斯坦福_数据库系统实现_Notes12

1、cs 245: database systemprinciplesnotes 12: distributed databaseshector garcia-molinadistributed databasesdistributed database systemdbms datadbmsjdatadbmsdatadbms=cdataadvantages of a ddbs modularity fault tolerance high performance data sharing low cost componentsissues data distribution exploiting

2、 parallelism concurrency and recovery heterogeneityparallelism: pidelining example: i select *from a where cond一 t2 join l and bparallelism: concurrent oderations example: select * from a where condjoin processing example: join a, b over attribute xaia2bib.x > 10a.x < 10a.x > 10b.x < 10j

3、oin strategyjoin processing example: join a, b over attribute xconcurrency & recovery two phase commitbankmain fra me2pc: atm withdraw! mainframe is coordinator phase 1: atm checks if money available; mainframe checks if account has funds (money and funds are ''reserved") phase 2: a

4、tm releases funds; mainframe debits accountreplicated data mangement key to fault-tolerance, durability illustrates transaction processing issues various concurrency control/recovery algorithms availableprimary copy algorithm updates run at primary site backups repeat writes;backups allow、'out-ofdate" readstl: a:5; c:6t2: b:9; c: 7a57b9 乂c7石yd25backup site 1|c 12back叩 site 2 arpropagate in orderto be covered in cs347 more replicated data algorithms more commit protocols distributed query processing map reduce peer to pee