Cassandra 2.2 & 3.0

Victor Coustenoble@vizanalytics

2.2 & 3.0

http://www.datastax.com/dev/blog/cassandra-2-2

Where did 2.2 come from?

Don't start Thrift rpc by default (CASSANDRA-9319)

New features• 2.2- JSON- User defined functions- User defined aggregates- Other useful features- http://docs.datastax.com/en/cassandra/2.2/cassandra/features.html

- http://www.datastax.com/dev/blog/cassandra-2-2

• 3.0- New storage engine (8099)- A new way to denormalise/duplicate : Materialized View

So who’s taken some data out of C* and serialised it as JSON?

Hello JSON• create TABLE user (username text primary key,

first_name text , last_name text , emails set<text> , country text);

• INSERT INTO user JSON '{"username": "chbatey", "first_name":"Christopher", "last_name": "Batey", “emails":["[email protected]"]}';

Goodbye Serialisation!

JSON + User Defined Types• CREATE TYPE movie (title text, time timestamp,

description text);• ALTER TABLE user ADD movies set<frozen<movie>>;• UPDATE user SET movies = {{ title:'Batman', time:'2011-02-03T04:05:00+0000', description: 'This film rocks' }} where username = 'chbatey';

Out it comes

• Run code on the server !Dangerous!- Disabled by default

• Java + Java Script supported out of the box

• Any language that supports the Java Scripting API (Java, Javascript, Ruby, Python …)

User Defined Functions

UDF example

CREATE TABLE user ( username text primary key, first_name text , last_name text , emails set<text> , country text);

Concat function

CREATE FUNCTION name ( first_name text, last_name text ) CALLED ON NULL INPUT RETURNS text LANGUAGE java AS ‘return first_name + " " + last_name;’;

cqlsh:twotwo> select name(first_name, last_name) FROM user;

twotwo.name(first_name, last_name)------------------------------------ Victor Coustenoble

User Defined Aggregates

CREATE AGGREGATE average ( int ) SFUNC averageState STYPE tuple<int,bigint> FINALFUNC averageFinal INITCOND (0, 0);

Called for every row state passed between

Initial state

Return type (CQL)

Optional function called onfinal state

State function (like a UDF)

CREATE FUNCTION averageState ( state tuple<int,bigint>, value int ) CALLED ON NULL INPUT RETURNS tuple<int,bigint> LANGUAGE java AS ' if (value != null) { state.setInt(0, state.getInt(0)+1); state.setLong(1, state.getLong(1)+val.intValue()); } return state; ';

Type Columns

Final function

CREATE FUNCTION averageFinal ( state tuple<int,bigint> ) CALLED ON NULL INPUT RETURNS double LANGUAGE java AS ' if (state.getInt(0) == 0) return null; double r = state.getLong(1) / state.getInt(0); return Double.valueOf(r); ';

State typeOverall return type

Putting it all together

Customer events

CREATE AGGREGATE count_by_type(text) SFUNC countEventTypes STYPE map<text, int> INITCOND {};

CREATE FUNCTION countEventTypes( state map<text, int>, type text ) CALLED ON NULL INPUT RETURNS map<text, int> LANGUAGE java AS ' Integer count = (Integer) state.get(type); if (count == null) count = 1; else count = count + 1; state.put(type, count); return state; ';

Customer events

Built in aggregates• count• max• min• avg• sum

https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/cql3/functions/AggregateFcts.java

Built in time functions

https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/cql3/functions/TimeFcts.java

Built in aggregates in action

1/ “Materialised views” with Spark

2/ Pure C*

2/ Pure C*

JSON, UDF and UDA available in DevCenter

Roles based Access

Other bits and pieces…• Compressed commit log• Resumable bootstrapping• New types- smallint - short- tinyint - byte- date - time

• Warnings now sent back to client- batch too large

http://www.datastax.com/dev/blog/new-in-cassandra-3-0-materialized-views

New Storage Engine• CASSANDRA-8099• More efficient storage• Aware of CQL structure• Reduce sstable size• Reduce memory used• …

Customer events tableCREATE TABLE if NOT EXISTS customer_events ( customer_id text, staff_id text, store_type text, time timeuuid , event_type text, PRIMARY KEY (customer_id, time))

create INDEX on customer_events (staff_id) ;

Indexes to the rescue?customer_id time staff_idchbatey 2015-03-03 08:52:45 trevorchbatey 2015-03-03 08:52:54 trevorchbatey 2015-03-03 08:53:11 billchbatey 2015-03-03 08:53:18 bill

rusty 2015-03-03 08:56:57 bill

rusty 2015-03-03 08:57:02 bill

rusty 2015-03-03 08:57:20 trevor

staff_id customer_idtrevor chbateytrevor chbateybill chbateybill chbateybill rustybill rustytrevor rusty

Secondary index are local • The staff_id partition in the secondary index is not

distributed like a normal table• The secondary index entries are only stored on the node

that contains the customer_id partition

Indexes to the rescue?

staff_id customer_idtrevor chbateytrevor chbateybill chbateybill chbatey

staff_id customer_idbill rusty

bill rusty

trevor rusty

A B

chbatey rusty

customer_id time staff_idchbatey 2015-03-03 08:52:45 trevorchbatey 2015-03-03 08:52:54 trevorchbatey 2015-03-03 08:53:11 billchbatey 2015-03-03 08:53:18 bill

rusty 2015-03-03 08:56:57 bill

rusty 2015-03-03 08:57:02 bill

rusty 2015-03-03 08:57:20 trevor

customer_events tablestaff_id customer_idtrevor chbateytrevor chbateybill chbateybill chbateybill rusty

bill rusty

trevor rusty

staff_id index

Do it yourself index ?CREATE TABLE if NOT EXISTS customer_events ( customer_id text, staff_id text, store_type text, time timeuuid , event_type text, PRIMARY KEY (customer_id, time))

CREATE TABLE if NOT EXISTS customer_events_by_staff ( customer_id text, staff_id text, store_type text, time timeuuid , event_type text, PRIMARY KEY (staff_id, time))

1.2 Logged batches

Cclient

C BATCH LOG

BL-R

BL-R

BL-R: Batch log replica

Pattern• Write only:- Duplicate with a different primary key- (Optional) Logged batch for eventual consistency

• Full updates:- No real difference

• Partial updates:- No staff id in update?

Score Data ModelCREATE TABLE scores( user TEXT, game TEXT, year INT, month INT, day INT, score INT, PRIMARY KEY (user, game, year, month, day))

Materialized ViewsCREATE MATERIALIZED VIEW alltimehigh AS

SELECT user FROM scores WHERE game IS NOT NULL AND

score IS NOT NULL ANDuser IS NOT NULL ANDyear IS NOT NULL ANDmonth IS NOT NULL ANDday IS NOT NULL

PRIMARY KEY (game, score, user, year, month, day) WITH CLUSTERING ORDER BY (score desc)

Materialized ViewsINSERT INTO scores (user, game, year, month, day, score) VALUES ('pcmanus', 'Coup', 2015, 05, 01, 4000)INSERT INTO scores (user, game, year, month, day, score) VALUES ('jbellis', 'Coup', 2015, 05, 03, 1750)INSERT INTO scores (user, game, year, month, day, score) VALUES ('yukim', 'Coup', 2015, 05, 03, 2250)INSERT INTO scores (user, game, year, month, day, score) VALUES ('tjake', 'Coup', 2015, 05, 03, 500)INSERT INTO scores (user, game, year, month, day, score) VALUES ('jmckenzie', 'Coup', 2015, 06, 01, 2000)INSERT INTO scores (user, game, year, month, day, score) VALUES ('iamaleksey', 'Coup', 2015, 06, 01, 2500)INSERT INTO scores (user, game, year, month, day, score) VALUES ('tjake', 'Coup', 2015, 06, 02, 1000)INSERT INTO scores (user, game, year, month, day, score) VALUES ('pcmanus', 'Coup', 2015, 06, 02, 2000)

SELECT user, score FROM alltimehigh WHERE game = 'Coup'user | score-----------+------- pcmanus | 4000iamaleksey | 2500 yukim | 2250 jmckenzie | 2000 pcmanus | 2000 jbellis | 1750 tjake | 1000 tjake | 500

KillrWeather data model

Combining aggregates + MVs

How it works…

http://www.datastax.com/dev/blog/new-in-cassandra-3-0-materialized-viewshttps://issues.apache.org/jira/browse/CASSANDRA-6477

For more details

Fine print

• All Primary Key columns must be present in your view• If the part of your primary key is NULL then it won't

appear in the materialised view• Performance will be a factor!- More operations to complete (read-before-write,

consistency check …)- Batch writes for MV

• Bad for low cardinality data (hot spot)

Conclusions

• We still denormalise and duplicate to achieve scalability and performance

• We just let C* do it for us :)

Find Out More

• Documentation: http://www.datastax.com/docs

• Developer Blog: http://www.datastax.com/dev/blog

• Academy: https://academy.datastax.com

• Community Site: http://planetcassandra.org