Master the principles of MySQL MVCC and improve data reading efficiency

Master the principles of MySQL MVCC and improve data reading efficiency

Introduction:
MySQL is a commonly used relational database management system, and MVCC (Multi- Version Concurrency Control) is a commonly used concurrency control mechanism in MySQL. Mastering the MVCC principle can help us better understand the internal working principles of MySQL and improve the efficiency of data reading. This article will introduce the principle of MVCC and how to use this principle to improve data reading efficiency.

1. The concept of MVCC
1.1 Definition of MVCC
MVCC is a mechanism to control concurrency when multiple transactions operate the database at the same time. It isolates conflicts between transactions, thereby Ensure data consistency and concurrency.

1.2 The basic principle of MVCC
The basic principle of MVCC is to perform version control on each transaction, and the data versions read and written between different transactions are different. Read operations can only read committed versions, while write operations create new versions.

2. How to implement MVCC
2.1 Undo log and version chain
In order to implement MVCC, MySQL internally maintains an Undo log and version chain. The Undo log records the data before modification, while the version chain records different versions of data.

2.2 Snapshot read and current read
In MySQL, snapshot read and current read are two common reading methods. Snapshot read reads the committed data version, while current read reads the latest data version.

3. How to improve data reading efficiency
3.1 Avoid long transactions
Long transactions will hold locks and occupy resources, causing other transactions to be unable to read or write data. Therefore, we should try to avoid the existence of long transactions.

3.2 Set the transaction isolation level appropriately
In MySQL, there are multiple transaction isolation levels to choose from. Choosing the appropriate isolation level can improve data reading efficiency to a certain extent.

3.3 Optimizing query statements
Properly designing and optimizing query statements can reduce unnecessary data reading and query operations and improve the efficiency of data reading.

3.4 Use appropriate indexes
By using appropriate indexes, you can reduce the number of data accesses and improve the efficiency of data reading. But at the same time, too many or inappropriate indexes can also reduce performance.

3.5 Reasonable partitioning of tables and partitions
Dividing and partitioning large data tables can reduce lock competition during queries and improve concurrency and data reading efficiency.

4. Summary
MVCC is a commonly used mechanism in MySQL concurrency control. Mastering the principles of MVCC is very important to improve data reading efficiency. By avoiding long transactions, setting reasonable transaction isolation levels, optimizing query statements, using appropriate indexes, and reasonably dividing tables and partitions, we can maximize the efficiency of MySQL data reading.

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