implement varadic EXISTS (#502)

StackExchange.Redis/StackExchange/Redis/Interfaces/IDatabase.cs

@@ -461,6 +461,15 @@ public interface IDatabase : IRedis, IDatabaseAsync
         /// <remarks>https://redis.io/commands/exists</remarks>
         bool KeyExists(RedisKey key, CommandFlags flags = CommandFlags.None);
 
+        /// <summary>
+        /// Indicates how many of the supplied keys exists.
+        /// </summary>
+        /// <param name="keys">The keys to check.</param>
+        /// <param name="flags">The flags to use for this operation.</param>
+        /// <returns>The number of keys that existed.</returns>
+        /// <remarks>https://redis.io/commands/exists</remarks>
+        long KeyExists(RedisKey[] keys, CommandFlags flags = CommandFlags.None);
+
         /// <summary>
         /// Set a timeout on key. After the timeout has expired, the key will automatically be deleted. A key with an associated timeout is said to be volatile in Redis terminology.
         /// </summary>

StackExchange.Redis/StackExchange/Redis/Interfaces/IDatabaseAsync.cs

@@ -424,6 +424,15 @@ public interface IDatabaseAsync : IRedisAsync
         /// <remarks>https://redis.io/commands/exists</remarks>
         Task<bool> KeyExistsAsync(RedisKey key, CommandFlags flags = CommandFlags.None);
 
+        /// <summary>
+        /// Indicates how many of the supplied keys exists.
+        /// </summary>
+        /// <param name="keys">The keys to check.</param>
+        /// <param name="flags">The flags to use for this operation.</param>
+        /// <returns>The number of keys that existed.</returns>
+        /// <remarks>https://redis.io/commands/exists</remarks>
+        Task<long> KeyExistsAsync(RedisKey[] keys, CommandFlags flags = CommandFlags.None);
+
         /// <summary>
         /// Set a timeout on key. After the timeout has expired, the key will automatically be deleted. A key with an associated timeout is said to be volatile in Redis terminology.
         /// </summary>

StackExchange.Redis/StackExchange/Redis/KeyspaceIsolation/DatabaseWrapper.cs

@@ -211,6 +211,10 @@ public bool KeyExists(RedisKey key, CommandFlags flags = CommandFlags.None)
         {
             return Inner.KeyExists(ToInner(key), flags);
         }
+        public long KeyExists(RedisKey[] keys, CommandFlags flags = CommandFlags.None)
+        {
+            return Inner.KeyExists(ToInner(keys), flags);
+        }
 
         public bool KeyExpire(RedisKey key, DateTime? expiry, CommandFlags flags = CommandFlags.None)
         {

StackExchange.Redis/StackExchange/Redis/KeyspaceIsolation/WrapperBase.cs

@@ -193,6 +193,11 @@ public Task<bool> KeyExistsAsync(RedisKey key, CommandFlags flags = CommandFlags
             return Inner.KeyExistsAsync(ToInner(key), flags);
         }
 
+        public Task<long> KeyExistsAsync(RedisKey[] keys, CommandFlags flags = CommandFlags.None)
+        {
+            return Inner.KeyExistsAsync(ToInner(keys), flags);
+        }
+
         public Task<bool> KeyExpireAsync(RedisKey key, DateTime? expiry, CommandFlags flags = CommandFlags.None)
         {
             return Inner.KeyExpireAsync(ToInner(key), expiry, flags);

StackExchange.Redis/StackExchange/Redis/RedisDatabase.cs

@@ -606,12 +606,24 @@ public bool KeyExists(RedisKey key, CommandFlags flags = CommandFlags.None)
             return ExecuteSync(msg, ResultProcessor.Boolean);
         }
 
+        public long KeyExists(RedisKey[] keys, CommandFlags flags = CommandFlags.None)
+        {
+            var msg = Message.Create(Database, flags, RedisCommand.EXISTS, keys);
+            return ExecuteSync(msg, ResultProcessor.Int64);
+        }
+
         public Task<bool> KeyExistsAsync(RedisKey key, CommandFlags flags = CommandFlags.None)
         {
             var msg = Message.Create(Database, flags, RedisCommand.EXISTS, key);
             return ExecuteAsync(msg, ResultProcessor.Boolean);
         }
 
+        public Task<long> KeyExistsAsync(RedisKey[] keys, CommandFlags flags = CommandFlags.None)
+        {
+            var msg = Message.Create(Database, flags, RedisCommand.EXISTS, keys);
+            return ExecuteAsync(msg, ResultProcessor.Int64);
+        }
+
         public bool KeyExpire(RedisKey key, TimeSpan? expiry, CommandFlags flags = CommandFlags.None)
         {
             var msg = GetExpiryMessage(key, flags, expiry, out ServerEndPoint server);