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maoyusu

maoyusu

V2EX member #48153, joined on 2013-10-28 18:19:29 +08:00
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有来有回,乐了
Aug 28, 2019
Replied to a topic by silenceeeee MySQL MySQL next-key lock 请教
首先记住下面三个规则:
1.当查询的索引仅含有唯一索引的时候,Next-Key Lock 会降级为 Record Lock。(联合唯一索引,每一个索引列都要查)
2.InnoDB 还会对锁住的辅助索引加 Next-Key Lock,并且会给下一个键值加 Gap Lock。
3.插入某记录时候,会检查插入记录的下一条记录是否被锁住了,如果锁住了,则不允许插入(阻塞)。

然后来分析你的 SQL:
SELECT * FROM tab WHERE a=7 FOR UPDATE;
会加如下几种锁:
1. id=3 的 Record Lock (规则 1)
2. a 属于 (4,7] 的 Next-Key Lock (规则 2 )
3. a 属于 (7,10) 的 Gap Lock (规则 2 )

根据规则 3,INSERT INTO tab(a) VALUES(4); 会阻塞
插入 5,6,7,8,9 被阻塞是因为 (4, 10)都上锁了。
10 会成功,因为 10 不在锁区间内。
Aug 28, 2019
Replied to a topic by silenceeeee MySQL MySQL next-key lock 请教
很简单,我去公司了给你解释一下。
为什么要转出去?阿里华为腾讯云都在贵州设立数据中心。
@InuYasha1987 你说的这些手机,全是亮屏四个小时出头的让人用起来很焦虑的手机。楼主买的 mate20 可以亮屏 7 小时
我也遇到了这个问题,暂时按照这个帖子的方法改一下。
hp39gs图形计算器说明书
Mar 21, 2014
Replied to a topic by maoyusu Python 获取英语单词的意思。。。
at错了orz,@solos 感谢感谢!
Mar 21, 2014
Replied to a topic by maoyusu Python 获取英语单词的意思。。。
感谢楼上各位大神啊,丝前几天已经解决了,直接用的linguist库的
en.noun.gloss()
en.verb.gloss()
en.adverb.gloss()
en.adjective.gloss()
不过是英文翻译......

@tabrisux 这个真是好东西啊,万分感谢o(∩_∩)o
用WinPython试一试
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