1. 查看表的具体情况
查看是不是分区表，有多少个分区、分区字段：
SQL> col table_name for a20
SQL> col column_name for a20
SQL> select a.table_name,a.partitioned,b.partition_count,c.column_name
2 from user_tables a, user_part_tables b, user_part_key_columns c
3 where a.table_name='STAT_SUBMIT_CENTER'
4 and b.table_name='STAT_SUBMIT_CENTER'
5 and c.name='STAT_SUBMIT_CENTER';
TABLE_NAME PAR PARTITION_COUNT COLUMN_NAME
-------------------- --- --------------- --------------------
STAT_SUBMIT_CENTER YES 50 MSGDATE
查看已使用的每个分区的大小：
SQL> select segment_name,partition_name,round(bytes/1024/1024) from user_segments
where segment_name ='STAT_SUBMIT_CENTER' and bytes/1024/1024>0.25 order by 3 desc;
SEGMENT_NAME PARTITION_NAME
SEGMENT_NAME PARTITION_NAME ROUND(BYTES/1024/1024)
-------------------------- ------------------------------ ----------------------
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20051101 1722
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20051021 1488
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20051111 1440
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20051121 1355
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20051221 1335
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20050911 1309
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20051211 1253
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20051201 1247
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20050921 1198
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20060101 1151
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20060111 1068
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20051001 1018
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20051011 865
STAT_SUBMIT_CENTER STAT_SUBMIT_CENTER_20060121 796
14 rows selected.
查看整个表的大小：
SQL> select segment_name,sum(bytes/1024/1024) from user_segments
where segment_name ='STAT_SUBMIT_CENTER' group by segment_name;
SEGMENT_NAME
SEGMENT_NAME SUM(BYTES/1024/1024)
-------------------------------- --------------------
STAT_SUBMIT_CENTER 17234
查看表的记录数：
SQL> set timing on
SQL> select count(*) from STAT_SUBMIT_CENTER;
COUNT(*)
----------
170341007
Elapsed: 00:14:18.60
查看这个表上的索引情况如下：
table STAT_SUBMIT_CENTER 17234 M
index IDX_SUBCEN_ADDRUSER 5155 M ADDRUSER
PK_STAT_SUBMIT_CENTER 10653 M MSGDATE,ADDRUSER,MSGID
然后，查看一些数据库参数情况：
SQL> show parameter work
NAME TYPE VALUE
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
workarea_size_policy string AUTO
SQL> show parameter pga
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
pga_aggregate_target big integer 209715200
SQL> select * from dba_temp_files;
FILE_NAME
------------------------------------------------------------------------------------------------------------------------
FILE_ID TABLESPACE_NAME BYTES BLOCKS STATUS RELATIVE_FNO AUT MAXBYTES MAXBLOCKS
---------- ------------------------------ ---------- ---------- --------- ------------ --- ---------- ----------
INCREMENT_BY USER_BYTES USER_BLOCKS
------------ ---------- -----------
/bgdata/Oracle/temp01.dbf
1 TEMP 3563061248 434944 AVAILABLE 1 YES 4294967296 5242886400 3562012672 434816
2. 需要考虑的几个方面
1）创建的索引需要几个G的磁盘空间。
2）创建索引需要排序，使用pga_aggregate_target，要把这个值从200M加大到2G。
3）假如内存不够，需要temp表空间，则要把temp表空间加大到8G——itpub上有一个帖子说过，15亿条记录用了34G空间。
4）在线创建，时间会比较长。讨论后，停止这个表的操作，非online创建。
3. 实际操作过程
1）数据文件够，不扩展；temp数据文件扩展：
alter database tempfile '/bgdata/oracle/temp01.dbf' resize 8192m;
2）在workarea_size_policy=AUTO的情况下，改pga_aggregate_target=2048m。对于串行操作，一个session能使用的pga=MIN(5%PGA_AGGREGATE_TARGET,100MB)，这样可以使得pga用到最大的值：
alter system set pga_aggregate_target=2048m;
3）因为这是一个比较长的过程，所以写脚本让后台运行：
nohup time createind.sh &
vi createind.sh
#!/bin/sh
sqlplus user/passWord <
create index IDX_SUBMIT_RECORDTIME on STAT_SUBMIT_CENTER(RECORDTIME) local;
exit
EOF
4）创建过程中可以观察v$sort_segment，v$sort_usage看排序情况：
nohup time createind.sh &
vi createind.sh
#!/bin/sh
sqlplus user/password <
Explained.
SQL> @?/rdbms/admin/utlxplp.sql
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------------------------
Id Operation Name Rows Bytes Cost Pstart Pstop
-------------------------------------------------------------------------------------------------
0 SELECT STATEMENT 1 9 4
1 SORT AGGREGATE 1 9
2 PARTITION RANGE ALL 1 50
* 3 INDEX FAST FULL SCAN IDX_SUBMIT_RECORDTIME 8878K 76M 4 1 50
-------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - filter("STAT_SUBMIT_CENTER"."RECORDTIME">TRUNC(SYSDATE@!))
Note: cpu costing is off
16 rows selected.
SQL> set autotrace on explain
SQL> set timing on
SQL> select count(*) from stat_submit_center where recordtime>trunc(sysdate);
aa^Cselect count(*) from stat_submit_center where recordtime>trunc(sysdate)
*
ERROR at line 1:
ORA-01013: user requested cancel of current operation
Elapsed: 00:11:49.85
SQL>
SQL> set autotrace off
上面可以看到，因为没有分析索引，虽然它走的是新建的IDX_SUBMIT_RECORDTIME索引，但是查询速度很慢，10分钟后也没有结果。下面我们分析一下：
SQL> Analyze index IDX_SUBMIT_RECORDTIME estimate statistics;
Index analyzed.
Elapsed: 00:00:06.84
SQL> set autotrace on explain
SQL> select count(*) from stat_submit_center where recordtime>trunc(sysdate);
COUNT(*)
----------
926736
Elapsed: 00:00:05.37
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=4360 Card=1 Bytes=9)
1 0 SORT (AGGREGATE)
2 1 PARTITION RANGE (ALL)
3 2 INDEX (RANGE SCAN) OF 'IDX_SUBMIT_RECORDTIME' (NON-UNI
QUE) (Cost=4360 Card=8878740 Bytes=79908660)
SQL> set autotrace off
索引分析之后，查询时间为5分钟左右，效率大大提高。
至此，完成全部操作。
作者简介：柔嘉维则；作者Email地址为baobaoc@hotmail.com；作者Blog为http://spaces.MSN.com/roujiaweize/
