docs: clarify that only INSERT and UPDATE triggers can mod. NEW

The point is that DELETE triggers cannot modify any values.

Reported-by: Eugen Konkov
Discussion: https://postgr.es/m/919823407.20191029175436@yandex.ru

Backpatch-through: 9.4

diff --git a/doc/src/sgml/trigger.sgml b/doc/src/sgml/trigger.sgml
index be9c2284481b0b7a075c30c0333b6efb7b822aef..f372f0ab8e9b9388899d569692c17d25513ff848 100644 (file)
--- a/doc/src/sgml/trigger.sgml
+++ b/doc/src/sgml/trigger.sgml
@@ -230,7 +230,7 @@
     used to signal that the trigger performed the necessary data
     modifications in the view.  This will cause the count of the number
     of rows affected by the command to be incremented. For
-    <command>INSERT</command> and <command>UPDATE</command> operations, the trigger
+    <command>INSERT</command> and <command>UPDATE</command> operations only, the trigger
     may modify the <varname>NEW</varname> row before returning it.  This will
     change the data returned by
     <command>INSERT RETURNING</command> or <command>UPDATE RETURNING</command>,