This changes the behavior of matching dotted field paths to null (eg. $in, $nin, $eq, $ne, $gte, $lte). In particular, if a document has

and we query for "a.b" $eq null, it will now match, whereas before it didn't. There is a new query knob that disables this fix and restores the old behavior, internalQueryLegacyDottedPathNullSemantics

Description of Linked Ticket

{$ne: null} has some counterintuitive behavior which has hurt us several times now:

db.c.insert({a: [1, {c: 1}]});
db.c.insert({a: [1]});
 
db.c.find({"a.b": {$exists: true}}) // Returns nothing.
db.c.find({"a.b": {$ne: null}}) // Returns {a: [1]} !!!!

That is, {$ne: null} doesn't necessarily return a subset of the things that {$exists: true} returns.

This ticket is to fix incorrect logic in matcher path to fix this.

This ticket is to track the work of changing the meaning of {$ne: null}.