Searching on undefined model values

[dupski]

How do we query for these?
in MongoDB there is a $exists: false operator and in SQL we'd do WHERE value = NULL

Proposal:

We add a _set operator for field criteria

e.g.

where: {
  _or: [
    { published: false },
    { published: { _set: false }}
  ]
}

In mongodb (and JS), there is undefined as well as null. My feeling is _set: false should match both undefined and null values since in most SQL databases, undefined == null.

The above criteria can then be used for the BooleanSearchField (currently it only matches records which are specifically set to false)