Aggregator grouping by attribute removes overlapped areas

Hi ​@georgiec ,

I think the Aggregator setting should work as expected if the original two parcels both are polygons with no holes. I would recommend you to check their geometry type with Feature Information in Visual Preview or FME Data Inspector.

Hi ​@takashi   

The data source shows both the parcel shapes as the same feature types see below

You have to see geometry type under the ”Geometry” section, not Attributes section.  

What are you expecting to see differently? Nothing in your screenshot indicates that the polygons have not been aggregated correctly. In this scenario the original two polygons and the multipolygon will look identical. Only when you select will you see a difference in terms of what is selected. 

It should be a multiarea of two parts e.g.

Perhaps this diagram will better illustrate my problem.  The white area has no selectable features.

It’s also clipped the ground floor parcel using the shape of the first floor parcel.

On further inspection of the Geometry (thanks ​@takashi )   

I found the main difference between the ground and first floor parcels is the convex value.  First floor = Yes and the Ground floor = No.

Ground floor feature:

First floor feature as much like above except Convex = Yes

The result I am wanting is to see one feature containing 2 geometries.  Akin to a multi-part feature in ArcGIS.

Have you checked that the geometries are valid? I’ve seen strange behaviour in the past when invalid geometries are present.

The aggregator should be working as you expect it to and create a multipart feature.

What version of FME are you using?

Version 2024.1
Also confirmed that the convex value is irrelevant.  Behaviour is happening even with features where convex values are same.
I am seeking support via our support agreement.  Will report back.

Reporting back in what I found with the assistance of our support.

The Aggregator output was fine, the issue of the ‘holes’ in the data actually occurs in the writing process.   It occurs when I write to ArcGIS and also writing to an ESRI geodatabase.   It relates to a limitation on the rendering of simple polygons where it does not deal with overlapping geometry.  Thus , some features appear to get holes cut from the overlapped component of their geometry. 

For more information on this limitation, here is a post that describes the issue.  Solved: Interiors and exteriors when working with multipol... - Esri Community

To get around this, I am going to just dissolve all features grouping on a common field value.  We can live without the internal component vectors for this particular application.