Splink4: How to enable comparison_levels with multiple input columns

[RobinL]

Splink4: How to enable comparison_levels with multiple input columns

[RobinL]

I agree with both points (avoiding super(), and there maybe should be an intermediate class)

As @ThomasHepworth has just pointed out, there are potential additions to InputColumn such as to_date, regex extract, lower, that make it even more complex (and hence harder to use for end user).

[ADBond]

I think this makes sense - not sure I was too convinced at any point that we needed col_name + input_column in general, especially as it only really fits for one-column levels.

As you say I think the fact is that users need to know (at least a little) about how InputColumn works anyway to form the SQL string, so why not just get them to use this.

There is also maybe something conceptually nice about not having to keep any data in the base class - each subclass ca just define what it needs, and not have to worry about passing things to super()__init__().

[ADBond]

However maybe there is an argument that we should have people use an intermediate class instead? InputColumn has a lot of stuff that goes with it (which is needed by the Linker), but which people writing comparison levels almost certainly shouldn't be directly messing around with - I worry that people might get a bit lost in all the methods when they basically only need name_l + name_r.

It would also mean we are more free to mess around with InputColumn without worrying so much about user-impact - in the same way that we are aiming to do with Comparison and ComparisonLevel