Clarify where different ids can be used

[simon-weber]

trafficstars

For example, nid cannot be used for deleting or streaming tracks.

[jamon]

In case someone else runs into this. "nid" does seem to work for all-access track streaming, but not for uploaded songs. "id" works for everything, so using that is probably the best bet.

[thebigmunch]

Just to throw some fun into it, it appears you can actually stream a library track using its nid if it was scanned and matched as it is different than the nid of the same song when uploaded.

[simon-weber]

I've gotten this question a few times recently, so here's a quick rundown I can point people to (and should probably be added to the docs):

• id: a library id
  • unique inside a single user's library
  • not present for tracks not added to the library (eg, store tracks directly added to a playlist)
  • never changes
  • works for most apis (streaming, adding to playlists, etc) with the exception of those explicitly expecting a store id; the preferred param when available
• nid: a "nautilus" id (the codename for Google's music database)
  • unique inside Google's music database (which includes more tracks than those they have licensed for sale)
  • not present for tracks Google can't identify
  • changes occasionally
  • doesn't work consistently for apis; should be avoided as a param
  • generally not useful; can signal that a track was matched, but trackType has this information too
• storeId: a store id, the nid for tracks that Google sells
  • unique inside Google's store
  • not present for tracks that Google doesn't sell
  • changes occasionally
  • works for all apis, but best used only for those that expect a store id, or as a backup when id is not present