total_records nested SELECT is slow about effective_datatables HOT 4 CLOSED

Hey @sheldond ,

This is a great idea! Anything I (we?) can do to speed up a method that's used on every datatable, is worth lots of attention!

I honestly don't remember why I used the SELECT COUNT from collection instead of just using .count on the ActiveRecord resource. My foggy memory tells me it has something to do with a collection that is using its own .select() calls, or maybe a complex join query that was doing the wrong thing. I would have run into this almost two years ago.

I think your idea of doing the fast way first, then fallback to the existing SELECT COUNT from collection method if that doesn't work, is the right approach. Perhaps making this a little dsl method to indicate "fallback_to_conservative_count_method" so the old method is still available.

I will have time to work on this issue in the next few days if you want to wait for me to release another version.

Or if you're the kind of person that wants to tinker, I think this is an easyish thing to add:

I would follow the default_entries pattern, as per models/effective/effective_datatable/dsl/datatable.rb and just create an instance variable to revert to the existing count behavior.

Thanks for your fresh eyes on this gem! :)

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Thanks @matt-riemer! It'd be super great if you could take a shot at it as I'm not 100% sure what you have in mind. No pressure though, if you can't get to this, I may look at it later.

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Hey again @sheldond

Try out effective_datatables 2.6.4

Here's the relevant commit:

2614285

Does this work for you on MySql?
Does it actually speed anything up? :)

Thanks,

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Hi @matt-riemer,

This is working great, and my count queries are now ~20ms.

Perfect! Thanks so much for taking the time for this! 😄

Sheldon

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