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1 B4M36DS2, BE4M36DS2: Database Systems 2 h p:// Prac cal Class 7 Redis Mar n Svoboda mar n.svoboda@fel.cvut.cz Charles University, Faculty of Mathema cs and Physics Czech Technical University in Prague, Faculty of Electrical Engineering

2 Redis Redis In-memory data structure store Open source, master-slave replica on architecture, sharding, high availability, various persistence levels, h p://redis.io/ Developed by Redis Labs Implemented in C First release in 2009 B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

3 Redis Func onality Standard key-value store Support for structured values (e.g. lists, sets, ) Time-to-live Transac ons Real-world users Twi er, GitHub, Pinterest, StackOver ow, Flicker, B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

4 Data Model Data model Instance databases objects Database = collec on of objects Databases do not have names but integer iden ers Object = key-value pair Key is a string (i.e. any binary data) Values can be Atomic: string Structured: list, set, sorted set, hash B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

5 Data Types Available data types String The only atomic data type May contain any binary data (e.g. string, integer counter, PNG image, ) Maximal allowed size is 512 MB List Ordered collec on of strings Elements should preferably be read / wri en at the head / tail B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

6 Data Types Available data types Set Unordered collec on of strings Duplicate values are not allowed Sorted set Ordered collec on of strings The order is given by a score ( oa ng number value) associated with each element (from the smallest to the greatest score) Hash Associa ve map between string elds and string values Field names have to be mutually dis nct B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

7 Interface command line client Two modes are available Basic Commands are passed as standard command line arguments E.g. Batch processing is possible as well E.g. Interac ve Users type database commands at the prompt RESP (REdis Serializa on Protocol) B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

8 First Steps Connect to our NoSQL server SSH / SFTP and PuTTY / WinSCP nosql.ms.m.cuni.cz:42222 Check Redis status Open Redis client (interac ve mode) Select your database Your database number: sent by B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

9 First Steps Basic Commands Provides basic informa on about Redis commands Clears the terminal screen Deletes all the keys in the currently selected database Saves the current dataset (asynchronously, on background) I.e. stores the database snapshot to the hard drive Closes the connec on B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

10 Strings Basic commands inserts / replaces a given string returns a given string String opera ons returns a string length appends a value at the end of a string returns a substring Both the boundaries are considered to be inclusive Posi ons start at 0 Nega ve o sets for posi ons star ng at the end replaces a substring Binary 0 are padded when the original string is not long enough B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

11 Strings Counter opera ons Increments / decrements a value by 1 Increments / decrements a value by a given amount B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

12 Objects Object querying determines whether a key exists nds all the keys matching a pa ern (*,?, ) E.g. Modi ca on of objects removes a given object / objects changes key of a given object Type informa on determines the type of a given object Types:,,, and B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

13 Vola le Objects Keys with limited me to live When a speci ed meout elapses, a given object is removed Works with any data type Commands Sets a meout for a given object, i.e. makes the object vola le Can be called repeatedly to change the meout Returns the remaining me to live for a key that has a meout Removes the exis ng meout, i.e. makes the object persistent B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

14 Lists Inser on of new elements Adds a new element to the head / tail Inserts an element before / a er another one Retrieval of elements Removes and returns the rst / last element B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

15 Lists Retrieval of elements gets an element by its index The rst item is at posi on 0 Nega ve posi ons are allowed as well gets a range of elements Removal of elements Removes a given number of matching elements from a list Posi ve / nega ve = moving from head to tail / tail to head 0 = all the items are removed Other opera ons gets the length of a list B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

16 Sets Basic opera ons Adds an element / elements into a set Removes an element / elements from a set Data querying Determines whether a set contains a given element gets all the elements of a set Other opera ons gets the number of elements in a set B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

17 Sets Set opera ons Calculates and returns a set union / intersec on / di erence of two or more sets B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

18 Hashes Basic opera ons sets the value of a hash eld gets the value of a hash eld Batch alterna ves Sets values of mul ple elds of a given hash Gets values of mul ple elds of a given hash B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

19 Hashes Field retrieval opera ons determines whether a eld exists gets all the elds and values Individual elds and values are interleaved gets all the elds in a given hash gets all the values in a given hash Other opera ons Removes a given eld / elds from a hash returns the number of elds in a given hash B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

20 Sorted Sets Basic opera ons Inserts one element / mul ple elements into a sorted set Removes one element / mul ple elements from a sorted set Working with score Gets the score associated with a given element Increments the score of a given element B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

21 Sorted Sets Retrieval of elements Returns all the elements within a given range based on posi ons Returns all the elements within a given range based on scores Other opera ons Gets the overall number of all elements Counts all the elements within a given range based on score B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis

22 References Commands h p://redis.io/commands Documenta on h p://redis.io/documenta on Data types h p://redis.io/topics/data-types B4M36DS2, BE4M36DS2: Database Systems 2 Prac cal Class 7: Redis