Save Mon Nov 14 12:35:01 AM CST 2022

Author: littleneko

读书笔记/CMU 15-445:645 Database Systems (Fall 2021)/Lecture #16: Two-Phase Locking.md

@@ -43,7 +43,7 @@ On its own, ==2PL is sufficient to **guarantee conflict serializability**==. ==I
 
 > **Tips**:
 >
-> 实际上这是一种脏读。
+> 上图表示了朴素的 2PL 导致的级联回滚的情况，所以需要 S2PL。（实际上这是一种脏读）
 
 There are also potential schedules that are serializable but would not be allowed by 2PL (locking can limit concurrency).
 

读书笔记/CMU 15-445:645 Database Systems (Fall 2021)/Lecture #17: Timestamp Ordering Concurrency Control.md

@@ -193,7 +193,7 @@ If *TS(T~i~ ) < TS(T~j~ )*, then one of the following three conditions must hold
 
 3. ==T~i~ completes its Read phase before T~j~ completes its Read phase==, and ==T~i~ does not write to any object that is either read or written by T~j~== .
 
-    (WriteSet(Ti ) ∩ ReadSet(T j) = Ø and WriteSet(Ti ) ∩ WriteSet(Tj ) = Ø)
+    (WriteSet(T~i~ ) ∩ ReadSet(T~j~) = Ø and WriteSet(T~i~ ) ∩ WriteSet(T~j~ ) = Ø)
 
    <img src="https://littleneko.oss-cn-beijing.aliyuncs.com/img/image-20220313014335756.png" alt="image-20220313014335756" style="zoom:25%;" />