transaction and concurrency control

I. Concurrency control for MySQL1, MySQL concurrency control at the server layer and the storage engine layer completedLocks: LockRead lock: Shared lock, can be read by several user colleagues, but cannot writeWrite Lock: Exclusive lock,Lock granularity: Lock table when lock table range (such as a user read the first t

MVCC is a variant of a row-level lock, but it avoids lock-up operations in many cases and therefore costs less. MySQL, including Oracle, PostgreSQL implements MVCC, although each relational database implementation is not the same, but most of the implementation of non-blocking read operations, write operations will only lock the necessary rows.The implementation principle of MVCC: the implementation principle of InnoDB MVCC is achieved by saving two hidden columns after each row of records. Thes

a little thought on the control of high concurrency traffic "Foreword" in the actual project, had encountered the peak of the line 5w+qps, also in the pressure measurement state experienced 10W+QPS Large flow request, the topic of this blog is his own high concurrency traffic control of a little thought. some id

In general development, I often see many students in the Java Concurrent development model will only use some basic methods. Like volatile,synchronized. High-level contracts such as lock and atomic are not often used by many people. I think most of the reasons are due to the nature of the principle. In the busy development work, who will be able to accurately grasp and use the correct concurrency model? So recently based on this idea, I intend to org

requests came in during the Execute time gap if (Currentvalidsessionid = =-1) { Use Object-lock to filter out other requests came in during the variable change time gap. Lock (Databasedoor) { Now there are only very little number of requests can reach below codes. if (Currentvalidsessionid = =-1) {//Now there would be is only one request can access the database Currentvalidsessionid = Currentrequest.sessionid; } } } if (Currentvalidsessionid = = Currentrequest.sessionid) {//here is the one! Try

MVCCBy adding two hidden columns to each table, one saves the creation time of the row, a time to save the row's expiration (or delete time), and the time corresponding to the versionCreates a new transaction that creates a new version numberPre-conditionsA. InnoDB only data rows with versions older than the current transaction version are foundB. The deleted version of the row is either undefined or larger

1. Transaction control If you start a transaction with the start transaction during the lock table, you will create an implied unlock tables commit and open a new transaction Mysql>commit and chain; Query OK, 0 rows Affected (0.00 sec) Close with exit to see if the database

View Storage Engine:show engines;InnoDB support transactions,MyISAM,MEMORY does not support transactions1, the nature of the transaction: (ACID)Atomicity: A transaction can no longer be split, either executed or not executed.Consistency: One transaction execution shifts data from one consistent state to another consistent stateIsolation: Execution of one

to the undo buffer, refresh the content in the undo buffer to the disk at the appropriate time. Like the redo buffer, the undo buffer is also a ring buffer, but when the buffer is full, the content in the undo buffer will be refreshed to the disk. Unlike the redo log, there is no separate undo log file on the disk. All undo logs are stored in the primary ibd data file (tablespace), even if each table is set to a data file on the client. Rollback segmentThe concept of rollback segments comes fr

This is a creation in Article, where the information may have evolved or changed. Objective Last time in the Go write a Lightweight SSH batch operation tool mentioned, we do golang concurrency to limit concurrency, the execution of Goroutine to have time-out control. That will not be discussed here. The following sample code can all run tests directly on the G

Intro A discussion of concurrency control using caching allows me to learn the balance between cost and benefit and what is true availability ... There are several ways to prevent concurrency, and this article only involves using cache memcached control. Concurrent Scenarios : use case: A person with senior membershi

based on index conditions and concurrent queries, such as some online transaction processing (OLTP) systems. This is also mentioned in the "Development" section of this book when introducing the selection of table types. In the following sections, we will focus on MySQL table locks and InnoDB row locks. Since bdb has been replaced by InnoDB, it is about to become a history and will not be further discussed here. MyISAM Table lock The MyISAM stora

Tags: style requires nbsp read lock commit commit tab Read/write Abiconcurrency control and transactions in the database are often asked during an interview, but the basic knowledge of the 2 aspects of the database must also be clear to guide their daily routine. Below I summarize, this 2 days I encountered problems, basically is the carding of the points of knowledge.concurrency controlBasic Theories and concepts: When dealing with

--when multiple users operate on the same data, the result of one user's behavior may result in invalid data being used by another user, and concurrency control through the transaction can ensure--simultaneous behavior does not conflict with the validity of the databegin Transaction Select * fromTeachers with(Holdl

In general development, I often see many students in the Java Concurrent development model will only use some basic methods. Like volatile,synchronized. High-level contracts such as lock and atomic are not often used by many people. I think most of the reasons are due to the nature of the principle. In the busy development work, who will be able to accurately grasp and use the correct concurrency model?So recently based on this idea, I intend to organ

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absolutely no 99.9%. So.public static Long Currentvalidsessionid = -1;public static Object Databasedoor = new Object (); void Readdatabase (Request c Urrentrequest) {//Use Currentvalidsessionid to filter out other requests came in during the Execute time gap if (CU Rrentvalidsessionid = =-1) {//Use Object-lock to ' filter out ' other requests came ' during the variable change Time Gap. Lock (Databasedoor) {//Now there are only very little number of requests can reach below cod

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classification of concurrency control methods for distributed databases 1. Methods based on a specific replica: Primary Replica method: Each data object is set to a unique primary replica, generally set in a frequently blocked site, the primary copy of the site is the main site of the data object, different data objects have a different main site. The lock on the data object is managed by the LM (lock man