Proposal: `geometrycolumn(x) = first(geometrycolumns(x))`

[asinghvi17]

It's difficult to teach users why they should have to use first(geometrycolumns(x)), and it's not easy to remember when starting out.

Would it make sense to have a convenience function geometrycolumn(x)? Then things like df[:, Not(GI.geometrycolumn(df))] just work, without exposing users to the annoyances inherent in geospatial datasets.

[rafaqz]

Makes sense to me, except it's easy to mix them up

[visr]

Do you want it to just pick one in case of multiple geometry columns, or to give an error? geometrycolumn(x) = only(geometrycolumns(x)) is also an option.

[evetion]

Can you provide an example where one would use first(...) like that? I wonder if we could provide something like getgeom on a table or similar. And maybe setting an active geometry column in the metadata (like geopandas)?

[asinghvi17]

Hmm, getgeom on a table might be better than this. But my thought was for simple operations like plotting:

# current state
df[!, first(GI.geometrycolumns(df))]
# alternatives
df[!, GI.geometrycolumn(df)]
# or
GI.getgeom(df)

Where this would really be useful is when constructing filter statements where you need a symbol:

# current state
filter(df, first(GI.geometrycolumns(df)) => x -> intersects(df, somegeom))
# alternative
filter(df, GI.geometrycolumn(df) => x -> intersects(df, somegeom))

An "active geometry column" would be nice, but that would be an extra bit of metadata.

[rafaqz]

I also think we should just have both