findAnnotations: match some fields case-sensitively

Requiring layer to have the right case is consistent with
addAnnotation(), and means the _layer[_like] index can be used. In my
testing, if itemsQuery specifies a single item, then postgres doesn't
bother with the layer index anyway; but if not, it makes a pretty big
(~3×) difference.

Matching public_id and item__public_id case-sensitively also seems
reasonable (it's consistent with get() and getAnnotation()).

(Is lower() redundant for the case-insensitive comparisons? ie. is
UPPER(x.lower()) == UPPER(x)? I'm not sure, it's cheap, let's leave it.)

pandora/annotation/managers.py

@@ -7,6 +7,12 @@ from oxdjango.query import QuerySet
 
 from item.utils import decode_id
 
+case_sensitive_keys = (
+    'public_id',
+    'layer',
+    'item__public_id',
+)
+
 
 def parseCondition(condition, user):
     '''
@@ -53,14 +59,24 @@ def parseCondition(condition, user):
         v = decode_id(v)
     if isinstance(v, bool): #featured and public flag
         key = k
-    elif k in ('lat', 'lng', 'area', 'south', 'west', 'north', 'east', 'matches',
+    elif k in ('places__id', 'events__id'):
-               'id', 'places__id', 'events__id'):
         key = "%s%s" % (k, {
             '>': '__gt',
             '>=': '__gte',
             '<': '__lt',
             '<=': '__lte',
         }.get(op, ''))
+    elif k in case_sensitive_keys:
+        key = "%s%s" % (k, {
+            '>': '__gt',
+            '>=': '__gte',
+            '<': '__lt',
+            '<=': '__lte',
+            '==': '__exact',
+            '=': '__contains',
+            '^': '__startswith',
+            '$': '__endswith',
+        }.get(op, '__contains'))
     else:
         key = "%s%s" % (k, {
             '>': '__gt',
@@ -75,7 +91,9 @@ def parseCondition(condition, user):
 
     key = str(key)
     if isinstance(v, unicode):
-        v = unicodedata.normalize('NFKD', v).lower()
+        v = unicodedata.normalize('NFKD', v)
+        if v not in case_sensitive_keys:
+            v = v.lower()
     if exclude:
         q = ~Q(**{key: v})
     else: