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
Jonathan Lewis

On Thu, Aug 13, 2020 at 12:04 AM Redacted sender Jay.Miller for DMARC < 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
>
> RH Linux 6.10
>
>
>
>
>
>
>
> Here are the old and new plans:
>
>
>
> 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
>
>
>
>
>
> Predicate information and outline hints are identical between the 2 plans.
>
>
>
>
>
> Thank you!
>
> Jay Miller
>

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