Mongodb Changestream Field Filter

MongoDB Change Stream Field Filter

Shape

Listener receives ChangeStreamDocument. For UPDATE, read updateDescription.updatedFields (a BsonDocument of dottedPath → value). Return a boolean isRelevant before handing off to the expensive processor.

Steps

1. Register listener via Spring Data MongoDB (reactive or blocking driver).
2. Branch on OperationType: INSERT / DELETE → always relevant.
3. UPDATE → updatedFields = event.getUpdateDescription().getUpdatedFields().
4. Exact check: updatedFields.containsKey("groupId").
5. Nested/wildcard: updatedFields.keySet().stream().anyMatch(k -> k.startsWith("tags.")).
6. Combine with OR over the "relevant fields" set; return the boolean.
7. Not relevant → log TRACE and skip. Relevant → delegate to processor.