CQL, past, present, and future, presented to Big Data DC on October 17, 2011

1. CQL In Cassandra 1.0 (and beyond)
Big Data DC Meetup #5
October 17, 2011
Eric Evans
eric@acunu.com
@jericevans, @acunu

2. ● Overview, history, motivation
● Changes in CQL 2.0 (Cassandra 1.0)
● Coming soon (?)
● Drivers status

3. What?
● Cassandra Query Language
● aka CQL
● aka /ˈsēkwəl/
● Exactly like SQL (except where it's not)
● Introduced in Cassandra 0.8.0
● Ready for production use

4. SQL? Almost.
–- Inserts or updates
INSERT INTO Standard1 (KEY, col0, col1)
VALUES (key, value0, value1)
vs.
–- Inserts or updates
UPDATE Standard1
SET col0=value0, col1=value1 WHERE KEY=key

5. SQL? Almost.
–- Get columns for a row
SELECT col0,col1 FROM Standard1 WHERE KEY=key
–- Range of columns for a row
SELECT col0..colN
FROM Standard1 WHERE KEY=key
–- First 10 results from a range of columns
SELECT FIRST 10 col0..colN
FROM Standard1 WHERE KEY=key
–- Invert the sorting of results
SELECT REVERSED col0..colN
FROM Standard1 WHERE KEY=key

6. Why?

7. Interface Instability

8. (Un)ease of use
Column col = new Column(ByteBuffer.wrap(“name”.getBytes()));
col.setValue(ByteBuffer.wrap(“value”.getBytes()));
col.setTimestamp(System.currentTimeMillis());
ColumnOrSuperColumn cosc = new ColumnOrSuperColumn();
cosc.setColumn(col);
Mutation mutation = new Mutation();
Mutation.setColumnOrSuperColumn(cosc);
List mutations = new ArrayList<Mutation>();
mutations.add(mutation);
Map mutations_map = new HashMap<ByteBuffer, Map<String, List<Mutation>>>();
Map cf_map = new HashMap<String, List<Mutation>>();
cf_map.set(“Standard1”, mutations);
mutations.put(ByteBuffer.wrap(“key”.getBytes()), cf_map)

9. CQL
INSERT INTO Standard1 (KEY, col0)
VALUES (key, value0)

10. Why? How about...
● Better stability guarantees
● Easier to use (you already know it)
● Better code readability / maintainability

11. Why? How about...
● Better stability guarantees
● Easier to use (you already know it)
● Better code readability / maintainability
● Irritates the NoSQL purists

12. Why? How about...
● Better stability guarantees
● Easier to use (you already know it)
● Better code readability / maintainability
● Irritates the NoSQL purists
● (Still )irritates the SQL purists

14. CQL 2.0

15. Wait, 2.0? You call that stable?
Yes yes, but...
● We had a few FUBARs in the first pass
● Not the norm, honest
● It's a mulligan
● Look, cats!

16. Changed in 2.0
● SELECT count(...) FROM now returns row,
not column count
● Terms / Types
● bytea became blob
● int became 4-bytes (was arbitrary precision)
● date became timestamp

17. Also new (but not breaking)
● Named keys (virtual columns)
● Counters
● Complete DDL support
● Timestamps and TTLs

18. Named Keys
–- An unnamed key uses the KEY keyword
CREATE TABLE Standard1
(KEY text PRIMARY KEY)
–- But you can also name one like so...
CREATE TABLE Standard1
(username text PRIMARY KEY)
–- The name will also be used in results!
SELECT email FROM Standard1
WHERE username = 'jericevans'

19. Counters
–- Counter increment
UPDATE Standard1
SET acount = acount + 1 WHERE KEY = key
–- Counter decrement
UPDATE Standard1
SET acount = acount - 1 WHERE KEY = key
–- 1 not enough? Go nuts.
UPDATE Standard1
SET acount = acount + 9 WHERE KEY = key

20. Timestamps and TTLs
–- Inserts or updates
UPDATE CFam USING TIMESTAMP 131851901600
SET col0=value0, col1=value1 WHERE KEY=key
–- Inserts or updates
UPDATE CFam USING TTL 86400
SET col0=value0, col1=value1 WHERE KEY=key

21. Coming Soon(ish)

22. Roadmap
● Prepared statements (CASSANDRA-2475)
● Compound columns (CASSANDRA-2474)
● Custom transport / protocol (CASSANDRA-2478)
● Performance testing (CASSANDRA-2268)
● Schema introspection (CASSANDRA-2477)
● Multiget support (CASSANDRA-3069)

23. Drivers

24. Drivers
● Hosted on Apache Extras (Google Code)
● Tagged cassandra and cql
● Licensed using Apache License 2.0
● Conforming to a standard for database
connectivity (if applicable)
● Coming soon, automated testing and
acceptance criteria

25. Drivers
Driver Platform Status
cassandra-jdbc Java Good
cassandra-dbapi2 Python Good
cassandra-ruby Ruby New
cassandra-pdo PHP New
cassandra-node Node.js Good
http://code.google.com/a/apache-extras.org/hosting/search?q=label%3aCassandra

26. The End