To: Pgsql Hackers <pgsql-hackers@postgresql.org>
From: Paul Jungwirth <pj@illuminatedcomputing.com>
Subject: Patch to fix documentation about AFTER triggers
Message-ID: <e24a6a6d-5670-739b-00f3-41a226a80f25@illuminatedcomputing.com>
Date: Fri, 12 May 2017 14:15:37 -0700
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Here is a patch to amend the docs here:

https://www.postgresql.org/docs/devel/static/plpgsql-trigger.html

In the example for an AFTER trigger, you see this code:

     --
     -- Create a row in emp_audit to reflect the operation performed on emp,
     -- make use of the special variable TG_OP to work out the operation.
     --
     IF (TG_OP = 'DELETE') THEN
         INSERT INTO emp_audit SELECT 'D', now(), user, OLD.*;
         RETURN OLD;
      ELSIF (TG_OP = 'UPDATE') THEN
         INSERT INTO emp_audit SELECT 'U', now(), user, NEW.*;
         RETURN NEW;
     ELSIF (TG_OP = 'INSERT') THEN
         INSERT INTO emp_audit SELECT 'I', now(), user, NEW.*;
         RETURN NEW;
     END IF;
     RETURN NULL; -- result is ignored since this is an AFTER trigger

What are all those RETURNs doing in there? The comment on the final 
RETURN is correct, so returning NEW or OLD above seems confusing, and 
likely a copy/paste error.

This patch just removes those three lines from the example code.

Thanks!
Paul

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diff --git a/doc/src/sgml/plpgsql.sgml b/doc/src/sgml/plpgsql.sgml
index a6088e9..dc29e7c 100644
--- a/doc/src/sgml/plpgsql.sgml
+++ b/doc/src/sgml/plpgsql.sgml
@@ -3999,13 +3999,10 @@ CREATE OR REPLACE FUNCTION process_emp_audit() RETURNS TRIGGER AS $emp_audit$
         --
         IF (TG_OP = 'DELETE') THEN
             INSERT INTO emp_audit SELECT 'D', now(), user, OLD.*;
-            RETURN OLD;
         ELSIF (TG_OP = 'UPDATE') THEN
             INSERT INTO emp_audit SELECT 'U', now(), user, NEW.*;
-            RETURN NEW;
         ELSIF (TG_OP = 'INSERT') THEN
             INSERT INTO emp_audit SELECT 'I', now(), user, NEW.*;
-            RETURN NEW;
         END IF;
         RETURN NULL; -- result is ignored since this is an AFTER trigger
     END;

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