对于OLAP系统，数据量特别大，而且不能随便扩空间，所以压缩也是比较好的方法，压缩比基本是：1：2
下面是压缩脚本，需要先创建log，记录压缩到哪张表的日志。
下面的例子是 ORACLE 11g的
-- Create table
create table TL_COMPRESS_LOG
(
OWNNAME VARCHAR2(30),
TABNAME VARCHAR2(30),
SUBPARNAME VARCHAR2(30),
TSNAME VARCHAR2(30),
BEGTIME DATE,
ENDTIME DATE,
OLD_MB NUMBER,
NEW_MB NUMBER,
OLD_ROWS NUMBER,
NEW_ROWS NUMBER
)
tablespace USERS;
-- Add comments to the table
comment on table TL_COMPRESS_LOG
is '压缩日志表';
-- Add comments to the columns
comment on column TL_COMPRESS_LOG.OWNNAME
is '属主';
comment on column TL_COMPRESS_LOG.TABNAME
is '表';
comment on column TL_COMPRESS_LOG.SUBPARNAME
is '子分区';
comment on column TL_COMPRESS_LOG.TSNAME
is '表空间';
comment on column TL_COMPRESS_LOG.BEGTIME
is '压缩开始时间';
comment on column TL_COMPRESS_LOG.ENDTIME
is '压缩结束时间';
comment on column TL_COMPRESS_LOG.OLD_MB
is '压缩前大小(MB)';
comment on column TL_COMPRESS_LOG.NEW_MB
is '压缩后大小(MB)';
comment on column TL_COMPRESS_LOG.OLD_ROWS
is '压缩前记录数';
comment on column TL_COMPRESS_LOG.NEW_ROWS
is '压缩后记录数';
DECLARE
VT1 DATE;
VT2 DATE;
VM1 NUMBER;
VM2 NUMBER;
VR1 NUMBER;
VR2 NUMBER;
BEGIN
FOR C IN (SELECT '用户名' OWNNAME,
TABLE_NAME TABNAME,
PARTITION_NAME PARNAME,
SUBPARTITION_NAME SUBPARNAME,
TABLESPACE_NAME TSNAME
FROM USER_TAB_SUBPARTITIONS
WHERE TABLE_NAME LIKE 'TM_%201208'
AND COMPRESSION != 'ENABLED'
ORDER BY TABLE_NAME, PARTITION_NAME ,SUBPARTITION_NAME) LOOP
VT1 := SYSDATE;
SELECT MAX(BYTES) / 1024 / 1024
INTO VM1
FROM DBA_SEGMENTS
WHERE OWNER = C.OWNNAME
AND SEGMENT_NAME = C.TABNAME
AND PARTITION_NAME = C.SUBPARNAME;
EXECUTE IMMEDIATE 'select /*+ parallel(t,4) */ count(*) from
' || C.TABNAME || ' subpartition (' || C.SUBPARNAME || ') t'
INTO VR1;
INSERT INTO TL_COMPRESS_LOG
VALUES
(C.OWNNAME,
C.TABNAME,
C.PARNAME,
C.TSNAME,
VT1,
NULL,
VM1,
NULL,
VR1,
NULL);
--
EXECUTE IMMEDIATE 'alter table ' || C.TABNAME || ' move subpartition
' || C.SUBPARNAME || ' compress tablespace ' || C.TSNAME;
--
VT2 := SYSDATE;
SELECT MAX(BYTES) / 1024 / 1024
INTO VM2
FROM DBA_SEGMENTS
WHERE OWNER = C.OWNNAME
AND SEGMENT_NAME = C.TABNAME
AND PARTITION_NAME = C.SUBPARNAME;
EXECUTE IMMEDIATE 'select /*+ parallel(t,4) */ count(*) from
' || C.TABNAME || ' subpartition (' || C.SUBPARNAME || ') t'
INTO VR2;
UPDATE TL_COMPRESS_LOG
SET ENDTIME = VT2, NEW_MB = VM2, NEW_ROWS = VR2
WHERE OWNNAME = C.OWNNAME
AND TABNAME = C.TABNAME
AND SUBPARNAME= C.PARNAME;
END LOOP;
END;
--由于ORACLE 10g不支持直接对子分区进行压缩，所以需要对主分区进行压缩如下：
--ORACLE 10g
DECLARE
VT1 DATE;
VT2 DATE;
VM1 NUMBER;
VM2 NUMBER;
VR1 NUMBER;
VR2 NUMBER;
BEGIN
FOR C IN (SELECT 'CTMX' OWNNAME,table_name TABNAME,partition_name PARNAME,
TABLESPACE_NAME TSNAME FROM
user_tab_partitions WHERE table_name LIKE '%201303'
AND compression='DISABLED') LOOP
VT1 := SYSDATE;
SELECT MAX(BYTES) / 1024 / 1024
INTO VM1
FROM DBA_SEGMENTS
WHERE OWNER = C.OWNNAME
AND SEGMENT_NAME = C.TABNAME
AND PARTITION_NAME = C.PARNAME;
EXECUTE IMMEDIATE 'select /*+ parallel(t,4) */ count(*) from
' || C.TABNAME || ' partition (' || C.PARNAME || ') t'
INTO VR1;
INSERT INTO TL_COMPRESS_LOG
VALUES
(C.OWNNAME,
C.TABNAME,
C.PARNAME,
C.TSNAME,
VT1,
NULL,
VM1,
NULL,
VR1,
NULL);
--
EXECUTE IMMEDIATE 'alter table ' || C.TABNAME || ' move partition
' || C.PARNAME ||' compress' ;
--
VT2 := SYSDATE;
SELECT MAX(BYTES) / 1024 / 1024
INTO VM2
FROM DBA_SEGMENTS
WHERE OWNER = C.OWNNAME
AND SEGMENT_NAME = C.TABNAME
AND PARTITION_NAME = C.PARNAME;
EXECUTE IMMEDIATE 'select /*+ parallel(t,4) */ count(*) from
' || C.TABNAME || ' partition (' || C.PARNAME || ') t'
INTO VR2;
UPDATE TL_COMPRESS_LOG
SET ENDTIME = VT2, NEW_MB = VM2, NEW_ROWS = VR2
WHERE OWNNAME = C.OWNNAME
AND TABNAME = C.TABNAME
AND SUBPARNAME= C.PARNAME;
END LOOP;
END;