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vault backup: 2026-05-21 19:31:28

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hhs
2026-05-21 19:31:28 +08:00
parent 531d4b7d8c
commit f9d21f0026
9 changed files with 1290 additions and 78 deletions
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hhs/MySQL/06-事务与并发控制/24-隔离级别与可见性.md
+13 -8
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@@ -124,25 +124,30 @@ sequenceDiagram
participant B as Transaction B
A->>RC_DB: BEGIN;
A->>RC_DB: SELECT * FROM t; -- Read View #1
A->>RC_DB: SELECT * FROM t; -- Read View #2 (new each time)
A->>RC_DB: SELECT * FROM t
Note over A,RC_DB: Read View #1
A->>RC_DB: SELECT * FROM t
Note over A,RC_DB: Read View #2 (new each time)
B->>RC_DB: BEGIN;
B->>RC_DB: INSERT INTO t VALUES (...);
B->>RC_DB: INSERT INTO t VALUES (...)
B->>RC_DB: COMMIT;
A->>RC_DB: SELECT * FROM t; -- Read View #3
A->>RC_DB: SELECT * FROM t
Note over A,RC_DB: Read View #3
Note over RC_DB: Can see new rows committed by B!
A->>RR_DB: BEGIN;
A->>RR_DB: SELECT * FROM t; -- Read View #1
A->>RR_DB: SELECT * FROM t; -- Reuses Read View #1
A->>RR_DB: SELECT * FROM t
Note over A,RR_DB: Read View #1
A->>RR_DB: SELECT * FROM t
Note over A,RR_DB: Reuses Read View #1
B->>RR_DB: BEGIN;
B->>RR_DB: INSERT INTO t VALUES (...);
B->>RR_DB: INSERT INTO t VALUES (...)
B->>RR_DB: COMMIT;
A->>RR_DB: SELECT * FROM t;
A->>RR_DB: SELECT * FROM t
Note over RR_DB: Cannot see B's rows - RV#1 was created before B committed
```