Function exec_stmt_case

src/pl/plpgsql/src/pl_exec.c:2499–2578

----------- * exec_stmt_case *----------- */

 *-----------
 */
static int
exec_stmt_case(PLpgSQL_execstate *estate, PLpgSQL_stmt_case *stmt)
{
	PLpgSQL_var *t_var = NULL;
	bool		isnull;
	ListCell   *l;

	if (stmt->t_expr != NULL)
	{
		/* simple case */
		Datum		t_val;
		Oid			t_typoid;
		int32		t_typmod;

		t_val = exec_eval_expr(estate, stmt->t_expr,
							   &isnull, &t_typoid, &t_typmod);

		t_var = (PLpgSQL_var *) estate->datums[stmt->t_varno];

		/*
		 * When expected datatype is different from real, change it. Note that
		 * what we're modifying here is an execution copy of the datum, so
		 * this doesn't affect the originally stored function parse tree. (In
		 * theory, if the expression datatype keeps changing during execution,
		 * this could cause a function-lifespan memory leak.  Doesn't seem
		 * worth worrying about though.)
		 */
		if (t_var->datatype->typoid != t_typoid ||
			t_var->datatype->atttypmod != t_typmod)
			t_var->datatype = plpgsql_build_datatype(t_typoid,
													 t_typmod,
													 estate->func->fn_input_collation,
													 NULL);

		/* now we can assign to the variable */
		exec_assign_value(estate,
						  (PLpgSQL_datum *) t_var,
						  t_val,
						  isnull,
						  t_typoid,
						  t_typmod);

		exec_eval_cleanup(estate);
	}

	/* Now search for a successful WHEN clause */
	foreach(l, stmt->case_when_list)
	{
		PLpgSQL_case_when *cwt = (PLpgSQL_case_when *) lfirst(l);
		bool		value;

		value = exec_eval_boolean(estate, cwt->expr, &isnull);
		exec_eval_cleanup(estate);
		if (!isnull && value)
		{
			/* Found it */

			/* We can now discard any value we had for the temp variable */