Solving the select+1 problem.

[Jonathan Slenders]

The "select+1" problem is a problem that people often face in Django.

Usually, something like select_related solves it, but I don't think that's always possible.

Facebook released Haxl today and there's an example of their apprach to the problem.

https://github.com/facebook/Haxl/tree/master/example/sql

I don't know enough Haskel to understand this code, but it could contain some very nice ideas that apply to our ORM as well.

Cheers,

Jonathan

[Jacob Kaplan-Moss]

I'm not great at Haskell, either, but this looks to me to be very similar to prefetch_related (https://docs.djangoproject.com/en/dev/ref/models/querysets/#prefetch-related).

Jacob

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[Alex Gaynor]

I also do not really know Haskell (I'm sensing a trend...), that said, it seems to me the cool part of haxl is that it can be automatic -- analagous to if writing {{ post.author.name }} in a template caused select_related("author") to automatically be applied to the queryset that yielded post.

Alex

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[Stratos Moros]

Given their sample code, my initial impression was that it was indeed
automatic. Looking a bit closer, there seems to be hardcoded logic
inside the DataSource (the thing I'm assuming provides getAllUserIds and
getUsernameById) to specifically fetch all ids and then all names for
those ids. So they're still doing a manual prefetch_related equivalent
but at a different abstraction level.

I should note that my Haskell knowledge is also minimal, so it is quite
possible that I'm misunderstanding something.

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