Information Technology Reference
In-Depth Information
10.6
Logging and Undoing Bulk Actions
In Algorithm
10.2
, tuples from a bulk are inserted into leaf page p using the
call
insert-bulk-into-page
.T;p;S/, which could be implemented by calling
insert-
into-page
.T;p;x;
v
/ (Algorithm
3.1
) on all tuples .x;
v
/ in S . In Algorithm
10.3
,
tuples are deleted from leaf page p using the call
delete-bulk-from-page
.T;p;S/,
which could similarly be implemented by calling
delete-from-page
.T;p;x/(Algo-
rithm
3.2
) on the keys x of tuples in S . The log then shows just an expanded
history of tuple-wise actions, which can be undone, if so needed, by the proce-
dures
undo-insert
.n;T;p;x;n
0
/ (Algorithm
4.7
)and
undo-delete
.n;T;p;x;
v
;n
0
/
(Algorithm
4.9
).
To save in the number of assignments of the
P
AGE
-LSN
of the page to be updated
and of the
U
NDO
-N
EXT
-LSN
of the transaction, we can use Algorithm
10.4
to insert
the tuples in S into page p and Algorithm
10.5
to delete the tuples in S from page
p. These algorithms log the tuple-wise actions as in
insert-into-page
.T;p;x;
v
/ and
delete-from-page
.T;p;x;
v
/, but only the
LSN
of the last tuple-wise update needs to
be stamped into the
P
AGE
-LSN
of page p.
Algorithm 10.4
Procedure
insert-bulk-into-page
.T;p;S/
n
0
U
NDO
-N
EXT
-LSN.T /
for
all tuples .x;
v
/ 2 S
do
insert .x;
v
/ into page p
log
.n;hT; I; p; x;
v
;n
0
i/
n
0
n
end for
P
AGE
-LSN.p/ n
U
NDO
-N
EXT
-LSN.T / n
Algorithm 10.5
Procedure
delete-bulk-from-page
.T;p;S/
n
0
U
NDO
-N
EXT
-LSN.T /
for
all tuples .x;
v
/ 2 S
do
delete .x;
v
/ from page p
log
.n;hT; D; p; x;
v
;n
0
i/
n
0
n
end for
P
AGE
-LSN.p/ n
U
NDO
-N
EXT
-LSN.T / n
