Bad performance view on views

Question

we have two views with equal key fields which perform very good (order less than 1 second).
Both views give extra fields from data sets.
I want to combine those extra fields in one record with equal key values. Because some key combinations can miss in either one of both sets, I make an extra view with a union only on the keyfields of both views and use this view as driver for the combination, so I join both original views open with this driver. When I now query the resultview the performance is bad (order 3.5 minutes).
(This is independent of the number of result records)
Explain plan shows no full table scans.
Any suggestions to improve this construction??

Answer 1

I have split the two parts of the union query, and analysed both parts separately, see below.
The subviews perform as follows:
c_contr_opb_CD with restriction on contract_no 7 rows in 0:02 seconds
without restrictions 2216 records in 3:34 minutes
c_contr_opb_B with restriction on contract_no 5 rows in 0:01 seconds
without restrictions 1567 records in 0:05 minutes
(in both views are 1332 records with common keys)
When I make the view over an open join of both views and I use the
c_contr_opb_B as driver then it performs with and without restriction
on contract_no the same, suggesting it performs the 'group by'-clause in
the view c_contr_opb_CD before applying the restriction.
When, on the other hand I use the view c_contr_opb_CD as driver it seems to
apply the restriction before the 'group by'-clause in the view.
Is there a way to always apply the restriction berore the 'group by' clause
select tB.Contract_no
, tB.agc
, tB.salesgroup
, tB.B_pricing
, tB.B_No_of_elements
, tB.B_m3_elements
, tB.C_complete
, tCD.C_pricing
, tCD.C_No_of_elements
, tCD.C_m3_elements
, tCD.D_pricing
, tCD.D_No_of_elements
, tCD.D_m3_elements
from c_contr_opb_CD tCD
, c_contr_opb_B tB
where (tCD.Contract_no(+) = tB.Contract_no
and tCD.agc(+) = tB.agc
and tCD.salesgroup(+) = tB.salesgroup)
and tB.contract_no=lpad('20042002',20);
query in 3:40 minutes, result 5 records
Options Object Operation
SELECT STATEMENT
OUTER MERGE JOIN
JOIN SORT
C_CONTR_OPB_B VIEW
GROUP BY SORT
VIEW
UNION-ALL
NESTED LOOPS
UNIQUE SCAN PK_CMHD INDEX
BY INDEX ROWID CMMT TABLE ACCESS
RANGE SCAN PK_CMMT INDEX
NESTED LOOPS
UNIQUE SCAN PK_CMHD INDEX
BY INDEX ROWID CMSV TABLE ACCESS
RANGE SCAN PK_CMSV INDEX
JOIN SORT
C_CONTR_OPB_CD VIEW
GROUP BY SORT
VIEW
UNION-ALL
NESTED LOOPS
RANGE SCAN X_SHP_CM INDEX
BY INDEX ROWID CMMT TABLE ACCESS
RANGE SCAN PK_CMMT INDEX
NESTED LOOPS
RANGE SCAN X_SHP_CM INDEX
BY INDEX ROWID CMSV TABLE ACCESS
RANGE SCAN PK_CMSV INDEX
28 rows selected.
select tCD.Contract_no
, tCD.agc
, tCD.salesgroup
, tB.B_pricing
, tB.B_No_of_elements
, tB.B_m3_elements
, tB.C_complete
, tCD.C_pricing
, tCD.C_No_of_elements
, tCD.C_m3_elements
, tCD.D_pricing
, tCD.D_No_of_elements
, tCD.D_m3_elements
from c_contr_opb_B tB
, c_contr_opb_CD tCD
where (tB.Contract_no(+) = tCD.Contract_no
and tB.agc(+) = tCD.agc
and tB.salesgroup(+) = tCD.salesgroup)
and tCD.contract_no=lpad('20042002',20);
query in 0:05 minutes, result 7 rows
Options Object Operation
SELECT STATEMENT
OUTER MERGE JOIN
JOIN SORT
C_CONTR_OPB_CD VIEW
GROUP BY SORT
VIEW
UNION-ALL
NESTED LOOPS
UNIQUE SCAN PK_CMHD INDEX
BY INDEX ROWID CMMT TABLE ACCESS
RANGE SCAN PK_CMMT INDEX
NESTED LOOPS
UNIQUE SCAN PK_CMHD INDEX
BY INDEX ROWID CMSV TABLE ACCESS
RANGE SCAN PK_CMSV INDEX
JOIN SORT
C_CONTR_OPB_B VIEW
GROUP BY SORT
VIEW
UNION-ALL
NESTED LOOPS
RANGE SCAN X_SHP_CM INDEX
BY INDEX ROWID CMMT TABLE ACCESS
RANGE SCAN PK_CMMT INDEX
NESTED LOOPS
RANGE SCAN X_SHP_CM INDEX
BY INDEX ROWID CMSV TABLE ACCESS
RANGE SCAN PK_CMSV INDEX
create or replace view c_contr_opb_B as
select     Contract_no
     ,     agc
     ,     salesgroup
     ,     min(C_complete)          C_complete
     ,     sum(B_pricing)          B_pricing
     ,     sum(B_No_of_elements)     B_No_of_elements
     ,     sum(B_m3_elements)     B_m3_elements
     from (     select     h.cm_num               Contract_no
          ,     ms.agc
          ,     ms.sales_group               salesgroup
          ,     decode(ms.closed_reason,'C001','*',' ')     C_complete
          ,     ms.unit_price*ms.ord_qty     B_pricing
          ,      decode(ms.agc,'PROJ',fnc_struct_m3(ms.ccn,ms.structure_id,ms.structure_rev)
                    ,0)*ms.ord_qty          B_m3_elements
          ,     ms.ord_qty                B_No_of_elements
          from     cmmt     ms
          ,     cmhd     h
          where     ms.ccn          = h.ccn
          and     ms.cm_num     = h.cm_num
          and     ms.price_bucket     = 'B'
          and     ms.closed_reason in ('C001',' ')
          and     h.ccn          = 'SPAN'
          UNION ALL
          select     h.cm_num               Contract_no
          ,     ms.agc
          ,     ms.sales_group               salesgroup
          ,     decode(ms.closed_reason,'C001','*',' ')     C_complete
          ,     ms.unit_price*ms.ord_qty     B_pricing
          ,      0                    B_m3_elememts
          ,     ms.ord_qty                B_No_of_elements
          from     cmsv     ms
          ,     cmhd     h
          where     ms.ccn          = h.ccn
          and     ms.cm_num     = h.cm_num
          and     ms.price_bucket     = 'B'
          and     ms.closed_reason in ('C001',' ')
          and     h.ccn          = 'SPAN'
     ) group by Contract_no
     ,     agc
     ,     salesgroup
create or replace view c_contr_opb_CD as
select     Contract_no
     ,     agc
     ,     salesgroup
     ,     sum(C_pricing)          C_pricing
     ,     sum(C_No_of_elements)     C_No_of_elements
     ,     sum(C_m3_elements)     C_m3_elements
     ,     sum(D_pricing)          D_pricing
     ,     sum(D_No_of_elements)     D_No_of_elements
     ,     sum(D_m3_elements)     D_m3_elements
     from (     select     h.cm_num               Contract_no
          ,     ms.agc
          ,     ms.sales_group               salesgroup
          ,     ms.unit_price*ms.ord_qty     C_pricing
          ,     ms.ord_qty                C_No_of_elements
          ,      decode(ms.agc,'PROJ',fnc_item_m3(ms.ccn,ms.item,ms.revision),0)
                    *ms.ord_qty          C_m3_elements
          ,     ms.unit_price*ms.ord_qty     D_pricing
          ,     decode(ms.agc,'PROJ',fnc_item_aantal_D(ms.ccn,ms.item,ms.revision),0)
                                   D_No_of_elements
          ,      decode(ms.agc,'PROJ',fnc_item_m3_D(ms.ccn,ms.item,ms.revision),0)
               * decode(ms.agc,'PROJ',fnc_item_aantal_D(ms.ccn,ms.item,ms.revision),0)
                                   D_m3_elements
          from     cmmt     ms
          ,     cmhd     h
          where     ms.ccn          = h.ccn
          and     ms.cm_num     = h.cm_num
          and     ms.price_bucket     = 'C'
          and     ms.closed_reason in ('F001','F003',' ')
          and     h.ccn          = 'SPAN'
          UNION ALL
          select     h.cm_num               Contract_no
          ,     ms.agc
          ,     ms.sales_group               salesgroup
          ,     ms.unit_price*ms.ord_qty     C_pricing
          ,     ms.ord_qty                C_No_of_elements
          ,      0                    C_m3_elememts
          ,     ms.unit_price*ms.ord_qty     D_pricing
          ,     0                    D_No_of_elements
          ,      0                    D_m3_elements
          from     cmsv     ms
          ,     cmhd     h
          where     ms.ccn          = h.ccn
          and     ms.cm_num     = h.cm_num
          and     ms.price_bucket     = 'C'
          and     ms.closed_reason in ('F001','F003',' ')
          and     h.ccn          = 'SPAN'
     ) group by Contract_no
     ,     agc
     ,     salesgroup