[Oracle] Index 사이즈 예측

exec dbms_stats.gather_table_stats(ownname => '', tabname=>'', estimate_percent=>100, block_sample=>true, method_opt=>'FOR ALL COLUMNS size 254');


declare 
	l_used_bytes number;
	l_alloc_bytes number;
begin
	dbms_space.create_index_cost ( 
		ddl => '',
		used_bytes => l_used_bytes,
		alloc_bytes => l_alloc_bytes
		); 
    dbms_output.put_line ('Used Bytes =' || l_used_bytes);
    dbms_output.put_line ('Allocated Bytes =' || l_used_bytes);
end;
/