Exception handling for database queries

ref-test/app/tools/data.py

@@ -1,8 +1,9 @@
 from ..models import Dataset
+from ..tools.logs import write
 
 from flask import current_app as app
-from flask import flash, redirect
-from flask.helpers import url_for
+from flask.helpers import abort, flash, redirect, url_for
+from sqlalchemy.exc import SQLAlchemyError
 
 import json
 from pathlib import Path
@@ -76,7 +77,10 @@ def get_tag_list(dataset:list):
 def check_dataset_exists(function):
     @wraps(function)
     def wrapper(*args, **kwargs):
-        datasets = Dataset.query.all()
+        try: datasets = Dataset.query.all()
+        except SQLAlchemyError as exception:
+            write('system.log', f'Database error when checking existing datasets: {exception}')
+            return abort(500)
         if not datasets:
             flash('There are no available question datasets. Please upload a question dataset first, or use the question editor to create a new dataset.', 'error')
             return redirect(url_for('admin._questions'))