In-memory sessions

mathics/core/evaluation.py

@@ -337,22 +337,10 @@ def evaluate():
         return result
 
     def get_stored_result(self, result):
-        from mathics.core.expression import Symbol
-
         # Remove outer format
         if result.has_form(FORMATS, 1):
             result = result.leaves[0]
 
-        # Prevent too large results from being stored, as this can exceed the
-        # DB's max_allowed_packet size
-        max_stored_size = self.output.max_stored_size(settings)
-        if max_stored_size is not None:
-            try:
-                data = pickle.dumps(result)
-                if len(data) > max_stored_size:
-                    return Symbol('Null')
-            except (ValueError, pickle.PicklingError):
-                return Symbol('Null')
         return result
 
     def stop(self) -> None:

mathics/web/models.py

@@ -4,6 +4,34 @@
 
 from django.db import models
 from django.contrib.auth.models import User
+from django.db.models.signals import pre_delete
+from django.contrib.sessions.models import Session
+
+from mathics.core.definitions import Definitions
+from mathics.core.evaluation import Evaluation, Output
+
+
+class WebOutput(Output):
+    pass
+
+_evaluations = {}
+
+
+def get_session_evaluation(session):
+    evaluation = _evaluations.get(session.session_key)
+    if evaluation is None:
+        definitions = Definitions(add_builtin=True)
+        evaluation = Evaluation(
+            definitions, format='xml', output=WebOutput())
+        _evaluations[session.session_key] = evaluation
+    return evaluation
+
+
+def end_session_evaluation(sender, **kwargs):
+    session_key = kwargs.get('instance').session_key
+    del _evaluations[session_key]
+
+pre_delete.connect(end_session_evaluation, sender=Session)
 
 
 class Query(models.Model):

mathics/web/views.py

@@ -18,7 +18,7 @@
 from mathics.core.definitions import Definitions
 from mathics.core.evaluation import Evaluation, Message, Result, Output
 
-from mathics.web.models import Query, Worksheet
+from mathics.web.models import Query, Worksheet, get_session_evaluation
 from mathics.web.forms import LoginForm, SaveForm
 from mathics.doc import documentation
 from mathics.doc.doc import DocPart, DocChapter, DocSection
@@ -39,10 +39,6 @@ def __init__(self, result={}):
         super(JsonResponse, self).__init__(response, content_type=JSON_CONTENT_TYPE)
 
 
-class WebOutput(Output):
-    pass
-
-
 def require_ajax_login(func):
     def new_func(request, *args, **kwargs):
         if not request.user.is_authenticated():
@@ -53,7 +49,6 @@ def new_func(request, *args, **kwargs):
 from mathics.settings import default_pymathics_modules
 definitions = Definitions(add_builtin=True, extension_modules=default_pymathics_modules)
 
-
 def require_ajax_login(f):
     return f
 
@@ -100,9 +95,7 @@ def query(request):
                           )
         query_log.save()
 
-    user_definitions = request.session.get('definitions')
-    definitions.set_user_definitions(user_definitions)
-    evaluation = Evaluation(definitions, format='xml', output=WebOutput())
+    evaluation = get_session_evaluation(request.session)
     feeder = MultiLineFeeder(input, '<notebook>')
     results = []
     try:
@@ -126,7 +119,6 @@ def query(request):
     result = {
         'results': [result.get_data() for result in results],
     }
-    request.session['definitions'] = definitions.get_user_definitions()
 
     if settings.LOG_QUERIES:
         query_log.timeout = evaluation.timeout
@@ -227,10 +219,7 @@ def login(request):
 
 
 def logout(request):
-    # Remember user definitions
-    user_definitions = request.session.get('definitions', {})
     auth.logout(request)
-    request.session['definitions'] = user_definitions
     return JsonResponse()