issues: 1376109308

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
1376109308 I_kwDOAMm_X85SBcL8 7045 Should Xarray stop doing automatic index-based alignment? 1217238 open 0     13 2022-09-16T15:31:03Z 2023-08-23T07:42:34Z   MEMBER      

What is your issue?

I am increasingly thinking that automatic index-based alignment in Xarray (copied from pandas) may have been a design mistake. Almost every time I work with datasets with different indexes, I find myself writing code to explicitly align them:

  1. Automatic alignment is hard to predict. The implementation is complicated, and the exact mode of automatic alignment (outer vs inner vs left join) depends on the specific operation. It's also no longer possible to predict the shape (or even the dtype) resulting from most Xarray operations purely from input shape/dtype.
  2. Automatic alignment brings unexpected performance penalty. In some domains (analytics) this is OK, but in others (e.g,. numerical modeling or deep learning) this is a complete deal-breaker.
  3. Automatic alignment is not useful for float indexes, because exact matches are rare. In practice, this makes it less useful in Xarray's usual domains than it for pandas.

Would it be insane to consider changing Xarray's behavior to stop doing automatic alignment? I imagine we could roll this out slowly, first with warnings and then with an option for disabling it.

If you think this is a good or bad idea, consider responding to this issue with a 👍 or 👎 reaction.

 
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     13221727 issue

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