Append hint not working

Question

Hi All,
SQL> select * from v$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - 64bit Production
PL/SQL Release 11.1.0.7.0 - Production
CORE    11.1.0.7.0      Production
TNS for Linux: Version 11.1.0.7.0 - Production
NLSRTL Version 11.1.0.7.0 - ProductionI am expecting direct path insert from my INSERT with APPEND hint. But thats not working.
Non of the tables involved are nologging, nor they have parallel mode enabled (code given below).
So, I am expecting, serial direct path insert, with logging.
SQL> select * from table( dbms_xplan.display_cursor('fb1hftqrnm9cy') ) ;
PLAN_TABLE_OUTPUT
SQL_ID  fb1hftqrnm9cy, child number 0
INSERT /*+ APPEND */ INTO NEW_TABLE SELECT * FROM
OLD_TABLE WHERE PROCESS_DATE = :B1
Plan hash value: 3268711246
| Id  | Operation                     | Name                           | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | INSERT STATEMENT              |                                |       |       |   588K(100)|          |
|   1 |  LOAD TABLE CONVENTIONAL      |                                |       |       |            |          |
|   2 |   TABLE ACCESS BY INDEX ROWID | OLD_TABLE                      |  6078K|   446M|   588K  (1)| 01:57:44 |
|   3 |    BITMAP CONVERSION TO ROWIDS|                                |       |       |            |          |
|*  4 |     BITMAP INDEX SINGLE VALUE | OLD_TABLE_IDX1                 |       |       |            |          |
Predicate Information (identified by operation id):
   4 - access("PROCESS_DATE"=:B1)Here, you can see the actual SQL (with APPEND hint) and the plan showing conventional loading.
The process here is, OLD_TABLE is a non-partitioned table with bitmap index on process_date column. NEW_TABLE is a partitioned table, with local index and foreign key (enabled). The insert command is inserting data for a given process_date to NEW_TABLE.
What am I missing here?
Thanks in advance.

Answer 1

If table has a foreign key column, data cannot be loaded with direct path:
SQL> select * from v$version;
BANNER
Oracle Database 11g Express Edition Release 11.2.0.2.0 - Production
PL/SQL Release 11.2.0.2.0 - Production
CORE    11.2.0.2.0      Production
TNS for 32-bit Windows: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production
SQL> drop table tp purge;
Table dropped.
SQL> drop table tc purge;
Table dropped.
SQL> create table tp(px int primary key);
Table created.
SQL> create table tc(cx int, cy references tp);
Table created.
SQL> insert into tp values(1);
1 row created.
SQL> commit;
Commit complete.
SQL> insert /*+ append */ into tc select 1,1 from dual;
1 row created.
SQL> select * from table( dbms_xplan.display_cursor()) ;
PLAN_TABLE_OUTPUT
SQL_ID  7wr256fb8tz82, child number 1
insert /*+ append */ into tc select 1,1 from dual
Plan hash value: 1388734953
| Id  | Operation                | Name | Rows  | Cost (%CPU)| Time     |
|   0 | INSERT STATEMENT         |      |       |     2 (100)|          |
|   1 |  LOAD TABLE CONVENTIONAL |      |       |            |          |
PLAN_TABLE_OUTPUT
|   2 |   FAST DUAL              |      |     1 |     2   (0)| 00:00:01 |
14 rows selected.
SQL> --
SQL> --
SQL> drop table tc purge;
Table dropped.
SQL> create table tc(cx int, cy int);
Table created.
SQL> commit;
Commit complete.
SQL> insert /*+ append */ into tc select 1,1 from dual;
1 row created.
SQL> select * from table( dbms_xplan.display_cursor()) ;
PLAN_TABLE_OUTPUT
SQL_ID  7wr256fb8tz82, child number 1
insert /*+ append */ into tc select 1,1 from dual
Plan hash value: 2781518217
| Id  | Operation        | Name | Rows  | Cost (%CPU)| Time     |
|   0 | INSERT STATEMENT |      |       |     2 (100)|          |
|   1 |  LOAD AS SELECT  |      |       |            |          |
PLAN_TABLE_OUTPUT
|   2 |   FAST DUAL      |      |     1 |     2   (0)| 00:00:01 |
14 rows selected.
SQL>See also http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1211797200346279484#2096268200346987629.
Edited by: P. Forstmann on 14 nov. 2011 13:18