select case when status='UNUSABLE' then 'alter index '||owner||'.'||index_name||' rebuild online compute statistics;' when to_number(degree)>1 then 'alter index '||owner||'.'||index_name||' noparallel;' end casefrom (select * from dba_indexes where degree<>‘DEFAULT') awhere status='UNUSABLE'or to_number(degree)>1and owner not in ('SYS','SYSTEM','MANAGER','WMSYS');

语句运行的速度很快，但是从statspack中发现这条语句的逻辑读单次高达26846。使用set autotrace比较了下9i和10g的执行计划和统计信息，发现9i查询这个视图的代价非常的高，而10g则有了一定的改善。在Oracle9i中，optimizer_mode默认是CHOOSE，所以查询数据字典使用了RBO，而Oracle10g则默认为ALL_ROWS，所以采用了CBO。

SQL> select * from v$version;BANNER----------------------------------------------------------------Oracle9i Enterprise Edition Release 9.2.0.6.0 - 64bit ProductionPL/SQL Release 9.2.0.6.0 - ProductionCORE 9.2.0.6.0 ProductionTNS for IBM/AIX RISC System/6000: Version 9.2.0.6.0 - ProductionNLSRTL Version 9.2.0.6.0 - ProductionSQL> set autot traceSQL> select * from dba_indexes;1242 rows selected.Execution Plan---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=CHOOSE 1 0 NESTED LOOPS (OUTER) 2 1 NESTED LOOPS (OUTER) 3 2 NESTED LOOPS 4 3 NESTED LOOPS 5 4 NESTED LOOPS (OUTER) 6 5 NESTED LOOPS 7 6 NESTED LOOPS (OUTER) 8 7 NESTED LOOPS 9 8 TABLE ACCESS (FULL) OF 'OBJ$' 10 8 TABLE ACCESS (BY INDEX ROWID) OF 'IND$' 11 10 INDEX (UNIQUE SCAN) OF 'I_IND1' (UNIQUE) 12 7 TABLE ACCESS (BY INDEX ROWID) OF 'OBJ$' 13 12 INDEX (UNIQUE SCAN) OF 'I_OBJ1' (UNIQUE) 14 6 TABLE ACCESS (BY INDEX ROWID) OF 'OBJ$' 15 14 INDEX (UNIQUE SCAN) OF 'I_OBJ1' (UNIQUE) 16 5 TABLE ACCESS (CLUSTER) OF 'USER$' 17 16 INDEX (UNIQUE SCAN) OF 'I_USER#' (NON-UNIQUE) 18 4 TABLE ACCESS (CLUSTER) OF 'USER$' 19 18 INDEX (UNIQUE SCAN) OF 'I_USER#' (NON-UNIQUE) 20 3 TABLE ACCESS (CLUSTER) OF 'USER$' 21 20 INDEX (UNIQUE SCAN) OF 'I_USER#' (NON-UNIQUE) 22 2 TABLE ACCESS (CLUSTER) OF 'SEG$' 23 22 INDEX (UNIQUE SCAN) OF 'I_FILE#_BLOCK#' (NON-UNIQUE) 24 1 TABLE ACCESS (CLUSTER) OF 'TS$' 25 24 INDEX (UNIQUE SCAN) OF 'I_TS#' (NON-UNIQUE)Statistics---------------------------------------------------------- 0 recursive calls 0 db block gets 42924 consistent gets 0 physical reads 0 redo size 98000 bytes sent via SQL*Net to client 1558 bytes received via SQL*Net from client 84 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 1242 rows processedSQL>select * from v$version;BANNER----------------------------------------------------------------Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64biPL/SQL Release 10.2.0.4.0 - ProductionCORE 10.2.0.4.0 ProductionTNS for IBM/AIX RISC System/6000: Version 10.2.0.4.0 - ProductioNLSRTL Version 10.2.0.4.0 - Production21:32:11 SYS@coll>set autot trace21:32:15 SYS@coll>select * from dba_indexes;1162 rows selected.Execution Plan----------------------------------------------------------Plan hash value: 3901056803----------------------------------------------------------------------------------------------| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |----------------------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 1164 | 330K| 237 (3)| 00:00:03 ||* 1 | HASH JOIN RIGHT OUTER | | 1164 | 330K| 237 (3)| 00:00:03 || 2 | TABLE ACCESS FULL | TS$ | 9 | 189 | 4 (0)| 00:00:01 ||* 3 | HASH JOIN RIGHT OUTER | | 1164 | 306K| 232 (3)| 00:00:03 || 4 | TABLE ACCESS FULL | SEG$ | 2635 | 102K| 18 (0)| 00:00:01 ||* 5 | HASH JOIN | | 1164 | 261K| 214 (3)| 00:00:03 || 6 | TABLE ACCESS FULL | USER$ | 35 | 560 | 2 (0)| 00:00:01 ||* 7 | HASH JOIN | | 1164 | 243K| 211 (3)| 00:00:03 || 8 | TABLE ACCESS FULL | USER$ | 35 | 560 | 2 (0)| 00:00:01 ||* 9 | HASH JOIN RIGHT OUTER | | 1164 | 225K| 208 (2)| 00:00:03 || 10 | TABLE ACCESS FULL | USER$ | 35 | 560 | 2 (0)| 00:00:01 ||* 11 | HASH JOIN | | 1164 | 206K| 206 (2)| 00:00:03 ||* 12 | HASH JOIN OUTER | | 1164 | 172K| 174 (2)| 00:00:03 || 13 | MERGE JOIN | | 1164 | 142K| 142 (2)| 00:00:02 ||* 14 | TABLE ACCESS BY INDEX ROWID| IND$ | 1164 | 104K| 109 (0)| 00:00:02 || 15 | INDEX FULL SCAN | I_IND1 | 1164 | | 2 (0)| 00:00:01 ||* 16 | SORT JOIN | | 10589 | 341K| 33 (7)| 00:00:01 ||* 17 | TABLE ACCESS FULL | OBJ$ | 10589 | 341K| 32 (4)| 00:00:01 || 18 | TABLE ACCESS FULL | OBJ$ | 10592 | 279K| 31 (0)| 00:00:01 || 19 | TABLE ACCESS FULL | OBJ$ | 10592 | 310K| 31 (0)| 00:00:01 |----------------------------------------------------------------------------------------------Predicate Information (identified by operation id):--------------------------------------------------- 1 - access("I"."TS#"="TS"."TS#"(+)) 3 - access("I"."FILE#"="S"."FILE#"(+) AND "I"."BLOCK#"="S"."BLOCK#"(+) AND "I"."TS#"="S"."TS#"(+)) 5 - access("IO"."OWNER#"="IU"."USER#") 7 - access("U"."USER#"="O"."OWNER#") 9 - access("ITO"."OWNER#"="ITU"."USER#"(+)) 11 - access("I"."BO#"="IO"."OBJ#") 12 - access("I"."INDMETHOD#"="ITO"."OBJ#"(+)) 14 - filter(BITAND("I"."FLAGS",4096)=0) 16 - access("O"."OBJ#"="I"."OBJ#") filter("O"."OBJ#"="I"."OBJ#") 17 - filter(BITAND("O"."FLAGS",128)=0)Statistics---------------------------------------------------------- 0 recursive calls 0 db block gets 876 consistent gets 0 physical reads 0 redo size 92582 bytes sent via SQL*Net to client 1339 bytes received via SQL*Net from client 79 SQL*Net roundtrips to/from client 1 sorts (memory) 0 sorts (disk) 1162 rows processedselect * from dba_indexes;1162 rows selected.Elapsed: 00:00:00.55Execution Plan----------------------------------------------------------Plan hash value: 2107813288--------------------------------------------------------------| Id | Operation | Name |--------------------------------------------------------------| 0 | SELECT STATEMENT | || 1 | NESTED LOOPS OUTER | || 2 | NESTED LOOPS OUTER | || 3 | NESTED LOOPS | || 4 | NESTED LOOPS | || 5 | NESTED LOOPS OUTER | || 6 | NESTED LOOPS | || 7 | NESTED LOOPS OUTER | || 8 | NESTED LOOPS | ||* 9 | TABLE ACCESS FULL | OBJ$ ||* 10 | TABLE ACCESS BY INDEX ROWID| IND$ ||* 11 | INDEX UNIQUE SCAN | I_IND1 || 12 | TABLE ACCESS BY INDEX ROWID | OBJ$ ||* 13 | INDEX UNIQUE SCAN | I_OBJ1 || 14 | TABLE ACCESS BY INDEX ROWID | OBJ$ ||* 15 | INDEX UNIQUE SCAN | I_OBJ1 || 16 | TABLE ACCESS CLUSTER | USER$ ||* 17 | INDEX UNIQUE SCAN | I_USER# || 18 | TABLE ACCESS CLUSTER | USER$ ||* 19 | INDEX UNIQUE SCAN | I_USER# || 20 | TABLE ACCESS CLUSTER | USER$ ||* 21 | INDEX UNIQUE SCAN | I_USER# || 22 | TABLE ACCESS CLUSTER | SEG$ ||* 23 | INDEX UNIQUE SCAN | I_FILE#_BLOCK# || 24 | TABLE ACCESS CLUSTER | TS$ ||* 25 | INDEX UNIQUE SCAN | I_TS# |--------------------------------------------------------------Predicate Information (identified by operation id):--------------------------------------------------- 9 - filter(BITAND("O"."FLAGS",128)=0) 10 - filter(BITAND("I"."FLAGS",4096)=0) 11 - access("O"."OBJ#"="I"."OBJ#") 13 - access("I"."INDMETHOD#"="ITO"."OBJ#"(+)) 15 - access("I"."BO#"="IO"."OBJ#") 17 - access("ITO"."OWNER#"="ITU"."USER#"(+)) 19 - access("U"."USER#"="O"."OWNER#") 21 - access("IO"."OWNER#"="IU"."USER#") 23 - access("I"."TS#"="S"."TS#"(+) AND "I"."FILE#"="S"."FILE#"(+) AND "I"."BLOCK#"="S"."BLOCK#"(+)) 25 - access("I"."TS#"="TS"."TS#"(+))Note----- - rule based optimizer used (consider using cbo)Statistics---------------------------------------------------------- 0 recursive calls 0 db block gets 25254 consistent gets 26 physical reads 0 redo size 93977 bytes sent via SQL*Net to client 1339 bytes received via SQL*Net from client 79 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 1162 rows processed