public inbox for [email protected]  

help / color / mirror / Atom feed

From: Josh Kupershmidt <[email protected]>
To: pgsql-docs <[email protected]>
Subject: lo_manage trigger on updates
Date: Thu, 11 Aug 2011 23:43:47 -0400
Message-ID: <CAK3UJRHaEuzfnZaxarcV8=RP1sC5xLxumzqx6iiyqpJVS89rjw@mail.gmail.com> (raw)

Hi all,

I think the doc section about using lo_manage() as a trigger:
   http://www.postgresql.org/docs/current/static/lo.html

could have its example tweaked to use a column-level BEFORE UPDATE
trigger, so as to save unnecessary trigger firings. Something like the
attached, perhaps?

On a similar note, the warning on that page about truncates could be
softened if we extended the lo_manage() function to handle truncates,
and set it up as on ON TRUNCATE trigger as well.

Josh


Attachments:

  [application/octet-stream] lo.diff (1.7K, 2-lo.diff)
  download | inline diff:
diff --git a/doc/src/sgml/lo.sgml b/doc/src/sgml/lo.sgml
new file mode 100644
index 3d56ba3..0ced3ae
*** a/doc/src/sgml/lo.sgml
--- b/doc/src/sgml/lo.sgml
***************
*** 69,82 ****
  <programlisting>
  CREATE TABLE image (title TEXT, raster lo);
  
! CREATE TRIGGER t_raster BEFORE UPDATE OR DELETE ON image
      FOR EACH ROW EXECUTE PROCEDURE lo_manage(raster);
  </programlisting>
  
    <para>
     For each column that will contain unique references to large objects,
     create a <literal>BEFORE UPDATE OR DELETE</> trigger, and give the column
!    name as the sole trigger argument.  If you need multiple <type>lo</>
     columns in the same table, create a separate trigger for each one,
     remembering to give a different name to each trigger on the same table.
    </para>
--- 69,90 ----
  <programlisting>
  CREATE TABLE image (title TEXT, raster lo);
  
! CREATE TRIGGER t_raster BEFORE UPDATE OF raster OR DELETE ON image
      FOR EACH ROW EXECUTE PROCEDURE lo_manage(raster);
  </programlisting>
  
    <para>
     For each column that will contain unique references to large objects,
     create a <literal>BEFORE UPDATE OR DELETE</> trigger, and give the column
!    name as the sole trigger argument.  You may wish to restrict the trigger
!    to only fire upon UPDATEs of the <type>lo</> column(s) in the table by
!    specifying the column name via BEFORE UPDATE OF 
!    <replaceable class="parameter">column_name</replaceable> as in the example
!    above.
!   </para>
! 
!   <para>
!    If you need multiple <type>lo</>
     columns in the same table, create a separate trigger for each one,
     remembering to give a different name to each trigger on the same table.
    </para>

view thread (5+ messages)  latest in thread

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected]
  Subject: Re: lo_manage trigger on updates
  In-Reply-To: <CAK3UJRHaEuzfnZaxarcV8=RP1sC5xLxumzqx6iiyqpJVS89rjw@mail.gmail.com>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox