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 < listLength ; i++)
            {
                var val = redis.ListRightPopLeftPush(listKey, destinationKey);

                Console.Write(val);    //output zyxwvutsrqponmlkjihgfedcba
            }
           
            Console.ReadKey();
        }
    }

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 < listLength ; i++)

{

var val = redis.ListRightPopLeftPush(listKey, destinationKey);

Console.Write(val); //output zyxwvutsrqponmlkjihgfedcba

}

Console.ReadKey();

}

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

Redis for .NET Developer – Hash Datatype

2 Comments

Alireza
December 19, 2018 at 6:32 am

Hi. this is good blog and ,this is good tutorial on Redis for .net Developers.
where can get a complete documentation ,beginner to advance about Redis for .net Developer
thanks
taswar
December 19, 2018 at 10:24 am

Thanks I intend to release a free ebook for all the redis items I have here probably you will be able to download from here in 2019. Will update you once I have it, also feel free to join my mailing list I will update everyone on my mailing list.

Redis for .NET Developers – Redis List Datatype

Redis List Datatype – Operations

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Redis for .NET Developers – Redis List Datatype

Redis List Datatype – Operations

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Opinions are my own and not the views of my employer

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