Ways to implement TaS for mapping table in Bw-Tree

1. PID Ptr
1 TAS
( )
1. metadata update
2. invalidation check
Invalidation Check
next node ~~~ delta chain lookup
insert
1. <key, value> insert node
2. update node <key, value>
delete
1. <key, value> delete node
2. update node <key, value>
update
1. <key, value> delete node
2. <key, value> insert node
3. <key, value> update node
4. <key, value> update node
Implementation

2. PID Ptr
0
1 2
node ( )1 2 node
1 -> 2 TAS
Implementation

3. PID Ptr
0
1 2
node ( )1 2 node
1 -> 2 TAS
1: TAS == . Delta chain lookup
Implementation

4. PID Ptr
0
1
1 2 node
1 -> 2 TAS
1: TAS == . Delta chain lookup
2: TAS 1 . 0
delta chain lookup
2
node ( )
Implementation

5. PID Ptr
0
1 2 3 4 5
Delta Chain Lookup
1: -
2: 1
3: 1~2
4: 1~3
5: 1~4
1~5 delta node
Delta Node Insertion Workflow
Previous:
do {
check abort
create delta node
} while (CAS)
TAS:
check abort
create delta node
TAS
Invalidation check & metadata update
Invalidation check & metadata update: node (
delta node ) .
length < # of threads
Invalidation Check

6. PID Ptr
0
1 2 3 4 5
1~5 delta node
:
1. Invalidation check node ?
valid / invalid
2. Abort delta node handling issue
invalid node ?
1) prev node next pointer next pointer =>
TAS ?
2) node validation bit
Invalidation Check

7. PID Ptr
i <5, 5> i <4, 4> i <3, 3> i <2, 2> i <1, 1>
1: i <6, 6> 2: i <7, 7> 3: i <6, 6> 4: d <5, 5> 5: d <5, 5>
Traverse
1~5 delta node
Invalidation Check not yet finished. (Consider as Valid)
Invalid delta node.
Valid delta node.
Node Traverse(lookup) requested by other thread.
Invalidation Check in progress

8. PID Ptr
i <5, 5> i <4, 4> i <3, 3> i <2, 2> i <1, 1>
1: i <6, 6> 2: i <7, 7> 3: i <6, 6> 4: d <5, 5> 5: d <5, 5>
Traverse
present_set
i <6, 6>
i <7, 7>
i <6, 6>
i <5, 5>
i <4, 4>
i <3, 3>
i <2, 2>
i <1, 1>
deleted_set
d <5, 5>
d <5, 5>
=
<1, 1>
<2, 2>
<3, 3>
<4, 4>
<5, 5>
<6, 6>
<7, 7>

9. PID Ptr
0: i <5, 5> i <4, 4> i <3, 3> i <2, 2> i <1, 1>
1: i <6, 6> 2: i <7, 7> 3: i <6, 6> 4: d <5, 5> 5: d <5, 5>
Traverse
Check delta Node 2 & 1
(since node 0 is initial starting point)
2: i <7, 7> => OK
1: i <6, 6> => invariant doesn't hold.
set invalid bit

10. PID Ptr
0: i <5, 5> i <4, 4> i <3, 3> i <2, 2> i <1, 1>
1: i <6, 6> 2: i <7, 7> 3: i <6, 6> 4: d <5, 5> 5: d <5, 5>
Traverse
present_set
i <6, 6>
i <7, 7>
i <6, 6>
i <5, 5>
i <4, 4>
i <3, 3>
i <2, 2>
i <1, 1>
deleted_set
d <5, 5>
d <5, 5>
=
<1, 1>
<2, 2>
<3, 3>
<4, 4>
<5, 5>
<6, 6>
<7, 7>

11. PID Ptr
0: i <5, 5> i <4, 4> i <3, 3> i <2, 2> i <1, 1>
1: i <6, 6> 2: i <7, 7> 3: i <6, 6> 4: d <5, 5> 5: d <5, 5>
Traverse
Check delta Node until reaching node 0
(since node 0 is initial starting point)
Both delta node is valid.

12. PID Ptr
0: i <5, 5> i <4, 4> i <3, 3> i <2, 2> i <1, 1>
1: i <6, 6> 2: i <7, 7> 3: i <6, 6> 4: d <5, 5> 5: d <5, 5>
Traverse
Check delta Node until reaching node 0
(since node 0 is initial starting point)
No matter which node starts
invalidation check first,
node 4 will be checked as valid
and node 5 will set invalid bit.

13. PID Ptr
0: i <5, 5> i <4, 4> i <3, 3> i <2, 2> i <1, 1>
1: i <6, 6> 2: i <7, 7> 3: i <6, 6> 4: d <5, 5> 5: d <5, 5>
Traverse
present_set
i <6, 6>
i <7, 7>
i <6, 6>
i <5, 5>
i <4, 4>
i <3, 3>
i <2, 2>
i <1, 1>
deleted_set
d <5, 5>
d <5, 5>
=
<1, 1>
<2, 2>
<3, 3>
<4, 4>
<5, 5>
<6, 6>
<7, 7>

14. PID Ptr
0: i <5, 5> i <4, 4> i <3, 3> i <2, 2> i <1, 1>
1: i <6, 6> 2: i <7, 7> 3: i <6, 6> 4: d <5, 5> 5: d <5, 5>
Traverse
<1, 1>
<2, 2>
<3, 3>
<4, 4>
<5, 5>
<6, 6>
<7, 7>
node traverse .
delta node .
e.g.) i <8, 8> & d <8, 8>
<8, 8> : abort i <8, 8>
<8, 8> : abort d <8, 8>