Count - %Integer
Flag1 - %Integer
Flag2 - %Integer

SELECT SUM(Count) ... WHERE Flag1 =  1  AND Flag2 =  2 

There are two types of index that you can create with HyperIndex – BitMap and BitSlice.  BitMap indices allow you to search, count, select and drilldown, BitSlice indices allow you to total, minimum, maximum and average the values of data field. A field can be indexed in either or both of these ways.


 6 . 3 	BitSlice Indices

If you wish to be able to sum, maximum, minimum or average a property (much faster than the equivalent SQL functions can do), then you need to add some BitSlice indices We will use the property Amount, assumed to be a float with  2  decimals, in our examples

To define a BitSlice index for the Amount field we add a BitSlice parameter:

Property TotalAmount As %Float;
	Parameter HiTotalAmount = ”BitSlice[Amount]( 2 )”

This tells the system to create a BitSlice index on the TotalAmount field, under the Category ‘Amount’ (which must be unique !), and to scale the value by  2  places (i.e.  100 )

In the case of a BitSlice index, rather than indexing on each value of the Amount property, the value is broken down into its binary value and then indexed on each bit of that value.

For example, if the TotalAmount for one record is  0 . 83 , this is scaled to  83  and then broken down into the binary value ‘ 1010011 ’ and the record is indexed under
	Amount bit  7  is set
	Amount bit  5  is set
	Amount bit  2  is set
	Amount bit  1  is set

This indexing is stored along with the BitMap indices, but a note is made that the Category ‘Amount’ here is a BitSlice category.