-
Type:
Bug
-
Resolution: Fixed
-
Priority:
Major - P3
-
Affects Version/s: 5.3.1
-
Component/s: None
-
None
-
Fully Compatible
-
ALL
-
None
-
3
-
None
-
None
-
None
-
None
-
None
-
None
-
None
The following experiment run in mongosh against MongoDB 5.3.1
use myDb
db.myColl.drop()
db.runCommand({"insert": "myColl", "documents": [
{"_id": 1, "partition": {"id": 10}, "field": 1},
{"_id": 2, "partition": {"id": 10}},
{"_id": 3, "partition": {"id": 20}, "field": 3}] })
db.runCommand({"aggregate": "myColl", "pipeline": [
{"$fill": {
"output": {
"field": {"method": "locf"}
},
"sortBy": {"_id": -1},
"partitionByFields": ["partition.id"] }},
{"$sort": {"_id": 1}},
{"$project": {"field": true, "_id": false} }],
"cursor": {} })
results in
MongoServerError: FieldPath field names may not contain '.'. Consider using $getField or $setField.
Replacing
"partitionByFields": ["partition.id"]
with
"partitionBy": {"p": "$partition.id"}
makes it work and produce
[ { field: 1 }, { field: null }, { field: 3 } ]
kateryna.kamenieva@mongodb.com confirmed that this is a bug and the dot notation for embedded documents was intended to be supported in $fill.partitionByFields similarly to how it is supported in $densify.partitionByFields: 
