索引是提高数据库查询性能的有力武器。没有索引，就好比图书馆没有图书标签一样，找一本书自己想要的书比登天还难。然而索引在使用的过程中，尤其是在批量的DML的情形下会产生相应的碎片，以及B树高度会发生相应变化，因此可以对这些变化较大的索引进行重构以提高性能。N久以前Oracle建议我们定期重建那些高度为4，已删除的索引条目至少占有现有索引条目总数的20%的这些表上的索引。但Oracle现在强烈建议不要定期重建索引。具体可以参考文章：Oracle 重建索引的必要性。尽管如此重建索引还是有必要的，只是不建议定期。本文给出了重建索引的脚本供大家参考。
1、重建索引shell脚本
robin@SZDB:~/dba_script s/custom/bin> more rebuild_unbalanced_indices.sh # +-------------------------------------------------------+ # + Rebulid unblanced indices | # + Author : Leshami | # + Parameter : No | # +-------------------------------------------------------+ #!/bin/bash # -------------------- # Define variable # -------------------- if [ -f ~/.bash_profile ]; then . ~/.bash_profile fi DT=`date +%Y%m%d`; export DT RETENTION=1 LOG_DIR=/tmp LOG=${LOG_DIR}/rebuild_unbalanced_indices_${DT}.log DBA=Leshami@12306.cn # ------------------------------------ # Loop all instance in current server # ------------------------------------- echo "Current date and time is : `/bin/date`">>${LOG} for db in `ps -ef | grep pmon | grep -v grep |grep -v asm |awk '{print $8}'|cut -c 10-` do echo "$db" export ORACLE_SID=$db echo "Current DB is $db" >>${LOG} echo "===============================================">>${LOG} $ORACLE_HOME/bin/sqlplus -S /nolog @/users/robin/dba_script s/custom/sql/rebuild_unbalanced_indices.sql>>${LOG} done; echo "End of rebuilding index for all instance at : `/bin/date`">>${LOG} # ------------------------------------- # Check log file # ------------------------------------- status=`grep "ORA-" ${LOG}` if [ -z $status ];then mail -s "Succeeded rebuilding indices on `hostname` !!!" ${DBA} <${LOG} else mail -s "Failed rebuilding indices on `hostname` !!!" ${DBA} <${LOG} fi # ------------------------------------------------ # Removing files older than $RETENTION parameter # ------------------------------------------------ find ${LOG_DIR} -name "rebuild_unb*" -mtime +$RETENTION -exec rm {} \; exit
2、重建索引调用的SQL脚本
robin@SZDB:~/dba_script s/custom/sql> more rebuild_unbalanced_indices.sql conn / as sysdba set serveroutput on; DECLARE resource_busy EXCEPTION; PRAGMA EXCEPTION_INIT (resource_busy, -54); c_max_trial CONSTANT PLS_INTEGER := 10; c_trial_interval CONSTANT PLS_INTEGER := 1; pmaxheight CONSTANT INTEGER := 3; pmaxleafsdeleted CONSTANT INTEGER := 20; CURSOR csrindexstats IS SELECT NAME, height, lf_rows AS leafrows, del_lf_rows AS leafrowsdeleted FROM index_stats; vindexstats csrindexstats%ROWTYPE; CURSOR csrglobalindexes IS SELECT owner,index_name, tablespace_name FROM dba_indexes WHERE partitioned = 'NO' AND owner IN ('GX_ADMIN'); CURSOR csrlocalindexes IS SELECT index_owner,index_name, partition_name, tablespace_name FROM dba_ind_partitions WHERE status = 'USABLE' AND index_owner IN ('GX_ADMIN'); trial PLS_INTEGER; vcount INTEGER := 0; BEGIN trial := 0; /* Global indexes */ FOR vindexrec IN csrglobalindexes LOOP EXECUTE IMMEDIATE 'analyze index ' || vindexrec.owner ||'.'|| vindexrec.index_name || ' validate structure'; OPEN csrindexstats; FETCH csrindexstats INTO vindexstats; IF csrindexstats%FOUND THEN IF (vindexstats.height > pmaxheight) OR ( vindexstats.leafrows > 0 AND vindexstats.leafrowsdeleted > 0 AND (vindexstats.leafrowsdeleted * 100 / vindexstats.leafrows) > pmaxleafsdeleted) THEN vcount := vcount + 1; DBMS_OUTPUT.PUT_LINE ( 'Rebuilding index ' || vindexrec.owner ||'.'|| vindexrec.index_name || '...'); <<alter_index>> BEGIN EXECUTE IMMEDIATE 'alter index ' || vindexrec.owner ||'.' || vindexrec.index_name || ' rebuild' || ' parallel nologging compute statistics' || ' tablespace ' || vindexrec.tablespace_name; EXCEPTION WHEN resource_busy OR TIMEOUT_ON_RESOURCE THEN DBMS_OUTPUT.PUT_LINE ( 'alter index - busy and wait for 1 sec'); DBMS_LOCK.sleep (c_trial_interval); IF trial <= c_max_trial THEN GOTO alter_index; ELSE DBMS_OUTPUT.PUT_LINE ( 'alter index busy and waited - quit after ' || TO_CHAR (c_max_trial) || ' trials'); RAISE; END IF; WHEN OTHERS THEN DBMS_OUTPUT.PUT_LINE ('alter index err ' || SQLERRM); RAISE; END; END IF; END IF; CLOSE csrindexstats; END LOOP; DBMS_OUTPUT.PUT_LINE ('Global indices rebuilt: ' || TO_CHAR (vcount)); vcount := 0; trial := 0; /* Local indexes */ FOR vindexrec IN csrlocalindexes LOOP EXECUTE IMMEDIATE 'analyze index ' || vindexrec.index_owner||'.' || vindexrec.index_name || ' partition (' || vindexrec.partition_name || ') validate structure'; OPEN csrindexstats; FETCH csrindexstats INTO vindexstats; IF csrindexstats%FOUND THEN IF (vindexstats.height > pmaxheight) OR ( vindexstats.leafrows > 0 AND vindexstats.leafrowsdeleted > 0 AND (vindexstats.leafrowsdeleted * 100 / vindexstats.leafrows) > pmaxleafsdeleted) THEN vcount := vcount + 1; DBMS_OUTPUT.PUT_LINE ( 'Rebuilding index ' || vindexrec.index_owner||'.'|| vindexrec.index_name || '...'); <<alter_partitioned_index>> BEGIN EXECUTE IMMEDIATE 'alter index ' || vindexrec.index_owner||'.' || vindexrec.index_name || ' rebuild' || ' partition ' || vindexrec.partition_name || ' parallel nologging compute statistics' || ' tablespace ' || vindexrec.tablespace_name; EXCEPTION WHEN resource_busy OR TIMEOUT_ON_RESOURCE THEN DBMS_OUTPUT.PUT_LINE ( 'alter partitioned index - busy and wait for 1 sec'); DBMS_LOCK.sleep (c_trial_interval); IF trial <= c_max_trial THEN GOTO alter_partitioned_index; ELSE DBMS_OUTPUT.PUT_LINE ( 'alter partitioned index busy and waited - quit after ' || TO_CHAR (c_max_trial) || ' trials'); RAISE; END IF; WHEN OTHERS THEN DBMS_OUTPUT.PUT_LINE ( 'alter partitioned index err ' || SQLERRM); RAISE; END; END IF; END IF; CLOSE csrindexstats; END LOOP; DBMS_OUTPUT.PUT_LINE ('Local indices rebuilt: ' || TO_CHAR (vcount)); END; / exit;
3、输入日志样本
Current date and time is : Sun Apr 20 02:00:02 HKT 2014 Current DB is SYBO2 =============================================== Rebuilding index GX_ADMIN.SYN_OUT_DATA_TBL_PK... Rebuilding index GX_ADMIN.IDX_TDBK_SPLNK_PARENT_REF... Rebuilding index GX_ADMIN.IDX_TDBK_SPLNK_CHILD_REF... Rebuilding index GX_ADMIN.PK_TRADE_BROKER_TBL... Rebuilding index GX_ADMIN.IDX_TDBK_INPUT_DATE... ................
4、后记
a、如果同一台服务器上有多个实例，且每个实例有相同的schema，此脚本会轮巡所有实例并根据analyze结果来rebuild。
a、大家应根据需要作相应调整，如脚本的路径信息等。
b、需要修改相应的schema name。
d、可根据系统环境调整相应的并行度。
