Merge branch 'master' of github.com:malcolmt/remember_me

minerva/questions.py

@@ -1,7 +1,12 @@
+import bisect
 import random
 
+from django.conf import settings
+from django.core.cache import cache
+
 from minerva.models import Word
 
+
 QUESTION_SCENARIOS = (
     # Question, answer
     ('word', 'meaning'),
@@ -22,10 +27,7 @@ def create_question(user, language, level, num_choices=4):
     # TODO: Right now, this is very simple (doesn't take into account the
     # user's performance at all). Eventually, it will be a graded selection
     # based on what the user finds difficult, etc.
-
-    # FIXME: Cache this, for each language.
-    pks = Word.objects.filter(lang_code__code=language, level=level). \
-            values_list("pk", flat=True)
+    pks = word_keys(language, level)
     sampled_words = list(Word.objects.filter(pk__in=random.sample(pks,
             num_choices)))
     question_attribute, answer_attribute = random.choice(QUESTION_SCENARIOS)
@@ -35,3 +37,20 @@ def create_question(user, language, level, num_choices=4):
             for item in sampled_words]
     return question_data, answers
 
+def word_keys(code, level):
+    """
+    Retrieves all the pk values for words for the language "code" and "level".
+    This interacts sensibly with the cache system to avoid unnecessary database
+    round trips.
+
+    Returns a list of pk values.
+    """
+    full_list = cache.get(code)
+    if not full_list:
+        full_list = tuple(Word.objects.filter(lang_code__code=code). \
+                values_list("level", "pk").order_by("level"))
+        cache.set(code, full_list, settings.LANG_CACHE_TIMEOUT)
+    start = bisect.bisect_right(full_list, (level - 1, 0))
+    end = bisect.bisect_left(full_list, (level + 1, 0))
+    return [item[1] for item in full_list[start : end]]
+

settings.py

@@ -101,5 +101,8 @@
     "INTERCEPT_REDIRECTS": False,
 }
 
+# Cache period, in seconds, for language data (which hardly ever changes)
+LANG_CACHE_TIMEOUT = 10800
+
 utils.load_external_settings("host_settings", globals())