clob变量值无法使用v$sql_bind_capture获得

clob情形：
SQL> variable test_c clob;
SQL> exec :test_c := "test";

PL/SQL procedure successfully completed.

SQL> select * from test_clob where dbms_lob.substr(name,4000)=dbms_lob.substr(:test_c,4000);

NAME
--------------------------------------------------------------------------------
test

SQL> select sql_id,sql_text from v$sql where sql_text like "select * from test_clob%";
65v08jhcjtuun
select * from test_clob where dbms_lob.substr(name,4000)=dbms_lob.substr(:test_c
,4000)


SQL> select value_string from v$sql_bind_capture where sql_id="65v08jhcjtuun";

VALUE_STRING
clob情形：
SQL> variable test_c clob;
SQL> exec :test