[Oracle]如何在億級記錄表中創建索引
2024-08-29 13:50:21
供稿：網友
1. 查看表的具體情況 查看是不是分區表，有多少個分區、分區字段： 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 查看已使用的每個分區的大?。?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. 查看整個表的大?。?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 查看表的記錄數： SQL> set timing on SQL> select count(*) from STAT_SUBMIT_CENTER; COUNT(*) ---------- 170341007 Elapsed: 00:14:18.60 查看這個表上的索引情況如下： table STAT_SUBMIT_CENTER 17234 M index IDX_SUBCEN_ADDRUSER 5155 M ADDRUSER PK_STAT_SUBMIT_CENTER 10653 M MSGDATE,ADDRUSER,MSGID然后，查看一些數據庫參數情況： 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. 需要考慮的幾個方面 1）創建的索引需要幾個G的磁盤空間。 2）創建索引需要排序，使用pga_aggregate_target，要把這個值從200M加大到2G。 3）假如內存不夠，需要temp表空間，則要把temp表空間加大到8G——itpub上有一個帖子說過，15億條記錄用了34G空間。 4）在線創建，時間會比較長。討論后，停止這個表的操作，非online創建。 3. 實際操作過程 1）數據文件夠，不擴展；temp數據文件擴展： alter database tempfile '/bgdata/oracle/temp01.dbf' resize 8192m; 2）在workarea_size_policy=AUTO的情況下，改pga_aggregate_target=2048m。對于串行操作，一個session能使用的pga=MIN(5%PGA_AGGREGATE_TARGET,100MB)，這樣可以使得pga用到最大的值： alter system set pga_aggregate_target=2048m; 3）因為這是一個比較長的過程，所以寫腳本讓后臺運行： 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）創建過程中可以觀察v$sort_segment，v$sort_usage看排序情況： 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，因為沒有分析索引，雖然它走的是新建的IDX_SUBMIT_RECORDTIME索引，但是查詢速度很慢，10分鐘后也沒有結果。下面我們分析一下： 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，查詢時間為5分鐘左右，效率大大提高。 至此，完成全部操作。 作者簡介：柔嘉維則；作者Email地址為baobaoc@hotmail.com；作者Blog為http://spaces.MSN.com/roujiaweize/
