Re: [HACKERS] Patch to fix documentation about AFTER triggers
On Mon, May 15, 2017 at 7:00 AM, Ashutosh Bapat wrote: > On Sat, May 13, 2017 at 2:45 AM, Paul Jungwirth > wrote: >> 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. > > https://www.postgresql.org/docs/devel/static/trigger-definition.html says > "The return value is ignored for row-level triggers fired after an > operation, and so they can return NULL.". There's nothing wrong with > the example, returning OLD or NEW, but as you have pointed out it's > confusing. So, +1 for this change. Committed. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Patch to fix documentation about AFTER triggers
On Sat, May 13, 2017 at 2:45 AM, Paul Jungwirth wrote: > 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. https://www.postgresql.org/docs/devel/static/trigger-definition.html says "The return value is ignored for row-level triggers fired after an operation, and so they can return NULL.". There's nothing wrong with the example, returning OLD or NEW, but as you have pointed out it's confusing. So, +1 for this change. -- Best Wishes, Ashutosh Bapat EnterpriseDB Corporation The Postgres Database Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
[HACKERS] Patch to fix documentation about AFTER triggers
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 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; -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
