Bug 211839 String grouping unit type needs to support interval range.
Build ID: I20071101-2000 As Chart has supported, the String grouping unit type can be set interval range, the interval range means that the string group will base on row count distinction. For instance, let's say we have a,b,c,d,e,f,g , and set interval range to 2, the grouping result should be a,c,e,g. Now it is a requirement that DtE support the grouping type.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/odi/IQuery.java
{
    	private int index = -1;
        private String field;
        private boolean ascendingOrder;
        
        public SortSpec( int index, String field, boolean ascendingOrder )
        {
        	this.index = index;
            this.field = field;
            this.ascendingOrder = ascendingOrder;
        }
        
        public int getIndex( )
		{
			return index;
		}
        
        public String getField()
        {
            return field;
        }
        
        public boolean isAscendingOrder()
        {
            return ascendingOrder;
        }       
    }