issue_comments: 297539517

This data as json

html_url issue_url id node_id user created_at updated_at author_association body reactions performed_via_github_app issue
https://github.com/pydata/xarray/issues/1385#issuecomment-297539517 https://api.github.com/repos/pydata/xarray/issues/1385 297539517 MDEyOklzc3VlQ29tbWVudDI5NzUzOTUxNw== 1217238 2017-04-26T20:59:23Z 2017-04-26T20:59:23Z MEMBER

For example, can I give a hint to xarray that this reindex_variables step is not necessary

Yes, adding an boolean argument prealigned which defaults to False to concat seems like a very reasonable optimization here.

But more generally, I am a little surprised by how slow pandas.Index.get_indexer and pandas.Index.is_unique are. This suggests we should add a fast-path optimization to skip these steps in reindex_variables: https://github.com/pydata/xarray/blob/ab4ffee919d4abe9f6c0cf6399a5827c38b9eb5d/xarray/core/alignment.py#L302-L306

Basically, if index.equals(target), we should just set indexer = np.arange(target.size). Although, if we have duplicate values in the index, the operation should arguably fail for correctness.

 
{
    "total_count": 0,
    "+1": 0,
    "-1": 0,
    "laugh": 0,
    "hooray": 0,
    "confused": 0,
    "heart": 0,
    "rocket": 0,
    "eyes": 0
}
   224553135