RE: Views and predicates.....
- From: "Mercadante, Thomas F" <thomas.mercadante@xxxxxxxxxxxxxxxxx>
- To: "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 30 Jan 2004 11:25:09 -0500
Mark,
this may be as simple as selecting the correct doc_id column. Is the
CPAG_CNST_UK01 index in the COMPRESSED_AGREEMENTS table? If not, then
change your select statement (within the view) to query the doc_id column
from the correct table.
Good Luck
Tom Mercadante
Oracle Certified Professional
-----Original Message-----
From: Bobak, Mark [mailto:Mark.Bobak@xxxxxxxxxxxxxxx]
Sent: Friday, January 30, 2004 11:09 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: Views and predicates.....
Ok, so I have a view defined as:
create or replace view xan_comp_view
as
select /*+ ordered use_nl(xcpag) */
distinct cpag.doc_id doc_id,
decode(xcpag.doc_id,NULL,cpag.cpag_text,xcpag.cpag_text)
cpag_text,
decode(xcpag.doc_id,NULL,length(cpag.cpag_text),length(xcpag.cpag_text))
cpag_text_length,
decode(xcpag.doc_id,NULL,max(cpag.cpag_day_effective) over
(partition by cpag.doc_id),
max(xcpag.cpag_day_effective) over
(partition by xcpag.doc_id)) cpag_day_effective,
decode(xcpag.doc_id,NULL,'PQ','XN') aud_type
from compressed_agreements cpag,
xan_compressed_agreements xcpag
WHERE decode(xcpag.doc_id,NULL,cpag.CPAG_DAY_EFFECTIVE,1) <=
decode(xcpag.doc_id,NULL,decode(sign(trunc(sysdate)-cpag.cpag_calc_date)
,-1,0, trunc(sysdate)-cpag.cpag_calc_date + NVL(cpag.C
PAG_DAY_EFFECTIVE,0)),1)
and decode(xcpag.doc_id,NULL,1,xcpag.CPAG_DAY_EFFECTIVE) <=
decode(xcpag.doc_id,NULL,1,decode(sign(trunc(sysdate)-xcpag.cpag_calc_da
te),-1,0,
trunc(sysdate)-xcpag.cpag_calc_date +
NVL(xcpag.CPAG_DAY_EFFECTIVE,0)))
and cpag.doc_id = xcpag.doc_id(+)
/
If I do 'select * from xan_comp_view;'
The plan is:
SQL> select * from xan_comp_view
2 /
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=496561 Card=1948518
Bytes=335145096)
1 0 VIEW OF 'XAN_COMP_VIEW' (Cost=496561 Card=1948518
Bytes=335145096)
2 1 SORT (UNIQUE) (Cost=496561 Card=1948518 Bytes=378012492)
3 2 WINDOW (SORT)
4 3 WINDOW (BUFFER)
5 4 FILTER
6 5 NESTED LOOPS (OUTER)
7 6 TABLE ACCESS (BY INDEX ROWID) OF
'COMPRESSED_AGREEMENTS' (Cost=6171 Card=2609173 Bytes=258308127)
8 7 INDEX (FULL SCAN) OF 'CPAG_CNST_UK01' (UNIQUE)
(Cost=6613 Card=2609173)
9 6 TABLE ACCESS (BY INDEX ROWID) OF
'COMPRESSED_AGREEMENTS' (Cost=1 Card=270 Bytes=25650)
10 9 INDEX (RANGE SCAN) OF 'CPAG_INDX_FK01'
(NON-UNIQUE)
This is fine, and I'm ok w/ it. But, I don't plan on ever using the
view this way. What I plan to do is something like:
'select * from xan_comp_view where doc_id = 1'
When I do that, the plan looks like:
SQL> select * from xan_mjb where doc_id =1;
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=496561 Card=1948518
Bytes=335145096)
1 0 VIEW OF 'XAN_MJB' (Cost=496561 Card=1948518 Bytes=335145096)
2 1 SORT (UNIQUE) (Cost=496561 Card=1948518 Bytes=378012492)
3 2 WINDOW (SORT)
4 3 WINDOW (BUFFER)
5 4 FILTER
6 5 NESTED LOOPS (OUTER)
7 6 TABLE ACCESS (BY INDEX ROWID) OF
'COMPRESSED_AGREEMENTS' (Cost=6171 Card=2609173 Bytes=258308127)
8 7 INDEX (FULL SCAN) OF 'CPAG_CNST_UK01' (UNIQUE)
(Cost=6613 Card=2609173)
9 6 TABLE ACCESS (BY INDEX ROWID) OF
'COMPRESSED_AGREEMENTS' (Cost=1 Card=270 Bytes=25650)
10 9 INDEX (RANGE SCAN) OF 'CPAG_INDX_FK01'
(NON-UNIQUE)
What I want to see here is an INDEX (UNIQUE SCAN) on CPAG_CNST_UK01',
since I'm providing the 'doc_id=1' predicate. However, it insists on
the FULL SCAN, which, of course, is killing my performance.
Can anyone think of a way that I can convince the optimizer to do what I
want? If I take the SQL that defines the view, and execute it as a SQL,
with the 'DOC_ID=1' predicate, it does exactly what I want. As soon as
I put the SQL into the view, it stops working.
Help!
Thanks in advance,
-Mark
Mark J. Bobak
Oracle DBA
ProQuest Company
Ann Arbor, MI
"Imagination was given to man to compensate him for what he is not, and
a sense of humor was provided to console him for what he is." --Horace
Walpole
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