RE: IOT index costing in 19c

From: Noveljic Nenad <nenad.noveljic_at_vontobel.com>
Date: Tue, 1 Sep 2020 17:26:06 +0000
Message-ID: <24232_1598981183_5F4E843F_24232_7498_1_03b919c0b5894984a6512db9076e232e_at_vontobel.com>



dba_indexes.PCT_DIRECT_ACCESS, but it has another name in set_index_stats

exec DBMS_STATS.SET_INDEX_STATS ( 'VAR', 'IX_BER02_GBZ_TIEFE', guessq => 0 ) ;

From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> On Behalf Of Jonathan Lewis Sent: Dienstag, 1. September 2020 19:23 To: Oracle L <oracle-l_at_freelists.org> Subject: Re: IOT index costing in 19c

Our email crossed - I wasted a couple of minutes checking the name of the column. GQL = Guess QuaLity ?

Regards
Jonathan Lewis

On Tue, Sep 1, 2020 at 6:15 PM Noveljic Nenad <nenad.noveljic_at_vontobel.com<mailto:nenad.noveljic_at_vontobel.com>> wrote: It wasn’t the Oracle upgrade. It was rather PCT_DIRECT_ACCESS – it went from 0 to 100. (Somebody updated block references.)

Sorry for the noise.

Best regards,

Nenad

From: Noveljic Nenad
Sent: Dienstag, 1. September 2020 18:51 To: ORACLE-L (oracle-l_at_freelists.org<mailto:oracle-l_at_freelists.org>) <oracle-l_at_freelists.org<mailto:oracle-l_at_freelists.org>> Subject: IOT index costing in 19c

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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Received on Tue Sep 01 2020 - 19:26:06 CEST

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