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Map value keeps recreating #1063
Description
I have a Map<enum_type, Map<String, my_class>> where the value Map<String, my_class> of any entry I add keeps resetting to a new HashMap.
The DB is created this way:
var db = DBMaker.fileDB(db_path).transactionEnable().make();
whereas the map itself is created this way:
Map<enum_type, Map<String, my_class>> my_map = (Map<enum_type, Map<String, my_class>>) db.hashMap(name).createOrOpen();
What could be the cause of this issue?
Activity
hiSandog commentedon Jul 3, 2026
This may be a serialization/mutability issue rather than MapDB recreating the value by itself. If the nested
Map<String, my_class>is a normalHashMap, each update needs to write the modified value back to the outer map, and the value serializer must be able to serializemy_classdeterministically. A minimal example showing whether the nested map is mutated afterput, whetherdb.commit()is called, and which serializer is configured would make the behavior much clearer.