add index_on_update! option

[barelyknown]

I needed to always index on update for some ActiveRecord classes. This provides an index_on_update! method to set that behavior for a class. I did not add tests for it yet but could.

[karmi]

Hey, this feels like a bandaid for the problems with update_document not picking up the "correct" JSON serialization of the model -- many issues are opened for that... I absolutely do think that something can be improved here, but preferably on a different level than a magical class level method? Some other way of configuration, different kind of introspection we do, etc...

[barelyknown]

I agree that there is probably a better way. In the project that I'm working on I would always want to call index_document on update and never update_document because there is content that is fetched from an external service that ActiveModel::Dirty doesn't know anything about. So, while it sounds important to improve update_document, it would never be right for me in this case. What do you think would be the "right" way specify that the indexing method that should be used on update?

[karmi]

Hmm, if that is the case, why not simply implement the after_save etc. hooks yourself, as documented in https://github.com/elasticsearch/elasticsearch-rails/blob/master/elasticsearch-model/README.md#custom-callbacks? (The "automatic callbacks" are really just a starting point,a default.)

[barelyknown]

Yeah. You're totally right. I had been thinking that the callbacks were more tied than they are to Elasticsearch::Model. I'm not sure why since I had read the code! Tired eyes 😴 😴 😴

[karmi]

I can totally understand that, what worries me that despite all the effort in the README to state that it's just a "starting point", people try to augment/customize/etc the default callbacks, instead of writing the three lines of Ruby to solve a problem cleanly :)