Database Final 3

Front 1

most important heuristics of query graph

Back 1

1. push down selects and projects
2. optimize logical plan, then physical plan

Front 2

ACID transactions

Back 2

Atomic: all of the transaction is done or none is done
Consistent: if a transaction is consistent, and the database is consistent at start, it will be consistent at the end
Isolation: appears to the user that only one process executes at a time
Durable: effects of a process survive a crash

Front 3

Commit

Back 3

causes a transaction to complete

Front 4

rollback

Back 4

causes the transaction to end, but by aborting

Front 5

two phase locking

Back 5

A transaction:
1. does not request any locks after
2. it has released a lock

Front 6

S1, S2 are conflict equivalent schedules if.....

Back 6

S1 can be transformed into S2 by a series of swaps on non conflicting actions

Front 7

a schedule is conflict serializable if....

Back 7

it is conflict equivalent to some serial schedule

Front 8

phases of transactions

Back 8

1. read
2. validate
3. write

Front 9

to implement validation, system keeps two sets:

Back 9

FIN: transactions that have finished phase 3 and are all done
VAL: transactions that have successfully finished phase 2