Opening Multiple Databases in Drift Causes Unnecessary Isolate Memory Overhead

[asimolmez]

Describe the bug

When running multiple isolates, each managing its own Drift database, memory usage in the Dart/Flutter heap grows significantly.

Closing the database connection for an isolate (with a 10-second delay) consistently frees up ~40 MB of heap memory per isolate. The chart below shows the drop in usage after each connection is closed.

Memory View

Isolates

Additional Informations

When all database connections are open and isolates are active

all connections are closed

[simolus3]

Thanks for the report! Could you also share how you're opening the databases for completeness? Would you prefer to use single background isolate for all database instances?

[asimolmez]

class ChatDatabase extends _$ChatDatabase {
  ChatDatabase(this.userId) : super(_openConnection(userId));

  final String userId;

  @override
  int get schemaVersion => 2;

  static QueryExecutor _openConnection(String pubkey) {
    return driftDatabase(name: 'conversation_database_$pubkey');
  }

@simolus3 I created it this way. I investigated, and I believe it’s not related to drift. It’s an expected behavior of the spawning isolate by Dart code.

https://github.com/flutter/flutter/wiki/Flutter-engine-operation-in-AOT-Mode/cf25b22544e2353d3f347e6e04758fa3ad162d59 Isolates launched by Dart code (e.g., Isolate.spawn) inherit the snapshots of their parents.

Additionally, all connections are open because I use watch for certain tables on each database. Do you recommend that we use a single background isolate for multiple databases?