Add support for direct_import parameter to skip loading default scope on import

[TikiTDO]

Proof of Concept to get around issue outlined in #636.

Currently there's no tests, as I wasn't sure how the spec files were structured for this project. I can add the specs if someone could point me to an example where I could exercise the functionality of importing objects with extra includes.

[TikiTDO]

@pyromaniac Does this implementation work for you?

[abraham-chan]

@TikiTDO I'm no maintainer but I see some import specs for active_record here:
https://github.com/toptal/chewy/blob/master/spec/chewy/type/adapter/active_record_spec.rb#L68

[TikiTDO]

@abraham-chan I've moved quite a far from this section of my project, and I've got work queued up for months ahead. If you wish to take over, then feel free to fork this branch, otherwise I might at best have time to look at this in a few months

[jeremyhaile]

I was amazed to realize that if you call import with an array of ActiveRecord objects, it reruns a query to get the same ActiveRecord objects and then uses those. Which means if you included associations it forces an N+1 query.

Can anyone (maybe @pyromaniac ?) explain why it re-queries for objects that are already in memory prior to sending to ES?

Is there any workarounds, or would this branch be needed in order to import AR objects that are already in memory without reloading them from the DB?

[toptal-bot]

Can one of the admins verify this patch?

[pyromaniac]

Well, I did it because it looks more reliable. I can merge this option as soon as some specs will be added.

[TikiTDO]

Looking at this I vaguely remember that this had something to do with a manual importer, but I can't actually recall the nature of the problem anymore.

@dtpowl you referenced this recently, is this something you could take over, or failing that could you remind me what issue this was trying to solve?

[dalthon]

@TikiTDO thanks for you contribution!
Your PR was rebased at #753 and your added option was covered with spec, soon we will merge that rebased PR