Add iterateAll method to Page, update example and snippet

[mziccard]

This PR fixes #330.

• Add an iterateAll method to Page interface and implements the iterator in PageImpl.
• Add unit test
• Update snippet and storage example

[mziccard]

Fixed in place.

[mziccard]

Sorry to insist but I am just trying to understand.

At some point the service might give up before any row matched the criteria returning an empty result but with a cursor to allow continuing the listing from the point it stopped.

According to which criteria? Is this documented somewhere?
In the GCS docs I read that the pageToken points to the last item in the returned list (i.e. not the last seen before giving up):

The pageToken is an encoded field representing the name and generation of the last object in the returned list.

So in your example what does prevent the next page request to give up again at the same point returning an empty result list?

I am being picky because I don't want to add a loop if I am not sure according to which criteria it terminates.

[aozarov]

No problem. The questions are great!

In the GCS docs I read that the pageToken points to the last item in the returned list (i.e. not the last seen before giving up):

Yes, you are right. I also verified that with @BrandonY a while back.
In the case of GCS it will always return at least one value or it will timeout.
I think that is a poor choice of the service and would rather have it behave like Datastore
which can make progress even without returning a result (due to time limit per request), and
let the timeout option be done by the client-side.

So in your example what does prevent the next page request to give up again at the same point
returning an empty result list?

Nothing stop also the next result to be empty, this is why it is in a loop.

I am being picky because I don't want to add a loop if I am not sure according to which criteria it terminates.

The only true indication that there are "no-more-results" is a null nextPageCursor.
which is exactly what the previous "example"/code-snippet that we provided did.

[mziccard]

Yes, you are right. I also verified that with @BrandonY a while back.
In the case of GCS it will always return at least one value or it will timeout.

This confused me, indeed. Thanks for the clarifications!
I added the loop.