?_group_count=country - return counts by specific column(s)

[simonw]

Imagine if this:

https://stateless-datasets-jykibytogk.now.sh/flights-07d1283/airports.jsono?country__contains=gu&_group_count=country

Turned into this:

https://stateless-datasets-jykibytogk.now.sh/flights-07d1283?sql=select%20country,%20count(*)%20as%20group_count_country%20from%20airports%20where%20country%20like%20%27%gu%%27%20group%20by%20country%20order%20by%20group_count_country%20desc

This would involve introducing a new precedent of query string arguments that start with an _ having special meanings. While we're at it, could try adding _fields=x,y,z

Tasks:

• Get initial version working
• Refactor code to not just "pretend to be a view"
• Get foreign key relationships expanded

[simonw]

I’m going to call this feature “count values”

[simonw]

This should support multiple columns, e.g. ?_group_count=precinct&_group_count=candidate

[simonw]

Should this support sum/avg/etc as well?

[simonw]

It would be great if this could support foreign key references and automatically resolve and hyperlink them if they are detected.

[simonw]

This would enable faceted search - moving it to the search milestone.

[simonw]

Some demos:

Single column: https://sf-trees-flat.now.sh/sf-trees-flat-ba738ce/Street_Tree_List?_group_count=qSpecies

Multi column: https://sf-trees-flat.now.sh/sf-trees-flat-ba738ce/Street_Tree_List?_group_count=qLegalStatus&_group_count=qSpecies