Daily Archives: 2011 年 09 月 09 日

Oracle DDL 并行(10G)

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1、CREATE INDEX 操作

SQL> conn chf/xifenfei
Connected.
SQL> EXPLAIN PLAN FOR create index ind_t2 on t1(object_name) online nologging PARALLEL(degree 4);

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 2130784087

--------------------------------------------------------------------------
| Id  | Operation                | Name     |    TQ  |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------
|   0 | CREATE INDEX STATEMENT   |          |        |      |            |
|   1 |  PX COORDINATOR          |          |        |      |            |
|   2 |   PX SEND QC (ORDER)     | :TQ10001 |  Q1,01 | P->S | QC (ORDER) |
|   3 |    INDEX BUILD NON UNIQUE| IND_T2   |  Q1,01 | PCWP |            |
|   4 |     SORT CREATE INDEX    |          |  Q1,01 | PCWP |            |
|   5 |      PX RECEIVE          |          |  Q1,01 | PCWP |            |
|   6 |       PX SEND RANGE      | :TQ10000 |  Q1,00 | P->P | RANGE      |
|   7 |        PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|   8 |         TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
--------------------------------------------------------------------------

SQL> conn chf/xifenfei
Connected.
SQL> ALTER SESSION ENABLE PARALLEL DDL;

Session altered.

SQL> EXPLAIN PLAN FOR create index ind_t2 on t1(object_name) online nologging PARALLEL(degree 4);

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 2130784087

--------------------------------------------------------------------------
| Id  | Operation                | Name     |    TQ  |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------
|   0 | CREATE INDEX STATEMENT   |          |        |      |            |
|   1 |  PX COORDINATOR          |          |        |      |            |
|   2 |   PX SEND QC (ORDER)     | :TQ10001 |  Q1,01 | P->S | QC (ORDER) |
|   3 |    INDEX BUILD NON UNIQUE| IND_T2   |  Q1,01 | PCWP |            |
|   4 |     SORT CREATE INDEX    |          |  Q1,01 | PCWP |            |
|   5 |      PX RECEIVE          |          |  Q1,01 | PCWP |            |
|   6 |       PX SEND RANGE      | :TQ10000 |  Q1,00 | P->P | RANGE      |
|   7 |        PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|   8 |         TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
--------------------------------------------------------------------------

2、REBUILD INDEX 操作

SQL> conn chf/xifenfei
Connected.
SQL> EXPLAIN PLAN FOR alter  index ind_t2 rebuild online nologging PARALLEL(degree 4);

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 2130784087

--------------------------------------------------------------------------
| Id  | Operation                | Name     |    TQ  |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------
|   0 | ALTER INDEX STATEMENT    |          |        |      |            |
|   1 |  PX COORDINATOR          |          |        |      |            |
|   2 |   PX SEND QC (ORDER)     | :TQ10001 |  Q1,01 | P->S | QC (ORDER) |
|   3 |    INDEX BUILD NON UNIQUE| IND_T2   |  Q1,01 | PCWP |            |
|   4 |     SORT CREATE INDEX    |          |  Q1,01 | PCWP |            |
|   5 |      PX RECEIVE          |          |  Q1,01 | PCWP |            |
|   6 |       PX SEND RANGE      | :TQ10000 |  Q1,00 | P->P | RANGE      |
|   7 |        PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|   8 |         TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
--------------------------------------------------------------------------

SQL> conn chf/xifenfei
Connected.
SQL> ALTER SESSION ENABLE PARALLEL DDL;

Session altered.

SQL> EXPLAIN PLAN FOR alter  index ind_t2 rebuild online nologging PARALLEL(degree 4);

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 2130784087

--------------------------------------------------------------------------
| Id  | Operation                | Name     |    TQ  |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------
|   0 | ALTER INDEX STATEMENT    |          |        |      |            |
|   1 |  PX COORDINATOR          |          |        |      |            |
|   2 |   PX SEND QC (ORDER)     | :TQ10001 |  Q1,01 | P->S | QC (ORDER) |
|   3 |    INDEX BUILD NON UNIQUE| IND_T2   |  Q1,01 | PCWP |            |
|   4 |     SORT CREATE INDEX    |          |  Q1,01 | PCWP |            |
|   5 |      PX RECEIVE          |          |  Q1,01 | PCWP |            |
|   6 |       PX SEND RANGE      | :TQ10000 |  Q1,00 | P->P | RANGE      |
|   7 |        PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|   8 |         TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
--------------------------------------------------------------------------

3、CREATE TABLE 操作

SQL> conn chf/xifenfei
Connected.
SQL> EXPLAIN PLAN FOR create table t_6 parallel (degree 4)
  2    as select /*+ parallel (t1,4) */ * from t1 where rownum<5000000;

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 2102891290

------------------------------------------------------------------------------
| Id  | Operation                    | Name     |    TQ  |IN-OUT| PQ Distrib |
------------------------------------------------------------------------------
|   0 | CREATE TABLE STATEMENT       |          |        |      |            |
|   1 |  PX COORDINATOR              |          |        |      |            |
|   2 |   PX SEND QC (RANDOM)        | :TQ20001 |  Q2,01 | P->S | QC (RAND)  |
|   3 |    LOAD AS SELECT            | T_6      |  Q2,01 | PCWP |            |
|   4 |     BUFFER SORT              |          |  Q2,01 | PCWC |            |
|   5 |      PX RECEIVE              |          |  Q2,01 | PCWP |            |
|   6 |       PX SEND ROUND-ROBIN    | :TQ20000 |        | S->P | RND-ROBIN  |
|   7 |        COUNT STOPKEY         |          |        |      |            |
|   8 |         PX COORDINATOR       |          |        |      |            |
|   9 |          PX SEND QC (RANDOM) | :TQ10000 |  Q1,00 | P->S | QC (RAND)  |
|  10 |           COUNT STOPKEY      |          |  Q1,00 | PCWC |            |
|  11 |            PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|  12 |             TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
------------------------------------------------------------------------------

SQL> conn chf/xifenfei
Connected.
SQL> ALTER SESSION ENABLE PARALLEL DDL;

Session altered.

SQL> EXPLAIN PLAN FOR create table t_6 parallel (degree 4)
  2    as select /*+ parallel (t1,4) */ * from t1 where rownum<5000000;

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 2102891290

------------------------------------------------------------------------------
| Id  | Operation                    | Name     |    TQ  |IN-OUT| PQ Distrib |
------------------------------------------------------------------------------
|   0 | CREATE TABLE STATEMENT       |          |        |      |            |
|   1 |  PX COORDINATOR              |          |        |      |            |
|   2 |   PX SEND QC (RANDOM)        | :TQ20001 |  Q2,01 | P->S | QC (RAND)  |
|   3 |    LOAD AS SELECT            | T_6      |  Q2,01 | PCWP |            |
|   4 |     BUFFER SORT              |          |  Q2,01 | PCWC |            |
|   5 |      PX RECEIVE              |          |  Q2,01 | PCWP |            |
|   6 |       PX SEND ROUND-ROBIN    | :TQ20000 |        | S->P | RND-ROBIN  |
|   7 |        COUNT STOPKEY         |          |        |      |            |
|   8 |         PX COORDINATOR       |          |        |      |            |
|   9 |          PX SEND QC (RANDOM) | :TQ10000 |  Q1,00 | P->S | QC (RAND)  |
|  10 |           COUNT STOPKEY      |          |  Q1,00 | PCWC |            |
|  11 |            PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|  12 |             TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
------------------------------------------------------------------------------

4、说明
1）本次测试的数据库版本为10.2.0.4，Linux环境，其他版本可能有差异
2）关于INDEX的并行操作，并行度可能不会和指定相同（测试为2倍）
3）操作过程中，是否指定ddl 并发，效果相同。建议指定未佳：
ALTER SESSION ENABLE PARALLEL DDL;
ALTER SESSION DISABLE PARALLEL DDL;
4）修改表结构操作，指定并发无效（待寻找方法）

Oracle DML并行

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1、UPDATE 操作

SQL> conn chf/xifenfei
Connected.
SQL> EXPLAIN PLAN FOR update /*+ parallel (t1,4) */ t1 set object_name='chengfei';

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 121765358

-----------------------------------------------------------------------
| Id  | Operation             | Name     |    TQ  |IN-OUT| PQ Distrib |
-----------------------------------------------------------------------
|   0 | UPDATE STATEMENT      |          |        |      |            |
|   1 |  UPDATE               | T1       |        |      |            |
|   2 |   PX COORDINATOR      |          |        |      |            |
|   3 |    PX SEND QC (RANDOM)| :TQ10000 |  Q1,00 | P->S | QC (RAND)  |
|   4 |     PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|   5 |      TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
--------------------------------------------------------------------------

SQL> conn chf/xifenfei
Connected.
SQL> ALTER SESSION ENABLE  PARALLEL DML;

Session altered.

SQL> EXPLAIN PLAN FOR update /*+ parallel (t1,4) */ t1 set object_name='chengfei';

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 3308547044

--------------------------------------------------------------------------
| Id  | Operation                | Name     |    TQ  |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------
|   0 | UPDATE STATEMENT         |          |        |      |            |
|   1 |  PX COORDINATOR          |          |        |      |            |
|   2 |   PX SEND QC (RANDOM)    | :TQ10001 |  Q1,01 | P->S | QC (RAND)  |
|   3 |    INDEX MAINTENANCE     | T1       |  Q1,01 | PCWP |            |
|   4 |     PX RECEIVE           |          |  Q1,01 | PCWP |            |
|   5 |      PX SEND RANGE       | :TQ10000 |  Q1,00 | P->P | RANGE      |
|   6 |       UPDATE             | T1       |  Q1,00 | PCWP |            |
|   7 |        PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|   8 |         TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
--------------------------------------------------------------------------

通过执行计划可以看出，只有执行了ALTER SESSION ENABLE PARALLEL DML后，UPDATE操作才真正的实现了并行操作，如果不执行该语句，只是执行了并发查询，并没有实现并发更新操作

2、DELETE 操作

SQL> conn chf/xifenfei
Connected.
SQL> EXPLAIN PLAN FOR delete /*+ parallel (t1,3) */ from t1;

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 3718066193

-----------------------------------------------------------------------
| Id  | Operation             | Name     |    TQ  |IN-OUT| PQ Distrib |
-----------------------------------------------------------------------
|   0 | DELETE STATEMENT      |          |        |      |            |
|   1 |  DELETE               | T1       |        |      |            |
|   2 |   PX COORDINATOR      |          |        |      |            |
|   3 |    PX SEND QC (RANDOM)| :TQ10000 |  Q1,00 | P->S | QC (RAND)  |
|   4 |     PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|   5 |      TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
-----------------------------------------------------------------------

SQL> conn chf/xifenfei
Connected.
SQL> ALTER SESSION ENABLE  PARALLEL DML;

Session altered.

SQL> EXPLAIN PLAN FOR delete /*+ parallel (t1,3) */ from t1;

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 2132458150

--------------------------------------------------------------------------
| Id  | Operation                | Name     |    TQ  |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------
|   0 | DELETE STATEMENT         |          |        |      |            |
|   1 |  PX COORDINATOR          |          |        |      |            |
|   2 |   PX SEND QC (RANDOM)    | :TQ10001 |  Q1,01 | P->S | QC (RAND)  |
|   3 |    INDEX MAINTENANCE     | T1       |  Q1,01 | PCWP |            |
|   4 |     PX RECEIVE           |          |  Q1,01 | PCWP |            |
|   5 |      PX SEND RANGE       | :TQ10000 |  Q1,00 | P->P | RANGE      |
|   6 |       DELETE             | T1       |  Q1,00 | PCWP |            |
|   7 |        PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|   8 |         TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
--------------------------------------------------------------------------

试验证明，也需要执行ALTER SESSION ENABLE PARALLEL DML，才能够实现真正的删除并发操作

3、INSERT 操作

SQL> conn chf/xifenfei
Connected.
SQL> EXPLAIN PLAN FOR INSERT  /*+ parallel (t_1,4) */ INTO t_1 SELECT /*+ parallel (t1,4) */* FROM t1;

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 2494645258

----------------------------------------------------------------------
| Id  | Operation            | Name     |    TQ  |IN-OUT| PQ Distrib |
----------------------------------------------------------------------
|   0 | INSERT STATEMENT     |          |        |      |            |
|   1 |  PX COORDINATOR      |          |        |      |            |
|   2 |   PX SEND QC (RANDOM)| :TQ10000 |  Q1,00 | P->S | QC (RAND)  |
|   3 |    PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|   4 |     TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
----------------------------------------------------------------------

SQL> conn chf/xifenfei
Connected.
SQL> ALTER SESSION ENABLE  PARALLEL DML;

Session altered.

SQL> EXPLAIN PLAN FOR INSERT  /*+ parallel (t_1,4) */ INTO t_1 SELECT /*+ parallel (t1,4) */* FROM t1;

Explained.

SQL> SELECT * FROM table (DBMS_XPLAN.display(NULL, NULL, 'BASIC +PARALLEL'));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 783041698

-------------------------------------------------------------------------
| Id  | Operation               | Name     |    TQ  |IN-OUT| PQ Distrib |
-------------------------------------------------------------------------
|   0 | INSERT STATEMENT        |          |        |      |            |
|   1 |  PX COORDINATOR         |          |        |      |            |
|   2 |   PX SEND QC (RANDOM)   | :TQ10001 |  Q1,01 | P->S | QC (RAND)  |
|   3 |    LOAD AS SELECT       | T_1      |  Q1,01 | PCWP |            |
|   4 |     PX RECEIVE          |          |  Q1,01 | PCWP |            |
|   5 |      PX SEND ROUND-ROBIN| :TQ10000 |  Q1,00 | P->P | RND-ROBIN  |
|   6 |       PX BLOCK ITERATOR |          |  Q1,00 | PCWC |            |
|   7 |        TABLE ACCESS FULL| T1       |  Q1,00 | PCWP |            |
-------------------------------------------------------------------------

通过这个执行计划可以发现，数据是被使用APPEND方式插入到表中，如果需要常规方式插入，需要加上noappend提示，同样设置了session 并行dml才能够实现真正意义上的插入并发操作

4、总结
通过上面的试验可以得出，如果要DML实现真正意义上的并发，在开始执行需要并发语句前，需要执行开启session并发
ALTER SESSION ENABLE PARALLEL DML;
在执行完语句后，需要执行关闭session并发
ALTER SESSION DISABLE PARALLEL DML;