issue_comments

I did some horrible things in https://github.com/cldellow/datasette-ui-extras/issues/2 to enable this in my plugin -- example here: https://dux-demo.fly.dev/cooking/posts?_facet=owner_user_id&owner_user_id=67

The implementation relies on two things:

• a filters_from_request hook that adds a good human description (unfortunately, without the benefit of the CSS styling you mention)
• doing something evil to hijack the exact and not operators in the Filters class. We can't leave them as is, or we'll get 2 human descriptions -- the built-in Datasette one and the one from my plugin. We can't remove them, or the filters UI will stop supporting the = and != operators

This got me thinking: it'd be neat if the list of operators that the filters UI supported wasn't a closed set.

A motivating example: adding a geospatial NEAR operator. Ideally it'd take two arguments - a target point and a radius, so you could express a filter like find me all rows whose lat/lng are within 10km of 43.4516° N, 80.4925° W. (Optionally, the UI could be enhanced if the geonames database was loaded and queried, so a user could say find me all rows whose lat/lng are within 10km of Kitchener, ON, and the city gets translated to a lat/lng for them)

Performance tests - I think most places don't have them as a formal gate enforced by CI. TypeScript and scalac seem to have tests that run to capture timings. The timings are included by a bot as a comment or build check, and also stored in a database so you can graph changes over time to spot regressions. Probably overkill for Datasette!

Window functions - oh, good point. Looks like Ubuntu shipped JSON1 support as far back as sqlite 3.11. I'll let this PR linger until there's a way to run against different SQLite versions. For now, I'm shipping this with datasette-ui-extras, since I think it's OK for a plugin to enforce a higher minimum requirement.

Tests - there actually did end up being test changes to capture the undercount bug of the current implementation, so the current implementation would fail against the new tests.

Perhaps a non-window function version could be written that uses random() instead of row_number() over () in order to get a unique key. It's technically not unique, but in practice, I imagine it'll work well.

I pushed a revised version which ends up being faster -- the example which currently takes 4 seconds now runs in 500ms.

Ack, this PR is broken. I see now that the inner.* is necessary for ensuring the correct count in the face of rows having duplicate values in views.

That fixes the overcounting, but I think can undercount when the rows have the same data, eg a view like:

sql SELECT '["bar"]' tags UNION ALL SELECT '["bar"]'

will produce a count of {"bar": 1 }, when it should be {"bar": 2}. In fact, this could apply in tables without primary keys, too.

If inner came from a base table that had a primary key or a rowid, we could use those column(s) to solve that case.

I guess a general solution would be to compute a window function so we have a distinct ID for each row. Will fiddle to see if I can get that working.

A +1 for switching to CustomRow: I think you currently only get a CustomRow if the result set had a column that was an fkey (this code)

Otherwise you get vanilla sqlite3.Rows, which will fail if you try to access .columns or lookup the cell by name, which surprised me recently