The regular subscriber API should work fine - there is no assumption on use-cases, and this should work fine. However, I do kinda agree that this is inbuilt functionality that could perhaps benefit from helper methods on the API, and perhaps a different delegate signature - to encapsulate the syntax of the keyapace notifications so that people don't need to duplicate it.
For that: I suggest you log an issue so that it doesn't get forgotten. First of all, it's important to check that Redis keyspace events are enabled. For example, events should be enabled on keys of type Set. The major difference between the two other than add 's String-only support is that put overwrites the previous presence of param with an existing key while add does not. In the above example, the web-server would only read the last value of key i.
As such, sorted sets are suitable when there are tons of updates. Because of this characteristic a common use case is leader boards. The typical application is a Facebook game where you combine the ability to take users sorted by their high score, plus the get-rank operation, in order to show the top-N users, and the user rank in the leader board e.
Bitmaps are not an actual data type, but a set of bit-oriented operations defined on the String type. Since strings are binary safe blobs and their maximum length is MB, they are suitable to set up to 2 32 different bits. Bit operations are divided into two groups: constant-time single bit operations, like setting a bit to 1 or 0, or getting its value, and operations on groups of bits, for example counting the number of set bits in a given range of bits e.
One of the biggest advantages of bitmaps is that they often provide extreme space savings when storing information. For example in a system where different users are represented by incremental user IDs, it is possible to remember a single bit information for example, knowing whether a user wants to receive a newsletter of 4 billion of users using just MB of memory.
The SETBIT command takes as its first argument the bit number, and as its second argument the value to set the bit to, which is 1 or 0. The command automatically enlarges the string if the addressed bit is outside the current string length. Out of range bits addressing a bit that is outside the length of the string stored into the target key are always considered to be zero.
For example imagine you want to know the longest streak of daily visits of your web site users. You start counting days starting from zero, that is the day you made your web site public, and set a bit with SETBIT every time the user visits the web site.
This way for each user you have a small string containing the visit information for each day. Bitmaps are trivial to split into multiple keys, for example for the sake of sharding the data set and because in general it is better to avoid working with huge keys. A HyperLogLog is a probabilistic data structure used in order to count unique things technically this is referred to estimating the cardinality of a set. Usually counting unique items requires using an amount of memory proportional to the number of items you want to count, because you need to remember the elements you have already seen in the past in order to avoid counting them multiple times.
The magic of this algorithm is that you no longer need to use an amount of memory proportional to the number of items counted, and instead can use a constant amount of memory! While you don't really add items into an HLL, because the data structure only contains a state that does not include actual elements, the API is the same:. An example of use case for this data structure is counting unique queries performed by users in a search form every day.
Redis is also able to perform the union of HLLs, please check the full documentation for more information. There are other important things in the Redis API that can't be explored in the context of this document, but are worth your attention:.
This tutorial is in no way complete and has covered just the basics of the API. Read the command reference to discover a lot more. The following is the list of all the data structures supported by Redis, which will be covered separately in this tutorial: Binary-safe strings. Lists: collections of string elements sorted according to the order of insertion. They are basically linked lists. Sets: collections of unique, unsorted string elements. Sorted sets, similar to Sets but where every string element is associated to a floating number value, called score.
The elements are always taken sorted by their score, so unlike Sets it is possible to retrieve a range of elements for example you may ask: give me the top 10, or the bottom Hashes, which are maps composed of fields associated with values.
Both the field and the value are strings. This is very similar to Ruby or Python hashes. Bit arrays or simply bitmaps : it is possible, using special commands, to handle String values like an array of bits: you can set and clear individual bits, count all the bits set to 1, find the first set or unset bit, and so forth. HyperLogLogs: this is a probabilistic data structure which is used in order to estimate the cardinality of a set. Don't be scared, it is simpler than it seems See later in the HyperLogLog section of this tutorial.
Streams: append-only collections of map-like entries that provide an abstract log data type. They are covered in depth in the Introduction to Redis Streams. A few other rules about keys: Very long keys are not a good idea. For instance a key of bytes is a bad idea not only memory-wise, but also because the lookup of the key in the dataset may require several costly key-comparisons. Even when the task at hand is to match the existence of a large value, hashing it for example with SHA1 is a better idea, especially from the perspective of memory and bandwidth.
Very short keys are often not a good idea. There is little point in writing "uflw" as a key if you can instead write "userfollowers". The latter is more readable and the added space is minor compared to the space used by the key object itself and the value object. While short keys will obviously consume a bit less memory, your job is to find the right balance. Try to stick with a schema. For instance "object-type:id" is a good idea, as in "user". Dots or dashes are often used for multi-word fields, as in "commentreply.
The maximum allowed key size is MB. A few quick info about Redis expires: They can be set both using seconds or milliseconds precision. However the expire time resolution is always 1 millisecond. Information about expires are replicated and persisted on disk, the time virtually passes when your Redis server remains stopped this means that Redis saves the date at which a key will expire.
Communication between processes, using a consumer-producer pattern where the producer pushes items into a list, and a consumer usually a worker consumes those items and executed actions. Any difference between these two commands? Improve this question. Add a comment. Active Oldest Votes. Improve this answer. Tim Cooper Tim Cooper k 36 36 gold badges silver badges bronze badges. From the link that you have shared, it also says that set also stores integers internally as strings.
So, Can it be said that integers can't be natively stored in redis? Sign up or log in Sign up using Google. Should the complete fix be for the next major release, as considering returning 1 instead of "1" be a possible breaking change? I sent in a fix here: Came across this today when we tried switching to redis. Why not just consistently serialize everything before storing it, like in the file and memcached stores?
A quick test shows me that the outcome of Cache::put 'test', with the cache drivers file , array , database , apc and memcached all return an integer, but for redis I get a string. These are some reasons for the inconsistency, although I don't think they are good enough:. I suggest to update Redis driver to only skip serialization if the data type is int, but not when the data is float or a numeric string.
This change probably is a breaking change for some other applications. Some configuration options may be helpful to make things BC and let users to store floats without serialization as well. It all boils down to the fact that redis don't have its own numerical type I suppose.
But I was not really aware of this before trying it out. I feel like this should be mentioned in the documentation somewhere, that integers and float types will not be preserved when using redis? So switching from anyone of the other cache providers to redis could easily cause problems in type-aware applications. But I'd much rather have consistency between caching providers than how it is right now.
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