QGIS Expression - overlay_intersects

[pigreco]

What is the bug or the crash?

I noticed that using the return_details and sort_by_intersection_size options does not give the expected results.

If the object to evaluate has more parts or is multipart, the output is incorrect, that is, the output returns only the length (or area) of the largest part.

In the image below I highlight the fact that the L-shaped segment is calculated only the length of the longest segment.

In the case of Multipolygon with separate parts, the area of ​​the largest overlap is calculated and not the overall area.

Steps to reproduce the issue

I attach an example project (use the views to correctly display the two cases)I attach an example project (use the views to correctly display the two cases)

progetto_overlap.zip

https://discourse.osgeo.org/t/espressione-di-qgis-overlay-intersects/111118/1

Versions

Versione di QGIS	3.41.0-Master
Revisione codice QGIS	fda2aa46e9
Librerie
Versione Qt	5.15.13
Versione Python	3.12.7
Versione GDAL/OGR	3.11.0dev-b281c45d9a
Versione PROJ	9.5.0
Versione database del Registro EPSG	v11.016 (2024-08-31)
Versione GEOS	3.13.0-CAPI-1.19.0
Versione SQLite	3.46.1
Versione PDAL	2.8.1
Versione client PostgreSQL	16.2
Versione SpatiaLite	5.1.0
Versione QWT	6.3.0
Versione QScintilla2	2.14.1
Versione SO	Windows 11 Version 2009
Questa copia di QGIS scrive messaggi di debug.
Plugins Python attivi
DataPlotly	4.2.0
felt	3.1.5
gps_replay	0.0.5
HCMGIS	24.10.20
mmqgis	2021.9.10
nominatim_locator_filter	0.3.2
profile-manager	0.31
qconsolidate	1.1.0
qduckdb	1.0.1
quick_map_services	0.19.34
relazioniplugin	1.1
SelectionFilter	1.0
db_manager	0.1.20
MetaSearch	0.3.6
processing	2.12.99

The problem is present on QGIS 3.34.12, QGIS 3.40.0 and the master

Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

Additional context

No response

[pigreco]

I add a demo:
note that the L-shaped sides

2024-11-11_14h03_45.mp4

[agiudiceandrea]

@elpaso, may you have a look at this?
From the docs and from the description of your PR #46683 it is unclear what the value of the 'overlap' key is supposed to contain exactly when the return_details parameter is set to true.

I would assume it should contain the area / length of the geometry resulting from the intersection between the current feature's geometry and each intersecting feature from the layer whose intersection is checked.

When the geometry resulting from the intersection is composed by a single part, that assumption seems correct.
When the geometry resulting from the intersection is composed by more then one part, then it looks like the value of the 'overlap' key contains the area / length of only (the greatest) one of the geometry's parts, instead of the area / length of the whole geometry.

Moreover, when the geometry resulting from the intersection is composed by e.g. a polygon and a line (i.e. a GeometryCollection), then the resulting array item is missing in the function result.