回答編集履歴
1
調整
test
CHANGED
|
@@ -9,10 +9,25 @@
|
|
|
9
9
|
に対して、遅延のトランザクションのテストは３パターンあります
|
|
10
10
|
# パターン1
|
|
11
11
|
```SQL
|
|
12
|
-
先行実行
|
|
13
12
|
/*先発実行*/
|
|
14
13
|
start transaction;
|
|
15
|
-
select id2 from tbl
|
|
14
|
+
select id2 from tbl for update;
|
|
15
|
+
select sleep(5);
|
|
16
|
+
insert into tbl(id2,val) values
|
|
17
|
+
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),400),
|
|
18
|
+
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),500);
|
|
19
|
+
commit;
|
|
20
|
+
|
|
21
|
+
/*後発実行*/
|
|
22
|
+
insert into tbl(id2,val) values
|
|
23
|
+
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),600),
|
|
24
|
+
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),700);
|
|
25
|
+
```
|
|
26
|
+
# パターン2
|
|
27
|
+
```SQL
|
|
28
|
+
/*先発実行*/
|
|
29
|
+
start transaction;
|
|
30
|
+
select id2 from tbl for update;
|
|
16
31
|
insert into tbl(id2,val) values
|
|
17
32
|
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),400),
|
|
18
33
|
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),500);
|
|
@@ -23,3 +38,24 @@
|
|
|
23
38
|
insert into tbl(id2,val) values
|
|
24
39
|
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),600),
|
|
25
40
|
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),700);
|
|
41
|
+
```
|
|
42
|
+
# パターン3
|
|
43
|
+
```SQL
|
|
44
|
+
/*先発実行*/
|
|
45
|
+
start transaction;
|
|
46
|
+
select sleep(5);
|
|
47
|
+
select id2 from tbl for update;
|
|
48
|
+
insert into tbl(id2,val) values
|
|
49
|
+
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),400),
|
|
50
|
+
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),500);
|
|
51
|
+
commit;
|
|
52
|
+
|
|
53
|
+
/*後発実行*/
|
|
54
|
+
insert into tbl(id2,val) values
|
|
55
|
+
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),600),
|
|
56
|
+
((select id2 from (select max(id2)+1 as id2 from tbl) as dummy),700);
|
|
57
|
+
```
|
|
58
|
+
トランザクションの考え方からすれば遅延はパターン１に限られます
|
|
59
|
+
ただし実質パターン２でも問題ないでしょう
|
|
60
|
+
パターン３のようにfor updateの前に遅延が発生した場合は、後発クエリのほうが先行して実行される可能性があります。
|
|
61
|
+
したがって後発クエリもトランザクションで実行し、優先順位を確定させてください
|