Bug 781470

> Description of problem:
Stored Procedure dbo.dwh_history_aggregate_level fails to execute successfully.

> Version-Release number of selected component (if applicable):
RHEV-M 4.5.4.51796 (2.2.4)

> How reproducible:
Always.

> Steps to Reproduce:
1. Insert several records onto the dbo.vm_disk_history table so that SUM (read_rate) and/or SUM (write_rate) exceed 2^32.
2. Execute SP with @AggrStart and @AggrGap providing a range so that SUM (read_rate) and/or SUM (write_rate) still exceed 2^32.
  
> Actual results:
Error 8115, Level 16, State 2, Procedure dwh_history_aggregate_level, Line 87, Message: Arithmetic overflow error converting expression to data type int.

> Expected results:
Successful execution of the SP.

> Additional info:

Issue is triggered by the following SQL statement on dwh_history_aggregate_level, lines 90-97:

--
insert into vm_disk_history 
select @Aggregeation_level, @AggrStart,
vm_guid, image_guid,MAX(actual_size) as actual_size_max,
MAX(size) as size,disk_interface,disk_type,imageStatus,
AVG(read_rate) AS read_rate_avg, AVG(write_rate) AS write_rate_avg
FROM		dbo.vm_disk_history
WHERE history_datetime>=@AggrStart and history_datetime<@AggrEnd
GROUP BY vm_guid, image_guid,imageStatus,disk_interface,disk_type
--

Columns read_rate and write_rate on table vm_disk_history are of type int. According to http://msdn.microsoft.com/en-us/library/ms177677%28v=SQL.90%29.aspx:

'The return type is determined by the type of the evaluated result of expression.'

So for integer data types, the return type will be 'int'.

As AVG () will attempt to return an 'int' if input data type is int, and the sum of all read_rate values exceed 4 bytes length (see http://msdn.microsoft.com/en-us/library/ms187745%28v=SQL.100%29.aspx for data type limits), the call 

Furthermore, the following is mentioned for SQL Server 2008's AVG () (http://msdn.microsoft.com/en-us/library/ms177677%28v=SQL.100%29.aspx):

'AVG () computes the average of a set of values by dividing the sum of those values by the count of nonnull values. If the sum exceeds the maximum value for the data type of the return value an error will be returned.'