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
assert propDefn != null;
		assert propDefn.getTypeCode( ) == IPropertyType.STRUCT_TYPE;
		assert !propDefn.isList( );
		refType = PROPERTY_MEMBER;
		member[0] = memberDef;
		index[0] = -1;
		depth = 1;
	}
	/**
	 * Reference to the the named member in the nth structure in the top-level
	 * list.
	 * <p>
	 * property.list[n].member
	 * 
	 * @param prop
	 *            the property definition
	 * @param n
	 *            the list index
	 * @param memberName
	 *            the name of a member
	 */
	MemberRef( ElementPropertyDefn prop, int n, String memberName )
	{
		propDefn = prop;
		assert propDefn != null;
		assert propDefn.getTypeCode( ) == IPropertyType.STRUCT_TYPE;
		assert propDefn.isList( );
		assert n >= 0;
		StructPropertyDefn memberDefn = (StructPropertyDefn) propDefn
				.getStructDefn( ).getMember( memberName );