BUG22880163: Fix memory leak on using Named Tuple Cursors

Currently separate namedtuple class is created for each single row retrieved
from DB. That is each single row has **its own** namedtuple class. Recreating
of separate namedtuple classes not only reduces performance, but also results
in higher memory usage and memory leaks.

This patch fixes the issue for both Pure python and C Extension.

Author: amitab

lib/mysql/connector/abstracts.py

@@ -26,13 +26,16 @@
 from abc import ABCMeta, abstractmethod, abstractproperty
 import re
 import time
+import weakref
 
 from .catch23 import make_abc, BYTE_TYPES
 from .conversion import MySQLConverterBase
 from .constants import ClientFlag, CharacterSet, DEFAULT_CONFIGURATION
 from .optionfiles import MySQLOptionsParser
 from . import errors
 
+NAMED_TUPLE_CACHE = weakref.WeakValueDictionary()
+
 @make_abc(ABCMeta)
 class MySQLConnectionAbstract(object):
 

lib/mysql/connector/cursor.py

@@ -29,7 +29,7 @@
 import weakref
 
 from . import errors
-from .abstracts import MySQLCursorAbstract
+from .abstracts import MySQLCursorAbstract, NAMED_TUPLE_CACHE
 from .catch23 import PY2
 
 SQL_COMMENT = r"\/\*.*?\*\/"
@@ -1293,9 +1293,14 @@ def _row_to_python(self, rowdata, desc=None):
 
         if row:
             # pylint: disable=W0201
-            self.named_tuple = namedtuple('Row', self.column_names)
+            columns = tuple(self.column_names)
+            try:
+                named_tuple = NAMED_TUPLE_CACHE[columns]
+            except KeyError:
+                named_tuple = namedtuple('Row', columns)
+                NAMED_TUPLE_CACHE[columns] = named_tuple
             # pylint: enable=W0201
-            return self.named_tuple(*row)
+            return named_tuple(*row)
 
     def fetchone(self):
         """Returns next row of a query result set

lib/mysql/connector/cursor_cext.py

@@ -30,7 +30,8 @@
 
 from _mysql_connector import MySQLInterfaceError  # pylint: disable=F0401,E0611
 
-from .abstracts import MySQLConnectionAbstract, MySQLCursorAbstract
+from .abstracts import (MySQLConnectionAbstract, MySQLCursorAbstract,
+                        NAMED_TUPLE_CACHE)
 from .catch23 import PY2, isunicode
 from . import errors
 from .errorcode import CR_NO_RESULT_SET
@@ -757,7 +758,12 @@ def _handle_resultset(self):
         """Handle a result set"""
         super(CMySQLCursorNamedTuple, self)._handle_resultset()
         # pylint: disable=W0201
-        self.named_tuple = namedtuple('Row', self.column_names)
+        columns = tuple(self.column_names)
+        try:
+            self.named_tuple = NAMED_TUPLE_CACHE[columns]
+        except KeyError:
+            self.named_tuple = namedtuple('Row', columns)
+            NAMED_TUPLE_CACHE[columns] = self.named_tuple
         # pylint: enable=W0201
 
     def fetchone(self):