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
2159674260,I_kwDOAMm_X86AugOU,8794,Difficult to convert `pd.DataFrame` to `Dataset` with multi-index,13053829,closed,0,,,2,2024-02-28T19:17:14Z,2024-03-09T22:33:17Z,2024-03-09T22:33:17Z,CONTRIBUTOR,,,,"### What is your issue?

## No direct way to create multi-index dataset

Unless I'm missing something, there is no easy way to convert a Pandas dataframe to a dataset with a multi-index. For example, `xr.Dataset.from_dataframe` automatically converts any Pandas multi-index into separate dimensions.

## Workaround is inefficient

One workaround is doing `xr.Dataset.from_dataframe(df).stack(...)` however this is very inefficient for sparse multi-indices.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/8794/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue
2159328369,I_kwDOAMm_X86AtLxx,8793,`.fillna()` slower than expected for sparse data arrays with `fill_value=nan`,13053829,open,0,,,1,2024-02-28T16:14:10Z,2024-02-28T16:14:15Z,,CONTRIBUTOR,,,,"### What is your issue?

## Expected behavior

`.fillna(0)` should be near instantaneous when applied to a sparse DataArray with `fill_value=nan`

## Why

`.fillna(0)` only needs to update the `fill_value` to `0`.

## Current behaviour

The normal `.where()` operation is applied on the DataArray instead of using the shortcut described above.

## Question

What would be required to improve the performance of `fillna()`? I'm happy to try taking a stab at it if pointed in the right direction.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/8793/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue