On Mon, Oct 10, 2011 at 01:18:56PM -0400, Robert Haas wrote:
> On Thu, Aug 11, 2011 at 11:43 PM, Josh Kupershmidt <[email protected]> wrote:
> > 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?
>
> Uh, wow. That syntax is horribly surprising, isn't it? My eyes want
> to parse it as:
>
> BEFORE (UPDATE OF raster) OR (DELETE ON image)
>
> ...which is totally wrong.
>
> I'm inclined to think that maybe we should leave that example as-is,
> and maybe add the variant you're proposing as a second example,
> showing how the basic version can be refined.
I have implemented this suggestion with the attached, applied patch to
9.3.
--
Bruce Momjian <[email protected]> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
diff --git a/doc/src/sgml/lo.sgml b/doc/src/sgml/lo.sgml
new file mode 100644
index 3d56ba3..0c11fdc
*** a/doc/src/sgml/lo.sgml
--- b/doc/src/sgml/lo.sgml
*************** CREATE TRIGGER t_raster BEFORE UPDATE OR
*** 76,82 ****
<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>
--- 76,90 ----
<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 can also restrict the trigger
! to only execute on updates to the column with:
!
! <programlisting>
! CREATE TRIGGER t_raster BEFORE UPDATE OF raster OR DELETE ON image
! FOR EACH ROW EXECUTE PROCEDURE lo_manage(raster);
! </programlisting>
!
! 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>
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