Function plpgsql_exec_trigger

src/pl/plpgsql/src/pl_exec.c:905–1138

---------- * plpgsql_exec_trigger Called by the call handler for * trigger execution. * ---------- */

 * ----------
 */
HeapTuple
plpgsql_exec_trigger(PLpgSQL_function *func,
					 TriggerData *trigdata)
{
	PLpgSQL_execstate estate;
	ErrorContextCallback plerrcontext;
	int			rc;
	TupleDesc	tupdesc;
	PLpgSQL_rec *rec_new,
			   *rec_old;
	HeapTuple	rettup;

	/*
	 * Setup the execution state
	 */
	plpgsql_estate_setup(&estate, func, NULL, NULL, NULL);
	estate.trigdata = trigdata;

	/*
	 * Setup error traceback support for ereport()
	 */
	plerrcontext.callback = plpgsql_exec_error_callback;
	plerrcontext.arg = &estate;
	plerrcontext.previous = error_context_stack;
	error_context_stack = &plerrcontext;

	/*
	 * Make local execution copies of all the datums
	 */
	estate.err_text = gettext_noop("during initialization of execution state");
	copy_plpgsql_datums(&estate, func);

	/*
	 * Put the OLD and NEW tuples into record variables
	 *
	 * We set up expanded records for both variables even though only one may
	 * have a value.  This allows record references to succeed in functions
	 * that are used for multiple trigger types.  For example, we might have a
	 * test like "if (TG_OP = 'INSERT' and NEW.foo = 'xyz')", which should
	 * work regardless of the current trigger type.  If a value is actually
	 * fetched from an unsupplied tuple, it will read as NULL.
	 */
	tupdesc = RelationGetDescr(trigdata->tg_relation);

	rec_new = (PLpgSQL_rec *) (estate.datums[func->new_varno]);
	rec_old = (PLpgSQL_rec *) (estate.datums[func->old_varno]);

	rec_new->erh = make_expanded_record_from_tupdesc(tupdesc,
													 estate.datum_context);
	rec_old->erh = make_expanded_record_from_exprecord(rec_new->erh,
													   estate.datum_context);

	if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
	{
		/*
		 * Per-statement triggers don't use OLD/NEW variables
		 */
	}