MERGE [DWH].[dbo].[FactContactLog] as t
USING
(
SELECT cs.[Country]
      ,cs.[ContactLogID]
      ,cs.[PromiseID]
      ,cs.[NumberContract]
	  ,fa.ContractID
	  ,cs.[DebtID]
      ,cs.[PhoneIDContact]
	  ,dcr.ContactResultKey
	  ,st.staffkey
	  ,case when fp.PhonesAttributeKey is null then (select PhonesAttributeKey from [DWH].[dbo].[DimPhonesAttribute] where [ActualFlag] = 0 and [ContactType] = 'NA' and [Relation] = 'NA' and Source = 'Contact') else fp.PhonesAttributeKey end as PhonesAttributeKey
	  ,fa.ApplicationAttributeKey
	  ,fa.ApplicationKey
	  ,fa.BorrowerKey
	  ,fa.GeographyKey
      ,cs.[Description]
      ,cs.[ContactDate]
      ,cs.[CreatePromiseDate]
      ,cs.[PromiseDate]
      ,cs.[PromiseSum]	 
  FROM [Staging].[dbo].[ContactLog_Stage] as cs
  left join [DWH].[dbo].[DimContactResult] as dcr
  on cs.result = dcr.Code
  left join [DWH].[dbo].[DimStaff] as st
  on cs.userid = st.staffidcontact 
  left join [DWH].[dbo].[FactContract] as fa
  on cs.NumberContract = fa.NumberContract and cs.Country = fa.Country
  left join [DWH].[dbo].FactPhones as fp 
  on cs.PhoneIDContact = fp.PhoneIDContact 
  ) as s
  on t.ContactLogID = s.ContactLogID
  when not matched by target then insert 
  ([Country],[ContactLogID],[PromiseID],[NumberContract],[ContractID],[DebtID],[ContactPhoneID],[StaffKey],[ContactResultKey],[PhonesAttributeKey],[ApplicationKey],[ApplicationAttributeKey],[BorrowerKey]
      ,[GeographyKey],[ContactDate],[CreatePromiseDate],[PromiseDate],[Description],[PromiseSum])
values
(s.[Country],s.[ContactLogID],s.[PromiseID],s.[NumberContract],s.[ContractID],s.[DebtID],s.[PhoneIDContact],s.[StaffKey],s.[ContactResultKey],s.[PhonesAttributeKey],s.[ApplicationKey],s.[ApplicationAttributeKey],s.[BorrowerKey]
      ,s.[GeographyKey],s.[ContactDate],s.[CreatePromiseDate],s.[PromiseDate],s.[Description],s.[PromiseSum]);

cкачать

 
select * into #FactContactLog
     from [ваш монстрик] as s
     where not exists( select * from [DWH].[dbo].[FactContactLog] as t where  t.ContactLogID = s.ContactLogID ); 
-- если будет медленно - вставляем только основную таблицу, остальное добиваем апдэйтом.
 
  alter table #FactContactLog add primary key(ContactLogID);


  merge [DWH].[dbo].[FactContactLog] as t using #FactContactLog as s
  ...

left join ( select {воспроизведите тут ТОЧНЫЙ перечень полей фильтрованного индекса} from [DWH].[dbo].FactPhones where {воспроизведите тут ТОЧНОЕ условие фильтрации индекса} ) as fp