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Commit9fcc0ba

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Doc: note that statement-level view triggers require an INSTEAD OF trigger.
If a view lacks an INSTEAD OF trigger, DML on it can only work by rewritingthe command into a command on the underlying base table(s). Then we willfire triggers attached to those table(s), not those for the view. Thisseems appropriate from a consistency standpoint, but nowhere was thebehavior explicitly documented, so let's do that.There was some discussion of throwing an error or warning if a statementtrigger is created on a view without creating a row INSTEAD OF trigger.But a simple implementation of that would result in dump/restore orderinghazards. Given that it's been like this all along, and we hadn't hearda complaint till now, a documentation improvement seems sufficient.Per bug #15106 from Pu Qun. Back-patch to all supported branches.Discussion:https://postgr.es/m/152083391168.1215.16892140713507052796@wrigleys.postgresql.org
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‎doc/src/sgml/ref/create_trigger.sgml

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@@ -409,6 +409,19 @@ UPDATE OF <replaceable>column_name1</replaceable> [, <replaceable>column_name2</
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rows.
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</para>
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<para>
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Statement-level triggers on a view are fired only if the action on the
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view is handled by a row-level <literal>INSTEAD OF</literal> trigger.
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If the action is handled by an <literal>INSTEAD</literal> rule, then
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whatever statements are emitted by the rule are executed in place of the
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original statement naming the view, so that the triggers that will be
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fired are those on tables named in the replacement statements.
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Similarly, if the view is automatically updatable, then the action is
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handled by automatically rewriting the statement into an action on the
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view's base table, so that the base table's statement-level triggers are
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the ones that are fired.
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</para>
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<para>
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In <productname>PostgreSQL</productname> versions before 7.3, it was
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necessary to declare trigger functions as returning the placeholder

‎doc/src/sgml/trigger.sgml

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@@ -56,15 +56,21 @@
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<para>
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On views, triggers can be defined to execute instead of
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<command>INSERT</command>, <command>UPDATE</command>, or
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<command>DELETE</command> operations. <literal>INSTEAD OF</> triggers
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<command>DELETE</command> operations.
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Such <literal>INSTEAD OF</literal> triggers
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are fired once for each row that needs to be modified in the view.
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It is the responsibility of the
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trigger's function to perform the necessary modifications to the
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underlying basetables and, where appropriate, return the modified
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trigger's function to perform the necessary modifications to the view's
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underlying basetable(s) and, where appropriate, return the modified
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row as it will appear in the view. Triggers on views can also be defined
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to execute once per <acronym>SQL</acronym> statement, before or after
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<command>INSERT</command>, <command>UPDATE</command>, or
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<command>DELETE</command> operations.
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However, such triggers are fired only if there is also
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an <literal>INSTEAD OF</literal> trigger on the view. Otherwise,
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any statement targeting the view must be rewritten into a statement
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affecting its underlying base table(s), and then the triggers
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that will be fired are the ones attached to the base table(s).
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</para>
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<para>

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