code: protected FieldDescriptor getFieldDescriptor(TableAlias aTableAlias, PathInfo aPathInfo)
      {
          FieldDescriptor fld = null;
          String colName = aPathInfo.column;
  
          if (aTableAlias != null)
          {
              fld = aTableAlias.cld.getFieldDescriptorByName(colName);
              if (fld == null)
              {
                  ObjectReferenceDescriptor ord = aTableAlias.cld.getObjectReferenceDescriptorByName(colName);
                  if (ord != null)
                  {
                      fld = getFldFromReference(aTableAlias, ord);
                  }
                  else
                  {
                      fld = getFldFromJoin(aTableAlias, colName);
                  }
              }
          }
  
          return fld;
      }
docs: Get the FieldDescriptor for the PathInfo
  
  @param aTableAlias
  @param aPathInfo
  @return FieldDescriptor