Thread

1. LISTEN/NOTIFY

   Cristóvão B. B. Dalla Costa <cbraga@bsi.com.br> — 2002-10-04T20:49:55Z

   I'm developing an e-commerce site using Apache/mod_perl and, for 
   performance, I intend to cache rows such as user and product information 
   inside Perl. I think the LISTEN/NOTIFY interface would be perfect for 
   invalidating the cache when a product/user gets updated, yet I have not 
   found a way to access it from Perl -- DBI, or DBD::Pg even, offer no way 
   to "listen". Also, I don't really like the vanilla Pg. So, my question 
   to you is, is there another efficient way to accomplish notification of 
   updates?
   
   Thank you
   
   Cristóvão
   
   
   

2. Re: LISTEN/NOTIFY

   Jeff Davis <list-pgsql-general@empires.org> — 2002-10-04T22:00:44Z

   I did something similar using python with a simple "getnotify()" function 
   (part of the python pg module). 
   
   I couldn't find a similar function for perl -- strange.
   
   I think the listening process needs to be a separate process anyway, since I 
   wouldn't think that an apache process would easily be able to wait for a 
   notification.
   
   You could just do the cache invalidation process in another language, like 
   python or C, and all that would do is listen for an update, read the updated 
   info, and replace the cache. It should be small enough that you don't mind 
   straying from perl, hopefully. 
   
   Of course it is weird that perl doesn't support that. Maybe I missed something 
   too.
   
   Regards,
   	Jeff Davis
   
   On Friday 04 October 2002 01:49 pm, Cristóvão Dalla Costa wrote:
   > I'm developing an e-commerce site using Apache/mod_perl and, for
   > performance, I intend to cache rows such as user and product information
   > inside Perl. I think the LISTEN/NOTIFY interface would be perfect for
   > invalidating the cache when a product/user gets updated, yet I have not
   > found a way to access it from Perl -- DBI, or DBD::Pg even, offer no way
   > to "listen". Also, I don't really like the vanilla Pg. So, my question
   > to you is, is there another efficient way to accomplish notification of
   > updates?
   >
   > Thank you
   >
   > Cristóvão
   >
   >
   > ---------------------------(end of broadcast)---------------------------
   > TIP 5: Have you checked our extensive FAQ?
   >
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3. Re: LISTEN/NOTIFY

   Tom Lane <tgl@sss.pgh.pa.us> — 2002-10-05T02:54:02Z

   =?ISO-8859-1?Q?Crist=F3v=E3o_Dalla_Costa?= <cbraga@bsi.com.br> writes:
   > I'm developing an e-commerce site using Apache/mod_perl and, for 
   > performance, I intend to cache rows such as user and product information 
   > inside Perl. I think the LISTEN/NOTIFY interface would be perfect for 
   > invalidating the cache when a product/user gets updated, yet I have not 
   > found a way to access it from Perl -- DBI, or DBD::Pg even, offer no way 
   > to "listen".
   
   I don't know what the DBI/DBD design philosophy is regarding
   database-specific extensions --- but it would seem reasonable to me
   for DBD::Pg to offer some way to get at LISTEN functionality.  Can
   anyone suggest how to do this in the context of DBI?
   
   I suggest moving any followups to pgsql-interfaces, where this
   discussion would be more on-topic.
   
   			regards, tom lane
   
   

4. Re: [INTERFACES] LISTEN/NOTIFY

   Alex Pilosov <alex@pilosoft.com> — 2002-10-06T00:29:03Z

   On Fri, 4 Oct 2002, Tom Lane wrote:
   
   > =?ISO-8859-1?Q?Crist=F3v=E3o_Dalla_Costa?= <cbraga@bsi.com.br> writes:
   > > I'm developing an e-commerce site using Apache/mod_perl and, for 
   > > performance, I intend to cache rows such as user and product information 
   > > inside Perl. I think the LISTEN/NOTIFY interface would be perfect for 
   > > invalidating the cache when a product/user gets updated, yet I have not 
   > > found a way to access it from Perl -- DBI, or DBD::Pg even, offer no way 
   > > to "listen".
   See this: 
   http://archives.postgresql.org/pgsql-interfaces/2002-01/msg00018.php
   
   
   > I don't know what the DBI/DBD design philosophy is regarding
   > database-specific extensions --- but it would seem reasonable to me for
   > DBD::Pg to offer some way to get at LISTEN functionality.  Can anyone
   > suggest how to do this in the context of DBI?
   It uses generic func() interface...
   
   > I suggest moving any followups to pgsql-interfaces, where this
   > discussion would be more on-topic.
   -alex
   
   
   

5. Re: [INTERFACES] LISTEN/NOTIFY

   Tom Lane <tgl@sss.pgh.pa.us> — 2002-10-06T01:08:28Z

   alex@pilosoft.com writes:
   > See this: 
   > http://archives.postgresql.org/pgsql-interfaces/2002-01/msg00018.php
   
   Ah, I'd forgotten about that.  Did it get accepted into DBD::Pg?
   
   			regards, tom lane