> c.drop()
true
> c.save({c:1})
> c.save({c:'a'})
> c.save({c:null})
> c.save({})
> c.find({c:{$all:[]}}) // seems to match nothing
> c.find({c:null}) // matches as expected
{ "_id" : ObjectId("4eec1e9942f62c7f2f5eedee"), "c" : null }
{ "_id" : ObjectId("4eec1e9d42f62c7f2f5eedef") }
> c.find({c:{$all:[null]}}) // seems to match everything
{ "_id" : ObjectId("4eec1e9542f62c7f2f5eedec"), "c" : 1 }
{ "_id" : ObjectId("4eec1e9742f62c7f2f5eeded"), "c" : "a" }
{ "_id" : ObjectId("4eec1e9942f62c7f2f5eedee"), "c" : null }
{ "_id" : ObjectId("4eec1e9d42f62c7f2f5eedef") }
> c.find({c:{$all:[1]}})
{ "_id" : ObjectId("4eec1e9542f62c7f2f5eedec"), "c" : 1 }
> c.ensureIndex({c:1})
> c.find({c:{$all:[]}})
> c.find({c:null})
{ "_id" : ObjectId("4eec1e9942f62c7f2f5eedee"), "c" : null }
{ "_id" : ObjectId("4eec1e9d42f62c7f2f5eedef") }
> c.find({c:{$all:[null]}}) // now matches are bounded by index range
{ "_id" : ObjectId("4eec1e9942f62c7f2f5eedee"), "c" : null }
{ "_id" : ObjectId("4eec1e9d42f62c7f2f5eedef") }
> c.find({c:{$all:[1]}})
{ "_id" : ObjectId("4eec1e9542f62c7f2f5eedec"), "c" : 1 }