What is the purpose of the nodes stored at the end of the 'nodes' index file

I saw that when importing the data from an osm.pbf file the import process saves at the end of the file the nodes that do not have any edge reference. My understanding suggests that these nodes are not accessible so my question is what is the purpose of them and if they serve no particular purpose can they be removed from the file for storage optimisation?

Do you have a pointer to the code of what you mean?

It’s not the code I am concerned but the binary file as it is. The file nodes stores some information about the nodes along which is the edge reference. I was wondering what purpose have the nodes that do not have an edge reference and it is set as FF FF FF FF.

Usually these nodes should be removed in the graph.optimize step. How many of these entries did you count? And are the valid entries coming after these entries?

About 5% of nodes are in that file for the osm.pbf file I am working with and that do not have an edge reference.

EDIT: I think it is usefull to know that these nodes are not even counted. In the nodeCount headers there are only as much nodes that have an edge reference. So the rest of them are not even taken in consideration I believe, yet they are in the file.

And you are calling graph.optimize?

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