Support deleting by query

[abhalla-atl]

The Scala client currently only supports deleting by objectId. It would be useful to delete by query, similar to what's supported in the Ruby client (https://www.algolia.com/doc/ruby#delete-by-query). In our case, our objectId is structured enough that we could also match a pattern/regex against the objectId field, but querying against fields in our search documents would work quite well, too.

[ElPicador]

tldr; For now we won't support the delete by query in the scala client.

Longer:
Delete by query is basically a full browse + delete by id.
A full browse is N sequential calls to the browse API using a cursor.

The issue is that browse returns a Future[Iterable[A]]. So chaining multiple browse will return something like a Iterable[Future[Iterable[A]]]], not so nice but manageable.
But as each call to browse needs the previous call to get the cursor, so we need to transform an asynchronous API to a synchronous one, not so nice either.

One possible solution would be to use an Iteratee, but it will add a new dependency to the client (scalaz).

For now, we don't think it's a good solution.

Maybe you have an idea on how to implement that?

[abhalla-atl]

We use Scalaz (v. 7.1.7, by the way), so that wouldn't be problematic for us, although it might be tricky to manage if there's some Scalaz version incompatibility down the road.

Would it be possible for you to change your REST API to support delete by query? If so, it would be trivial to implement in any client. :)

[ElPicador]

Nice to hear people using Scalaz :)
The issue is that you are not the only users, so we prefer not to add a dependency to Scalaz.

As for the REST API, it's currently not in our roadmap, as every API client has it (but scala).

[abhalla-atl]

I don't have a better idea for implementation, but it seems that a synchronous implementation would be better than no implementation at all. Otherwise the consumers will be implementing the same sort of API independently, and you'll have little control over making improvements to their implementation.

[ElPicador]

Ok, we'll implement a synchronous deleteByQuery