Lazy store current time in sparql query context

This improves performance when doing a lot of small queries.

1 files changed, 7 insertions, 2 deletions

diff --git a/rdflib/plugins/sparql/sparql.py b/rdflib/plugins/sparql/sparql.py
index f24aa564..43aee3ed 100644
--- a/rdflib/plugins/sparql/sparql.py
+++ b/rdflib/plugins/sparql/sparql.py
@@ -223,7 +223,6 @@ class FrozenBindings(FrozenDict):
 
 
 class QueryContext(object):
-
     """
     Query context - passed along when evaluating the query
     """
@@ -245,10 +244,16 @@ class QueryContext(object):
             self.graph = graph
 
         self.prologue = None
-        self.now = datetime.datetime.now(isodate.tzinfo.UTC)
+        self._now = None
 
         self.bnodes = collections.defaultdict(BNode)
 
+    @property
+    def now(self) -> datetime.datetime:
+        if self._now is None:
+            self._now = datetime.datetime.now(isodate.tzinfo.UTC)
+        return self._now
+
     def clone(self, bindings=None):
         r = QueryContext(
             self._dataset if self._dataset is not None else self.graph,