database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-26 01:22:12 +03:00
Code Activity

Small wording improvement and clarification in PL/pgSQL trigger documentation

Browse Source
This commit is contained in:
Peter Eisentraut
2009-12-28 19:11:51 +00:00
parent 0d399d57d5
commit 50ef9f7b06
1 changed files with 18 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
doc/src/sgml/plpgsql.sgml
View File

@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.148 2009/12/19 01:49:02 tgl Exp $ --> <!-- $PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.149 2009/12/28 19:11:51 petere Exp $ -->
<chapter id="plpgsql"> <chapter id="plpgsql">
<title><application>PL/pgSQL</application> - <acronym>SQL</acronym> Procedural Language</title> <title><application>PL/pgSQL</application> - <acronym>SQL</acronym> Procedural Language</title>
@ -3197,16 +3197,26 @@ RAISE unique_violation USING MESSAGE = 'Duplicate user ID: ' || user_id;
for this row). If a nonnull for this row). If a nonnull
value is returned then the operation proceeds with that row value. value is returned then the operation proceeds with that row value.
Returning a row value different from the original value Returning a row value different from the original value
of <varname>NEW</> alters the row that will be inserted or updated of <varname>NEW</> alters the row that will be inserted or
(but has no direct effect in the <command>DELETE</> case). updated. Thus, if the trigger function wants the triggering
To alter the row to be stored, it is possible to replace single values action to succeed normally without altering the row
directly in <varname>NEW</> and return the modified <varname>NEW</>, value, <varname>NEW</varname> (or a value equal thereto) has to be
or to build a complete new record/row to return. returned. To alter the row to be stored, it is possible to
replace single values directly in <varname>NEW</> and return the
modified <varname>NEW</>, or to build a complete new record/row to
return. In the case of a before-trigger
on <command>DELETE</command>, the returned value has no direct
effect, but it has to be nonnull to allow the trigger action to
proceed. Note that <varname>NEW</varname> is null
in <command>DELETE</command> triggers, so returning that is
usually not sensible. A useful idiom in <command>DELETE</command>
triggers might be to return <varname>OLD</varname>.
</para> </para>
<para> <para>
The return value of a <literal>BEFORE</> or <literal>AFTER</> The return value of a row-level trigger
statement-level trigger or an <literal>AFTER</> row-level trigger is fired <literal>AFTER</literal> or a statement-level trigger
fired <literal>BEFORE</> or <literal>AFTER</> is
always ignored; it might as well be null. However, any of these types of always ignored; it might as well be null. However, any of these types of
triggers might still abort the entire operation by raising an error. triggers might still abort the entire operation by raising an error.
</para> </para>