Re: IOT index costing in 19c

I hadn't tried - but when you emailed I re-ran my test from the blog, and nothing (apparently) went wrong in 12c or 19.3.

So I thought about what I had changed recently and the only change was that I used to have rowsource execution statistics enabled until a little while ago but switched it off quite recently.

I've done a couple of tests, and I'm not 100% certain yet but trace file dump seems to happen when statistics_level = all (or, perhaps, specifically, when "_rowsource_execution_statistics" = true.

Don't believe it, so still testing - it's a bit of a pain in a PDB.

Regards
Jonathan Lewis

On Thu, Sep 3, 2020 at 2:06 PM Noveljic Nenad <nenad.noveljic_at_vontobel.com> wrote:

> Exactly! Thanks.
>
>
>
> Have you tried to suppress or reduce the trace content with an event?
>
>
>
> Best regards,
>
>
>
> Nenad
>
>
>
> https://nenadnoveljic.com/blog
>
>
>
>
>
> *From:* oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> *On
> Behalf Of *Jonathan Lewis
> *Sent:* Donnerstag, 3. September 2020 14:41
> *To:* Oracle L <oracle-l_at_freelists.org>
> *Subject:* Re: IOT index costing in 19c
>
>
>
>
>
> This bug ? (Neither number public)
>
> https://jonathanlewis.wordpress.com/2019/12/16/iot-bug/
>
>
>
> - Bug 30733525 – ALERT LOG ENTRIES RE BLOCK GUESSES IN THE SECONDARY
> INDEXES OF IOTS POINTING TO OVERFLOW SEGMENT INSTEAD OF INDEX SEGMENT
> - Bug 30733563 – WRONG GUESS DBA IN INDEX
>
>
>
> Regards
>
> Jonathan Lewis
>
>
>
>
>
> On Thu, Sep 3, 2020 at 12:49 PM Noveljic Nenad <
> nenad.noveljic_at_vontobel.com> wrote:
>
> The primary reason for the bad performance in 19c with the secondary index
> weren’t the obsolete references, as I first speculated.
>
>
>
> According to captured stacks, the process was being mostly busy with
> spooling blocks into the trace:
>
>
>
> 00007fff999783da __write () + a
>
> 00000000075671ad sdbgrfuwf_write_file () + 3d
>
> 000000000756711c sdbgrfwf_write_file () + 3c
>
> 000000000754a55d dbgtfdFileWrite () + 20d
>
> 00000000074ececf dbgtfdFileAccessCbk () + 19f
>
> 000000000756dfe7 dbgtfPutStr () + 2d7
>
> 000000000756d75e dbktPri () + ce
>
> 00000000074fe039 ksdfmw () + 1e9
>
> 00000000077578d0 krvtwdb () + e0
>
> 00000000077568a1 kdr4dmp () + c91
>
> 000000000775505d kdb4dmp1 () + a8d
>
> 00000000077545ac kdb4dmp () + 4c
>
> 00000000136f0e37 kdbdmp_full () + 427
>
> 00000000136f1b18 kdbdmp () + 38
>
> 000000000a4ff05a ktbtdu () + 7a
>
> 000000000a4f1d9f ktbdbhw () + 19f
>
> 000000000774f69c kcbtdu1 () + 63c
>
> 0000000007748e68 kcbzdh () + 2478
>
> 000000000624b2c4 kcbzib () + a5a4
>
> 000000000628c07c kcbgtcr () + 264c
>
> 00000000063511bd ktrgtc2 () + 3dd
>
> 000000000634f944 qeilbk1 () + 1b24
>
> 000000000634ddde qeilbk0 () + e
>
> 0000000017316da1 qerixFetchByLogicalRowid () + 311
>
> 000000000c423022 qerstFetch () + 542
>
> 00000000067935de rwsfcd () + 6e
>
> 000000000c423022 qerstFetch () + 542
>
> 0000000017293f7b qerhnFetch () + 56b
>
> 000000000c4230a0 qerstFetch () + 5c0
>
> 0000000006ba3fd3 qerjoFetch () + 383
>
> 000000000c423022 qerstFetch () + 542
>
> 00000000067935de rwsfcd () + 6e
>
> 000000000c423022 qerstFetch () + 542
>
> 00000000172947d4 qerhnFetch () + dc4
>
> 000000000c423022 qerstFetch () + 542
>
> 00000000064522c2 qervwFetch () + a2
>
> 000000000c423022 qerstFetch () + 542
>
> 00000000067935de rwsfcd () + 6e
>
> 000000000c423022 qerstFetch () + 542
>
> 0000000006ba2c96 qerusFetch () + 316
>
> 000000000c423022 qerstFetch () + 542
>
> 00000000124eb76a UpsOnlyInsertExe () + 27a
>
> 0000000006ba24e5 upsexe () + e65
>
> 000000000613a7aa opiexe () + 3dda
>
> 000000000678dc1a kpoal8 () + b5a
>
> 0000000006128c09 opiodr () + 439
>
> 0000000006132843 ttcpip () + 5f3
>
> 000000000612e23c opitsk () + 9ec
>
> 000000000612cd58 opiino () + 4a8
>
> 0000000006128c09 opiodr () + 439
>
> 00000000061281cf opidrv () + 33f
>
> 0000000006127e07 sou2o () + 97
>
> 0000000006127c51 opimai_real () + 121
>
> 000000000612772b ssthrdmain () + 26b
>
> 0000000006127499 main () + a9
>
> 000000000778ad44 ???????? ()
>
>
>
>
>
> The reason is in the trace file: “kcbzib: encounter logical error
> ORA-1410, try re-reading from other mirror..”
>
>
>
> That looks like the latest mutation of some everlasting IOT bug (see MOS).
>
>
>
> The query, though, ran without errors. Presumably, following rowids didn’t
> work (notice qerixFetchByLogicalRowid on the stack), but then the execution
> felt back on PK lookup.
>
>
>
> Rebuilding the index resolved the problem. Still have to see for how long.
>
>
>
> By adjusting guessq (alias pct_direct_access) I just avoided the corrupted
> index.
>
>
>
> Best regards
>
>
>
> Nenad
>
>
>
> https://nenadnoveljic.com/blog
>
>
>
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