Decide if we want to rename All to Cols

[bkamins]

When JuliaData/DataAPI.jl#16 is decided. But we should have this decision before 0.21 release as it is potentially breaking.

[bkamins]

Moving to 1.x, as All will stay anyway, and Cols can be added any time.

[CameronBieganek]

I vote for adding Cols.

Is there an argument for keeping both All and Cols, aside from being non-breaking? It seems like it would be a little confusing to have both if they do exactly the same thing.

[bkamins]

Well - they do not do exactly the same thing and that is the point I guess :).

Cols will be added. Probably we will keep support for All as it does not hurt, but just stop advertising it. As long as DataAPI.jl has All we will support it (as other packages might support it and if people write cross-Tables.jl code it should work).

[CameronBieganek]

Ohhhh, right. I had to look really closely at the docstrings to discern the difference:

All:

If `cols == ()`, select *all* columns.

Cols:

If `cols == ()`, select *no* columns.

(Emphasis mine.)

[bkamins]

Closing as the semantics is set. Only All() is allowed and it is the same as :. Otherwise use Cols.