测试如下：

SQL> create table test(a char(1),b long) tablespace users;

Table created.

SQL> insert into test values('1','aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa');

1 row created.

SQL> commit;

Commit complete.

SQL> exec dbms_stats.gather_table_stats(user,'test',cascade=>true);

PL/SQL procedure successfully completed.

SQL> select table_name,num_rows,avg_row_len from user_tables where table_name='TEST';

TABLE_NAME                       NUM_ROWS AVG_ROW_LEN
------------------------------ ---------- -----------
TEST                                    1           2

SQL> drop table test;

Table dropped.

SQL>  create table test(a char(1),b long) tablespace users;

Table created.

SQL>  insert into test values('1','aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa');

1 row created.

SQL> commit;

Commit complete.

SQL> analyze table test compute statistics;

Table analyzed.

SQL> select table_name,num_rows,avg_row_len from user_tables where table_name='TEST';

TABLE_NAME                       NUM_ROWS AVG_ROW_LEN
------------------------------ ---------- -----------
TEST                                    1          89

显然，analyze命令收集long字段的长度，而dbms_stats没有收集，而对于clob字段，dbms_stats包却又收集了其长度信息：

SQL>  create table test(a char(1),b clob) tablespace users;

Table created.

SQL> insert into test values('1','aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa');

1 row created.

SQL> commit;

Commit complete.

SQL> exec dbms_stats.gather_table_stats(user,'test',cascade=>true);

PL/SQL procedure successfully completed.

SQL> select table_name,num_rows,avg_row_len from user_tables where table_name='TEST';

TABLE_NAME                       NUM_ROWS AVG_ROW_LEN
------------------------------ ---------- -----------
TEST                                    1         188

这是否意味着oracle彻底不想使用long类型了。