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CS-695 NoSQL DatabaseRedis (part 1 of 2)

Dr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck Cartledge

19 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 201519 Nov. 2015

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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

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Corrections and additions since last lecture.

Assignment #07 is available

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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 — — idtable bucket table collection — —row key-value row document node id key-valuerowid key — id — keycol. — col. fam. — — keyschema — — database —join — — DBRef — INT— — — — rel. id —

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Words of explanation.

The full text is available at:http://www.cs.odu.edu/~ccartled/Teaching/2015-Fall/NoSQL/Assignments/07/

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 beminimal based on how keys aredefined)

6 Plot data

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It is young

Redis means REmote Dictionary Server[4]

Some characterize it as amore of a data store than adata base

Based on key/value pairs,value can be:

Lists,Sets,Sorted strings,Hash tables,Other data types.

Commands for each datatype

Supports publish/subscribe,master/slave replication,persistence, scripting [1]

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What is in the backend?

Not to clear.

In memory data storage

Data is persisted at regularintervals

Slaves get copies frommaster

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Pre-CRUDy stuff

There is a server and a CLI.

Databases exist if the server is running.

Default port:6379

There are default databasesnumbered 0 through 15(inclusive)

At CLI, use the command:select 1 to select databasenumber 1

You can also telnet to theserver and issue commandsdirectly.

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CRUDy stuff

Creating data[3]

Redis is a key value data store, so . . .

Create a key1

Associate a value with the key

Multiple creation and sets can be combined as one operation

Format: SET key value valueExample: SET 7wks http://www.sevenweeks.org/Example: MSET gog http://www.google.com yahhttp://www.yahoo.com

1Many of the following examples use a colon (:) as a separator. The colondoes not have any significance.

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CRUDy stuff

Reporting data

Redis is a key value data store, so . . .

Values are reported based on the key used to search thedatabase

Wild cards can be used to search for keys

Multiple key value searches can be batched2

Format: GET key valueFormat: MGET key value key valueFormat: KEYS patternExample: GET 7wksExample: KEYS *

2Not recommended for production systems. Consider SCAN or sets.

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CRUDy stuff

Updating data

Redis is a key value data store, so . . .

Updating a key/value pair is simply using the old key with anew value, or

Appending a new string to the current value

Format: SET key value valueFormat: MSET key value value key value valueFormat: APPEND key value valueExample: SET 7wks http://www.sevenweeks.org/Example: MSET gog http://www.google.com yahhttp://www.yahoo.comExample: APPEND mykey “Hello”

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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 valueFormat: MDEL key valueExample: DEL 7wksExample: MDEL gog yah fiddle

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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). Ahash can have one or more values. The hash can be used to returnthe things it points at:

Single key/value pairs,

Multiple key/value pairs.

Format: HSET hash value key value valueFormat: HMSET hash value key value value key value value . . .Example: HSET myhash field1 “Hello”Example: HMSET user:eric name “Eric Redmond” passwords3cret

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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 valueFormat: HKEYS hash valueFormat: HGET hash value key valueExample: HVALS user:ericExample: HKEYS user:ericExample: HGET user:eric password

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A collection of operations that aren’t strictly CRUDy related

Redis does lists.

Lists are ordered values associated with one key value. Lists canact 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 valueExample: RPUSH mylist “hello” “world”Example: RPOP mylist

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A collection of operations that aren’t strictly CRUDy related

Redis does sets.

“Sets are unordered collections with no duplicatevalues and are an excellent choice for performing complexoperations between two or more key values, such asunions or intersections.”

Redmond and Wilson [2]

Format: SADD set value value value . . .Format: SMEMBERS set valueFormat: SINT set value1 set value2Example: SADD news nytimes.com pragprog.comExample: SADD tech pragprog.com apple.comExample: SMEMBERS newsExample: SINTER news tech

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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 commentsExample: PUBLISH comments “Check out this shortcoded site!7wks”

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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 akey-value pair. Except when you want to do math.

You can increment/decrement a value,

By an integer, or a float.

Format: INCR key valueFormat: INCRBY key value valueExample: INCR stats:page:aboutExample: INCRBY ratings:video:12333 5Lots of commands dealing with math, values, and time3.

3http://redis.io/commands

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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 typeof key to get the name of the operator for that type of key. Forexample:

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 time4.

4http://redis.io/commands

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What have we covered?

Reviewed assignment #07Covered some of the RedisCRUDy stuffNo class 26 Nov. 2015Next class 3 Dec. 2015Assignment #07 due beforenext class

Next time: continued Redis exploration

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References I

[1] Josiah L Carlson, Redis in action, Manning Publications Co., 2013.

[2] Eric Redmond and Jim R Wilson, Seven databases in seven weeks,Pragmatic Bookshelf, 2012.

[3] Redis Staff, Commands, http://redis.io/commands, 2015.

[4] Wikipedia Staff, Redis, 2015.