Documentation

[kenseii]

Hello,

Is there any documentation besides the Readme that discusses the way photon indexes data and the way it extracts the name/POI from the data?

Thank you

[lonvia]

No, sorry, we only have the source code as documentation. https://github.com/komoot/photon/blob/master/src/main/java/de/komoot/photon/nominatim/NominatimConnector.java is the starting point. This copies the data out of the Nominatim database.

photon/src/main/java/de/komoot/photon/Utils.java

Line 26 in 40a2f66

public static XContentBuilder convert(PhotonDoc doc, String[] languages) throws IOException {

is the central function that converts the whole thing then into ElasticSearch format.

Note, however, that Photon just imports Nominatim data which is already conveniently in a format suitable for geocoding. It's Nominatim that does the complex step of processing raw OpenStreetMap data and extracting names and addresses. There is not much documentation on the Nominatim code either, I'm afraid.

[kenseii]

Thank you very much for the information,

So when a search request occurs, photon gets the data from elastic indexes, how about when a lat,lon is passed next to the search query is photon using elastic's distance feature query to get the only the results near the given lat long?

Sorry if i might be asking something obvious but i don't use java so navigating the code didn't help much.

[lonvia]

It uses a score function to rerank the results. The relevant code is around here: https://github.com/komoot/photon/blob/master/src/main/java/de/komoot/photon/query/PhotonQueryBuilder.java#L109

There is also a bbox parameter that really filters by location, which uses ES's geographic filters: https://github.com/komoot/photon/blob/master/src/main/java/de/komoot/photon/query/PhotonQueryBuilder.java#L127

[kenseii]

Thank you very much for the info, it was helpful