Information Technology Reference
In-Depth Information
Algorithm 15.3
Procedure
relocate-and-flush-pages
.M /
P ;
for
all buffer control blocks b in the LRU chain
do
q
page-id
.b/
if
modified-bit
.b/ D 1
and
page q is unlatched
then
fix-and-write-latch
.q/
p
parent-link
.q/
if
q is a B-tree page
and
p 6D null
and
page p is buffered and unlatched
then
fix-and-write-latch
.p/
if
p and q are pages of the same B-tree
and
p contains an index record .x; q/ for child
q
then
q
0
new page-id
P P [f.p;x;q;q
0
/g
if
jPjM
then
exit from the
for
loop
end if
else
parent-link
.q/ null
unlatch-and-unfix
.p/
unlatch-and-unfix
.q/
end if
else
unlatch-and-unfix
.q/
end if
end if
end for
for
all .p;x;q;q
0
/ 2 P
do
stamp q
0
in the header of page q
parent-link
.q
0
/ p
change the buffer control block of page q to that of q
0
change the write latch on page q to that on q
0
end for
n D maxfP
AGE
-LSN.q
0
/ j .p;x;q;q
0
/ 2 Pg
flush all the not-yet-flushed log records up to and including that with LSN n
flush the pages q
0
with .p;x;q;q
0
/ 2 P using a single disk write
if
the disk write succeeded
then
for
all .p;x;q;q
0
/ 2 P
do
b
0
the buffer control block of page q
0
modified-bit
.b
0
/ 0
delete the entry for q from the modified-page table
replace the index record .x; q/ in page p by .x; q
0
/
log
.n;h
page-id-change
;p;x;q;q
0
i/
P
AGE
-LSN.p/ n
unlatch-and-unfix
.q
0
/
end for
unlatch-and-unfix
.p/ for all p with some .p;x;q;q
0
/ 2 P
else
invalidate the pages q with .p;x;q;q
0
/ 2 P and initialize redo recovery for them
end if
