Implement variadic exists? to replace exists as the boolean method

lib/redis.rb

@@ -560,6 +560,16 @@ def exists(key)
     end
   end
 
+  # Determine if any of the keys exists.
+  #
+  # @param [String, Array<String>] keys
+  # @return [Boolean]
+  def exists?(*keys)
+    synchronize do |client|
+      client.call([:exists, *keys], &Boolify)
+    end
+  end
+
   # Find all keys matching the given pattern.
   #
   # @param [String] pattern

lib/redis/distributed.rb

@@ -175,6 +175,15 @@ def exists(key)
       node_for(key).exists(key)
     end
 
+    # Determine if any of the keys exists.
+    def exists?(*args)
+      keys_per_node = args.group_by { |key| node_for(key) }
+      keys_per_node.each do |node, keys|
+        return true if node.exists?(*keys)
+      end
+      false
+    end
+
     # Find all keys matching the given pattern.
     def keys(glob = "*")
       on_each_node(:keys, glob).flatten

test/lint/value_types.rb

@@ -11,6 +11,14 @@ def test_exists
       assert_equal true,  r.exists("foo")
     end
 
+    def test_exists?
+      assert_equal false, r.exists?("{1}foo", "{1}bar")
+
+      r.set("{1}foo", "s1")
+
+      assert_equal true,  r.exists?("{1}foo")
+    end
+
     def test_type
       assert_equal "none", r.type("foo")