Re: Join 2 FACT Tables partitioned on same KEY column
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 23 Jun 2005 19:59:40 +0100
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@xxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
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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