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Support triggers on views.

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This patch adds the SQL-standard concept of an INSTEAD OF trigger, which
is fired instead of performing a physical insert/update/delete.  The
trigger function is passed the entire old and/or new rows of the view,
and must figure out what to do to the underlying tables to implement
the update.  So this feature can be used to implement updatable views
using trigger programming style rather than rule hacking.

In passing, this patch corrects the names of some columns in the
information_schema.triggers view.  It seems the SQL committee renamed
them somewhere between SQL:99 and SQL:2003.

Dean Rasheed, reviewed by Bernd Helmle; some additional hacking by me.
This commit is contained in:
Tom Lane
2010-10-10 13:43:33 -04:00
parent f7b15b5098
commit 2ec993a7cb
47 changed files with 2815 additions and 759 deletions
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16
doc/src/sgml/pltcl.sgml
View File

@@ -591,8 +591,8 @@ SELECT 'doesn''t' AS ret
<term><varname>$TG_when</varname></term>
<listitem>
<para>
The string <literal>BEFORE</> or <literal>AFTER</> depending on the
type of trigger event.
The string <literal>BEFORE</>, <literal>AFTER</>, or
<literal>INSTEAD OF</>, depending on the type of trigger event.
</para>
</listitem>
</varlistentry>
@@ -665,10 +665,14 @@ SELECT 'doesn''t' AS ret
the operation (<command>INSERT</>/<command>UPDATE</>/<command>DELETE</>) that fired the trigger will proceed
normally. <literal>SKIP</> tells the trigger manager to silently suppress
the operation for this row. If a list is returned, it tells PL/Tcl to
return a modified row to the trigger manager that will be inserted
instead of the one given in <varname>$NEW</>. (This works for <command>INSERT</> and <command>UPDATE</>
only.) Needless to say that all this is only meaningful when the trigger
is <literal>BEFORE</> and <command>FOR EACH ROW</>; otherwise the return value is ignored.
return a modified row to the trigger manager. This is only meaningful
for row-level <literal>BEFORE</> <command>INSERT</> or <command>UPDATE</>
triggers for which the modified row will be inserted instead of the one
given in <varname>$NEW</>; or for row-level <literal>INSTEAD OF</>
<command>INSERT</> or <command>UPDATE</> triggers where the returned row
is used to support <command>INSERT RETURNING</> and
<command>UPDATE RETURNING</> commands. The return value is ignored for
other types of triggers.
</para>
<para>