1. Apache Cassandra for the SQLServer DBA

2. It’s all about me...

3. Case studies

4. History Originally developed at Facebook for its Inbox Search feature
Released to Google Code as open source in 2006
Became an Apache Incubator project in 2008
Top-level project in 2010
Named after a character from geek Greek mythology
(something about a curse on an Oracle)

5. CAP theorem Cassandra is “AP” Not to say that C isn’t possible
Consistency is ‘tune-able’
Consistency
Availability
Partition tolerance 5

6. Peer-to-peer
Cluster
Nodes
Token Ranges / vNodes 6

7. Token Assignment
Token ranges

8. Availability / Tolerance
1 - 20 24 F 78 K 24 F
RF = 3 78 K 24 F 78 K

9. Consistency Levels ALL – All replicas must respond
ANY – Closest available replica
ONE – Closest available repl… wait….what ??!??
QUORUM – for RF3, 2 out of 3
LOCAL_QUORUM – for RF3, 2 out of…. wait… not again ??!!??
…plus some others that are less easy to describe….
ANY is for write consistency, ONE is for read.

10. Consistency ALL
A !
A !
32 = A ?
A !

11. Consistency ONE
A !
A !
32 = A?
A !

12. Consistency QUORUM
B !
A !
32=B ?
B !

13. Write path
Commit Log
Data
MemTable
SSTable

14. Write path 1 A 2 B 4 c 1 A 2 B 3 A 4 c 1 A 2 B 3 A 5 F 4 c 5 F 5 F 4 c

15. Compaction Worth mentioning here, so I have
Quite complex to cover in less than an hour
Optimises SStables
based on Level, Size-tier (default), or Time- Window strategies
Has a major impact on your storage requirements
It happens…

16. Demo – Creating a keyspace

17. Design for speed Table per query Partition per query

18. CQL “SELECT * FROM ?? WHERE x = “ INSERT UPDATE DELETE
…it’s quite simple, really…

19. Simple datatypes 17 data types, 12 of which are most common CQL Type
Constants
Description
bigint
integers
64-bit signed long
counter
Distributed counter value (64-bit long)
float
integers, floats
32-bit IEEE-754 floating point Java type
int
32-bit signed integer
text
strings
UTF-8 encoded string
timestamp
integers, strings
Date plus time, encoded as 8 bytes since epoch (01/01/1970)
timeuuid
uuids
Type 1 UUID only
uuid
A UUID in standard UUID format
varchar
list
n/a
A collection of one or more ordered elements
map
A JSON-style array of literals: { literal : literal, literal : literal ... }
set
A collection of one or more elements

20. Consider this table… CREATE TABLE pubs (id INT, title TEXT,
author TEXT,
genre TEXT,
published INT,
PRIMARY KEY (id) );

21. Cassandra data layout
Cells
Key
Value
Partitions
Partition Key

22. Primary Key determines partition key
PRIMARY KEY (id)

23. Composite Partition Keys
CREATE TABLE pubs_by_title_year
(title TEXT,
author TEXT,
genre TEXT,
published INT,
PRIMARY KEY ((title, published)) );
Note double brackets on PRIMARY KEY – we’ll come on to that later. 25

24. Clustering columns
CREATE TABLE pubs_by_year_title
(published INT,
title TEXT,
author TEXT,
genre TEXT,
id INT,
PRIMARY KEY ((published), title) );
Clustering columns need to be part of the Primary Key to be searchable, but not part of the Partition Key.
They divide the rows between the partitions. 26

25. Effect on layout 2014 I did DBCC you coming : author
I did DBCC you coming : Genre
O. DeeBeaSea
Horror
Slow train to SOS_Scheduler : author
Slow train to SOS_Scheduler : Genre
R.T. Fishall
Humour
2015
Mamma Mia ! That index… !! : author
Mamma Mia ! That index… !! : Genre
Richard Munn
Horror
Plan the plan's planny plan : author
Plan the plan's planny plan : Genre
A. Noob
Management

26. Demo – creating tables and adding data

27. Things to remember INSERT vs. UPDATE Tombstones
Garbage collection removes tombstoned records – default interval 10 days. Cleaned up on compaction
Hinted hand-off
Anti-entropy operations (read-repair)

28. Things you can’t do JOIN * Use Foreign Keys Implement 3rd Normal form
Actually, throw away any thought of normalisation
Add additional indexes *
Create Stored Procedures – use BATCH instead
Maths (except min, max, avg, sum, and count)
Use non-key columns as search predicates

29. Demo - Let’s do some shenanigans….

30. exit;