Tag：deadlock
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Time：2021-12-17
1： Background 1. Tell a story At the beginning of this month, a friend on the planet came to me and said that his program had a deadlock. He suspected that some of his writing methods had led to such an embarrassing situation in mongodb. The screenshot is as follows: To tell you the truth, […]
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Time：2021-11-15
preface: During MySQL operation and maintenance, lock waiting and deadlock problems are a headache for DBAs and development students. Such problems will cause business rollback, jamming and other failures, especially in busy systems. The impact will be more serious after deadlock problems occur. In this article, let’s learn what is lock waiting and deadlock, and […]
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Time：2021-10-5
deadlock Four conditions of deadlock Inalienable The resources obtained by a thread cannot be deprived by other threads before they are used up. They can only be released after they are used up. Request hold Thread T1 keeps one resource R1 occupied, but makes another resource R2 request. At this time, resource R2 is occupied […]
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Time：2021-9-27
What is a deadlock? In the go process, a deadlock is usually permanently blocked. You take my things and ask me to give them to you first and then to me. I take your things and ask you to give them to me first, otherwise I won’t give them to you. If we both think […]
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Time：2021-7-21
Deadlock is no stranger to DBAs or database developers. It causes a variety of problems. Generally speaking, the developers of database applications will have certain considerations when designing, so as to avoid deadlock as much as possible, Some hard to catch deadlocks may appear, which may affect the business. Here we introduce the key search […]
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Time：2021-3-20
Every time we explain locking & blocking in SQL server, we will encounter the problem: why do we need to update locks in SQL Server? Before we explain the reasons for the specific needs, first of all, I would like to introduce to you how the update (U) lock itself responds to its compatibility when […]
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Time：2020-11-11
After some processes in Oracle are killed, the status is set to “killed”. However, the locked resources are not released for a long time. Sometimes there is no way to do so, so you have to restart the database. Now we provide a way to solve this problem, which is to kill those that cannot […]
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Time：2019-9-22
Neither session 1 nor session 2 can continue until the other party releases resources. So, SQL Server chooses a session in a deadlock as a “deadlock victim”. Note: The session of the deadlock victim is killed and the transaction is rolled back. Be careful:deadlockAnd normalblockThey are two often confused concepts. Some reasons for deadlock: 1. […]
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Time：2019-9-12
Deadlocks: refers to the phenomenon that two or more processes (threads) are waiting for each other because of competing for resources in the execution process. Without external force, they will not be able to advance. At this time, it is said that the system is in a deadlock state or that the system has a […]
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Time：2019-9-2
Through many difficult single-step debugging late at night, an ideal breakpoint has been found, and most of the lock acquisition process can be seen.The code is inlock0lock.cOfstatic enum db_err lock_rec_lock() In the function, this function shows the process of acquiring the lock and whether the lock was successful or not. Scenario 1: Delete by primary […]
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Time：2019-9-1
In the beginner’s understanding of MySQL deadlock from source code, the process of using debugging MySQL source code to view deadlock is introduced. This article describes a common case.This time we’re going to talk about love and hatred between S lock and X lock, the only index. Let’s look at a simplified example. # Constructing […]
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Time：2019-8-31
Previous articles have introduced the use of source code to debug lock-related information. Here we also use this tool to solve an online real deadlock case. It is also the first two cases of deadlock caused by SQL that we introduced. Because of the complexity of the online table structure, some simplifications are made as […]
