Support for UNION, INTERSECT & EXCEPT in SQLContext

[csubhodeep]

Problem description

I wish Polars SQL could support combination of results from multiple queries using set operations.

Relates to #8743.

References:

1. Combining Queries (UNION, INTERSECT, EXCEPT)

[alexander-beedie]

UNION is now done: #8936

[xdev-x]

Is it possible for UNION to concatenate with the diagonal strategy ?

[cmdlineluser]

@xdev-x I thought UNION BY NAME was supposed to do that.

df1 = pl.DataFrame({"a": [1, 2, 3], "b": [4, 5, 6]})
df2 = pl.DataFrame({"c": [4, 5, 6, 7]})

pl.SQLContext(frames={"df1": df1, "df2": df2}).execute("""
select * from df1 union by name select * from df2
""").collect()

# ShapeError: unable to append to a dataframe of width 2 with a dataframe of width 1

[alexander-beedie]

Is it possible for UNION to concatenate with the diagonal strategy ?

It will be in the upcoming 0.19.8; we have just committed support for UNION BY NAME and UNION ALL BY NAME ✌️

[alexander-beedie]

FYI: this was closed by #16960 👌
All three of these set ops will be available in the 1.0 release.