Add is / is_not to Expr

[Sytten]

For Sqlite, they are the same as eq and neq but treat NULL differently.
I put them behind a flag since I don't think other DBMS allow random values with those operators.

Adds

• IS and IS NOT operators for Sqlite

[ikrivosheev]

@Sytten thank you for the PR!
I don't understand... You add a doc test for Postgres backend and for MySQL backend but hide is under the feature flag: backend-sqlite. How should this work?

[Sytten]

Right I will remove it, I did a stupid copy paste

[ikrivosheev]

@Sytten as I know in postgresql we can use IS TRUE for example. Also we didnot want to add feature flag to Expr.

[tyt2y3]

@Sytten as I know in postgresql we can use IS TRUE for example. Also we didnot want to add feature flag to Expr.

Agreed

[Sytten]

So how do we wish to proceed? Just leave it open for any backend?

[tyt2y3]

Yes. We don't feature guard the frontend (unless a feature is only relevant to one backend), because it's only determined when building the query.

[Sytten]

@tyt2y3 @ikrivosheev I made the changes

[ikrivosheev]

@Sytten thank you! LGTM!

[tyt2y3]

Thank you all