CQL has evolved over time from an alternative to the Thrift API in Cassandra 0.8 to become the primary interface for Cassandra queries. It started with basic keywords like SELECT, UPDATE, and DELETE in V1.0 and has expanded functionality with each new version, including features in the unreleased V3 that could change before its finalization. While CQL aims to use familiar SQL syntax, there is some debate around its design and some terminology challenges as it rapidly develops to match Cassandra's growth from a small project. The document argues that despite controversies, CQL is ready for production use based on the author's experience with their 150GB per day cluster.

1. CQL, ‘THEN AND NOW’
Cassandra London
Feb, 20th 2012
Courtney Robinson
courtney@crlog.info
@zcourts
http://crlog.info
github.com/zcourts

2. IN THE BEGINNING
 ...horrible thrift code here

3. AND THEN THERE WAS...
 ...better looking hector code here

4. NOT QUITE
 ...slightly better (my hector wrapper)
 Still not excellent, but better (I think)
 Remember, not all languages have clients as good as
hector.
 Usability varied* vastly between the supported languages
 So much so I chose Play! Framework over PHP for a
small admin front end.

5. YAY! CQL TO SAVE THE DAY!
 ...because not everyone has an Ops team to torture.
 Upgrading wasn’t such a pain, little or no code breaking
 CQL offered stability (ish)...

6. BRIEF INTRO – WHAT IS IT?
 Simple, structured query language for Cassandra
 Very much SQL (except where it can’t be)
 Alternative to the Thrift RPC API.
 Available since Cassandra version 0.8.0
 In keeping with Eric Evan’s attempts, just pronounce it
‘siːkwəl’
 Isn’t much* to say about CQL, its does what it says on the
tin

7. CONTROVERSY, POLITICS AND OUT RIGHT BI***ING
 Always been an outspoken (some more than others)
few against it
 Never been much in the way of facts to backup their claims
such as:
 SQL like syntax is a very idiomatic RDMS thing.
 Parsing a string will be slow, just because its parsing a string
and for no other reason
 The aforementioned will make Cassandra ‘as vulnerable’ to
injection
 ...etc (all speculation mind you)

8. SO WHAT, CAN I USE THIS THING?
 CQL is very much production ready.
 If anyone tells you otherwise, ask them to prove its not before you
decide.
 My tiny 5 Node cluster is nothing to boast about, but it handles a good
150+ GB of data a day
 Every* query is done with CQL
 Except on a single CF which uses super columns.
 CQL does not and most likely will not ever support super columns.
 Compound column (CASSANDRA-2474 monster ticket) resolved (ish).

9. CQL V1.0.0 - DEBUT KEYWORDS
 USE
 SELECT
That’s right!
 UPDATE
 DELETE
No INSERT...?
 TRUNCATE
 DROP
 BATCH
SPECIAL STATEMENTS
 CREATE KEYSPACE
 CREATE COLUMNFAMILY
 CREATE INDEX 10
total

10. TIME TELLS NO LIES, CQL V2
 ALTER COLUMNFAMILY
 BATCH Create table is nothing more
than an alias to create
 CREATE INDEX
columnfamily
 CREATE KEYSPACE
 CREATE COLUMNFAMILY
 CREATE TABLE (CASSANDRA-2743)
 DELETE
Rational: ‘create an
 DROP COLUMNFAMILY alias to be friendlier
 DROP INDEX to existing tools’
 DROP KEYSPACE
 INSERT
 SELECT
 TRUNCATE 15
total
 UPDATE
 USE

11. CQL V3, AKA CASSANDRA-3761
 About 13 sub-tickets
 Most unresolved
 It’d be unwise to list features
 Any of these could be dropped/altered before V3 is
finalized (C* V1.1.1 is the roadmap release for V3)
 Backwards incompatibility (hence major version jump)
 Not the little project it used to be, would take all night to
cover each feature with enough details

12. TERMINOLOGY WAR...
 CQL’s changing fast (maybe too fast?)
 Terminology looks to be changing
 Creating over lap in some places
 May become, or already is confusing
 Not sure those in charge are seeing it
 At a stage where its probably as confusing as other, more
complicated C* features
 Progress is great, but so is usability & simplicity...

14. COURTNEY ROBINSON @ZCOURTS
Thank you for listening.
Questions?
Links:
https://github.com/apache/cassandra/blob/trunk/doc/cql/CQL.textile
http://crlog.info/2011/09/17/cassandra-query-language-cql-v2-0-reference/
https://issues.apache.org/jira/browse/CASSANDRA-2743