Testing RENAME LOB (Segment) in 23ai

Another new feature of 23ai is the ability to rename a LOB (Segment) in-place without having to use the MOVE clause.

A quick demo :

SQL> -- Version 23ai Free Edition
SQL> select banner from v$version;

BANNER
---------------------------------------------------------------------------------------------------------------------------------
Oracle Database 23ai Free Release 23.0.0.0.0 - Develop, Learn, and Run for Free

SQL>
SQL>
SQL> DROP TABLE my_lob_objects purge;

Table dropped.

SQL>
SQL> -- create the table with a LOB, column name "c",  lob segment name also "c"
SQL> CREATE TABLE my_lob_objects (object_id NUMBER primary key, c CLOB)
  2        lob (c) STORE AS SECUREFILE c
  3        ( TABLESPACE users
  4          DISABLE STORAGE IN ROW
  5          NOCACHE LOGGING
  6          RETENTION AUTO
  7          COMPRESS
  8        );

Table created.

SQL>
SQL> -- query the data dictionary
SQL> select table_name, column_name, segment_name, tablespace_name from user_lobs;

TABLE_NAME       COLUMN_NAME      SEGMENT_NAME         TABLESPACE_NAME
---------------- ---------------- -------------------- ----------------
MY_LOB_OBJECTS   C                C                    USERS

SQL>
SQL> -- insert three rows
SQL> insert into my_lob_objects values (1, dbms_random.string('X',100));

1 row created.

SQL> insert into my_lob_objects values (2, dbms_random.string('X',100));

1 row created.

SQL> insert into my_lob_objects values (3, dbms_random.string('X',100));

1 row created.

SQL>
SQL> -- verify the column name when querying the table
SQL> select * from my_lob_objects;

 OBJECT_ID C
---------- --------------------------------------------------------------------------------
         1 IBGOGKA9QKK56O746IJL3C56ZK9LEO0G1W4LWBN11T8EWCFTTLUW9TPIVQAU8BPSGPQ2ZV57BS0ZPK0S
         2 7K04DVVYDQB1URIQ1OQ2458M8ZOURHWW50XIZDMVGAZH6XVN2KKN4PIGKPY5CSVIQ9KU45LHZPJB33AA
         3 2G5194Z7TSR3XG0K698G587AOZOJ8VN6KFCTCH3074TNCOWCSMOPRJLRGTLIZMDD73XAY4KDD14IW4MG

SQL>
SQL> -- now rename the column
SQL> alter table my_lob_objects rename column c to clob_col;

Table altered.

SQL>
SQL> -- query the data dictionary
SQL> select table_name, column_name, segment_name, tablespace_name from user_lobs;

TABLE_NAME       COLUMN_NAME      SEGMENT_NAME         TABLESPACE_NAME
---------------- ---------------- -------------------- ----------------
MY_LOB_OBJECTS   CLOB_COL         C                    USERS

SQL>
SQL> -- now rename the lob segment
SQL> alter table my_lob_objects rename lob(clob_col) c to my_lob_objects_clob;

Table altered.

SQL>
SQL> -- query the data dictionary
SQL> select table_name, column_name, segment_name, tablespace_name from user_lobs;

TABLE_NAME       COLUMN_NAME      SEGMENT_NAME         TABLESPACE_NAME
---------------- ---------------- -------------------- ----------------
MY_LOB_OBJECTS   CLOB_COL         MY_LOB_OBJECTS_CLOB  USERS

SQL>
SQL> -- verify the column name when querying the table
SQL> select * from my_lob_objects;

 OBJECT_ID CLOB_COL
---------- --------------------------------------------------------------------------------
         1 IBGOGKA9QKK56O746IJL3C56ZK9LEO0G1W4LWBN11T8EWCFTTLUW9TPIVQAU8BPSGPQ2ZV57BS0ZPK0S
         2 7K04DVVYDQB1URIQ1OQ2458M8ZOURHWW50XIZDMVGAZH6XVN2KKN4PIGKPY5CSVIQ9KU45LHZPJB33AA
         3 2G5194Z7TSR3XG0K698G587AOZOJ8VN6KFCTCH3074TNCOWCSMOPRJLRGTLIZMDD73XAY4KDD14IW4MG

SQL>
SQL> -- identify the segment
SQL> select tablespace_name, segment_name, segment_type, bytes/1024 Size_KB
  2  from user_segments
  3  where segment_name = 'MY_LOB_OBJECTS_CLOB'
  4  /

TABLESPACE_NAME  SEGMENT_NAME         SEGMENT_TYPE         SIZE_KB
---------------- -------------------- ------------------ ---------
USERS            MY_LOB_OBJECTS_CLOB  LOBSEGMENT              2304

SQL>

First I create a Table where the Column and LOB (Segment) are both called "C".  In recent versions, SECUREFILE is the default and recommended for LOBs (e.g. with the COMPRESS, DEDUPLICATION and ENCRYPTION advantages).

Then I insert 3 rows.

I then rename the column "C" to "CLOB_COL".

Next, I rename the LOB (Segment) to "MY_LOB_OBJECTS_CLOB".  I include the Table Name because the LOB segment is an independent segment that I might query in USER_SEGMENTS (where Table Name) is not available.  This RENAME LOB clause is new in 23ai and does not require the use of MOVE LOB.

I then verify the new Segment Name for the LOB as well.

Yes, the 2,304KB "size" seems excessive but this will make sense (with the COMPRESS attribute) when the LOB grows much much larger as new rows with long Character-Strings are inserted.