Description

When Parameters (params) or User Attributes (user_attrs) contain numeric values, they are serialized as strings by the backend. The frontend TrialTable currently relies on a default sorting mechanism (likely "natural" or alphanumeric sorting).

While this mechanism correctly handles positive integers (e.g., sorting 2 before 10), it fails for negative numbers. The sorting logic appears to treat the minus sign as a character and sorts based on the magnitude of the number following it.

Current Behavior:

• Positive numbers sort correctly: 2, 10, 100
• Negative numbers sort incorrectly (inverted order): -1, -2, -10 (instead of -10, -2, -1).

Expected Behavior:
The dashboard should detect if the column (Parameter or User Attribute) contains numeric values and apply a true numeric sort function that correctly accounts for negative signs.

How to Reproduce

1. Create a Python script (reproduce_issue.py) to generate a study with negative values in both parameters and user attributes:

import optuna

def objective(trial):
    # 1. Create a parameter with a negative range
    x = trial.suggest_int("x_param", -10, 10)

    # 2. Set the same value as a user attribute
    trial.set_user_attr("x_attr", x)

    return x ** 2

if __name__ == "__main__":
    study = optuna.create_study(storage="sqlite:///db.sqlite3", study_name="sort_bug_test")
    study.optimize(objective, n_trials=20)

2. Run the script: python reproduce_issue.py
3. Launch the dashboard: optuna-dashboard sqlite:///db.sqlite3
4. Open the Trials tab (Trial Table).
5. Click the header for Param x_param and UserAttribute x_attr to sort them.
6. Observe that for both columns, negative numbers are sorted by magnitude.

Python version

Python 3.12.12

Optuna version

4.4.0

optuna-dashboard version or git revision

0.20.0

Web browser

Microsoft Edge Beta