Question

I have a table that is partitioned by month (partmonth int). The stored proc used to query the table only receives a date range. I need to find a way to get all of the month numbers in the date range and pass them into a where in (1,2…) clause for the partitioned table. I have tried creating a temp table of the month numbers and using a where in (select monthnumber from #tmp), but this seems to execute the #tmp on each record or scan all partitions. I have also tried to join the partitioned table to the tmp table, but this seems to scan all partitions as well. I assume the query optimizer need hard values for the partmonth where.

query to get all month numbers:

declare @months varchar(100)

select d.* into #tmp
from
(select distinct MonthNumber from [date] where [date] between '1/1/2010' and '4/1/2010') d

select @months = coalesce(@months + ', ', '')  + cast(monthnumber as varchar(2)) from #tmp
select @months
drop table #tmp

Now I need to be able to use these month numbers in a select statement so that they trigger the correct partitions to be used.

Something like the following that does not work:
select * from [transactions]
where partmonth in (@months)

Answer 1

I have found using a select statment for “where in (…)” works for table partition filtering. The table scan I was seeing was due to other criteria used, i get the scan even if I pass in where in (10).

I have also found that you can use the partition function for partition selection also, but in my environment and schema, it caused and index scan vs index seek.

DECLARE @months TABLE (MonthNumber int)
insert into @months
select distinct MonthNumber from [date] where [date] between '10/1/2010' and '10/7/2010'

select * from [transaction] t
WHERE $Partition.TransactionPartitionFunction(t.partmonth) in (select monthnumber from @months) 

Actual Execution plan resutls with set statistics xml on.
Without where in:

<RunTimePartitionSummary>
  <PartitionsAccessed PartitionCount="13">
    <PartitionRange Start="1" End="13" />
  </PartitionsAccessed>
</RunTimePartitionSummary>

With where in:

<RunTimePartitionSummary>
  <PartitionsAccessed PartitionCount="1">
    <PartitionRange Start="10" End="10" />
  </PartitionsAccessed>
</RunTimePartitionSummary>