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/4147#issuecomment-642953710,https://api.github.com/repos/pydata/xarray/issues/4147,642953710,MDEyOklzc3VlQ29tbWVudDY0Mjk1MzcxMA==,14808389,2020-06-11T22:02:38Z,2020-06-11T22:02:38Z,MEMBER,"It seems that's because adding (potentially big) Dataset / DataArray objects using https://github.com/pydata/xarray/blob/4071125feedee690364272e8fde9b94866f85bc7/xarray/core/parallel.py#L39-L40 is really slow and the stacktrace from sending `KeyboardInterrupt` says that `_iter` is called (if I understand it correctly, that is iterating over all values of the `DataArray` / `Dataset` using a python loop).

Looking at the code of `map_blocks`, the object arrays (`npargs` ) is only used because of its indexing and we might be able to use a list / tuple and `itertools` to get the same result, but without iterating over values. Am I missing something? cc @dcherian","{""total_count"": 1, ""+1"": 1, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,637227979