Bug 183579 Model need hold on DimensionConditionHandle and DimensionJoinConditionHandle signleton or overwrites the equals and hashcode method
The Dataset Joint Editor need join two Editparts which have the same model. But the DimensionConditionHandle and the DimensionJoinConditionHandle are create a new instance erery time when I get them. So model need hold on them signleton or overwrites the equals and hashcode method.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/MemberRef.java
* Reference to the nth item within the top-level property list.
	 * <p>
	 * property.list[n]
	 * 
	 * @param prop
	 *            the property definition
	 * @param n
	 *            the list index
	 */
	MemberRef( ElementPropertyDefn prop, int n )
	{
		propDefn = prop;
		assert propDefn != null;
		assert propDefn.getTypeCode( ) == IPropertyType.STRUCT_TYPE;
		assert propDefn.isList( );
		assert n >= 0;
		refType = PROPERTY_LISTn;
		index[0] = n;
		depth = 1;
	}
	/**
	 * Reference to a member of a top-level structure.
	 * <p>
	 * property.member
	 * 
	 * @param prop
	 *            the element property definition which is structure or
	 *            structure list type
	 * @param memberName
	 *            the structure member name of the element property definition