implement support for count(_, :distinct)

[aseigo]

See #169

This appears to work. Tried it out on a database I have, as well as ensuring the tests pass. But perhaps @rhcarvalho could test this branch as well on their use case?

[rhcarvalho]

Hey thanks! The implementation looks straightforward, I wonder if there are any gotchas as @warmwaffles hinted in the issue🤔

[warmwaffles]

@rhcarvalho I think this is okay. What I think I need is a test with an obscure distinct in it.

[warmwaffles]

@aseigo try removing this line in your PR

ecto_sqlite3/integration_test/test_helper.exs

Lines 127 to 128 in 455bee6

	# Distinct with options not supported
	:distinct_count,

This will pick up the integration tests for distinct counts.

[aseigo]

Integration tests enabled, and they work.

And yes, I'm wondering if there is some weirdo edge case lurking as well .. at least we can maybe find out this way! :)

[aseigo]

Hey thanks! The implementation looks straightforward, I wonder if there are any gotchas as @warmwaffles hinted in the issue🤔

Have you managed to give it a try with your query in your codebase? It would be nice to have "real world" confirmations!

[warmwaffles]

If it passes those integration tests, I'm happy. I don't remember the edge case, but I'm sure if someone finds it, they'll open a ticket and we can fix it 😛

[warmwaffles]

I'm gonna make a cut this evening for both exqlite and the adapters.

[rhcarvalho]

Thank you @aseigo and @warmwaffles! Shipping to production today.

[warmwaffles]

@rhcarvalho just keep an eye out for errors please and report back findings.