Oracle12c中分区（Partition）新特性之TRUNCATEPARTITION和EXCHANGE PARTITION级联功能

TRUNCATE [SUB]PARTITION和EXCHANGE [SUB]PARTITION命令如今可以包括CASCADE子句，从而允许参照分区表向下级联这些操作。为确保该选项正常，相关外键也必须包括DELETE子句。

1.        设置

下面创建一个分区父表（T1）和一个参照的分区子表（T2）。每个分区被插入一行数据。

DROP TABLE t2 PURGE;

DROP TABLE t1 PURGE;

CREATE TABLE t1 (

id           NUMBER,

info        VARCHAR2(50),

crt_dateDATE,

CONSTRAINT t1_pk PRIMARY KEY (id)

)

PARTITION BY RANGE (crt_date)

(PARTITION part_2014 VALUES LESS THAN(TO_DATE('01/01/2015', 'DD/MM/YYYY')) TABLESPACE users,

PARTITION part_2015 VALUES LESS THAN(TO_DATE('01/01/2016', 'DD/MM/YYYY')) TABLESPACE users);

CREATE TABLE t2 (

id             NUMBER NOT NULL,

t1_id          NUMBER NOT NULL,

info           VARCHAR2(50),

crt_date   DATE,

CONSTRAINT t2_pk PRIMARY KEY (id),

CONSTRAINTt2_t1_fk FOREIGN KEY (t1_id) REFERENCES t1 (id) ON DELETE CASCADE

)

PARTITION BY REFERENCE (t2_t1_fk);

INSERT INTO t1 VALUES (1, 't1 data',TO_DATE('05/05/2014', 'DD/MM/YYYY'));

INSERT INTO t1 VALUES (2, 't1 data',TO_DATE('05/05/2015', 'DD/MM/YYYY'));

INSERT INTO t2 VALUES (1, 1, 't2 data',TO_DATE('05/05/2014', 'DD/MM/YYYY'));

INSERT INTO t2 VALUES (2, 2, 't2 data',TO_DATE('05/05/2015', 'DD/MM/YYYY'));

COMMIT;

EXEC DBMS_STATS.gather_table_stats(USER,'t1');

EXEC DBMS_STATS.gather_table_stats(USER,'t2');

SELECT table_name,

partition_name,

num_rows

FROM  user_tab_partitions

ORDER BY 1,2;

TABLE_NAME           PARTITION_NAME         NUM_ROWS

-------------------- ------------------------------

T1                   PART_2014                     1

T1                   PART_2015                     1

T2                   PART_2014                     1

T2                   PART_2015                     1

SQL>

2.        TRUNCATE PARTITION ... CASCADE

通过TRUNCATE PARTITION ... CASCADE命令，我们可以清空父表分区和子表分区。

ALTER TABLE t1 TRUNCATE PARTITION part_2014CASCADE UPDATE INDEXES;

EXEC DBMS_STATS.gather_table_stats(USER,'t1');

EXEC DBMS_STATS.gather_table_stats(USER, 't2');

SELECT table_name,

partition_name,

num_rows

FROM  user_tab_partitions

ORDER BY 1,2;

TABLE_NAME           PARTITION_NAME         NUM_ROWS

-------------------- ------------------------------

T1                   PART_2014                     0

T1                   PART_2015                     1

T2                   PART_2014                     0

T2                   PART_2015                     1

SQL>

3.        EXCHANGE PARTITION ... CASCADE

为了测试EXCHANGE PARTITION ...CASCADE命令，创建如下非分区表。为确保层级功能正常，从交换级别开始往下的所有表必须存在。

DROP TABLE t2_temp;

DROP TABLE t1_temp;

CREATE TABLE t1_temp (

id           NUMBER,

info  VARCHAR2(50),

crt_dateDATE,

CONSTRAINT t1_temp_pk PRIMARY KEY (id)

);

CREATE TABLE t2_temp (

id             NUMBER NOT NULL,

t1_id          NUMBER NOT NULL,

info    VARCHAR2(50),

crt_date   DATE,

CONSTRAINT t2_temp_pk PRIMARY KEY (id),

CONSTRAINT t2_temp_t1_temp_fk FOREIGN KEY (t1_id) REFERENCES t1_temp(id) ON DELETE CASCADE

);

INSERT INTO t1_temp VALUES (2, 't1_temp data',TO_DATE('05/05/2015', 'DD/MM/YYYY'));

INSERT INTO t2_temp VALUES (2, 2, 't2_tempdata', TO_DATE('05/05/2015', 'DD/MM/YYYY'));

COMMIT;

如下交换父表和子表分区后，检查表中数据。

-- 交换分区

ALTER TABLE t1

EXCHANGE PARTITION part_2015

WITHTABLE t1_temp

CASCADE

UPDATEINDEXES;

-- 检查分区中的数据

COLUMN t1_info FORMAT A20

COLUMN t2_info FORMAT A20

SELECT t1.info AS t1_info,

t2.info AS t2_info

FROM  t1

JOIN t2 ON t2.t1_id = t1.id;

T1_info              T2_info

-------------------- --------------------

t1_temp data          t2_temp data

SQL>

-- 检查临时表中的数据。

COLUMN t1_temp_info FORMAT A20

COLUMN t2_temp_info FORMAT A20

SELECT t1_temp.info AS t1_temp_info,

t2_temp.info AS t2_temp_info

FROM  t1_temp

JOIN t2_temp ON t2_temp.t1_id = t1_temp.id;

T1_TEMP_info         T2_TEMP_info

-------------------- --------------------

t1 data               t2 data

SQL>

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