers".

PostgreSQL has them too.

It's not (afaik) supported by DB-API, but could be used in a DA that talks
to some lower level API.

> A client database connection can register to listen to these events.
>
> I don't know if any Zopeish Interbase access method supports this (ODBC
> doesn't to my knowledge) but it would be incredibly useful for synching
> cached database objects. Zope could hold a representation of the table
data
> in cached objects for quick access. Each object could have one or more
> "event" methods which related to a database event. When the database
adaptor
> received an event message from Interbase it could inform all objects with
a
> matching event method (these methods would refresh their cached data with
> current values from the database).
>
> In this way database and Zope cache could be synced *without* having to
poll
> the database at an interval. In all, a very efficient mechanism.
>
> Just an idea I wanted to put out there.

Thanks for getting it out.

I have been contemplating the same for PostgreSQL but have been too lazy to
do
it myself ;)

------------------
Hannu

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