【专题技术】Apache Cassandra.pdf

文档介绍：Apache Cassandra
An Introduction for Java Developers
Nate McCall
nate@
***@zznate
What is Apache Cassandra?
CAP Theorem
Consistency
Availability
Partition Tolerance
“Though shalt have but 2”
- Conjecture made by Eric Brewer in 2000
- Published as formal proof in 2002
- See: http://en./wiki/CAP_theorem for more
Apache Cassandra Concepts
- Explicit choice of partition tolerance and availability. Consistency
is tunable.
- No read before write
- Merge on read
- Idempotent
- Schema Optional
- All nodes share the same roll
- Still performs well with larger-than-memory data sets
plements another
system(s)
(Not intended to be one-size-fits-all)
*** You should always use the right tool for the right job anyway
How does this differ from an RDBMS?
How does this differ from an RDBMS?
Substantially.
vs. RDBMS - No Joins
Unless:
- you do them on the client
- you do them via Map/Reduce
vs. RDBMS - Schema Optional
(Though you can add meta information for validation and type
checking)
*** Supports secondary indexes too:
“… WHERE state = 'TX' ”
vs. RDBMS - Prematerialized and
Transaction-less
- No ACID transactions
- Limited support for ad-hoc queries