While doing some lightweight testing of early 3.4 new features during the MongoDB Bug Hunt Meetup, I deliberately passed in increasingly large decimal numbers.

I was attempting to test:

• Approximate max number of significant digits using new decimal feature
• Appropriate error when number too large
• Quality of error message

Decimal number were correctly saved until my number was too large and an error message appeared. This error message was, "Error: Input out of range of Decimal128 value (inexact)."

This error message makes it clear what the problem was. However, it could be more helpful. To figure out how many significant digits (34) are allowed in the Decimal128, I tried looking it up online and talking to a MongoDB engineer who was present. Including this information and/or the valid range in the error message would be very helpful.