Problems comparing empty tuples/arrays

• EdgeDB Version: 1-beta1

I’ve been experimenting with DISTINCT and discovered a few things:

1. When different types are passed to distinct, it leaks implementation details (UNION) in error:

edgedb> select distinct {1, "1"};
ERROR: QueryError: operator 'UNION' cannot be applied to operands of type 'std::int64' and 'std::str'
  Hint: Consider using an explicit type cast or a conversion function.

1. It has some problems comparing empty tuples:

edgedb> select distinct {(), (), ()};
{(), (), ()}

Note: this doesn’t work with empty arrays, compiler makes me annotate 2nd argument.

Trying to figure out what’s going on, I tried comparing empty tuples manually. This is what I’ve got:

edgedb> select <tuple<str>>{} = ("",);
{}
edgedb> select <array<str>>{} = ["",];
{}

Not sure if these are issues that should be fixed or I misunderstood something.

[1st1]

@elprans

ERROR: QueryError: operator ‘UNION’ cannot be applied to operands of type ‘std::int64’ and ‘std::str’

This is not about DISTINCT, you cannot UNION two incompatible types, and the set literal { … } is a syntax sugar over the UNION operator.

Maybe we should improve this error message. The fact that {x, y} is compiled to x UNION y isn’t an obvious thing, especially to beginners. The error message we raise right now is just hard to interpret.

[1st1]

@vpetrovykh please see if you can improve the error message.