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@ -87,9 +87,10 @@ Simplified version (to get the idea)
for each tuple tr in r: (for each tuple ts in s: test pair (tr, ts)) for each tuple tr in r: (for each tuple ts in s: test pair (tr, ts))
``` ```
// TODO: Add seek information Block transfer cost: $n_r ∗ b_s + b_r$ block transfers would be required,
Block transfer cost: $n_r dot b_s + b_r$ block transfers would be required, where $b_r$ -- blocks in relation $r$, same for $s$. Each scan of the inner
where $b_r$ -- blocks in relation $r$, same for $s$. relation requires one seek, and the scan of the outer relation requires one
seek per block, leading to a total of $2 ∗b_r$ seeks.
== Block-nested join == Block-nested join
@ -275,7 +276,8 @@ The concept of conflict equivalence leads to the concept of conflict
serializability. We say that a schedule $S$ is *conflict serializable* if it is serializability. We say that a schedule $S$ is *conflict serializable* if it is
conflict equivalent to a serial schedule. conflict equivalent to a serial schedule.
=== Serializability graph // TODO: rename to precedence
=== Precedence graph
Simple and efficient method for determining the conflict seriazability of a Simple and efficient method for determining the conflict seriazability of a
schedule. Consider a schedule $S$. We construct a directed graph, called a schedule. Consider a schedule $S$. We construct a directed graph, called a
@ -304,11 +306,19 @@ serializable.
== Protocols == Protocols
We say that a schedule S is *legal* under a given locking protocol if S is a We say that a schedule S is *legal* under a given locking protocol if S is a possible
possible schedule for a set of transactions that follows the rules of the schedule for a set of transactions that follows the rules of the locking protocol. We say
locking protocol. We say that a locking protocol ensures conflict that a locking protocol ensures conflict serializability if and only if all legal schedules
serializability if and only if all legal schedules are *conflict serializable*; are *conflict serializable*; in other words, for all legal schedules the associated →relation
in other words, for all legal schedules the associated $->$ relation is acyclic. is acyclic.
\ *Recoverable* schedule is one where, for each pair of transactions $T_i$ and
$T_j$ such that $T_j$ reads a data item previously written by $T_i$, the commit
operation of $T_i$ appears before the commit operation of $T_j$.
\ *Cascadeless* schedule is one where, for each pair of transactions $T_i$ and
$T_j$ such that $T_j$ reads a data item previously written by $T_i$, the commit
operation of $T_i$ appears before the read operation of $T_j$.
Every cascadeless schedule is also recoverable.
=== Lock-based === Lock-based