Dr. Chuck Cartledge. 19 Nov. 2015

Transcription

1 CS-695 NoSQL Database Redis (part 1 of 2) Dr. Chuck Cartledge 19 Nov /21

2 Table of contents I 1 Miscellanea 2 DB comparisons 3 Assgn. #7 4 Historical origins 5 Data model 6 CRUDy stuff 7 Other operations 8 Conclusion 9 References 2/21

3 Corrections and additions since last lecture. Assignment #07 is available 3/21

4 How different DBs compare to a RDBMS We have some terms to compare now[2] RDBMS K/V Columnar Doc. Graphic Redis DB. instance cluster cluster instance database namespace id table bucket table collection row key-value row document node id key-value rowid key id key col. col. fam. key schema database join DBRef INT rel. id 4/21

5 Words of explanation. The full text is available at: In general terms: 1 Design the database, particularially the definition of a key 2 Parse data 3 Populate the database 4 Query the database using the keys 5 Manipulate the results (may be minimal based on how keys are defined) 6 Plot data 5/21

6 It is young Redis means REmote Dictionary Server[4] Some characterize it as a more of a data store than a data base Based on key/value pairs, value can be: Lists, Sets, Sorted strings, Hash tables, Other data types. Commands for each data type Supports publish/subscribe, master/slave replication, persistence, scripting [1] 6/21

7 What is in the backend? Not to clear. In memory data storage Data is persisted at regular intervals Slaves get copies from master 7/21

8 Pre-CRUDy stuff There is a server and a CLI. Databases exist if the server is running. Default port:6379 There are default databases numbered 0 through 15 (inclusive) At CLI, use the command: select 1 to select database number 1 You can also telnet to the server and issue commands directly. 8/21

9 CRUDy stuff Creating data[3] Redis is a key value data store, so... Create a key 1 Associate a value with the key Multiple creation and sets can be combined as one operation Format: SET key value value Example: SET 7wks Example: MSET gog yah 1 Many of the following examples use a colon (:) as a separator. The colon does not have any significance. 9/21

10 CRUDy stuff Reporting data Redis is a key value data store, so... Values are reported based on the key used to search the database Wild cards can be used to search for keys Multiple key value searches can be batched 2 Format: GET key value Format: MGET key value key value Format: KEYS pattern Example: GET 7wks Example: KEYS * 2 Not recommended for production systems. Consider SCAN or sets. 10/21

11 CRUDy stuff Updating data Redis is a key value data store, so... Updating a key/value pair is simply using the old key with a new value, or Appending a new string to the current value Format: SET key value value Format: MSET key value value key value value Format: APPEND key value value Example: SET 7wks Example: MSET gog yah Example: APPEND mykey Hello 11/21

12 CRUDy stuff Deleting data Redis is a key value data store, so... Deleting a key/value pair is simply deleting the key Format: DEL key value Format: MDEL key value Example: DEL 7wks Example: MDEL gog yah fiddle 12/21

13 A collection of operations that aren t strictly CRUDy related A hash can contain multiple values Hash values are faster than simple keys (for some operations). A hash can have one or more values. The hash can be used to return the things it points at: Single key/value pairs, Multiple key/value pairs. Format: HSET hash value key value value Format: HMSET hash value key value value key value value... Example: HSET myhash field1 Hello Example: HMSET user:eric name Eric Redmond password s3cret 13/21

14 A collection of operations that aren t strictly CRUDy related Retrieving data associated with a hash. There are different ways of getting the a hashed value: Get all the values associated with a hash, Get all the keys associated with a hash, Get a single key/value pair associated with a hash. Format: HVALS hash value Format: HKEYS hash value Format: HGET hash value key value Example: HVALS user:eric Example: HKEYS user:eric Example: HGET user:eric password 14/21

15 A collection of operations that aren t strictly CRUDy related Redis does lists. Lists are ordered values associated with one key value. Lists can act as queues or stacks. Redis supports pushes, pops, and copy operations. Create a list, Add a value to the list (beginning or end), Remove a value (head or tail). (Only stack operations shown.) Format: RPUSH list value value value... Format: RPOP list value Example: RPUSH mylist hello world Example: RPOP mylist 15/21

16 A collection of operations that aren t strictly CRUDy related Redis does sets. Sets are unordered collections with no duplicate values and are an excellent choice for performing complex operations between two or more key values, such as unions or intersections. Redmond and Wilson [2] Format: SADD set value value value... Format: SMEMBERS set value Format: SINT set value1 set value2 Example: SADD news nytimes.com pragprog.com Example: SADD tech pragprog.com apple.com Example: SMEMBERS news Example: SINTER news tech 16/21

17 A collection of operations that aren t strictly CRUDy related Built in publish-subscribe support Consumers subscribes to a channel. A producer publishes to a channel. All updates to a channel are sent to all subscribers. Format: SUBSCRIBE channel [channel...] Format: PUBLISH channel message Example: SUBSCRIBE comments Example: PUBLISH comments Check out this shortcoded site! 7wks 17/21

18 A collection of operations that aren t strictly CRUDy related Redis knows math. Most of the time Redis doesn t care about the value in a key-value pair. Except when you want to do math. You can increment/decrement a value, By an integer, or a float. Format: INCR key value Format: INCRBY key value value Example: INCR stats:page:about Example: INCRBY ratings:video: Lots of commands dealing with math, values, and time /21

19 A collection of operations that aren t strictly CRUDy related There is a logic to naming Redis operators. Many times you can take the base operator and prepend the type of key to get the name of the operator for that type of key. For example: GET get a single value based on a single key MGET get multiple values based on multiple keys HMGET get multiple values based on a given hash value LPOP get and remove the first element in a list RPOP get and remove the last element in a list SPOP get some number of elements from a set Lots of commands (over 175) dealing with math, values, sets, persistence, and time /21

20 What have we covered? Reviewed assignment #07 Covered some of the Redis CRUDy stuff No class 26 Nov Next class 3 Dec Assignment #07 due before next class Next time: continued Redis exploration 20/21

21 References I [1] Josiah L Carlson, Redis in action, Manning Publications Co., [2] Eric Redmond and Jim R Wilson, Seven databases in seven weeks, Pragmatic Bookshelf, [3] Redis Staff, Commands, [4] Wikipedia Staff, Redis, /21