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Home -> Community -> Mailing Lists -> Oracle-L -> Fwd: Re: Join 2 FACT Tables partitioned on same KEY column
Note: forwarded message attached.
attached mail follows:
Is the 'PARTITION RANGE ITERATOR' instead of
'PARTITION RANGE SINGLE' in the plan due to the fact
that more than 1 partition of T2 are scanned?
You are right in saying that with Nested Loop it is possible. Is the 'PARTITION RANGE ITERATOR' on T2 confirming the fact that only certain (not all) partitions of T2 are probed?
--
Is this possible with a Hash-join? Say, in your
example, D1 and T1 join results in 10 rows, and those
pertain to 2 partitions. Wouldn't it make sense to
probe only those 2 partiitons of T2 'USING a HASH'?
Since I am not seeing that with a Hash join between T1
and T2, but hypothetically speaking, should the plan
show something like:
HASH
NESTED LOOP
TABLE ACCESS FULL DRIVER
PARTITION RANGE ALL
<T1>
PARTIITON RANGE ITERATOR
<T2>
Thanks,
Deepak
--- Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
wrote:
>
> I think this should be possible, but only if the
> join between core_fact and param_fact is a
> nested loop
>
> You'll have to cut the example below and
> paste it into a fixed font editor to read it,
> but in my test case:
>
> T1 and T2 are partitioned on ID.
>
> The join from DRIVER to T1 has to do
> partition range (ALL) because there is
> no partitioning column visible in the join.
>
> Running with event 10128 set showed that
> only the correct two partitions had been
> visited the correct number of times from
> the second fact table. (I am a little surprised
> that the plan says ITERATOR rather than
> SINGLE).
>
> SQL> l
> 1 select
> 2 /*+ ordered use_nl(t1) use_nl(t2) */
> 3 t1.small_vc,
> 4 t2.small_vc
> 5 from
> 6 driver d1,
> 7 t1,
> 8 t2
> 9 where
> 10 d1.id between 1 and 100
> 11 and t1.n1 = d1.n1
> 12 and t2.id = t1.id
> 13*
>
>
-----------------------------------------------------------------------------------------------------
> | Id | Operation |
> Name | Rows | Bytes
> | Cost | Pstart| Pstop |
>
-----------------------------------------------------------------------------------------------------
> | 0 | SELECT STATEMENT |
> | 100 | 3800
> | 1204 | | |
> | 1 | TABLE ACCESS BY LOCAL INDEX ROWID | T2
> | 1 | 14
> | 2 | | |
> | 2 | NESTED LOOPS |
> | 100 | 3800
> | 1204 | | |
> | 3 | NESTED LOOPS |
> | 100 | 2400
> | 1004 | | |
> |* 4 | TABLE ACCESS FULL |
> DRIVER | 100 | 600
> | 4 | | |
> | 5 | PARTITION RANGE ALL |
> | |
> | | 1 | 9 |
> | 6 | TABLE ACCESS BY LOCAL INDEX ROWID| T1
> | 1 | 18
> | 10 | 1 | 9 |
> |* 7 | INDEX RANGE SCAN |
> T1_N1 | 1 |
> | 9 | 1 | 9 |
> | 8 | PARTITION RANGE ITERATOR |
> | |
> | | KEY | KEY |
> |* 9 | INDEX RANGE SCAN |
> T1_I1 | 1 |
> | 1 | KEY | KEY |
>
-----------------------------------------------------------------------------------------------------
>
> Predicate Information (identified by operation id):
> ---------------------------------------------------
>
> 4 - filter("D1"."ID">=1 AND "D1"."ID"<=100)
> 7 - access("T1"."N1"="D1"."N1")
> 9 - access("T2"."ID"="T1"."ID")
>
>
>
> Regards
>
> Jonathan Lewis
>
> http://www.jlcomp.demon.co.uk/faq/ind_faq.html
> The Co-operative Oracle Users' FAQ
>
> http://www.jlcomp.demon.co.uk/appearances.html
> Public Appearances - schedule updated June 22nd 2005
>
>
>
>
>
>
> ----- Original Message -----
> From: "Deepak Sharma" <sharmakdeep_oracle_at_yahoo.com>
> To: <oracle-l_at_freelists.org>
> Sent: Thursday, June 23, 2005 7:32 PM
> Subject: Join 2 FACT Tables partitioned on same KEY
> column
>
>
> > We have 3 tables in our DW -- DATE_DIM D1,
> CORE_FACT
> > F1 and PARAM_FACT F2
> >
> > The tables F1 and F2 are both partitioned on a
> column
> > TEST_KEY. Also, as an example, we are sure that a
> row
> > with TEST_KEY value 100, if exists in Partition
> P10 of
> > table F1, then it will definitely be in Partition
> P10
> > of table F2.
> >
> > To give an example of what we expect to see :
> >
> > SELECT f2.column1, f2.column2, f2.column3
> > FROM CORE_FACT f1, PARAM_FACT f2, DATE_DIM d1
> > WHERE f1.TEST_KEY = f2.TEST_KEY
> > AND f1.DATE_KEY = d1.DATE_KEY
> > AND d1.ACTUAL_DATE between (sysdate-2) and
> > (sysdate);
> >
> > Based on a condition placed on DATE_DIM, rows from
> > CORE_FACT are retrieved. Let's say the number of
> rows
> > returned by that join is 100. Those 100 rows, say,
> lie
> > in 3 partitions P2, P13 and P25, of table
> CORE_FACT.
> >
> > What we expect to see is that when CORE_FACT joins
> to
> > PARAM_FACT (as above), only specific partitions
> P2,
> > P13 and P25 of PARAM_FACT should be accessed.
> >
> > I have a TAR open with Oracle Support on this
> issue,
> > and they say it is not possible/supported. Any
> > comments?
> >
> >
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Received on Thu Jun 23 2005 - 23:08:07 CDT
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