idn locks

Excerpt from: http://www.cnblogs.com/lxconan/archive/2011/10/20/sql_transaction_n_locks_1.htmlA recent stress test in a project has encountered a deadlock problem with the database, in short, the following code causes a deadlock at the SERIALIZABLE isolation level: 1234567891011121314 SELECT@findCount=COUNT(id) FROMMyTableWHERE[fk_related_id][emailprotected]IF (@findCount > 0)BEGINROLLBACKTRANSACTIONRETURNERROR_CODEENDINSERTINTOMyTable ([fk_related_id],…)VALUES(@Argument,…)COMMI

Label:A recent stress test in a project has encountered a deadlock problem with the database, in short, the following code causes a deadlock at the SERIALIZABLE isolation level: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 SELECT@findCount=COUNT(id) FROMMyTable WHERE[fk_related_id][emailprotected]IF (@findCount > 0) BEGIN ROLLBACK TRANSACTION RETURNERROR_CODE ENDINSERTINTOMyTable ([fk_related_id],…) VALUES(@Argument,…)COMMITTRANSACTION RETURNSUCCESS_CODE In the process o

In MySQL, table locks are not deadlocked when table-level locking is used for storage engines. This means that all necessary locks are requested immediately at the beginning of a query and the tables are always locked in the same order. In MySQL, table locks are not deadlocked when table-level locking is used for storage engines. This means that all necessary

Relationship between locks and isolation levels One. net project, occasionally some strange problems, recently made up effort to troubleshoot and found that it is caused by a deadlock, the following is a deadlock situation map tracked using SQL Server Profiler: When I see this picture, it is really drunk to tell the truth. It is rare that such a complicated deadlock occurs in a business system that is not complex yet. The cause of this problem is ver

Research on multiple threads in Android (9) -- read/write locks and multiple threads in androidI. What is a lock? The lock interfaces and classes in the Java util. concurrent. locks package are as follows: First look at a piece of code: Package com. codeing. snail Il. test; public class ReadWriteLockTest {public static void main (String [] args) {final Output output = new Output (); new Thread () {public

Talking about high concurrency (vi) Implementation of several spin locks (i) two major spin locks are implemented in this article: Taslock and Ttaslock, and their problem is frequent CAS operations. A large amount of cache consistency traffic is raised, resulting in poor lock performance.An improvement to Ttaslock is Backofflock, which will rollback the thread in case of high contention, reduce contention,

Read-Write Lock Reentrantreadwritelock OverviewA very important piece of content in a large web site is the reading and writing of data, although Reentrantlock has a completely mutually exclusive effect (that is, only one thread is performing the task behind lock at the same time), but it is very inefficient. So a read-write lock Reentrantreadwritelock is provided in the JDK, which can be used to speed up operational efficiency.Read-write locks repres

Read/write locks: ReadWriteLock and cache instances; readwritelock instancesRead/write locks: Multiple read locks are not mutually exclusive. Read locks are mutually exclusive with some locks. Write locks and write

Use of various locks in iOS/Mac DevelopmentNSRecursiveLock recursive lockThe so-called recursive lock means that the lock can be reentrant on the same thread. It is equivalent to a common mutex lock for different threads. The lock defined by the NSRecursiveLock class can be locked multiple times in the same thread without causing a deadlock. Recursive locks track how many times it is locked. Each successful

level. By name we can know that at this level of transaction isolation, one transaction can read data that is uncommitted to another transaction.UNCOMMITTED read Database lock condition (Implementation principle) The transaction does not lock the data when it reads the data. Add row-level shared locks only to data when modifying data. Phenomenon: When transaction 1 reads a row record, transaction 2 can also read and updat

there can be access statements, modify statements in the transaction--level of isolation supported by Oracle: (Dirty read not supported)SET TRANSACTION Isolation Level READ COMMITTED --do not allow dirty reads, allow fantasy read and non-repeatable readSET TRANSACTION Isolation Level SERIALIZABLE --None of the above three types allow serialzable to perform DML operations--The SQL standard also supports READ UNCOMMITTED (three types are allowed) and repeatable read (does not allow non-repe

Oracle automatically acquires row and table locks for DML operations, and the type of operation determines the behavior of the lock, which summarizes the situation of the DML operation Lock: SQL Statement Row Locks Table Lock Mode RS RX S SRX X SELECT...FROMtable... —— None Y Y Y Y Y INSER

Tags: personal img nbsp Logs release other data Select blogMySQL lock mechanism is divided into table-level locks and row-level locks, this article will share with you my MySQL row-level lock in the shared lock and exclusive lock to share the exchange. Shared locks, also known as read locks, referred to as the S-lock,

, you do not allow any other transaction to manipulate the resource until the exclusive lock is released, preventing multiple operations on the same resource at the same time. Update Lock (U): Prevent deadlock in the lock mode, two transactions to a data resource read first in the case of modification, use of shared and exclusive locks sometimes deadlock phenomenon, and the use of update locks can avoid

CPUThread synchronization: MutexType of Mutex:Mutex = thread lock = MutexThread lock, read and write locks, spin locks, condition variables @ Line Cheng class: 1) Normal lock 2) default lock 3) high speed lock 4) error Check lock 5) loopback lockLocks are used for asynchronousint Pthread_mutex_lock (pthread_mutex_t *mutex);int Pthread_mutex_trylock (pthread_mutex_t *mutex);int Pthread_mutex_unlock (pthread

Guidance:When we sendDDLCommand is automatically added to the object to be processedDDL lockTo prevent objects from being modified by other users. When the DDL command ends, the DDL lock is released. We cannot explicitly request a DDL lock. Only when the object structure is modified or referenced will the DDL lock be added to the object. For example, when a stored procedure is created or compiled, a ddl lock is added to the referenced object. When creating a view, it also adds DDL

Mysql locks and deadlocks are summarized below. some experiences on the network are referenced. MyISAM and MEMORY storage engines use table-level locking The BDB storage engine uses page-level locking, but also supports table-level locks. The InnoDB storage engine supports row-level locking and table-level locking. However, row-level locks are used by defaul

A file lock is a file read/write mechanism that allows only one process to access one file at any specific time. Using this mechanism can make the process of reading and writing a single file more secure. In this article, we will explore different types of File locks in Linux and use the example program to understand the differences between them. We will take the following example to explain why file locks

Redis distributed locks in the right way (Java version) Distributed locks generally have three kinds of implementation methods: 1. Database optimistic lock; 2. Distributed lock based on Redis; 3. Distributed locks based on zookeeper. This blog will introduce the second way to implement distributed locks based on Redis

Label:First, the use of Rowlock 1, Rowlock Row-level lock to ensure that the user gets the updated row, to the row to update, this period of time is not modified by other users. So the row-level lock can guarantee the consistency of data, and can improve the concurrency of data operation. 2. Rowlock tells SQL Server to use only row-level locks, rowlock syntax can be used in select,update and DELETE statements. 3. In the SELECT statement, for example