1、制作测试表
create table t1 as select * from FW_T_GTXLOG
insert into t1 select * from t1;
create table t2 compress as select * from t1
create table t3 as select * from t1
2、查看测试表数据量
select count(*) from t1;
select count(*) from t2;
select count(*) from t3;
3、查看测试表物理大小
SQL> select t.bytes/1024/1024/1024,t.blocks from dba_segments t where t.segment_name=‘T1‘;
T.BYTES/1024/1024/1024 BLOCKS
---------------------- ----------
16.8876953G 2213504
Elapsed: 00:00:00.14
SQL> select t.bytes/1024/1024/1024,t.blocks from dba_segments t where t.segment_name=‘T2‘;
T.BYTES/1024/1024/1024 BLOCKS
---------------------- ----------
13.0625G 1712128
Elapsed: 00:00:00.10
SQL> select t.bytes/1024/1024/1024,t.blocks from dba_segments t where t.segment_name=‘T3‘;
T.BYTES/1024/1024/1024 BLOCKS
---------------------- ----------
16.8359375G 2206720
Elapsed: 00:00:00.09
4、查看测试表索引大小
SQL> select t.bytes/1024/1024/1024,t.blocks*8192 from dba_segments t where t.segment_name=‘IND_GUID_1‘;
T.BYTES/1024/1024/1024 T.BLOCKS*8192
---------------------- -------------
3.125 3355443200
Elapsed: 00:00:00.10
SQL> select t.bytes/1024/1024/1024,t.blocks*8192 from dba_segments t where t.segment_name=‘IND_GUID_2‘;
T.BYTES/1024/1024/1024 T.BLOCKS*8192
---------------------- -------------
.5390625 578813952
Elapsed: 00:00:00.09
SQL> select t.bytes/1024/1024/1024,t.blocks*8192 from dba_segments t where t.segment_name=‘IND_GUID_3‘;
T.BYTES/1024/1024/1024 T.BLOCKS*8192
---------------------- -------------
.5390625 578813952
Elapsed: 00:00:00.10
5、查看测试表定义语句
-- Create table T1
create table T1
(
GUID NVARCHAR2(32) not null,
GTXID NVARCHAR2(200),
STARTTIME NVARCHAR2(32),
SOURCETX NUMBER(1),
STATUS NUMBER(1),
ENDTIME NVARCHAR2(32),
DOMAIN NVARCHAR2(50)
)
tablespace EFMIS
pctfree 10
initrans 1
maxtrans 255
storage
(
initial 64
next 8
minextents 1
maxextents unlimited
);
-- Create/Recreate indexes
create index IND_GUID_1 on T1 (GUID)
tablespace EFMIS
pctfree 10
initrans 2
maxtrans 255
storage
(
initial 64K
next 1M
minextents 1
maxextents unlimited
);
-- Create table T2
create table T2
(
GUID NVARCHAR2(32) not null,
GTXID NVARCHAR2(200),
STARTTIME NVARCHAR2(32),
SOURCETX NUMBER(1),
STATUS NUMBER(1),
ENDTIME NVARCHAR2(32),
DOMAIN NVARCHAR2(50)
)
tablespace EFMIS
pctfree 0
initrans 1
maxtrans 255
storage
(
initial 64
next 8
minextents 1
maxextents unlimited
)
compress; -------------------------------------------------------------------------------
-- Create/Recreate indexes
create index IND_GUID_2 on T2 (GUID)
tablespace EFMIS
pctfree 10
initrans 2
maxtrans 255
storage
(
initial 64K
next 1M
minextents 1
maxextents unlimited
)
compress; ---------------------------------------------------
-- Create table T3
create table T3
(
GUID NVARCHAR2(32) not null,
GTXID NVARCHAR2(200),
STARTTIME NVARCHAR2(32),
SOURCETX NUMBER(1),
STATUS NUMBER(1),
ENDTIME NVARCHAR2(32),
DOMAIN NVARCHAR2(50)
)
tablespace EFMIS
pctfree 10
initrans 1
maxtrans 255
storage
(
initial 64
next 8
minextents 1
maxextents unlimited
);
-- Create/Recreate indexes
create index IND_GUID_3 on T3 (GUID)
tablespace EFMIS
pctfree 10
initrans 2
maxtrans 255
storage
(
initial 64K
next 1M
minextents 1
maxextents unlimited
)
compress; ---------------------------------------------------------------------
6、收集3张表统计信息
begin
dbms_stats.gather_table_stats(ownname => ‘FASP_62‘,
tabname => ‘T1‘,
estimate_percent => 30,
method_opt => ‘FOR ALL COLUMNS SIZE 10‘,
degree => 4,
cascade => TRUE);
END;
7、测试具体查询语句效率：table access full
SQL> select count(*) from t1;
COUNT(*)
----------
37458112
Elapsed: 00:00:31.22
SQL> select count(*) from t2;
COUNT(*)
----------
37458112
Elapsed: 00:00:08.66
SQL> select count(*) from t3;
COUNT(*)
----------
37458112
Elapsed: 00:00:08.25
8、测试具体查询语句效率：index fasp full scan
SQL> select count(guid) from t1 where guid like ‘%BA92A682D9%‘;
COUNT(GUID)
-----------
32
Elapsed: 00:00:34.52
SQL> select count(guid) from t2 where guid like ‘%BA92A682D9%‘;
COUNT(GUID)
-----------
32
Elapsed: 00:00:18.27
SQL> select count(guid) from t3 where guid like ‘%BA92A682D9%‘;
COUNT(GUID)
-----------
32
Elapsed: 00:00:20.27
结论：t2\t3表的索引为压缩索引，从以上执行结果可知，索引重复率情况下，compress压缩对于select而言，具有一定的效果，提高速度一半以上。
9、结论
1、非唯一性索引可以建立compress索引。
create index IND_GUID_3 on T3 (GUID) tablespace EFMIS compress;
2、可以通过以下命令查看索引或者表占据的硬盘容量：
select t.bytes/1024/1024/1024,t.blocks*8192 from dba_segments t where t.segment_name=‘IND_GUID_3‘;
select t.bytes/1024/1024/1024,t.blocks*8192 from dba_segments t where t.segment_name=‘IND_GUID_1‘;
以上sql查询出的索引大小与为压缩的索引大小相差悬殊，择证明压缩后可以提高查询效率。