explain plan question

From: Gurelei <gurelei_at_YAHOO.COM>
Date: Thu, 06 Jun 2002 13:48:08 -0800
Message-ID: <F001.00476CF8.20020606134808@fatcity.com>

Hi.

I have executed an explain plan on a dev and prod databases. Both databases have the same data, use the same version of ORacle (8.1.7.0) and the same OS (AIX 4.3.3). All the tables are analyzed. The plans however are somewhat different (below). What could explan the differences? For example, index usage (one plan uses an index to get to all the data, another - access the index and then the table). All the indices are the same on both databases. when I tried to force ORacle to use the indices with hints, the cost grew from 322 to 566. MY concernt is that I may not be able to tune a query if I can't replicate the explain plan exactly in dev as it is in production.

Thanks for any input

Gene

0-0-3211.321 SELECT STATEMENT    SQL1 Cost = 321
1-0-1 2.1 SORT GROUP BY
2-1-1  3.1 NESTED LOOPS
3-2-1   4.1 HASH JOIN OUTER
4-3-1    5.1 HASH JOIN OUTER
5-4-1     6.1 HASH JOIN
6-5-1      7.1 TABLE ACCESS FULL TELESLS_EMPL
7-5-2      7.2 INDEX RANGE SCAN TS_EMP_HST_ALT1 UNIQUE
8-4-2     6.2 INDEX FAST FULL SCAN PERF_STATS_ALT1

UNIQUE
9-3-2 5.2 INDEX FAST FULL SCAN PRDCT_STAT_ALT1 UNIQUE
10-2-2 4.2 INDEX UNIQUE SCAN ORG_UNT_HST_PK UNIQUE vs

0-0-3231.323 SELECT STATEMENT    SQL1 Cost = 323
1-0-1 2.1 SORT GROUP BY
2-1-1  3.1 NESTED LOOPS OUTER
3-2-1   4.1 NESTED LOOPS OUTER
4-3-1    5.1 NESTED LOOPS
5-4-1     6.1 HASH JOIN
6-5-1      7.1 TABLE ACCESS FULL TELESLS_EMPL
7-5-2      7.2 INDEX RANGE SCAN TS_EMP_HST_ALT1 UNIQUE
8-4-2     6.2 INDEX UNIQUE SCAN ORG_UNT_HST_PK UNIQUE
9-3-2    5.2 TABLE ACCESS BY INDEX ROWID PERF_STATS
10-9-1     6.1 INDEX RANGE SCAN PERF_STATS_FK2_X

NON-UNIQUE
11-2-2 4.2 TABLE ACCESS BY INDEX ROWID PRDCT_STATS 12-11-1 5.1 INDEX RANGE SCAN PRDCT_STAT_FK1_X NON-UNIQUE

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Author: Gurelei
  INET: gurelei_at_yahoo.com

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