Google Drive API v3, is there a way to get a list of folders that are parents of a fileId?

Question

In v2 it was possible to make a call to /files with the query fileId in children to get a list of DriveFile objects that were parents of the supplied file.

Now, it seems to be required to make a call to /files/:fileId?fields=parents, then make a separate call to /files/:parentId for each returned parent, possibly turning one call into a dozen.

Is this correct, and if so why? This is a huge performance hit to our app, so hopefully there's an undocumented method.

Answer 1

The query "'fileId' in children'" doesn't publicly exist (not documented/supported) in v2 either and I don't recall it ever existing. What does exist in V2 is the Parents collection which effectively answers the same question. In v3, to get the parents of a file you just get the child and ask for the parents field.

As for whether or not that is a performance hit, I don't think it is in practice. The Parents resource in v2 was very light to begin with, and other than the ID the only useful field was the 'isRoot' property. That you can calculate yourself by calling files/root up front to get the ID of the root folder for that user (just once and save it, it won't change for that user.)

If you need to get more information about the parents than just the IDs and are worried about the # of calls you have to make, use batching to fetch them. If you just have one parent, no need to batch (it's just overhead.) If you find that a file has multiple parents, create a batch request. That'll be sent as a single HTTP request/response and is handled very efficiently on the back end.

Point is, if you just need IDs, it's no worse than before. It's one call to get the parents of a file.

If you need more than IDs, it's at most 2 HTTP requests (outside really bizarre edge cases like 1000+ parents which would exceed the batch size :)