Sql query slowness due to rank and columns with null values - sql

Question

EDITED:
I have the following table in database with around 10 millions records:
Declaration:
create table PropertyOwners (
[Key] int not null primary key,
PropertyKey int not null,
BoughtDate DateTime,
OwnerKey int null,
GroupKey int null
)
go
[Key] is primary key and combination of PropertyKey, BoughtDate, OwnerKey and GroupKey is unique.
With the following index:
CREATE NONCLUSTERED INDEX [IX_PropertyOwners] ON [dbo].[PropertyOwners]
(
[PropertyKey] ASC,
[BoughtDate] DESC,
[IsGroup] ASC
)
INCLUDE ( [OwnerKey], [GroupKey])
go
Description of the case:
For single BoughtDate one property can belong to multiple owners or single group, for single record there can either be OwnerKey or GroupKey but not both so one of them will be null for each record. I am trying to retrieve the data from the table using following query for the OwnerKey. If there are same property rows for owners and group at the same time than the rows having OwnerKey with be preferred, that is why I am using "IsGroup" in Rank function.
declare #ownerKey int = 40000
select PropertyKey, BoughtDate, OwnerKey, GroupKey
from (
select PropertyKey, BoughtDate, OwnerKey, GroupKey,
RANK() over (partition by PropertyKey order by BoughtDate desc, IsGroup) as [Rank]
from PropertyOwners
) as result
where result.[Rank]=1 and result.[OwnerKey]=#ownerKey
It is taking 2-3 seconds to get the records when ever I use the [Rank]=1 with any of PropertyKey/OwnerKey/GroupKey. But when I tried to get the records for the PropertyKey/OwnerKey/GroupKey without using [Rank]=1 in the same query, it is executing in milliseconds. See following query:
declare #ownerKey int = 40000
select PropertyKey, BoughtDate, OwnerKey, GroupKey
from (
select PropertyKey, BoughtDate, OwnerKey, GroupKey,
RANK() over (partition by PropertyKey order by BoughtDate desc, IsGroup) as [Rank]
from PropertyOwners
) as result
where result.[OwnerKey]=#ownerKey
I have also tried to use the Indexed view to pre ranked them but I can't use it in my query as Rank function is not supported in indexed view.
Please note this table is updated once a day and using Sql Server 2008 R2. Any help will be
greatly appreciated.

Answer 1

If I understood your query correctly, it basically does as follows: "for a given owner, return all properties for which this owner is the latest one".
This can also be achieved in other ways, without ranking the entire 10M table, such as:
select po.*
from dbo.PropertyOwners po
where po.OwnerKey = #OwnerKey
and not exists (
select 0 from dbo.PropertyOwners lo
where lo.PropertyKey = po.PropertyKey
and lo.BoughtDate > po.BoughtDate
-- Other group-related conditions here, if need be
);
Essentially the same, just a little bit different wording:
select po.*
from dbo.PropertyOwners po
left join dbo.PropertyOwners lo on lo.PropertyKey = po.PropertyKey
and lo.BoughtDate > po.BoughtDate
-- Other group-related conditions here, if need be
where po.OwnerKey = #OwnerKey
and lo.PropertyKey is null;
You will definitely need different indices for these, and I can't be sure they will help. But at least give it a try.