add keepttl option to set command.

fixes #1304
fixes #1280

Author: laixintao

CHANGES

@@ -21,6 +21,7 @@
     * Reset the watched state of pipelines after calling exec. This saves
       a roundtrip to the server by not having to call UNWATCH within
       Pipeline.reset(). Thanks @nickgaya, #1299/#1302
+    * Add the KEEPTTL option for the SET command. Thanks @laixintao #1304/#1280
 * 3.4.1
     * Move the username argument in the Redis and Connection classes to the
       end of the argument list. This helps those poor souls that specify all

redis/client.py

@@ -1761,7 +1761,8 @@ def restore(self, name, ttl, value, replace=False):
             params.append('REPLACE')
         return self.execute_command('RESTORE', *params)
 
-    def set(self, name, value, ex=None, px=None, nx=False, xx=False):
+    def set(self, name, value,
+            ex=None, px=None, nx=False, xx=False, keepttl=False):
         """
         Set the value at key ``name`` to ``value``
 
@@ -1774,6 +1775,9 @@ def set(self, name, value, ex=None, px=None, nx=False, xx=False):
 
         ``xx`` if set to True, set the value at key ``name`` to ``value`` only
             if it already exists.
+
+        ``keepttl`` if True, retain the time to live associated with the key.
+            (Available since Redis 6.0)
         """
         pieces = [name, value]
         if ex is not None:
@@ -1791,6 +1795,10 @@ def set(self, name, value, ex=None, px=None, nx=False, xx=False):
             pieces.append('NX')
         if xx:
             pieces.append('XX')
+
+        if keepttl:
+            pieces.append('KEEPTTL')
+
         return self.execute_command('SET', *pieces)
 
     def __setitem__(self, name, value):

tests/test_commands.py

@@ -867,6 +867,15 @@ def test_set_multipleoptions(self, r):
         assert r.set('a', '1', xx=True, px=10000)
         assert 0 < r.ttl('a') <= 10
 
+    @skip_if_server_version_lt('5.9.0')  # 6.0-rc1
+    def test_set_keepttl(self, r):
+        r['a'] = 'val'
+        assert r.set('a', '1', xx=True, px=10000)
+        assert 0 < r.ttl('a') <= 10
+        r.set('a', '2', keepttl=True)
+        assert r.get('a') == b'2'
+        assert 0 < r.ttl('a') <= 10
+
     def test_setex(self, r):
         assert r.setex('a', 60, '1')
         assert r['a'] == b'1'