If you want to write trigger functions using Tcl, then PL/PTcl allows you to do all the good stuff that you have learned so far, using PL/pgSQL, PL/Perl, and PL/Python. Let's rewrite an example we demonstrated in Chapter 5, PL/pgSQL Trigger Functions. Recall the simple, "Hey, I am called" trigger. This is how the PL/Tcl version of the example looks:
CREATE OR REPLACE FUNCTION notify_trigger_pltcl() RETURNS TRIGGER
AS $$
set result [format "Hi, I got %s invoked FOR %s %s %s on %s" $TG_name $TG_level $TG_when $TG_op $TG_table_name]
if {$TG_op == "UPDATE"} {
append result [format " OLD = %s AND NEW=%s" $OLD(i) $NEW(i)]
set NEW(i) [expr $OLD(i) + $NEW(i)]
elog NOTICE $result
return [array get NEW]
} elseif {$TG_op == "DELETE"} {
elog NOTICE "DELETE"
return SKIP
} elog NOTICE $result
return OK
$$ LANGUAGE pltcl;
CREATE TABLE notify_test_pltcl(i int);
CREATE TRIGGER notify_insert_pltcl_trigger
BEFORE INSERT OR UPDATE...