Use Case

As a javascript user
I want javascript numbers to remain doubles when serialized
So that even integer-like doubles do not get converted to int32s

User Impact

• JS numbers that are integers and are within an int32 range are serialized as int32
  • This leads to behavior like: c.insertOne({ a: 1.7 + 0.3 }), a becoming an int32 here because the arithmetic resulted in a small integer-like value.
• If BSON were to always use doubles it would increase the default storage usage for numbers.
• MongoDB has flexible number comparison, generally lookups are not impacted by numbers changing type information.

Dependencies

• NODE-4780: promoteValues is the opposite side of the problem here, if enabled the flag will return Double instances, this can be useful for preserving the roundtrip type information

Unknowns

• How would serializing JS numbers to doubles with either a flag or by default impact the driver's messages to the server? (Non-user data, hellos, etc.)

Acceptance Criteria

Implementation Requirements

• Write up a document with investigation findings.

Follow Up Requirements

• Downstream impacts; Does mongosh want to offer or adopt this flag to offer legacy shell behavior. What granularity is necessary?