From 2e4603998c22e64565c0d48d8c6a76b7c0510179 Mon Sep 17 00:00:00 2001
From: Jeremy Daer <jeremydaer@gmail.com>
Date: Wed, 12 Apr 2017 18:40:10 -0700
Subject: [PATCH] Distributed: support mget and mapped_mget

Map the keys to their nodes, mget them on each node, and stitch the
results together.
---
 lib/redis/distributed.rb                     |  9 +++++---
 test/distributed_commands_on_strings_test.rb | 24 +++++++++++++++-----
 2 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/lib/redis/distributed.rb b/lib/redis/distributed.rb
index df4914831..648aa769b 100644
--- a/lib/redis/distributed.rb
+++ b/lib/redis/distributed.rb
@@ -277,13 +277,16 @@ def get(key)
       node_for(key).get(key)
     end
 
-    # Get the values of all the given keys.
+    # Get the values of all the given keys as an Array.
     def mget(*keys)
-      raise CannotDistribute, :mget
+      mapped_mget(*keys).values_at(*keys)
     end
 
+    # Get the values of all the given keys as a Hash.
     def mapped_mget(*keys)
-      raise CannotDistribute, :mapped_mget
+      keys.group_by { |k| node_for k }.inject({}) do |results, (node, subkeys)|
+        results.merge! node.mapped_mget(*subkeys)
+      end
     end
 
     # Overwrite part of a string at key starting at the specified offset.
diff --git a/test/distributed_commands_on_strings_test.rb b/test/distributed_commands_on_strings_test.rb
index ad83c12e5..e8a7f5456 100644
--- a/test/distributed_commands_on_strings_test.rb
+++ b/test/distributed_commands_on_strings_test.rb
@@ -9,15 +9,27 @@ class TestDistributedCommandsOnStrings < Test::Unit::TestCase
   include Lint::Strings
 
   def test_mget
-    assert_raise Redis::Distributed::CannotDistribute do
-      r.mget("foo", "bar")
-    end
+    r.set("foo", "s1")
+    r.set("bar", "s2")
+
+    assert_equal ["s1", "s2"]     , r.mget("foo", "bar")
+    assert_equal ["s1", "s2", nil], r.mget("foo", "bar", "baz")
   end
 
   def test_mget_mapped
-    assert_raise Redis::Distributed::CannotDistribute do
-      r.mapped_mget("foo", "bar")
-    end
+    r.set("foo", "s1")
+    r.set("bar", "s2")
+
+    response = r.mapped_mget("foo", "bar")
+
+    assert_equal "s1", response["foo"]
+    assert_equal "s2", response["bar"]
+
+    response = r.mapped_mget("foo", "bar", "baz")
+
+    assert_equal "s1", response["foo"]
+    assert_equal "s2", response["bar"]
+    assert_equal nil , response["baz"]
   end
 
   def test_mset