Oliver Eilhard

[This line](https://github.com/olivere/elastic/blob/release-branch.v6/scroll.go#L332) and [this line](https://github.com/olivere/elastic/blob/release-branch.v6/scroll.go#L453) are the ones returning `io.EOF`. Do you have any reproducible test case where they get there and swallow an error? I don't see it atm....

I agree that we should handle this with more care. I think the slicing feature added a side-effect that I wasn't aware of. Before that, I think, the `ScrollService` should've...

I will have to review why that is. Maybe it was a temporary problem we were trying to fix. Seems wrong to me as well: fiddling with the URL encoding.

It came in with #962, and was carried over from [this client](https://github.com/sha1sum/aws_signing_client/blob/master/client.go#L87-L90). Can you check if that hack is still required?

I see what you're after. I'm a bit hesitant to opening it up because using it without thinking twice may result in a performance problem. That `estimateSizeInBytes` is quite slow,...

That could definitely work. Will have to tinker with that idea.

@ArcticSnowman I finally found some time to tinker around with this issue. Do you mind reviewing the [`bulk.estimated-size.issue-931` branch](https://github.com/olivere/elastic/tree/bulk.estimated-size.issue-931)? It currently only has [this commit](https://github.com/olivere/elastic/commit/dfdc72955bb633a2c3ae16e5c12e5ec7200c0e92).

> An _interface type_ is defined as a set of method signatures. https://tour.golang.org/methods/9

A few initial comments on this PR: - Don't use documentation links with `current` or `N.x` (e.g. `6.x`). These refer to the current version or the working version for 6.x....

Can we use this PR instead of #956, i.e. do you try to implement the same thing?