Cassandra is a scalable, masterless database. It uses a column family data structure with rows and columns mapped to keys. Data is stored in SSTables. Cassandra supports composite primary keys and secondary indexes. Examples show creating tables, inserting data, and performing queries. Normalization and denormalization techniques are discussed. References provide additional resources on Cassandra data modeling best practices.

1. Cassandra data modeling
Andrey Kozlov

2. Cassandra features
● “Masterless” architecture
● Scalable
● Fast inserts

3. SSTable for storing data

4. Cassandra Data Structure
● Column Family
o Row
 Column
Map<RowKey, Map<ColumnKey, ColumnValue>>

5. Simple Data Table
CREATE TABLE employees (
name text,
age int,
role text,
PRIMARY KEY (name));
INSERT INTO employees (name, age,
role) VALUES ('john', 37, 'dev');
INSERT INTO employees (name, age,
role) VALUES ('eric', 38, 'ceo');
name | age | role
------+-----+------
eric | 38 | ceo
john | 37 | dev
age role
john 37 dev
age role
eric 38 ceo

6. Data Table with Composite key
CREATE TABLE employees (
company text,
name text,
age int,
role text,
PRIMARY KEY (company,name)
);
company | name | age | role
---------+------+-----+------
OSC | eric | 38 | ceo
OSC | john | 37 | dev
RKG | anya | 29 | lead
RKG | ben | 27 | dev
RKG | chan | 35 | ops
eric:age eric:role john:age joghn:role
OSC 38 dev 37 dev
anya:age anya:role ben:age ben:role chad:age chad:role
RKG 29 lead 27 dev 35 ops

7. Select by Composite key
CREATE TABLE no_column_skip(
a int,
b int,
c int,
d int,
e int,
PRIMARY KEY (a, b, c, d));
Valid:
SELECT ... WHERE a=0 AND (b, c) > (1, 2)
SELECT ... WHERE a=0 AND (b) > (3)
SELECT ... WHERE a=0 AND (b, c, d) > (1, 2, 5)
Not Valid:
SELECT ... WHERE a=0 AND (b, d) > (1, 2)
SELECT ... WHERE a=0 AND (c) > (3)
SELECT ... WHERE (b, c, d) > (1, 2)

8. Many to Many

9. Normalized with one additional table

10. Normalized with two tables

11. Particular denormalization

12. Particular denormalization with composite
keys

13. Event data for time period

14. Event data for time period

15. Secondary index template
CREATE TABLE playlists (
id uuid,
song_order int,
song_id uuid,
title text,
album text,
artist text,
PRIMARY KEY (id, song_order ) );
INSERT INTO playlists (id, song_order, song_id, title, artist, album)
VALUES (playlist_1, 1, song_1, 'La Grange', 'ZZ Top', 'Tres Hombres');
INSERT INTO playlists (id, song_order, song_id, title, artist, album)
VALUES (playlist_1, 2, song_2, 'Moving in Stereo', 'Fu Manchu', 'We Must Obey');
INSERT INTO playlists (id, song_order, song_id, title, artist, album)
VALUES (playlist_2, 3, song_3, 'Hang On', 'Fu Manchu', 'California Crossing');
CREATE INDEX ON playlists( artist );

16. Secondary index template
id song_oder song_id title artist album
playlist_1 1 song_1 La Grange ZZ Top Tres Hombres
2 song_2 Moving in Stereo Fu Manchu We Must Obey
...
playlist_2 1 song_3 Hang On Fu Manchu California Crossing
...
artist playlist_id song_order
ZZ Top playlist_1 1
...
Fu manchu playlist_1 2
playlist_2 1
...

17. Secondary index distribution

18. Thank you for attention

19. References
• https://ru.wikipedia.org/wiki/BigTable
• http://www.datastax.com/documentation/cassandra/2.1/cassandra/gettingStartedCassandraIntro.ht
ml
• http://www.datastax.com/documentation/cassandra/2.1/cassandra/dml/dml_write_path_c.html
• http://www.datastax.com/documentation/cassandra/2.1/cassandra/dml/architectureClientRequests
Read_c.html
• http://www.datastax.com/documentation/cassandra/2.1/cassandra/dml/dml_config_consistency_c.
html#concept_ds_umf_5xx_zj__table_vs2_f2s_gk
• http://rollerweblogger.org/roller/entry/composite_keys_in_cassandra
• http://www.ebaytechblog.com/2012/07/16/cassandra-data-modeling-best-practices-part-
1/#.VPNAcvmUeUT
• https://highlyscalable.wordpress.com/2012/03/01/nosql-data-modeling-techniques/
• http://habrahabr.ru/post/203200/