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 ___ Zope maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Interbase / Cacheing - A thought
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" [EMAIL PROTECTED] To: "Ian Sparks" [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] 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 ___ Zope maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope-dev ) ___ Zope maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope-dev )
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. They are supported by the TCL interface that comes with PostgreSQL (src/interfaces/libpgtcl in the PostgreSQL source tree) if you are looking for examples of how they work. (Search for listen and notify in pgtclCmds.c -- cary 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 --__--__-- ___ Zope maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Interbase / Cacheing - A thought
Cary O'Brien wrote: 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. They are supported by the TCL interface that comes with PostgreSQL (src/interfaces/libpgtcl in the PostgreSQL source tree) if you are looking for examples of how they work. (Search for listen and notify in pgtclCmds.c The lower level python interfaces (_pg, pg) support them too. - Hannu ___ Zope maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Interbase / Cacheing - A thought
Ian Sparks wrote: Hannu, Does PostgresSQL allow you to have dynamic events? By this I mean can you do things like : PostEvent "Update_tblUsers_Record_" + new.RecordID; No, but it may change sometime (possibly soon) as PostgreSQL is an open-source product ... 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. The same is true for postgrSQL, only the syntax is LISTEN/NOTIFY. Hannu ___ Zope maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope-dev )
