Re: IOT index costing in 19c

You also have a change in the GQL value.

Is there a difference in the pct_direct_access that we can't see - Oracle has (used to have) an algorithm that changed the cost based on the value of pct_direct_access.

Regards
Jonathan Lewis

On Tue, Sep 1, 2020 at 5:52 PM Noveljic Nenad <nenad.noveljic_at_vontobel.com> wrote:

> The cost estimation of an IOT secondary index dropped in 19c:
>
>
>
>
>
> 19
>
> Index Stats::
>
> Index: IX Col#: 1 4
>
> LVLS: 3 #LB: 291921 #DK: 807941 LB/K: 1.00 DB/K: 26.00 CLUF:
> 21625156.00 NRW: 40118629.00 SSZ: 0.00 LGR: 0.00 CBK: 0.00 GQL: 100.00
> CHR: 0.00 KQDFLG: 909455669 BSZ: 1
>
> KKEISFLG: 1
>
> 12.2
>
> Index Stats::
>
> Index: IX Col#: 1 4
>
> LVLS: 3 #LB: 272824 #DK: 699585 LB/K: 1.00 DB/K: 29.00 CLUF:
> 20503378.00 NRW: 38686507.00 SSZ: 0.00 LGR: 0.00 CBK: 0.00 GQL: 0.00 CHR:
> 0.00 KQDFLG: 1 BSZ: 1
>
> KKEISFLG: 1
>
>
>
>
>
> 19
>
> ****** Costing Index IX
>
> OPTIMIZER PERCENT INDEX CACHING = 0
>
> SPD: Return code in qosdDSDirSetup: NODIR, estType = INDEX_SCAN
>
> Estimated selectivity: 2.9279e-06 , col: #1
>
>
>
> SPD: Return code in qosdDSDirSetup: NODIR, estType = INDEX_FILTER
>
>
>
> Estimated selectivity: 2.9279e-06 , col: #1
>
> Access Path: index (RangeScan)
>
> Index: IX
>
> resc_io: 67.317355 resc_cpu: 531351
>
> ix_sel: 2.9279e-06 ix_sel_with_filters: 2.9279e-06
>
> Cost: 67.339481 Resp: 67.339481 Degree: 1
>
> ****** Costing Index IX_BER02_PARTNER
>
>
>
>
>
> 12.2
>
> ****** Costing Index IX
>
> OPTIMIZER PERCENT INDEX CACHING = 0
>
> SPD: Return code in qosdDSDirSetup: NODIR, estType = INDEX_SCAN
>
> Estimated selectivity: 2.9439e-06 , col: #1
>
>
>
> SPD: Return code in qosdDSDirSetup: NODIR, estType = INDEX_FILTER
>
>
>
> Estimated selectivity: 2.9439e-06 , col: #1
>
> Access Path: index (RangeScan)
>
> Index: IX
>
> resc_io: 332.496503 resc_cpu: 2412554
>
> ix_sel: 2.9439e-06 ix_sel_with_filters: 2.9439e-06
>
> Cost: 332.596968 Resp: 332.596968 Degree: 1
>
>
>
> The cost slumped from 332 in 12c to 67 in 19c.
>
>
>
> A significant difference in the statistics is KQDFLG.
>
>
>
> Does anybody understand this?
>
>
>
> Best regards,
>
>
>
> Nenad
>
>
>
> http://nenadnoveljic.com/blog/
>
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