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Hi, dba friends:
Look at the following test result, the first one is from oracle9.2, and the second is from the oracle 817. The table is same, and as you see, the execution path is the same. But there is difference in statistics: db_block_gets, in oracle92, it is 0, and in oracle817, it is not. And i noticed that in oracle8i, all sql that does only query with execution path full scan of table/index,there will always be db_block_gets, while in 9i, select won't make db_block_gets. As tom said, db_block_gets is increased when data is accessed for update, how does this query generate this statistics?
ORA92> select count(*) from abc;
COUNT(*)
10000
Execution Plan
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=6 Card=1)
1 0 SORT (AGGREGATE)
2 1 TABLE ACCESS (FULL) OF 'ABC' (Cost=6 Card=10000)
Statistics
0 recursive calls 0 db block gets 27 consistent gets 0 physical reads 0 redo size 379 bytes sent via SQL*Net to client 503 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 1 rows processed
ORA817> select count(*) from abc;
COUNT(*)
10000
Elapsed: 00:00:00.26
Execution Plan
0 SELECT STATEMENT Optimizer=CHOOSE
1 0 SORT (AGGREGATE)
2 1 TABLE ACCESS (FULL) OF 'ABC'
Statistics
0 recursive calls 12 db block gets 28 consistent gets 24 physical reads 0 redo size 367 bytes sent via SQL*Net to client 425 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 1 rows processed
Regards
zhu chao
msn:chao_ping_at_163.com
www.happyit.net
www.cnoug.org(China Oracle User Group)
-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: chao_ping INET: chao_ping_at_vip.163.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Wed Jan 22 2003 - 00:53:50 CST