Le 12/20/13 9:21 AM, Emmanuel Lécharny a écrit :
> After a second thought, it might be simpler to use 2 tables to store the
> references to the current BTrees and to the modified btrees.
This second thought was palin wrong. We *need* a tree of btrees,
otherwise we won't be able to keep old revisions (we have to be able to
retreive a previous version of a btree for wich the root page has been
swapped out, and we can only do that if we have a btree of btrees).
This btree of btrees will store references to btrees offset associated
with a btree name and a revision :
<<name, revision>, btree offset>
Here is the new diagram :
Mavibot header
+---------------------------------------+
| PageIO size |
+---------------------------------------+
| number of managed btrees |
+---------------------------------------+
| offset of the current btree of btrees |--+
+---------------------------------------+ \
| offset of the new btree of btrees |----)------------+
+---------------------------------------+ / |
| |
+---------------------------+ |
| |
V V
Btree Header Btree Header
+------------------+ +------------------+
| revision | | revision |
+------------------+ +------------------+
| nbElems | | nbElems
|
+------------------+ +------------------+
| rootPage offset |---+ | rootPage offset |---+
+------------------+ | +------------------+ |
| pageSize | | | pageSize | |
+------------------+ | +------------------+ |
| btree name | | | btree name | |
+------------------+ | +------------------+ |
| key serializer | | | key serializer | |
+------------------+ | +------------------+ |
| value serializer | | | value serializer | |
+------------------+ | +------------------+ |
| dups allowed | | | dups allowed | |
+------------------+ | +------------------+ |
| |
| .
+ +
/ \ . .
/ \ . .
/ \
. .
/ \
/ \
/ \
/ \
/ \
/ \
/ \
+ +
| |
V V
Node Leaf
+-----------------+ +-------------------+
| revision | | revision |
+-----------------+ +-------------------+
| nbElems | | nbElems |
+-----------------+ +-------------------+
| dataSize | | dataSize |
+-----------------+ +-------------------+
| child[0] | | value[0] length |
+-----------------+ +-------------------+
| key[0] length | | value[0] |---> Btree 1
+-----------------+ +-------------------+
| key[0] | | key[0] length |
+-----------------+ +-------------------+
| child[1] | | key[0] |
+-----------------+ +-------------------+
| key[1] length | | value[1] length |
+-----------------+ +-------------------+
| key[1] | | value[1] |---> Btree 2
+-----------------+ +-------------------+
| . | | key[1] length |
| . | +-------------------+
| . | | key[1] |
+-----------------+ +-------------------+
| child[N-1] | | . |
+-----------------+ | . |
| key[N-1] length | | . |
+-----------------+ +-------------------+
| key[N-1] | | value[N-1] length |
+-----------------+ +-------------------+
| child[N] | | value[N-1] |---> Btree 3
+-----------------+ +-------------------+
| key[N-1] length |
+-------------------+
| key[N-1] |
+-------------------+
--
Regards,
Cordialement,
Emmanuel Lécharny
www.iktek.com
