The stats are up to date. Yes, all of the dates in the column have time = 00:00:00. Still, the optimizer trace shows that this index was not even considered; I'm also unable to get the index to be used via a hint. No matter how bad the index, shouldn't it be considered? Paul Baumgartel CREDIT SUISSE Information Technology Securities Processing Databases Americas One Madison Avenue New York, NY 10010 USA Phone 212.538.1143 paul.baumgartel@xxxxxxxxxxxxxxxxx www.credit-suisse.com -----Original Message----- From: Hemant K Chitale [mailto:hkchital@xxxxxxxxxxxxxx] Sent: Saturday, September 29, 2007 9:25 AM To: Baumgartel, Paul; oracle-l Subject: Re: Optimizer sees index, but ignores it in access path decision process For Index: NUK_TCONTRACT_TRD_DT Col#: 35 USING COMPOSITE STATS LVLS: 3 #LB: 402118 #DK: 80 LB/K: 5026.00 DB/K: 52071.00 CLUF: 4165752.00 The Distinct Keys are only 80 and Leaf Blocks per Key is a very high 5,026. If the indexed column is a date are all the values inserted into the table as TRUNC(SYSDATE) ? Or does Oracle have the wrong statistics for the index ? Hemant At 04:35 AM Saturday, Baumgartel, Paul wrote: >Oracle 10.2.0.3 on Solaris. > >Table is range-partitioned on TCONTRACT_TRADE_DATE. Query is > >select >min(TCONTRACT_TRADE_DATE) >from ods.ods_tcontract; > >A single-column partitioned index (NUK_TCONTRACT_TRD_DT) exists on >TCONTRACT_TRADE_DATE. Another (composite) index contains that >column in position 2. Optimizer chooses the second index every >time, even when a hint specifies the first one. > >Optimizer (event 10053) trace shows awareness of the preferred index: > >Index Stats:: > Index: NUK_TCONTRACT_BUSDATE_CUSIP Col#: 52 20 > USING COMPOSITE STATS > LVLS: 3 #LB: 713238 #DK: 384265 LB/K: 1.00 DB/K: > 86.00 CLUF: 33203958.00 > Index: NUK_TCONTRACT_CUSIP Col#: 20 35 57 1 > USING COMPOSITE STATS > LVLS: 3 #LB: 955919 #DK: 112199564 LB/K: 1.00 DB/K: > 1.00 CLUF: 43217198.00 > Index: NUK_TCONTRACT_TRD_DT Col#: 35 > USING COMPOSITE STATS > LVLS: 3 #LB: 402118 #DK: 80 LB/K: 5026.00 DB/K: > 52071.00 CLUF: 4165752.00 > >But, in next section of trace, in which access paths are considered, >NUK_TCONTRACT_TRD_DT does not appear at all (see below). How can that be? > >Paul Baumgartel >CREDIT SUISSE >Information Technology >Securities Processing Databases Americas >One Madison Avenue >New York, NY 10010 >USA >Phone 212.538.1143 >paul.baumgartel@xxxxxxxxxxxxxxxxx ><file://www.credit-suisse.com>www.credit-suisse.com > > >SINGLE TABLE ACCESS PATH > Table: ODS_TCONTRACT Alias: ODS_TCONTRACT > Card: Original: 115569516 Rounded: 115569516 Computed: > 115569516.00 Non Adjusted: 115569516.00 > Access Path: TableScan > Cost: 7280284.59 Resp: 7280284.59 Degree: 0 > Cost_io: 7028169.00 Cost_cpu: 193577124940 > Resp_io: 7028169.00 Resp_cpu: 193577124940 > Access Path: index (index (FFS)) > Index: NUK_TCONTRACT_CUSIP > resc_io: 489938.00 resc_cpu: 20271467483 > ix_sel: 0.0000e+00 ix_sel_with_filters: 1 > Access Path: index (FFS) > Cost: 516339.64 Resp: 516339.64 Degree: 1 > Cost_io: 489938.00 Cost_cpu: 20271467483 > Resp_io: 489938.00 Resp_cpu: 20271467483 > Access Path: index (index (FFS)) > Index: UK_TCONTRACT_TICKER > resc_io: 364308.00 resc_cpu: 18525881475 > ix_sel: 0.0000e+00 ix_sel_with_filters: 1 > Access Path: index (FFS) > Cost: 388436.18 Resp: 388436.18 Degree: 1 > Cost_io: 364308.00 Cost_cpu: 18525881475 > Resp_io: 364308.00 Resp_cpu: 18525881475 > Access Path: index (FullScan) > Index: NUK_TCONTRACT_CUSIP > resc_io: 955985.00 resc_cpu: 29247902618 > ix_sel: 1 ix_sel_with_filters: 1 > Cost: 864847.50 Resp: 864847.50 Degree: 1 > Access Path: index (FullScan) > Index: UK_TCONTRACT_TICKER > resc_io: 710868.00 resc_cpu: 27502316610 > ix_sel: 1 ix_sel_with_filters: 1 > Cost: 649617.80 Resp: 649617.80 Degree: 1 > ****** trying bitmap/domain indexes ****** > Access Path: index (FullScan) > Index: NUK_TCONTRACT_CUSIP > resc_io: 955985.00 resc_cpu: 29247902618 > ix_sel: 1 ix_sel_with_filters: 1 > Cost: 864847.50 Resp: 864847.50 Degree: 0 > Access Path: index (FullScan) > Index: UK_TCONTRACT_TICKER > resc_io: 710868.00 resc_cpu: 27502316610 > ix_sel: 1 ix_sel_with_filters: 1 > Cost: 649617.80 Resp: 649617.80 Degree: 0 >******** Begin index join costing ******** > ****** trying bitmap/domain indexes ****** > Access Path: index (FullScan) > Index: NUK_TCONTRACT_CUSIP > resc_io: 955985.00 resc_cpu: 29247902618 > ix_sel: 1 ix_sel_with_filters: 1 > Cost: 864847.50 Resp: 864847.50 Degree: 0 > Access Path: index (FullScan) > Index: UK_TCONTRACT_TICKER > resc_io: 710868.00 resc_cpu: 27502316610 > ix_sel: 1 ix_sel_with_filters: 1 > Cost: 649617.80 Resp: 649617.80 Degree: 0 > Access Path: index (FullScan) > Index: UK_TCONTRACT_TICKER > resc_io: 710868.00 resc_cpu: 27502316610 > ix_sel: 1 ix_sel_with_filters: 1 > Cost: 649617.80 Resp: 649617.80 Degree: 0 >******** End index join costing ******** > Best:: AccessPath: IndexFFS Index: UK_TCONTRACT_TICKER > Cost: 388436.18 Degree: 1 Resp: 388436.18 Card: > 115569516.00 Bytes: 0 > > >======================================================================= ======= >Please access the attached hyperlink for an important electronic >communications disclaimer: > >http://www.credit-suisse.com/legal/en/disclaimer_email_ib.html >======================================================================= ======= Hemant K Chitale http://web.singnet.com.sg/~hkchital and http://hemantscribbles.blogspot.com and http://hemantoracledba.blogspot.com "There is more to life than increasing its speed." 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