Query including subquery and group by slower than expected - sql

Question

The whole query below runs incredibly slowly.
The subquery query [alias Stage_1] takes only 1.37 minutes returning 9514 records, however the whole query takes over 20 minutes, returning 2606 records.
I could use a #temp table to hold the subquery to improve the performance however I would prefer not to.
An overview of the query is that table WeeklySpace inner joins to Spaceblock_Name_to_PG table on SpaceblockName_SID, this cuts down the results in WeeklySpace and includes PG_Code with the results in WeeklySpace. WeeklySpace is then Full Outer Joined to Sales_PG_Wk across 3 fields. The where clause focuses the results, and may be changed. The results from the subquery are then sum'd. You cannot do the final sum'ing in the subquery due to the group by and sum over used.
I believe the issue is due to the subquery re calculation repeatedly during the group by in the final sum'ing. The field SpaceblockName_SID also appears to be involved in causing the issue as without it the run time with a group by in the subquery isn't affected.
I have read though loads of suggestion, trying them all to resolve the issue.
These include;
Adding TOP 2147483647 with Order by to force intermediate
materialization, both in the subquery and using a CTE.
Adding a join after stage_1.
Cast'ing SpaceblockName_SID from an int to a varchar and back again
The execution plan (cut in two parts, shown below the code) for both the subquery and the whole query appear similar. The cost is around the Full Outer Join (Hash Match), which I expected.
The query is running on T-SQL 2005.
Any help greatly appreciated!
select
Cost_centre
, Fin_week
, SpaceblockName_SID
, sum(Propor_rep_SRV) as Total_SpaceblockName_SID_SRV
from
(
select
coalesce(space_side.fin_week , sales_side.fin_week) as Fin_week
,coalesce(space_side.cost_centre , sales_side.cost_Centre) as Cost_centre
,space_side.SpaceblockName_SID
,case
when space_side.SpaceblockName_SID is null
then sales_side.SalesExVAT
else sum(space_side.TLM)
/nullif(sum (sum(space_side.TLM) ) over (partition by coalesce(space_side.fin_week , sales_side.fin_week)
, coalesce(space_side.cost_centre , sales_side.cost_Centre)
, coalesce( Spaceblock_Name_to_PG.PG_Code, sales_side.PG_Code)) ,0)*sales_side.SalesExVAT
end as Propor_rep_SRV
from
WeeklySpace as space_side
INNER JOIN
Spaceblock_Name_to_PG
ON space_side.SpaceblockName_SID = Spaceblock_Name_to_PG.SpaceblockName_SID
and Spaceblock_Name_to_PG.PG_Code < 10000
full outer join
sales_pg_wk as sales_side
on space_side.fin_week = sales_side.fin_week
and space_side.Cost_Centre = sales_side.Cost_Centre
and Spaceblock_Name_to_PG.PG_code = sales_side.pg_code
where
coalesce(space_side.fin_week, sales_side.fin_week) between 201538 and 201550
and
coalesce(space_side.cost_centre, sales_side.cost_Centre) in (3, 2800)
group by
coalesce(space_side.fin_week, sales_side.fin_week)
,coalesce(space_side.cost_centre, sales_side.cost_Centre)
,coalesce( Spaceblock_Name_to_PG.PG_Code, sales_side.PG_Code)
,sales_side.SalesExVAT
,space_side.SpaceblockName_SID
) as stage_1
group by
Cost_centre
, Fin_week
, SpaceblockName_SID
Execution plan left hand side
Execution plan right hand side

Answer 1

You didn't mentioned about indices are created or not on those columns those you used in your query. If not then create and check performance of the query

Answer 2

In looking at you logic I think you split this in two with a UNION
One with Spaceblock_Name_to_PG.PG_Code < 10000 and the other with Spaceblock_Name_to_PG.PG_Code >= 10000
And consider this change
If may be doing a bunch of join that you are going to throw out anyway
full outer join sales_pg_wk as sales_side
on space_side.fin_week = sales_side.fin_week
and space_side.Cost_Centre = sales_side.Cost_Centre
and Spaceblock_Name_to_PG.PG_code = sales_side.pg_code
and space_side.fin_week between 201538 and 201550
and sales_side.fin_week between 201538 and 201550
and space_side.cost_centre in (3, 2800)
and sales_side.cost_Centre in (3, 2800)