ZSCAN|HSCAN|SSCAN resumable iterators

StackExchange.Redis.Tests/DatabaseWrapperTests.cs

@@ -148,7 +148,7 @@ public void HashLength()
         [Test]
         public void HashScan()
         {
-            wrapper.HashScan("key", "pattern", 123, CommandFlags.HighPriority);
+            wrapper.HashScan("key", "pattern", 123, flags: CommandFlags.HighPriority);
             mock.Verify(_ => _.HashScan("prefix:key", "pattern", 123, CommandFlags.HighPriority));
         }
 
@@ -603,7 +603,7 @@ public void SetRemove_2()
         [Test]
         public void SetScan()
         {
-            wrapper.SetScan("key", "pattern", 123, CommandFlags.HighPriority);
+            wrapper.SetScan("key", "pattern", 123, flags: CommandFlags.HighPriority);
             mock.Verify(_ => _.SetScan("prefix:key", "pattern", 123, CommandFlags.HighPriority));
         }
 
@@ -773,7 +773,7 @@ public void SortedSetRemoveRangeByValue()
         [Test]
         public void SortedSetScan()
         {
-            wrapper.SortedSetScan("key", "pattern", 123, CommandFlags.HighPriority);
+            wrapper.SortedSetScan("key", "pattern", 123, flags: CommandFlags.HighPriority);
             mock.Verify(_ => _.SortedSetScan("prefix:key", "pattern", 123, CommandFlags.HighPriority));
         }
 

StackExchange.Redis/StackExchange/Redis/ExceptionFactory.cs

@@ -82,6 +82,12 @@ internal static Exception NotSupported(bool includeDetail, RedisCommand command)
             if (includeDetail) AddDetail(ex, null, null, s);
             return ex;
         }
+        internal static Exception NoCursor(RedisCommand command)
+        {
+            string s = GetLabel(false, command, null);
+            var ex = new RedisCommandException("Command cannot be used with a cursor: " + s);
+            return ex;
+        }
 
         internal static Exception Timeout(bool includeDetail, string errorMessage, Message message, ServerEndPoint server)
         {

StackExchange.Redis/StackExchange/Redis/IDatabase.cs

@@ -138,7 +138,14 @@ public interface IDatabase : IRedis, IDatabaseAsync
         /// </summary>
         /// <returns>yields all elements of the hash.</returns>
         /// <remarks>http://redis.io/commands/hscan</remarks>
-        IEnumerable<HashEntry> HashScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisDatabase.ScanUtils.DefaultPageSize, CommandFlags flags = CommandFlags.None);
+        IEnumerable<HashEntry> HashScan(RedisKey key, RedisValue pattern, int pageSize, CommandFlags flags);
+
+        /// <summary>
+        /// The HSCAN command is used to incrementally iterate over a hash
+        /// </summary>
+        /// <returns>yields all elements of the hash.</returns>
+        /// <remarks>http://redis.io/commands/hscan</remarks>
+        IEnumerable<HashEntry> HashScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisBase.CursorEnumerable.DefaultPageSize, long cursor = RedisBase.CursorEnumerable.Origin, CommandFlags flags = CommandFlags.None);
 
         /// <summary>
         /// Sets the specified fields to their respective values in the hash stored at key. This command overwrites any existing fields in the hash. If key does not exist, a new key holding a hash is created.
@@ -572,7 +579,14 @@ public interface IDatabase : IRedis, IDatabaseAsync
         /// </summary>
         /// <returns>yields all elements of the set.</returns>
         /// <remarks>http://redis.io/commands/sscan</remarks>
-        IEnumerable<RedisValue> SetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisDatabase.ScanUtils.DefaultPageSize, CommandFlags flags = CommandFlags.None);
+        IEnumerable<RedisValue> SetScan(RedisKey key, RedisValue pattern, int pageSize, CommandFlags flags);
+
+        /// <summary>
+        /// The SSCAN command is used to incrementally iterate over set
+        /// </summary>
+        /// <returns>yields all elements of the set.</returns>
+        /// <remarks>http://redis.io/commands/sscan</remarks>
+        IEnumerable<RedisValue> SetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisBase.CursorEnumerable.DefaultPageSize, long cursor = RedisBase.CursorEnumerable.Origin, CommandFlags flags = CommandFlags.None);
 
         /// <summary>
         /// Sorts a list, set or sorted set (numerically or alphabetically, ascending by default); By default, the elements themselves are compared, but the values can also be
@@ -758,7 +772,14 @@ public interface IDatabase : IRedis, IDatabaseAsync
         /// </summary>
         /// <returns>yields all elements of the sorted set.</returns>
         /// <remarks>http://redis.io/commands/zscan</remarks>
-        IEnumerable<SortedSetEntry> SortedSetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisDatabase.ScanUtils.DefaultPageSize, CommandFlags flags = CommandFlags.None);
+        IEnumerable<SortedSetEntry> SortedSetScan(RedisKey key, RedisValue pattern, int pageSize, CommandFlags flags);
+
+        /// <summary>
+        /// The ZSCAN command is used to incrementally iterate over a sorted set
+        /// </summary>
+        /// <returns>yields all elements of the sorted set.</returns>
+        /// <remarks>http://redis.io/commands/zscan</remarks>
+        IEnumerable<SortedSetEntry> SortedSetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisBase.CursorEnumerable.DefaultPageSize, long cursor = RedisBase.CursorEnumerable.Origin, CommandFlags flags = CommandFlags.None);
         /// <summary>
         /// Returns the score of member in the sorted set at key; If member does not exist in the sorted set, or key does not exist, nil is returned.
         /// </summary>

StackExchange.Redis/StackExchange/Redis/IServer.cs

@@ -237,7 +237,7 @@ public partial interface IServer : IRedis
         /// <remarks>Warning: consider KEYS as a command that should only be used in production environments with extreme care.</remarks>
         /// <remarks>http://redis.io/commands/keys</remarks>
         /// <remarks>http://redis.io/commands/scan</remarks>
-        IEnumerable<RedisKey> Keys(int database = 0, RedisValue pattern = default(RedisValue), int pageSize = 10, long cursor = 0, CommandFlags flags = CommandFlags.None);
+        IEnumerable<RedisKey> Keys(int database = 0, RedisValue pattern = default(RedisValue), int pageSize = RedisBase.CursorEnumerable.DefaultPageSize, long cursor = RedisBase.CursorEnumerable.Origin, CommandFlags flags = CommandFlags.None);
 
         /// <summary>
         /// Return the time of the last DB save executed with success. A client may check if a BGSAVE command succeeded reading the LASTSAVE value, then issuing a BGSAVE command and checking at regular intervals every N seconds if LASTSAVE changed.

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

@@ -608,17 +608,30 @@ public TimeSpan Ping(CommandFlags flags = CommandFlags.None)
             return this.Inner.Ping(flags);
         }
 
-        public IEnumerable<HashEntry> HashScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = 10, CommandFlags flags = CommandFlags.None)
+
+        IEnumerable<HashEntry> IDatabase.HashScan(RedisKey key, RedisValue pattern, int pageSize, CommandFlags flags)
+        {
+            return HashScan(key, pattern, pageSize, RedisBase.CursorEnumerable.Origin, flags);
+        }
+        public IEnumerable<HashEntry> HashScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisBase.CursorEnumerable.DefaultPageSize, long cursor = RedisBase.CursorEnumerable.Origin, CommandFlags flags = CommandFlags.None)
         {
             return this.Inner.HashScan(this.ToInner(key), pattern, pageSize, flags);
         }
 
-        public IEnumerable<RedisValue> SetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = 10, CommandFlags flags = CommandFlags.None)
+        IEnumerable<RedisValue> IDatabase.SetScan(RedisKey key, RedisValue pattern, int pageSize, CommandFlags flags)
         {
-            return this.Inner.SetScan(this.ToInner(key), pattern, pageSize, flags);
+            return SetScan(key, pattern, pageSize, RedisBase.CursorEnumerable.Origin, flags);
+        }
+        public IEnumerable<RedisValue> SetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisBase.CursorEnumerable.DefaultPageSize, long cursor = RedisBase.CursorEnumerable.Origin, CommandFlags flags = CommandFlags.None)
+        {
+            return this.Inner.SetScan(this.ToInner(key), pattern, pageSize, cursor, flags);
         }
 
-        public IEnumerable<SortedSetEntry> SortedSetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = 10, CommandFlags flags = CommandFlags.None)
+        IEnumerable<SortedSetEntry> IDatabase.SortedSetScan(RedisKey key, RedisValue pattern, int pageSize, CommandFlags flags)
+        {
+            return SortedSetScan(key, pattern, pageSize, RedisBase.CursorEnumerable.Origin, flags);
+        }
+        public IEnumerable<SortedSetEntry> SortedSetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisBase.CursorEnumerable.DefaultPageSize, long cursor = RedisBase.CursorEnumerable.Origin, CommandFlags flags = CommandFlags.None)
         {
             return this.Inner.SortedSetScan(this.ToInner(key), pattern, pageSize, flags);
         }

StackExchange.Redis/StackExchange/Redis/RedisBase.cs

@@ -141,9 +141,9 @@ private ResultProcessor.TimingProcessor.TimerMessage GetTimerMessage(CommandFlag
         }
 
 
-        internal abstract class CursorEnumerableBase
+        internal abstract class CursorEnumerable
         {
-            internal const int DefaultPageSize = 10;
+            internal const int Origin = 0, DefaultPageSize = 10;
             internal static bool IsNil(RedisValue pattern)
             {
                 if (pattern.IsNullOrEmpty) return true;
@@ -152,7 +152,7 @@ internal static bool IsNil(RedisValue pattern)
                 return rawValue.Length == 1 && rawValue[0] == '*';
             }
         }
-        internal abstract class CursorEnumerableBase<T> : CursorEnumerableBase, IEnumerable<T>, IScanning
+        internal abstract class CursorEnumerable<T> : CursorEnumerable, IEnumerable<T>, IScanning
         {
             private readonly RedisBase redis;
             private readonly ServerEndPoint server;
@@ -161,7 +161,7 @@ internal abstract class CursorEnumerableBase<T> : CursorEnumerableBase, IEnumera
             protected readonly int pageSize;
             protected readonly long initialCursor;
 
-            protected CursorEnumerableBase(RedisBase redis, ServerEndPoint server, int db, int pageSize, long cursor, CommandFlags flags)
+            protected CursorEnumerable(RedisBase redis, ServerEndPoint server, int db, int pageSize, long cursor, CommandFlags flags)
             {
                 this.redis = redis;
                 this.server = server;
@@ -217,8 +217,8 @@ protected ScanResult Wait(Task<ScanResult> pending)
 
             class CursorEnumerator : IEnumerator<T>, IScanning
             {
-                private CursorEnumerableBase<T> parent;
-                public CursorEnumerator(CursorEnumerableBase<T> parent)
+                private CursorEnumerable<T> parent;
+                public CursorEnumerator(CursorEnumerable<T> parent)
                 {
                     if (parent == null) throw new ArgumentNullException("parent");
                     this.parent = parent;

StackExchange.Redis/StackExchange/Redis/RedisDatabase.cs

@@ -193,11 +193,17 @@ public Task<long> HashLengthAsync(RedisKey key, CommandFlags flags = CommandFlag
             return ExecuteAsync(msg, ResultProcessor.Int64);
         }
 
-        public IEnumerable<HashEntry> HashScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisDatabase.ScanUtils.DefaultPageSize, CommandFlags flags = CommandFlags.None)
+        IEnumerable<HashEntry> IDatabase.HashScan(RedisKey key, RedisValue pattern, int pageSize, CommandFlags flags)
         {
-            var scan = TryScan<HashEntry>(key, pattern, pageSize, flags, RedisCommand.HSCAN, HashScanResultProcessor.Default);
+            return HashScan(key, pattern, pageSize, CursorEnumerable.Origin, flags);
+        }
+
+        public IEnumerable<HashEntry> HashScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = CursorEnumerable.DefaultPageSize, long cursor = CursorEnumerable.Origin, CommandFlags flags = CommandFlags.None)
+        {
+            var scan = TryScan<HashEntry>(key, pattern, pageSize, cursor, flags, RedisCommand.HSCAN, HashScanResultProcessor.Default);
             if (scan != null) return scan;
 
+            if (cursor != 0) throw ExceptionFactory.NoCursor(RedisCommand.HGETALL);
             if (pattern.IsNull) return HashGetAll(key, flags);
             throw ExceptionFactory.NotSupported(true, RedisCommand.HSCAN);
         }
@@ -1017,11 +1023,17 @@ public Task<long> SetRemoveAsync(RedisKey key, RedisValue[] values, CommandFlags
             return ExecuteAsync(msg, ResultProcessor.Int64);
         }
 
-        public IEnumerable<RedisValue> SetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisDatabase.ScanUtils.DefaultPageSize, CommandFlags flags = CommandFlags.None)
+        IEnumerable<RedisValue> IDatabase.SetScan(RedisKey key, RedisValue pattern, int pageSize, CommandFlags flags)
         {
-            var scan = TryScan<RedisValue>(key, pattern, pageSize, flags, RedisCommand.SSCAN, SetScanResultProcessor.Default);
+            return SetScan(key, pattern, pageSize, CursorEnumerable.Origin, flags);
+        }
+
+        public IEnumerable<RedisValue> SetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = CursorEnumerable.DefaultPageSize, long cursor = CursorEnumerable.Origin, CommandFlags flags = CommandFlags.None)
+        {
+            var scan = TryScan<RedisValue>(key, pattern, pageSize, cursor, flags, RedisCommand.SSCAN, SetScanResultProcessor.Default);
             if (scan != null) return scan;
 
+            if(cursor != 0) throw ExceptionFactory.NoCursor(RedisCommand.SMEMBERS);
             if (pattern.IsNull) return SetMembers(key, flags);
             throw ExceptionFactory.NotSupported(true, RedisCommand.SSCAN);
         }
@@ -1239,11 +1251,17 @@ public Task<long> SortedSetRemoveRangeByScoreAsync(RedisKey key, double start, d
             return ExecuteAsync(msg, ResultProcessor.Int64);
         }
 
-        public IEnumerable<SortedSetEntry> SortedSetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = RedisDatabase.ScanUtils.DefaultPageSize, CommandFlags flags = CommandFlags.None)
+        IEnumerable<SortedSetEntry> IDatabase.SortedSetScan(RedisKey key, RedisValue pattern, int pageSize, CommandFlags flags)
+        {
+            return SortedSetScan(key, pattern, pageSize, CursorEnumerable.Origin, flags);
+        }
+
+        public IEnumerable<SortedSetEntry> SortedSetScan(RedisKey key, RedisValue pattern = default(RedisValue), int pageSize = CursorEnumerable.DefaultPageSize, long cursor = CursorEnumerable.Origin, CommandFlags flags = CommandFlags.None)
         {
-            var scan = TryScan<SortedSetEntry>(key, pattern, pageSize, flags, RedisCommand.ZSCAN, SortedSetScanResultProcessor.Default);
+            var scan = TryScan<SortedSetEntry>(key, pattern, pageSize, cursor, flags, RedisCommand.ZSCAN, SortedSetScanResultProcessor.Default);
             if (scan != null) return scan;
 
+            if (cursor != 0) throw ExceptionFactory.NoCursor(RedisCommand.ZRANGE);
             if (pattern.IsNull) return SortedSetRangeByRankWithScores(key, flags: flags);
             throw ExceptionFactory.NotSupported(true, RedisCommand.ZSCAN);
         }
@@ -1955,7 +1973,7 @@ private RedisCommand SetOperationCommand(SetOperation operation, bool store)
             }
         }
 
-        private IEnumerable<T> TryScan<T>(RedisKey key, RedisValue pattern, int pageSize, CommandFlags flags, RedisCommand command, ResultProcessor<ScanIterator<T>.ScanResult> processor)
+        private IEnumerable<T> TryScan<T>(RedisKey key, RedisValue pattern, int pageSize, long cursor, CommandFlags flags, RedisCommand command, ResultProcessor<ScanIterator<T>.ScanResult> processor)
         {
             if (pageSize <= 0) throw new ArgumentOutOfRangeException("pageSize");
             if (!multiplexer.CommandMap.IsAvailable(command)) return null;
@@ -1964,8 +1982,8 @@ private IEnumerable<T> TryScan<T>(RedisKey key, RedisValue pattern, int pageSize
             var features = GetFeatures(Db, key, flags, out server);
             if (!features.Scan) return null;
 
-            if (ScanUtils.IsNil(pattern)) pattern = (byte[])null;
-            return new ScanIterator<T>(this, server, key, pattern, pageSize, flags, command, processor).Read();
+            if (CursorEnumerable.IsNil(pattern)) pattern = (byte[])null;
+            return new ScanIterator<T>(this, server, key, pattern, pageSize, cursor, flags, command, processor);
         }
 
         private Message GetLexMessage(RedisCommand command, RedisKey key, RedisValue min, RedisValue max, Exclude exclude, long skip, long take, CommandFlags flags)
@@ -2013,110 +2031,51 @@ public Task<long> SortedSetRemoveRangeByValueAsync(RedisKey key, RedisValue min,
             return ExecuteAsync(msg, ResultProcessor.Int64);
         }
 
-        internal static class ScanUtils
-        {
-            public const int DefaultPageSize = 10;
-            public static bool IsNil(RedisValue pattern)
-            {
-                if (pattern.IsNullOrEmpty) return true;
-                if (pattern.IsInteger) return false;
-                byte[] rawValue = pattern;
-                return rawValue.Length == 1 && rawValue[0] == '*';
-            }
-        }
 
-        internal class ScanIterator<T>
+        internal class ScanIterator<T> : CursorEnumerable<T>
         {
-            private readonly RedisCommand command;
-
-            private readonly RedisDatabase database;
-
-            private readonly CommandFlags flags;
-
             private readonly RedisKey key;
-
-            private readonly int pageSize;
-
             private readonly RedisValue pattern;
-
+            private readonly RedisCommand command;
             private readonly ResultProcessor<ScanResult> processor;
 
-            private readonly ServerEndPoint server;
-
-            public ScanIterator(RedisDatabase database, ServerEndPoint server, RedisKey key, RedisValue pattern, int pageSize, CommandFlags flags,
+            public ScanIterator(RedisDatabase database, ServerEndPoint server, RedisKey key, RedisValue pattern, int pageSize, long cursor, CommandFlags flags,
                 RedisCommand command, ResultProcessor<ScanResult> processor)
+                : base(database, server, database.Database, pageSize, cursor, flags)
             {
                 this.key = key;
-                this.pageSize = pageSize;
-                this.database = database;
                 this.pattern = pattern;
-                this.flags = flags;
-                this.server = server;
                 this.command = command;
                 this.processor = processor;
             }
-
-            public IEnumerable<T> Read()
-            {
-                var msg = CreateMessage(0, false);
-                ScanResult current = database.ExecuteSync(msg, processor, server);
-                Task<ScanResult> pending;
-                do
-                {
-                    // kick off the next immediately, but don't wait for it yet
-                    msg = CreateMessage(current.Cursor, true);
-                    pending = msg == null ? null : database.ExecuteAsync(msg, processor, server);
-
-                    // now we can iterate the rows
-                    var values = current.Values;
-                    for (int i = 0; i < values.Length; i++)
-                        yield return values[i];
-
-                    // wait for the next, if any
-                    if (pending != null)
+            protected override ResultProcessor<CursorEnumerable<T>.ScanResult> Processor
             {
-                        current = database.Wait(pending);
-                    }
-
-                } while (pending != null);
+                get { return processor; }
             }
-
-            Message CreateMessage(long cursor, bool running)
+            protected override Message CreateMessage(long cursor)
             {
-                if (cursor == 0 && running) return null; // end of the line
-                if (ScanUtils.IsNil(pattern))
+                if (IsNil(pattern))
                 {
-                    if (pageSize == ScanUtils.DefaultPageSize)
+                    if (pageSize == DefaultPageSize)
                     {
-                        return Message.Create(database.Database, flags, command, key, cursor);
+                        return Message.Create(db, flags, command, key, cursor);
                     }
                     else
                     {
-                        return Message.Create(database.Database, flags, command, key, cursor, RedisLiterals.COUNT, pageSize);
+                        return Message.Create(db, flags, command, key, cursor, RedisLiterals.COUNT, pageSize);
                     }
                 }
                 else
                 {
-                    if (pageSize == ScanUtils.DefaultPageSize)
+                    if (pageSize == DefaultPageSize)
                     {
-                        return Message.Create(database.Database, flags, command, key, cursor, RedisLiterals.MATCH, pattern);
+                        return Message.Create(db, flags, command, key, cursor, RedisLiterals.MATCH, pattern);
                     }
                     else
                     {
-                        return Message.Create(database.Database, flags, command, key, new RedisValue[] { cursor, RedisLiterals.MATCH, pattern, RedisLiterals.COUNT, pageSize });
-                    }
+                        return Message.Create(db, flags, command, key, new RedisValue[] { cursor, RedisLiterals.MATCH, pattern, RedisLiterals.COUNT, pageSize });
                     }
                 }
-
-            internal struct ScanResult
-            {
-                public readonly long Cursor;
-                public readonly T[] Values;
-                public ScanResult(long cursor, T[] values)
-                {
-                    this.Cursor = cursor;
-                    this.Values = values;
-                }
             }
         }
 

StackExchange.Redis/StackExchange/Redis/RedisServer.cs

@@ -271,13 +271,13 @@ public Task<string> InfoRawAsync(RedisValue section = default(RedisValue), Comma
 
         IEnumerable<RedisKey> IServer.Keys(int database, RedisValue pattern, int pageSize, CommandFlags flags)
         {
-            return Keys(database, pattern, pageSize, 0, flags);
+            return Keys(database, pattern, pageSize, CursorEnumerable.Origin, flags);
         }
 
-        public IEnumerable<RedisKey> Keys(int database = 0, RedisValue pattern = default(RedisValue), int pageSize = CursorEnumerableBase.DefaultPageSize, long cursor = 0, CommandFlags flags = CommandFlags.None)
+        public IEnumerable<RedisKey> Keys(int database = 0, RedisValue pattern = default(RedisValue), int pageSize = CursorEnumerable.DefaultPageSize, long cursor = CursorEnumerable.Origin, CommandFlags flags = CommandFlags.None)
         {
             if (pageSize <= 0) throw new ArgumentOutOfRangeException("pageSize");
-            if (CursorEnumerableBase.IsNil(pattern)) pattern = RedisLiterals.Wildcard;
+            if (CursorEnumerable.IsNil(pattern)) pattern = RedisLiterals.Wildcard;
 
             if (multiplexer.CommandMap.IsAvailable(RedisCommand.SCAN))
             {
@@ -286,7 +286,7 @@ public IEnumerable<RedisKey> Keys(int database = 0, RedisValue pattern = default
                 if (features.Scan) return new KeysScanEnumerable(this, database, pattern, pageSize, cursor, flags);
             }
 
-            if (cursor != 0) throw new InvalidOperationException("A cursor cannot be used with KEYS");
+            if (cursor != 0) throw ExceptionFactory.NoCursor(RedisCommand.KEYS);
             Message msg = Message.Create(database, flags, RedisCommand.KEYS, pattern);
             return ExecuteSync(msg, ResultProcessor.RedisKeyArray);
         }
@@ -640,7 +640,7 @@ public static RedisValue Hash(string value)
             }
         }
 
-        sealed class KeysScanEnumerable : CursorEnumerableBase<RedisKey>
+        sealed class KeysScanEnumerable : CursorEnumerable<RedisKey>
         {
             private readonly RedisValue pattern;