mvcc database

concurrency is one of the most important issues in the database domain, but as of today, there are many proven solutions to the control of transactional concurrency, and the principles of these scenarios are what this article wants to introduce, and the three most common concurrency control mechanisms are described in this article: Respectively pessimistic concurrency control, optimistic concurrency control and multi-version concurrency control, in

1 plus write lock, start the transaction;2, Transaction 2 is a pure read operation, you need to read Line 1, attempting to add a read lock on row 1, because transaction 1 has been written lock, so transaction 2 waits until transaction 1 completes.3. If transaction 2 starts first, transaction 1 also needs to wait until transaction 2 is complete and the read lock is released before it can begin execution.Even if a write operation on a row blocks all read operations on that row, a read operation o

Wen/Ho DengchengGuide:The MySQL kernel technology researcher from the NetEase Research Institute, Ho Dengcheng, InnoDB the multi-version control (abbreviated: MVCC) of the MySQL database and the storage engine, doing in-depth research and detailed text chart analysis, Easy to understand the InnoDB storage engine implementation of the multi-version control technology (abbreviation:

Text/He dengcheng Guidance: He dengcheng, a researcher from the MySQL kernel technology of Netease Research Institute, implements the multi-Version Control (MVCC) of the InnoDB Storage engine of MySQL database, after in-depth research and detailed analysis of text charts, you can easily understand the multi-version control technology (MVCC) implemented by the

application of the database to be pinned.2. What does the actual presentation look like? Look at the following actions:1. Open two client instances, set the transaction isolation level to read Committed, and open the transaction separately.settransaction isolation level read committed;setautocommit=0;begin；2. Client 1 Does the update operation:update testsetname=‘测试‘whereid=32;The results are as follows:3. Client 2 To do the query operation:sel

Principle analysis of MySQL database InnoDB storage engine multi-version control (MVCC) Text/He Dengcheng Guidance: He Dengcheng, a researcher from the MySQL kernel technology of NetEase Research Institute, implements the multi-version control (MVCC) of the InnoDB storage engine of MySQL database, after in-depth resea

. In other words, the change is actually serialized, and because there is no blocking between the different changes, the MVCC scheme consumes more compute resources (all failed commits are re-made). As a result, Lmdb has serialized all the change operations with a lock. These are the most important points in lmdb implementation. Original link: http://www.jianshu.com/p/yzFf8jThe data generated by LEVELDB and Lmdb Caffe is divided into 2 formats: Lmdb a

Tags: database mvccDistributed database data table is divided into multiple parition, distributed on different servers, topology is each server maintenance different version timestamp, compared to the single-machine database, provide MVCC is much more complex, of course, if you have spanner atomic clock, it would be mu

persistence design is continuous, but it is unclear whether it is in the full-durability scene. Some other notable technical details include: The Memsql can be run in a multi-temperature environment, with DDL manual control. That is, the newer data will be put into the memsql, the old data into MySQL one point I think is the best practice, the Memsql team also uphold this concept, is to be confirmed in two or more server RAM, the first time to commit to write parallel group by, This Memsql team

span of repeatable read. Do not allow other transactions to modify this record while reading.3.update A statement, this time will be added to the record row-level exclusive lock (x Lock), and to the end of the transaction, in this scenario, the other read transactions will be blocked. 2. What is the real situation like? Reading does not affect writing, writing does not affect reading. 1. Read does not affect write: The transaction modifies the original data in the form of an

implementation, if (key! = NULL) {Get = new get (key. getrow (); get. addfamily (family); Result = get (get, null);} This problem occurs when an empty result is obtained. Why is this problem. First, let's talk about the principles of hbase MVCC. MVCC is a means to ensure data consistency. During data writing, hbase needs to write hlog, write memstore, and update MVCC