Remove unnecessary first
aggregation from groupby agg code
#951
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Right now, if group columns are specified for a groupby aggregation (e.g.
select name, sum(x) from df group by name
), we include afirst
aggregation to grab the relevant row values for each grouping. This shouldn't be necessary, as Dask groupby aggregations already provide this info in the resulting index.This PR removes this
first
aggregation and retains the lost information by instead dropping the groupby agg index withreset_index(drop=False)
when group columns are specified.