The following bug has been logged on the website:
Bug reference: 7846
Logged by: Mike Sherrill
Email address: mike@fontling.com
PostgreSQL version: 9.1.6
Operating system: Ubuntu Linux 12.04
Description: =
Documentation for the SQL UPDATE statement doesn't mention that it sets the
FOUND variable. (Refer to sql-update.html, "Outputs".) That behavior *is*
documented, but only in plpgsql-statements.html (Basic Statements, section
39.5.5).
I understand the difference between a SQL statement and a PL/PGSQL
statement. But if I were looking for the effects and side-effects of an
UPDATE statement, I'd go to the docs for UPDATE, not for PL/PGSQL basic
statements. I think that's what most people would do, especially if they
didn't have prior knowledge of the FOUND variable.