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Re: Passing a variable from the user interface to PostgreSQL

From: Mladen Gogala <mladen(dot)gogala(at)vmsinfo(dot)com>
To: Chris Campbell <ccampbell(at)cascadeds(dot)com>
Cc: "pgsql-novice(at)postgresql(dot)org" <pgsql-novice(at)postgresql(dot)org>
Subject: Re: Passing a variable from the user interface to PostgreSQL
Date: 2011-01-22 05:38:47
Message-ID: 4D3A6D67.6050203@vmsinfo.com (view raw or flat)
Thread:
Lists: pgsql-novice
Chris Campbell wrote:
>
> Using:
>
> Windows 7 64bit
>
> VB.net 2010
>
> The latest devart.data.PostgreSQL (.net data connection)
>
> PostgreSQL 9.0.2
>
>  
>
> Hi all,
>
>  
>
> Question: Is there a way to pass a variable from an application’s user 
> interface to the database such that it would be visible inside a 
> database trigger and any corresponding function call?
>
>  
>
> When a record gets deleted, a table trigger fires that writes to a log 
> table.  What I want to do is pass a variable from the user interface 
> to the trigger function so I can write the variable’s value to the log 
> record that I create in a function called from the trigger event.  I’m 
> not sure how this could even be accomplished unless somehow it was 
> possible to pass a variable through the data connection itself.  But 
> even then, how would the trigger function be able to see it and pass 
> it along?  Is there some other mechanism or approach I should be taking?
>
>  
>
> I’m thinking it’s not possible but thought I would ask anyway.
>
>  
>
> Thanks for any comments,
>
>  
>
> Chris Campbell
>
> ccampbell(at)CascadeDS(dot)com <mailto:ccampbell(at)CascadeDS(dot)com>
>
>  
>
Well, obviously, it isn't possible to pass a variable from UI to a 
trigger. What is possible is to send the record primary key, along with 
any messages you need, to a background process, using some kind of a 
message passing mechanism, and there are plenty of those. The background 
process can delete the row and write message in a single transaction. It 
can even converse with the UI using message passing system. An excellent 
example of such a system, priced exactly right, is Apache ActiveMQ. 
Apache ActiveMQ price is exactly half of the  Postgres price.

-- 
Mladen Gogala 
Sr. Oracle DBA
1500 Broadway
New York, NY 10036
(212) 329-5251
www.vmsinfo.com 


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