[TYPO3-Solr] Merging solr searches

[Heiko Kromm | Paints]

Hi list, 

does anyone have some experience in merging solr results from different indexes? 
What I want to do, is to have a universal search over my websites. 
For example I have website test1.com with an index and test2.com with a different index. 
When I search on test1.com I want to have teh test1 results and below that somthing like "Additional Results from test2.com". 
Or perhaps a facet to filter between test1.com and test2.com? 
Perhaps someone made some tests on that or has a best practice. 

Regards 
Heiko