src\backend\cdb\cdbvars.c:
bool
gpvars_check_statement_mem(int *newval, void **extra, GucSource source)
{
	if (*newval >= max_statement_mem)
	{
		GUC_check_errmsg("Invalid input for statement_mem, must be less than max_statement_mem (%d kB)",
						 max_statement_mem);
	}

	return true;
}