InnoDB MVCC Architecture (by 권건우)
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Transcript of InnoDB MVCC Architecture (by 권건우)
© Copyrights 2001~2017 EXEM CO.,LTD. All Rights Reserved.
InnoDB MVCC Architecture
엑셈 | 권건우 상무
© Copyrights 2001~2017 EXEM CO.,LTD. All Rights Reserved.
02. MySQL/InnoDB MVCC Architecture
01. MySQL/InnoDB Undo Architecture
Table of Agenda
MySQL Deep Internal
© Copyrights 2001~2017 EXEM CO.,LTD. All Rights Reserved.
MySQL Deep InternalMVCC Architecture 발전
1970
1978
1981
E.F. Codd
PHILIP A. BERNSTEIN AND NATHAN GOODMAN
- the data independence objective- the communicability objective - the set-processing objective
Our approach is quite different. We regard an object that is modifiable as asequence of immutable versions. each version is the state of the object afteran update is made to the object.
Multiversion Concurrency Control
1984 The first shipping, commercial database software product featuring MVCC
was Digital's VAX Rdb/ELN. The second was InterBase, both of which are still
active, commercial products.
Jim Starkey
1986 Oracle version 6 에서 Rollback Segment 도입
Bob Miner
1999 Mikheev Vadim B.PostgreSQL 6.5 에 MVCC 아키텍쳐를 도입함
David P. Reed
MySQL Deep Internal
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MySQL Deep InternalMVCC Architecture의 두가지 접근법
• PostgreSQL, Firebird/Interbase, SQL Server 해당
• 데이터베이스에 다중 버전의 레코드를 저장
• 더 이상 필요하지 않을 때 모아둔 레코드를 버림
접근법 1
• Oracle, MySQL/InnoDB 해당
• 최신 버전의 데이터만 데이터베이스 내에 저장
• 언두를 이용하여 이전 버전의 데이터를 재구성
접근법 2
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MySQL/InnoDB Undo Architecture
MySQL Deep Internal
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MySQL Deep Internal
slot 0 4
slot 1 5
…
slot 1023
(1,5) Undo log
06d1 Rec001, A
T1.ibd space f9
Page 0
Page 1
Page 2
Page 3
Page 4 …
Page64
MySQL/InnoDB Undo Architecture
ibdata1 space 0
Page 0
Page 1
Page 2
Page 3
Page 4
Page 5
…
(0,5) TRX_SYS Rseg 0 (0,6)
Rseg 1
…
Rseg 33 (1,3)
Rseg 127
undo001 space 1
Page 0
Page 1
Page 2
Page 3
Page 4
Page 5
… Page 8
ibtmp1
Rseg1
Rseg2
Rseg3
Rseg4
…Rseg
32
Page (f9,3)Rec001, A(TRX_ID 0x778c, Roll_PTR (5,06d1))
(1,3) Rollback Segment
System Tablespace
User Tablespace
Undo Tablespace
Temp Tablespace
MySQL Deep Internal
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MySQL Deep Internal
slot 0 4
slot 1
…
slot 1023
(1,4) Undo log
0110 Rec001, A
(1,3) Rollback Segment
T1.ibd space f9
Page 0
Page 1
Page 2
Page 3
Page 4 …
Page64
Page (f9,3)Rec001, A(TRX_ID 0x778b, Roll_PTR (4,0110))
MySQL/InnoDB Undo Architecture (select 시)
0x7f0208608000Data Page (f9,3)Rec001, A(TRX_ID 0x778b, Roll_PTR (4,0110))
Insert A 후, Select * from t1;
TRX_SYSmax_trx_id = 0x778crw_trx_list->count = 0mvcc->m_views->count = 1
Rseg 0 (0,6)
Rseg 1
…
Rseg 33 (1,3)
Rseg 127
ibdata1 space 0
Page 0
Page 1
…Page
5…
(0,5) TRX_SYS
undo001 space 1
Page 0
Page 1
Page 2
Page 3
Page 4
Page 5
… Page 8
Buffer Pool
User Tablespace
System Tablespace
Undo Tablespace
MySQL Deep Internal
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MySQL Deep Internal
slot 0 4
slot 1 5
…
slot 1023
(1,5) Undo log
06d1 Rec001, A
(1,3) Rollback Segment
T1.ibd space f9
Page 0
Page 1
Page 2
Page 3
Page 4 …
Page64
Page (f9,3)Rec001, B(TRX_ID 0x778c, Roll_PTR (5,06d1))
MySQL/InnoDB Undo Architecture (update 시)
0x7f0208608000Data Page (f9,3)Rec001, B(TRX_ID 0x778c, Roll_PTR (5,06d1))
A를 B로 update (Update t1 Set c2 = B;)
TRX_SYSmax_trx_id = 0x778drw_trx_list->count = 0mvcc->m_views->count = 1
Rseg 0 (0,6)
Rseg 1
…
Rseg 33 (1,3)
Rseg 127
ibdata1 space 0
Page 0
Page 1
…Page
5…
(0,5) TRX_SYS
undo001 space 1
Page 0
Page 1
Page 2
Page 3
Page 4
Page 5
… Page 8
0x7f0208608000Data Page (f9,3)Rec001, A(TRX_ID 0x778b, Roll_PTR (4,0110))
TRX_ID : 0x778caddr=0x1b74a750page_no=5offset=0x6d1
Buffer Pool
User Tablespace
System Tablespace
Undo Tablespace
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MySQL/InnoDB MVCC Architecture
1) MVCC
2) Readview
MySQL Deep Internal
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MySQL Deep Internal
slot 0 4
slot 1 5
…
slot 1023(1,5) Undo log
(1,3) Rollback Segment
MySQL/InnoDB MVCC Architecture
TRX_SYSmax_trx_id = 0x778drw_trx_list->count = 0mvcc->m_views->count = 0
Rseg 0 (0,6)
Rseg 1
…
Rseg 33 (1,3)
Rseg 127
ibdata1 space 0
Page 0
Page 1
…Page
5…
(0,5) TRX_SYS
undo001 space 1
Page 0
Page 1
Page 2
Page 3
Page 4
Page 5
… Page 8
System Tablespace
Undo Tablespace
Readview Readview Readview Readview
TRX_STRUCTURE TRX_STRUCTURE TRX_STRUCTURE TRX_STRUCTURE
MySQL Deep Internal
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MySQL Deep InternalMySQL/InnoDB MVCC Architecture
Rseg 0 (0,6)
Rseg 1
…
Rseg 33 (1,3)
Rseg 127
ibdata1 space 0
Page 0
Page 1
…Page
5…
System Tablespace
slot 0 4
slot 1
…
slot 1023
(1,4) Undo log(1,3) Rollback Segment
Undo Tablespace
Undo Page (1,4)Rec001, A(TRX_ID 0x778b)
1. 초기상태
Insert into t1 values(‘Rec001’,’A’);
Commit ;
Session 0
T1.ibd space f9
Page 0 …
Page 3
Page 4 …
Page64
Page (f9,3)Rec001, A(TRX_ID 0x778b, Roll_PTR (4,110))
Buffer Pool
User Tablespace
TRX_SYSmax_trx_id = 0x778crw_trx_list->count = 0mvcc->m_views->count = 0
MySQL Deep Internal
© Copyrights 2001~2017 EXEM CO.,LTD. All Rights Reserved.
MySQL Deep InternalMySQL/InnoDB MVCC Architecture
Session 0
Rseg 0 (0,6)
Rseg 1
…
Rseg 33 (1,3)
Rseg 127
ibdata1 space 0
Page 0
Page 1
…Page
5…
(0,5) TRX_SYS
System Tablespace
T1.ibd space f9
Page 0 …
Page 3
Page 4 …
Page64
Page (f9,3)Rec001, A(TRX_ID 0x778b, Roll_PTR (4,110))
Buffer Pool
User Tablespace
slot 0 4
slot 1
…
slot 1023
(1,3) Rollback Segment
Undo Tablespace
TRX_SYSmax_trx_id = 0x778crw_trx_list->count = 0mvcc->m_views->count = 1
Select * from t1;Rec001, A
Readview : 0x35dd108
Session 1
Readview : 0x35dd108m_low_limit_no = 0x778cm_low_limit_id = 0x778cm_up_limit_id = 0x778cm_ids->m_size = 0
0x7f0208608000Data Page (f9,3)Rec001, A(TRX_ID 0x778b,ROLL_PTR (4,110)
2. 세션1 Select
MySQL Deep Internal
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MySQL Deep InternalMySQL/InnoDB MVCC Architecture
Rseg 0 (0,6)
Rseg 1
…
Rseg 33 (1,3)
Rseg 127
ibdata1 space 0
Page 0
Page 1
…Page
5…
(0,5) TRX_SYS
System Tablespace
T1.ibd space f9
Page 0 …
Page 3
Page 4 …
Page64
Page (f9,3)Rec001, B(TRX_ID 0x778c)
Buffer Pool
User Tablespace
slot 0 4
slot 1 5
…
slot 1023
(1,3) Rollback Segment
Undo Tablespace
TRX_SYSmax_trx_id = 0x778drw_trx_list->count = 0mvcc->m_views->count = 1
Readview : 0x35dd108m_low_limit_no = 0x778cm_low_limit_id = 0x778cm_up_limit_id = 0x778cm_ids->m_size = 0
TRX ID 0x778caddr=0x1b74a750
0x7f02083b4000Undo Page (1,5)Rec001, A(TRX_ID 0x778b)
0x7f0208608000Data Page (f9,3)Rec001, B(TRX_ID 0x778c,ROLL_PTR (5,6d1))
Undo Page (1,5)(0x6d1)Rec001, A (TRX_ID 0x778b)
(1,5) Undo log
Update t1 Set c2 = B;
Session 0
Select * from t1;Rec001, A
Readview : 0x35dd108
Session 1
3. 세션0 Update
MySQL Deep Internal
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MySQL Deep InternalMySQL/InnoDB MVCC Architecture
Rseg 0 (0,6)
Rseg 1
…
Rseg 33 (1,3)
Rseg 127
ibdata1 space 0
Page 0
Page 1
…Page
5…
(0,5) TRX_SYS
System Tablespace
T1.ibd space f9
Page 0 …
Page 3
Page 4 …
Page64
Page (f9,3)Rec001, B(TRX_ID 0x778c)
Buffer Pool
User Tablespace
slot 0 4
slot 1 5
…
slot 1023
(1,3) Rollback Segment
Undo Tablespace
TRX_SYSmax_trx_id = 0x778erw_trx_list->count = 0mvcc->m_views->count = 2m_views->start = 0x35dd068
Readview : 0x35dd068m_low_limit_no = 0x778em_low_limit_id = 0x778em_up_limit_id = 0x778em_ids->m_size = 0
0x7f02083b4000Undo Page (1,5)Rec001, A(TRX_ID 0x778b)
0x7f0208608000Data Page (f9,3)Rec001, B(TRX_ID 0x778c,ROLL_PTR (5,6d1))
Undo Page (1,5)(0x6d1)Rec001, A (TRX_ID 0x778b)
(1,5) Undo log
Session 0
Select * from t1;Rec001, A
Readview : 0x35dd108
Session 1
4. 세션2 Select
Select * from t1;Rec001, B
Readview : 0x35dd068
Session 2
Readview : 0x35dd108m_low_limit_no = 0x778cm_low_limit_id = 0x778cm_up_limit_id = 0x778cm_ids->m_size = 0
MySQL Deep Internal
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MySQL Deep InternalMySQL/InnoDB MVCC Architecture
Rseg 0 (0,6)
Rseg 1
…
Rseg 33 (1,3)
Rseg 127
ibdata1 space 0
Page 0
Page 1
…Page
5…
(0,5) TRX_SYS
System Tablespace
T1.ibd space f9
Page 0 …
Page 3
Page 4 …
Page64
Page (f9,3)Rec001, C(TRX_ID 0x778e)
Buffer Pool
User Tablespace
slot 0 4
slot 1 5
…
slot 1023
(1,3) Rollback Segment
Undo Tablespace
TRX_SYSmax_trx_id = 0x778erw_trx_list->count = 0mvcc->m_views->count = 2m_views->start = 0x35dd068
Readview : 0x35dd068m_low_limit_no = 0x778em_low_limit_id = 0x778em_up_limit_id = 0x778em_ids->m_size = 0
(1,5) Undo log
Update t1 set c2 = C;
Session 0
Select * from t1;Rec001, A
Readview : 0x35dd108
Session 1
5. 세션0 Update
Select * from t1;Rec001, B
Readview : 0x35dd068
Session 2
Readview : 0x35dd108m_low_limit_no = 0x778cm_low_limit_id = 0x778cm_up_limit_id = 0x778cm_ids->m_size = 0
TRX ID 0x778eaddr=0x1b74a750
0x7f02083b4000Undo Page (1,5)(0x6d1)Rec001, A(TRX_ID 0x778b)
0x7f02083b4000Undo Page (1,5)(0x7be)Rec001, B(TRX_ID 0x778cROLL_PTR (5,6d1))
0x7f0208608000Data Page (f9,3)Rec001, B(TRX_ID 0x778c,ROLL_PTR (5,6d1))
Undo Page (1,5)0x6d1Rec001, A (TRX_ID 0x778b)
Undo Page (1,5)(0x7be)Rec001, B (TRX_ID 0x778cROLL_PTR (5,6d1))
MySQL Deep Internal
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MySQL Deep InternalMySQL/InnoDB MVCC Architecture
Rseg 0 (0,6)
Rseg 1
…
Rseg 33 (1,3)
Rseg 127
ibdata1 space 0
Page 0
Page 1
…Page
5…
(0,5) TRX_SYS
System Tablespace
T1.ibd space f9
Page 0 …
Page 3
Page 4 …
Page64
Page (f9,3)Rec001, C(TRX_ID 0x778e)
Buffer Pool
User Tablespace
slot 0 4
slot 1 5
…
slot 1023
(1,3) Rollback Segment
Undo Tablespace
TRX_SYSmax_trx_id = 0x7790rw_trx_list->count = 0mvcc->m_views->count = 3m_views->start = 0x35ddfc8
Readview : 0x35dcfc8m_low_limit_no = 0x7790m_low_limit_id = 0x7790m_up_limit_id = 0x7790m_ids->m_size = 0
(1,5) Undo log
Session 0
Select * from t1;Rec001, A
Readview : 0x35dd108
Session 1
6. 세션3 Select
Select * from t1;Rec001, B
Readview : 0x35dd068
Session 2
Readview : 0x35dd068m_low_limit_no = 0x778em_low_limit_id = 0x778em_up_limit_id = 0x778em_ids->m_size = 0
0x7f02083b4000Undo Page (1,5)(0x6d1)Rec001, A(TRX_ID 0x778b)
0x7f02083b4000Undo Page (1,5)(0x7be)Rec001, B(TRX_ID 0x778cROLL_PTR (5,6d1))
0x7f0208608000Data Page (f9,3)Rec001, C(TRX_ID 0x778e,ROLL_PTR (5,7be))
Undo Page (1,5)0x6d1Rec001, A (TRX_ID 0x778b)
Undo Page (1,5)(0x7be)Rec001, B (TRX_ID 0x778cROLL_PTR (5,6d1))
Select * from t1;Rec001, C
Readview : 0x35ddfc8
Session 2
Readview : 0x35dd108m_low_limit_no = 0x778cm_low_limit_id = 0x778cm_up_limit_id = 0x778cm_ids->m_size = 0
MySQL Deep Internal
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MySQL Deep InternalReadview
정의 및 목적
• 트랜잭션이 발생하면, COMMIT 시점이 아닌 트랜잭션 시작 시점의 TRX_ID 가 저장됨
• 쿼리 시작시점의 액티브 트랜잭션들의 집합 (COMMIT/ROLLBACK 하지 않은 상태)
• MVCC 구현에 반드시 필요
Component Description
low_limit_no- 해당 값을 Purge thread가 참조하여 불필요한 Undo log들을 처리하는 purge 작업에 사용된다.- low_limit_no = Readview 생성시 trx_sys의 max_trx_id값
low_limit_id- low_limit_id보다 크거나 같은 TRX_ID (trx_id >= low_limit_id) 는 해당 readview에서 조회 안 됨- low_limit_id = Readview 생성시 trx_sys의 max_trx_id값
up_limit_id- up_limit_id(trx_id < up_limit_id) 보다 작은 트랜잭션
TRX_ID 는 해당 readview에서 모두 조회됨- up_limit_id = readview 생성시, active 트랜잭션 중 가장 작은 TRX_ID
trx_ids[] - 모든 액티브 트랜잭션 id로 구성된 그룹
view_list - Readview list (doubly linked list)
MySQL Deep Internal
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MySQL Deep InternalReadview
New TRX Structure
mutex
max_trx_id = 0x98fd
rw_trx_listcount = 3start = 0x4fe4fae0
mvcc->m_viewscount = 3start = 0x25b9f08
…
trx_sys Trx linked list
trx id = 0x98fc
update_undo :page_no = 6offset = 0x86c
trx_listprev = 0x00next = 0x4fe4fe70
…
trx id = 0x98fb
update_undo :page_no = 7offset = 0x370
trx_listprev = 0x4fe4fae0next = 0x4fe4f750
…
trx id = 0x98f8
update_undo :page_no = 5offset = 0x2c4
trx_listprev = 0x4fe4fe70next = 0x00
…
trx0 0x4fe4fae0 trx1 0x4fe4fe70 trx2 0x4fe4f750
New Readview
Readview linked list
m_low_limit_no = 0x98fd
m_low_limit_id = 0x98fd
m_up_limit_id = 0x98f8
m_view_listprev = 0x0next = 0x25b9fa8
m_ids->m_size = 3
m_ids[0] = 0x98f8m_ids[1] = 0x98fbm_ids[2] = 0x98fc
readview0 0x25b9f08
m_low_limit_no = 0x98fc
m_low_limit_id = 0x98fc
m_up_limit_id = 0x98f8
m_view_listprev = 0x25b9f08next = 0x25ba048
m_ids->m_size = 2
m_ids[0] = 0x98f8m_ids[1] = 0x98fb
readview1 0x25b9fa8
m_low_limit_no = 0x98fb
m_low_limit_id = 0x98fb
m_up_limit_id = 0x98f8
m_view_listprev = 0x25b9fa8next = 0x0
m_ids->m_size = 1
m_ids[0] = 0x98f8
readview2 0x25ba048
MySQL Deep Internal
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MySQL Deep InternalReadview
1. t1 Table 생성
create table t1 (id int primary key, comment
char(50), filler char(2)) engine = innodb;
2. Secondary index 생성
create index test_idx on test(comment); T1
.ibd
sp
ace
17
3
Page0
Page1
Page2
Page3
Page4
Page5
…
UN
DO
00
1 s
pac
e 1
Page0
Page1
Page2
Page3
Page4
Page5
…
Secondary Index
source : InnoDBTransaction/Lock/Multi-version analysis, 网易杭研-何登成
Clustering Index
Page 4
MySQL Deep Internal
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MySQL Deep InternalReadview
3. TRX_ID가 0x96f6 일때, t1에 1건 Insert
insert into t.test values (65, 'aaa',' ') ;
T1
.ibd
sp
ace
17
3
Page0
Page1
Page2
Page3
Page4
Page5
…
Deleted: 0
65
DB_TRX_ID (0x96f6)
DB_ROLL_PTR (4,110)
aaa
Deleted: 0
aaa
PK: 65
UN
DO
00
1 s
pac
e 1
Page0
Page1
Page2
Page3
Page4
Page5
…
Insert Undo
aaa
PK: 65
source : InnoDBTransaction/Lock/Multi-version analysis, 网易杭研-何登成
Secondary Index
Clustering Index
Page 4
MySQL Deep Internal
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MySQL Deep InternalReadview
4. Primary key 업데이트
update t.test set id = 67 where id = 65 ;
T1
.ibd
sp
ace
17
3
Page0
Page1
Page2
Page3
Page4
Page5
…
Deleted: 1
65
DB_TRX_ID (0x96fc)
DB_ROLL_PTR (7,110)
aaa
Deleted: 1
aaa
PK: 65
UN
DO
00
1 s
pac
e 1
Page0
Page1
Page2
Page3
Page4
…
Page7
Update Undo
aaa
PK: 65
source : InnoDBTransaction/Lock/Multi-version analysis, 网易杭研-何登成
• 새로운 레코드 (67, aaa)가 추가됨
(Insert 발생하는 것처럼 Insert Undo에 저장)
• 이전 레코드 (65, aaa)는 삭제 표시됨 (삭제 flag, trx_id, roll_ptr를
설정하고, before-image를 Update Undo에 저장)
• Secondary Index 페이지에서도 레코드 (aaa, 65) 는 삭제 설정하고
레코드 (aaa,67)가 추가됨
Deleted: 0
67
DB_TRX_ID (0x96fc)
DB_ROLL_PTR (4,11d)
aaa
Deleted: 0
aaa
PK: 67
Insert Undo
aaa
PK: 67
Secondary Index
Clustering Index
Page 4 Page 7
MySQL Deep Internal
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MySQL Deep InternalReadview
5. Secondary key 업데이트
update t.test set comment = 'ccc' where id = 67 ;
T1
.ibd
sp
ace
17
3
Page0
Page1
Page2
Page3
Page4
Page5
…
Deleted: 1
65
DB_TRX_ID (0x96fc)
DB_ROLL_PTR (7,110)
aaa
Deleted: 1
aaa
PK: 65
UN
DO
00
1 s
pac
e 1
Page0
Page1
Page2
Page3
Page4
…
Page7
Update Undo
aaa
PK: 65
source : InnoDBTransaction/Lock/Multi-version analysis, 网易杭研-何登成
• 레코드 (67,aaa)를 레코드 (67,ccc)로 변경하고, before-image를
Update Undo에 저장
• Secondary Index 페이지에서도 레코드 (aaa,67)는 삭제 설정되고,
레코드 (ccc,67)가 추가됨.
Deleted: 0
67
DB_TRX_ID (0x9700)
DB_ROLL_PTR (7,224)
ccc
Deleted: 1
aaa
PK: 67
Update Undo
aaa
PK: 67
Deleted: 0
ccc
PK: 67
Secondary Index
Clustering Index
Page 7
MySQL Deep Internal
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MySQL Deep InternalReadview
Session 0 (DML)
Session 1 (DML)
Session 2 (DML)
Session 3 (Read)
Session 4 (Read)
Session 5 (Read)
UPDATE(67, ‘ccc’)
INSERT (65, ‘aaa’)
UPDATE(67, ‘aaa’)
0x96f5
0x96f6
0x96fb 0x96fc 0x97000x96ff 0x97060x96fd 0x97090x9705
READVIEW 0 0x25c0ee8UP:0x96f5 ~ LOW:0x96fdTrx:0x96f5, 0x96fb, 0x96fcSelect * from test (65,aaa)
READVIEW 1 0x25c0e48UP:0x96fb ~ LOW:0x9705Trx:0x96fb, 0x96ff, 0x9700Select * from test (67,aaa) READVIEW 2 0x25c0da8
UP:0x9706~ LOW:0x9709Trx:0x9706Select * from test (67,ccc)
TX 0x96f5
TX 0x96fb
TX 0x96fc
TX 0x9700
TX 0x96ff
TX 0x9706
MySQL Deep Internal
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MySQL Deep Internal
source : InnoDBTransaction/Lock/Multi-version analysis, 网易杭研-何登成
Readview
select * from t1;
case up_limit_id low_limit_id trx_ids [ ] query result
Readview0 Primary Key 변경 0x96f5 0x96fd 0x96f5, 0x96fb, 0x96fc (65, aaa)
Readview1 Secondary Key 변경 0x96fb 0x9705 0x96fb, 0x96ff, 0x9700 (67, aaa)
Readview2해당 테이블에
트랜잭션이 없을 경우0x9706 0x9709 0x9706 (67, ccc)
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