Add how="leftanti" support for cudf-backed merge
#1073
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rjzamora
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May 29, 2024
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Thanks @charlesbluca - Seems reasonable to add "leftanti" support given that the necessary logic is pretty simple, and the legacy dask.dataframe API supports it.
| df2 = df2.rename(columns={"aa": "dd"}) | ||
| assert_eq( | ||
| df1.merge(df2, how="leftanti", left_on="aa", right_on="dd"), | ||
| pdf1[~pdf1.aa.isin(pdf2.aa)], |
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Seems like we could just do this in merge_chunk for pandas data to support how="leftanti" for cpu as well.
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Yeah good point, can look into this a bit more
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Pushed some commits to dask/dask#11150 that, in conjunction with this PR, should unblock left anti/semi joins on CPU
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Looks like we should unblocked to support left anti joins when
dataframe.backend="cudf", similar to the case in legacy Dask dataframe:https://github.com/dask/dask/blob/df4de6ea53054790b09006c8ea68ef8725d39025/dask/dataframe/multi.py#L565
Note that like the legacy code, we'll fail somewhere down in the comptutation stack if we try this on CPU - not sure if it makes sense to check the backend if
how="leftanti"and eagerly raise aNotImplementedErrorifdataframe.backend != "cudf".cc @rjzamora