Lower default GridFS chunk size to 255k, PYTHON-661.

Author: ajdavis

gridfs/grid_file.py

@@ -45,7 +45,8 @@
 NEWLN = b("\n")
 
 """Default chunk size, in bytes."""
-DEFAULT_CHUNK_SIZE = 256 * 1024
+# Slightly under a power of 2, to work well with server's record allocations.
+DEFAULT_CHUNK_SIZE = 255 * 1024
 
 
 def _create_property(field_name, docstring,

test/test_grid_file.py

@@ -124,7 +124,7 @@ def test_grid_in_default_opts(self):
         self.assertRaises(AttributeError, getattr, a, "length")
         self.assertRaises(AttributeError, setattr, a, "length", 5)
 
-        self.assertEqual(256 * 1024, a.chunk_size)
+        self.assertEqual(255 * 1024, a.chunk_size)
         self.assertRaises(AttributeError, setattr, a, "chunk_size", 5)
 
         self.assertRaises(AttributeError, getattr, a, "upload_date")
@@ -157,7 +157,7 @@ def test_grid_in_default_opts(self):
         self.assertEqual(0, a.length)
         self.assertRaises(AttributeError, setattr, a, "length", 5)
 
-        self.assertEqual(256 * 1024, a.chunk_size)
+        self.assertEqual(255 * 1024, a.chunk_size)
         self.assertRaises(AttributeError, setattr, a, "chunk_size", 5)
 
         self.assertTrue(isinstance(a.upload_date, datetime.datetime))
@@ -216,7 +216,7 @@ def test_grid_out_default_opts(self):
         self.assertEqual(None, b.content_type)
         self.assertEqual(None, b.name)
         self.assertEqual(None, b.filename)
-        self.assertEqual(256 * 1024, b.chunk_size)
+        self.assertEqual(255 * 1024, b.chunk_size)
         self.assertTrue(isinstance(b.upload_date, datetime.datetime))
         self.assertEqual(None, b.aliases)
         self.assertEqual(None, b.metadata)

test/test_gridfs.py

@@ -130,7 +130,7 @@ def test_empty_file(self):
         self.assertEqual(0, raw["length"])
         self.assertEqual(oid, raw["_id"])
         self.assertTrue(isinstance(raw["uploadDate"], datetime.datetime))
-        self.assertEqual(256 * 1024, raw["chunkSize"])
+        self.assertEqual(255 * 1024, raw["chunkSize"])
         self.assertTrue(isinstance(raw["md5"], basestring))
 
     def test_alt_collection(self):