[Developers] mql boolean constraint

[Tim Sturge]

That would be really nice, but unfortunately MQL doesn't work that way.

null in MQL is a special value which indicates the absence of a value. 
So bar: null (there is no value for bar) is like name: null (there is no 
name).

false is just another value, so bar: false is like name: "anything 
here", there's a value that you can exactly match on. Likewise the 
integer 0 and the floating point value 0.0 are just values like any 
other integer or floating point value.

There's currently no way in MQL to ask "give me only the things that 
don't have a value for bar (or for name)". It's been requested several 
times, but is hard to implement (mostly because you have to look at 
everything to decide that nothing matches).

I'm trying to think of a way to work around this, but nothing obvious 
comes to mind. Since it's pretty common just to use true and leave 
things that should be false unset entirely I agree MQL should provide a 
way to ask for "false or not set at all" even if we don't solve the 
general "things that don't have a value" problem (although whether this 
one case is easier than the general problem is doubtful.)

Tim

Dae Park wrote:
> If I have a unique property (i.e., /type/foo/bar) who's expected type  
> is /type/boolean, does providing a "false" constraint on that  
> property also match those that have null values for that property.  
> For example:
>
> [{
>    id: null,
>    type: "/type/foo",
>    bar: false
> }]
>
> Will this give me all instances of /type/foo that has not yet set a  
> boolean value for the "bar" property?
>
> -dae
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