Oracle 11g: 合并分區表-merge partition

Merging Partitions

　　使用ALTER TABLE .. MERGE PARTITION語句將兩個分區的內容合并到另外一個分區，兩個來源資料分割和關聯的local index都會被drop

　　不能用於 hash分區表或 hash subpartitions of a composite *-hash partitioned table

　　不能用於合并引用分區表(reference-partitioned table)

合并定界分割

　　允許合并兩個臨近範圍的分區到另外分區，不相鄰分區無法合并。合并結果分區繼承兩個來源資料分割的最大邊界。

demo:

-- Create a Table with four partitions each on its own tablespace
-- Partitioned by range on the data column.
CREATE TABLE four_seasons
(
        one DATE,
        two VARCHAR2(60),
        three NUMBER
)
PARTITION  BY RANGE ( one )
(
PARTITION quarter_one
  VALUES LESS THAN ( TO_DATE('01-apr-1998','dd-mon-yyyy'))
  TABLESPACE quarter_one,

PARTITION quarter_two
  VALUES LESS THAN ( TO_DATE('01-jul-1998','dd-mon-yyyy'))
  TABLESPACE quarter_two,

PARTITION quarter_three
  VALUES LESS THAN ( TO_DATE('01-oct-1998','dd-mon-yyyy'))
  TABLESPACE quarter_three,

PARTITION quarter_four
  VALUES LESS THAN ( TO_DATE('01-jan-1999','dd-mon-yyyy'))
  TABLESPACE quarter_four

);

-- Create local PREFIXED index on Four_Seasons
-- Prefixed because the leftmost columns of the index match the
-- Partitioning key CREATE INDEX i_four_seasons_l ON four_seasons ( one,two )
LOCAL (
PARTITION i_quarter_one TABLESPACE i_quarter_one,
PARTITION i_quarter_two TABLESPACE i_quarter_two,
PARTITION i_quarter_three TABLESPACE i_quarter_three,
PARTITION i_quarter_four TABLESPACE i_quarter_four
);

下一步，合并分區.

-- Merge the first two partitions
--
ALTER TABLE four_seasons
MERGE PARTITIONS quarter_one, quarter_two INTO PARTITION quarter_two
UPDATE INDEXES;

如果不顯式聲明 UPDATE INDEXES 語句,就必須給受影響的分區 rebuild the local index.

-- Rebuild index for quarter_two, which has been marked unusable
-- because it has not had all of the data from Q1 added to it.
-- Rebuilding the index will correct this.
--
ALTER TABLE four_seasons MODIFY PARTITION
quarter_two REBUILD UNUSABLE LOCAL INDEXES;

合并Interval Partitions
 
同RANGE一樣，必須兩個相鄰分區才能合并
合并 List partitions則沒有限制