implement SWAPDB (#551)

StackExchange.Redis/StackExchange/Redis/Enums/RedisCommand.cs

@@ -152,6 +152,7 @@ internal enum RedisCommand
         SUNION,
         SUNIONSTORE,
         SSCAN,
+        SWAPDB,
         SYNC,
 
         TIME,

StackExchange.Redis/StackExchange/Redis/Interfaces/IServer.cs

-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -537,6 +537,18 @@ public partial interface IServer : IRedis
         /// <remarks>https://redis.io/commands/pubsub</remarks>
         Task<long> SubscriptionSubscriberCountAsync(RedisChannel channel, CommandFlags flags = CommandFlags.None);
 
+        /// <summary>
+        /// Swaps two Redis databases, so that immediately all the clients connected to a given database will see the data of the other database, and the other way around
+        /// </summary>
+        /// <remarks>https://redis.io/commands/swapdb</remarks>
+        void SwapDatabases(int first, int second, CommandFlags flags = CommandFlags.None);
+
+        /// <summary>
+        /// Swaps two Redis databases, so that immediately all the clients connected to a given database will see the data of the other database, and the other way around
+        /// </summary>
+        /// <remarks>https://redis.io/commands/swapdb</remarks>
+        Task SwapDatabasesAsync(int first, int second, CommandFlags flags = CommandFlags.None);
+
         /// <summary>
         /// The TIME command returns the current server time.
         /// </summary>

StackExchange.Redis/StackExchange/Redis/Message.cs

@@ -182,6 +182,7 @@ public bool IsAdmin
                     case RedisCommand.SHUTDOWN:
                     case RedisCommand.SLAVEOF:
                     case RedisCommand.SLOWLOG:
+                    case RedisCommand.SWAPDB:
                     case RedisCommand.SYNC:
                         return true;
                     default:
@@ -381,6 +382,7 @@ public static bool IsMasterOnly(RedisCommand command)
                 case RedisCommand.SPOP:
                 case RedisCommand.SREM:
                 case RedisCommand.SUNIONSTORE:
+                case RedisCommand.SWAPDB:
                 case RedisCommand.ZADD:
                 case RedisCommand.ZINTERSTORE:
                 case RedisCommand.ZINCRBY:

StackExchange.Redis/StackExchange/Redis/RedisServer.cs

@@ -505,6 +505,18 @@ public Task<long> SubscriptionSubscriberCountAsync(RedisChannel channel, Command
             return ExecuteAsync(msg, ResultProcessor.PubSubNumSub);
         }
 
+        public void SwapDatabases(int first, int second, CommandFlags flags = CommandFlags.None)
+        {
+            var msg = Message.Create(-1, flags, RedisCommand.SWAPDB, first, second);
+            ExecuteSync(msg, ResultProcessor.DemandOK);
+        }
+
+        public Task SwapDatabasesAsync(int first, int second, CommandFlags flags = CommandFlags.None)
+        {
+            var msg = Message.Create(-1, flags, RedisCommand.SWAPDB, first, second);
+            return ExecuteAsync(msg, ResultProcessor.DemandOK);
+        }
+
         public DateTime Time(CommandFlags flags = CommandFlags.None)
         {
             var msg = Message.Create(-1, flags, RedisCommand.TIME);