BUG21420633: Fix CExtension crashing while fetching large number of NULL values

peeyushgupta · peeyushgupta · commit 3953b11c9312 · 2015-07-14T12:59:56.000+05:30
CExtension was crashing with "Fatal Python error: deallocating None" when
a large number of NULL values were fetched. With this patch we fix this
issue by incrementing reference to None whenver a NULL value is fetched.

A test case has been added for BUG#21420633.
diff --git a/src/mysql_capi.c b/src/mysql_capi.c
@@ -2237,6 +2237,7 @@ MySQL_fetch_row(MySQL *self)
     for (i= 0; i < num_fields; i++) {
     	if (row[i] == NULL)
     	{
+                Py_INCREF(Py_None);
     		PyTuple_SET_ITEM(result_row, i, Py_None);
     		continue;
         }
diff --git a/tests/test_bugs.py b/tests/test_bugs.py
@@ -3657,3 +3657,44 @@ def sleepy_select(cnx):
         self.assertEqual(str(self.cnx.test_error),
                          "1317 (70100): Query execution was interrupted")
         self.cnx.close()
+
+class BugOra21420633(tests.MySQLConnectorTests):
+    """BUG#21420633: CEXTENSION CRASHES WHILE FETCHING LOTS OF NULL VALUES
+    """
+    def setUp(self):
+        config = tests.get_mysql_config()
+        cnx = connection.MySQLConnection(**config)
+        cur = cnx.cursor()
+
+        self.tbl = 'Bug21420633'
+        cur.execute("DROP TABLE IF EXISTS {0}".format(self.tbl))
+
+        create = ("CREATE TABLE {0} (id INT, dept VARCHAR(5)) "
+                  "DEFAULT CHARSET latin1".format(self.tbl))
+        cur.execute(create)
+        cur.close()
+        cnx.close()
+
+    def tearDown(self):
+        config = tests.get_mysql_config()
+        cnx = connection.MySQLConnection(**config)
+        cur = cnx.cursor()
+        cur.execute("DROP TABLE IF EXISTS {0}".format(self.tbl))
+        cur.close()
+        cnx.close()
+
+    @foreach_cnx()
+    def test_null(self):
+        cur = self.cnx.cursor()
+        sql = "INSERT INTO {0} VALUES(%s, %s)".format(self.tbl)
+
+        data = [(i, None) for i in range(10000)]
+
+        cur.executemany(sql, data)
+        cur.close()
+
+        cur = self.cnx.cursor(named_tuple=True)
+        cur.execute("SELECT * FROM {0}".format(self.tbl))
+
+        res = cur.fetchall()
+        cur.close()

Original file line number	Diff line number	Diff line change
`@@ -2237,6 +2237,7 @@ MySQL_fetch_row(MySQL *self)`
`2237`	`2237`	`for (i= 0; i < num_fields; i++) {`
`2238`	`2238`	`if (row[i] == NULL)`
`2239`	`2239`	`{`
	`2240`	`+ Py_INCREF(Py_None);`
`2240`	`2241`	`PyTuple_SET_ITEM(result_row, i, Py_None);`
`2241`	`2242`	`continue;`
`2242`	`2243`	`}`