10053 shows bitmap index not being used - why ?
- From: "Stefan Knecht" <knecht.stefan@xxxxxxxxx>
- To: oracle-l <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 25 Oct 2006 11:51:48 +0200
Hi all,
looking at the tracefile output below:
SINGLE TABLE ACCESS PATH
COLUMN: DBE_MTH(CHARACTER) Col#: 12 Table:
MKER_F_DECKUNGSBEITRAG Alias: T_DEB
Size: 7 NDV: 24 Nulls: 0 Density: 1.0015e-08
Histogram: Freq #Bkts: 24 UncompBkts: 1497795 EndPtVals: 24
TABLE: MKER_F_DECKUNGSBEITRAG Alias: T_DEB
Original Card: 49926500 Rounded: 2080271 Computed: 2080270.83 Non
Adjusted: 2080270.83
Access Path: table-scan Resc: 347730 Resp: 347730
Access Path: index (skip-scan)
ss sel 4.1667e-02 andv 2035954
ss cost 2035954 vs. index scan io cost 16684
Skip Scan rejected
Access Path: index (scan)
Index: MK_IDX_00
rsc_cpu: 12885810654 rsc_io: 1617892
ix_sel: 4.1667e-02 ix_sel_with_filters: 4.1667e-02
Access Path: index (skip-scan)
ss sel 4.1667e-02 andv 2027407
ss cost 2027407 vs. index scan io cost 6781
Skip Scan rejected
Access Path: index (scan)
Index: MK_IDX_01
rsc_cpu: 1731092408 rsc_io: 52339
ix_sel: 4.1667e-02 ix_sel_with_filters: 4.1667e-02
Access Path: index (equal)
Index: MK_BMIDX
rsc_cpu: 412879 rsc_io: 55
ix_sel: 4.1667e-02 ix_sel_with_filters: 4.1667e-02
******** Bitmap access path rejected ********
Cost: 334275 Cost_io: 332673 Cost_cpu: 3627695115 Selectivity: 0
Not believed to be index-only.
BEST_CST: 53103.41 PATH: 4 Degree: 1
Grouping column cardinality [T008_ITN_I] 2
Grouping column cardinality [T130_ACT_R] 561224
Looking at the bitmap index,
Access Path: index (equal)
Index: MKER_F_DECKUNGSBEITRAG_BMIDX
rsc_cpu: 412879 rsc_io: 55
It's got by far the lowest rsc_* values - yet it's not being considered
(Bitmap access path rejected) do these values not show estimated cost ?
What could be the reason ? Would appreciate someone shedding some light on
this :)
Stefan
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