RE: Never seen this line in an execution plan before
Date: Fri, 14 Aug 2020 13:43:29 +0000
Message-ID: <DM6PR08MB6297B8E274AABFBD97B6720AFE400_at_DM6PR08MB6297.namprd08.prod.outlook.com>
Never mind, turns out to be an unpublished Oracle bug - Bug 29665260<https://support.oracle.com/epmos/faces/BugDisplay?id=29665260&parent=SrDetailText&sourceId=3-23781833841>
They still didn’t explain the PARTITION REFERENCE AND though 😊.
From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> On Behalf Of dmarc-noreply_at_freelists.org
Sent: Friday, August 14, 2020 9:13 AM
He just reported back that the pstart/pstop did move to KEY(AP) but that the number of hash partitions changed from 32 to 128 so it’s still a power of 2
From: Jonathan Lewis <jlewisoracle_at_gmail.com<mailto:jlewisoracle_at_gmail.com>>
Sent: Thursday, August 13, 2020 3:29 AM
To: Miller, Jay <Jay.Miller_at_tdameritrade.com<mailto:Jay.Miller_at_tdameritrade.com>>
Cc: Oracle L <oracle-l_at_freelists.org<mailto:oracle-l_at_freelists.org>>
Subject: Re: Never seen this line in an execution plan before
I've not seen exactly this operation before, but I'll take a guess.
You didn't show the pstart/pstop columns of the plan but I'm going to guess that they changed from KEY(I) to KEY(AP), and I'm going to guess that the increase in hash partitions means you've moved from a power of 2 to a number of partitions that hasn't yet reached the next power of 2.
Regards
On Thu, Aug 13, 2020 at 12:04 AM Redacted sender Jay.Miller for DMARC <dmarc-noreply_at_freelists.org<mailto:dmarc-noreply_at_freelists.org>> wrote:
A fellow DBA asked me to take a look at this. He had increased the number of hash partitions in a table in our performance testing environment. The plan changed and performance got much, much worse (all in cpu usage).
What is weird is that the only thing in the plan that changed was the line PARTITION REFERENCE ITERATOR became PARTITION REFERENCE AND. I’ve never heard of PARTITION REFERENCE AND. Googling and searching Metalink did not produce any hits. We have a ticket open with Oracle but they aren’t answering the question of what the significance is of that difference so I thought I’d throw it out to the collective wisdom of the freelisters. Anyone know what this line means?
Oracle 12.2.0.1
Here are the old and new plans:
Predicate information and outline hints are identical between the 2 plans.
Thank you!
To: jlewisoracle_at_gmail.com
Cc: oracle-l_at_freelists.org
Subject: RE: Never seen this line in an execution plan before
Jonathan Lewis
RH Linux 6.10
Pred Op Par. #Sib Query Block ms spent in Consistent Rowsource Real #rows Est. rows Opt. Card. Current Physical Physical Memory Workarea Optimizer
#Col ID ID ling Row Source name this operation gets starts returned total misestimate gets read blks write blks used (MB) Passes Cost
----- ----- ----- ----- ------------------------------------------------------------------------ -------------------- -------------- ---------- ---------- ----------- ------------- --------------- ---------- ---------- ---------- ------------- ------------- -----------
0 SELECT STATEMENT >>> Plan totals >>> 202
F 1 0 1 FILTER SEL$1
2 1 1 INLIST ITERATOR
3 2 1 PARTITION REFERENCE ITERATOR 202
4 3 1 TABLE ACCESS BY LOCAL INDEX ROWID BATCHED [ORDER_ACTIVITY] SEL$1 202
A#1 5 4 1 INDEX RANGE SCAN [ORDER_STRATEGY_ORDER_ACTIVI_FK] SEL$1 58
6 1 2 SORT AGGREGATE SEL$2
7 6 1 PARTITION REFERENCE SINGLE 7
F 8 7 1 TABLE ACCESS BY LOCAL INDEX ROWID BATCHED [ORDER_ACTIVITY] SEL$2 7
A#1 9 8 1 INDEX RANGE SCAN [ORDER_STRATEGY_ORDER_ACTIVI_FK] SEL$2 4
Pred Op Par. #Sib Query Block ms spent in Consistent Rowsource Real #rows Est. rows Opt. Card. Current Physical Physical Memory Workarea Optimizer
#Col ID ID ling Row Source name this operation gets starts returned total misestimate gets read blks write blks used (MB) Passes Cost
----- ----- ----- ----- ------------------------------------------------------------------------ -------------------- -------------- ---------- ---------- ----------- ------------- --------------- ---------- ---------- ---------- ------------- ------------- -----------
0 SELECT STATEMENT >>> Plan totals >>> 364
F 1 0 1 FILTER SEL$1
2 1 1 INLIST ITERATOR
3 2 1 PARTITION REFERENCE AND 364
4 3 1 TABLE ACCESS BY LOCAL INDEX ROWID BATCHED [ORDER_ACTIVITY] SEL$1 364
A#1 5 4 1 INDEX RANGE SCAN [ORDER_STRATEGY_ORDER_ACTIVI_FK] SEL$1 103
6 1 2 SORT AGGREGATE SEL$2
7 6 1 PARTITION REFERENCE SINGLE 7
F 8 7 1 TABLE ACCESS BY LOCAL INDEX ROWID BATCHED [ORDER_ACTIVITY] SEL$2 7
A#1 9 8 1 INDEX RANGE SCAN [ORDER_STRATEGY_ORDER_ACTIVI_FK] SEL$2 4
Jay Miller
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Received on Fri Aug 14 2020 - 15:43:29 CEST