Redis for .NET Developers – Redis List Datatype

Redis List Datatype are similar in C# world as LinkeList e.g LinkedList. Just like in LinkedList in C#, Redis can store items at Head or Tail of a List. The nice thing about them is that the insertion speed is just O(1), but do note that if you have a large list, the reading speed goes down since it sequentially traverses through the items (i.e walking down the chain). One could also say its an advantage since Redis was made to write faster than read, and LinkedList are great data type for such things. List are ideal candidate for logs, since the write speed is more important than read when dealing with logs.

Redis List Datatype – Operations

• LPUSH: Prepends the values to the left of the list O(1).
• RPUSH: Prepends the values to the right of the list O(1).
• LPUSHX: Prepends the values to the left of the list if key exist O(1).
• RPUSHX: Prepends the values to the right of the list if key exist O(1).
• LINSERT: Inserts a value in the list after position calculated from left O(N).
• LSET: Sets the value of an element in a list based on index O(N).
• LRANGE: Gets the sub list of elements based on start and end position O(S+E).
• LTRIM: Deletes the elements outside the range specified O(N), where N is the length.
• RPOP: Removes the last element O(1).
• LREM: Removes the element at the index point O(N) , where N is the length.
• LPOP: Removes the first element of the list O(1).
• LINDEX: Gets the element from the list based on the index O(N) where N is the length of traverse.
• LLEN: This command gets the length of the list O(1).
• RPOPLPUSH: Operates on two lists source and destination list, takes the last element on the source list and push it to the first element of the destination list O(1).

C# code using Redis List Datatype

  class Program
    {
        static void Main(string[] args)
        {
            var redis = RedisStore.RedisCache;

            var listKey = "listKey";

            redis.KeyDelete(listKey, CommandFlags.FireAndForget);

            redis.ListRightPush(listKey, "a");

            var len = redis.ListLength(listKey);
            Console.WriteLine(len); //output  is 1

            redis.ListRightPush(listKey, "b");

            Console.WriteLine(redis.ListLength(listKey)); //putput is 2

            //lets clear it out
            redis.KeyDelete(listKey, CommandFlags.FireAndForget);
          
            redis.ListRightPush(listKey, "abcdefghijklmnopqrstuvwxyz".Select(x => (RedisValue) x.ToString()).ToArray());

            Console.WriteLine(redis.ListLength(listKey)); //output is 26

            Console.WriteLine(string.Concat(redis.ListRange(listKey))); //output is abcdefghijklmnopqrstuvwxyz

            var lastFive = redis.ListRange(listKey, -5);

            Console.WriteLine(string.Concat(lastFive)); //output vwxyz

            var firstFive = redis.ListRange(listKey, 0, 4);

            Console.WriteLine(string.Concat(firstFive)); //output abcde

            redis.ListTrim(listKey, 0, 1);

            Console.WriteLine(string.Concat(redis.ListRange(listKey))); //output ab

            //lets clear it out
            redis.KeyDelete(listKey, CommandFlags.FireAndForget);

            redis.ListRightPush(listKey, "abcdefghijklmnopqrstuvwxyz".Select(x => (RedisValue)x.ToString()).ToArray());

            var firstElement = redis.ListLeftPop(listKey);

            Console.WriteLine(firstElement); //output a, list is now bcdefghijklmnopqrstuvwxyz

            var lastElement = redis.ListRightPop(listKey);

            Console.WriteLine(lastElement); //output z, list is now bcdefghijklmnopqrstuvwxy

            redis.ListRemove(listKey, "c");                               

            Console.WriteLine(string.Concat(redis.ListRange(listKey))); //output is bdefghijklmnopqrstuvwxy   
            
            redis.ListSetByIndex(listKey, 1, "c");

            Console.WriteLine(string.Concat(redis.ListRange(listKey))); //output is bcefghijklmnopqrstuvwxy   

            var thirdItem = redis.ListGetByIndex(listKey, 3);

            Console.WriteLine(thirdItem); //output f  

            //lets clear it out
            var destinationKey = "destinationList";
            redis.KeyDelete(listKey, CommandFlags.FireAndForget);
            redis.KeyDelete(destinationKey, CommandFlags.FireAndForget);

            redis.ListRightPush(listKey, "abcdefghijklmnopqrstuvwxyz".Select(x => (RedisValue)x.ToString()).ToArray());

            var listLength = redis.ListLength(listKey);

            for (var i = 0; i 
So this covers the basic usage of Redish List Datatype, in the next blog post I will cover using Sets Datatype.
For the code please visit

https://github.com/taswar/RedisForNetDevelopers/tree/master/5.RedisList/RedisList
For previous Redis topics

Intro to Redis for .NET Developers
Redis for .NET Developer – Connecting with C#
Redis for .NET Developer – String Datatype
Redis for .NET Developer – String Datatype part 2
Redis for .NET Developer - Hash Datatype



Related posts:

Redis for .NET Developers – Redis Pipeline Batching
Redis for .NET Developers – Redis Sorted Sets Datatype
Redis for .NET Developers – Redis Sets Datatype
Redis for .NET Developers – Redis HyperLogLog Datatype