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/impl/QueryExecutorUtil.java
else
			interval = DataType.ANY_TYPE;
		return interval;
	}
	
	/**
	 * Common code to extract the name of a column from a JS expression which is
	 * in the form of "row.col". If expression is not in expected format,
	 * returns null
	 * 
	 * @param cx
	 * @param expr
	 * @return
	 */
	public static ColumnInfo getColInfoFromJSExpr( Context cx, String expr )
	{
		int colIndex = -1;
		String colName = null;
		CompiledExpression ce = ExpressionCompilerUtil.compile( expr, cx );
		if ( ce instanceof ColumnReferenceExpression )
		{
			ColumnReferenceExpression cre = ( (ColumnReferenceExpression) ce );
			colIndex = cre.getColumnindex( );
			colName = cre.getColumnName( );
		}
		return new ColumnInfo( colIndex, colName );
	}
	
}