Performance issues when updating

[rafalnawojczyk]

I've encountered performance issue while updating a record in the database.

My model looks like that for Session:

export default class Session extends Model {
  static table = "sessions";

  static associations = {
    solves: { type: "has_many" as const, foreignKey: "session_id" },
  };

  @readonly @date("created_at") createdAt!: Date;

  @nochange @field("user_id") userId!: string;

  @date("used") used!: Date;
  @text("name") name!: string;
  @field("cube") cube!: CubeType;
  @field("amount") amount!: number;
  @field("full_amount") fullAmount!: number;
  @field("stdev") stdev!: number;
  @field("average") average!: number;
  @field("best") best!: number;
  @field("is_trainer") isTrainer!: boolean;
  @json("valid_times", jsonValue => jsonValue) validTimes!: number[];
  @field("threshold_1") threshold1!: number;
  @field("threshold_2") threshold2!: number;
  @field("threshold_3") threshold3!: number;
  @field("threshold_4") threshold4!: number;

  @children("solves") solves!: Query<Solve>;
}

and for solve:

export default class Solve extends Model {
  static table = "solves";
  static associations = {
    sessions: { type: "belongs_to" as const, key: "session_id" },
  };

  @field("time") time!: number;
  @field("scramble") scramble!: string;
  @text("note") note?: string;
  @field("flag") flag?: SolveFlagType;
  @field("inspection") inspection?: number;
  @field("star") star?: boolean;
  @field("is_trainer") isTrainer!: boolean;
  @field("training_alg") trainingAlg!: string;
  @date("created_at") createdAt!: number;
  @relation("sessions", "session_id") session!: Relation<Session>;
}

When I'm making an update on Session - it takes around 80ms, when there is only 5-6 solves in this session(one to many relation).
When there is around 600 solves that are related to the session - i takes around 500ms just to execute this empty update:

 await currentSession.update(session => {});

Is there anything wrong with the models that I've missed, and what is causing this?