Data consistency and isolation level: comparison between MySQL and TiDB

Data consistency and isolation level: Comparison between MySQL and TiDB

Data consistency and isolation level are very important concepts in the database system. In this article, we will compare two widely used database systems, MySQL and TiDB, to see how they handle data consistency and isolation levels, and provide code examples to illustrate.

1. MySQL’s data consistency and isolation level

MySQL is an open source relational database management system with a long history of development and wide application. MySQL achieves data consistency through the use of transactions and supports multiple isolation levels.

1. Data consistency

MySQL ensures data consistency by using ACID properties. ACID refers to Atomicity, Consistency, Isolation and Durability.

For example, when we execute a transaction in MySQL, if part of the operation in the transaction fails, the entire transaction will be rolled back and the data will be restored to its original state to ensure data consistency.

2. Isolation Level

MySQL supports four isolation levels: Read Uncommitted, Read Committed, and Repeatable Read. and serializable.

The following is an example of using transactions and isolation levels in MySQL:

BEGIN; --开始一个事务
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ; --设置隔离级别为可重复读
SELECT * FROM table_name WHERE column1 = 'value'; --执行SQL查询操作
UPDATE table_name SET column2 = 'new_value' WHERE column1 = 'value'; --执行SQL更新操作
COMMIT; --提交事务

2. TiDB’s data consistency and isolation levels

TiDB is an open source distributed relationship A database that achieves data consistency by using distributed transactions and the Raft consensus algorithm. In TiDB, data consistency and isolation levels are achieved through multi-version concurrency control (MVCC).

1. Data consistency

TiDB uses MVCC to achieve data consistency. When we execute a transaction in TiDB, TiDB creates a snapshot for each read request. If part of the operation in the transaction fails, TiDB can use previous snapshots to restore data to ensure data consistency.

2. Isolation Level

TiDB supports four isolation levels: Read Uncommitted, Read Committed, and Repeatable Read. and serializable. TiDB's default isolation level is repeatable read.

The following is an example of using transactions and isolation levels in TiDB:

START TRANSACTION; --开始一个事务
SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ; --设置隔离级别为可重复读
SELECT * FROM table_name WHERE column1 = 'value'; --执行SQL查询操作
UPDATE table_name SET column2 = 'new_value' WHERE column1 = 'value'; --执行SQL更新操作
COMMIT; --提交事务

3. Comparison between MySQL and TiDB

1. Data consistency

Both MySQL and TiDB use transactions to ensure data consistency. However, TiDB uses MVCC to achieve data consistency and can restore data through snapshots. In contrast, MySQL can only roll back the entire transaction when an error occurs.

2. Isolation Level

Both MySQL and TiDB support four isolation levels, and the isolation level can be set according to specific needs. However, TiDB's default isolation level is Repeatable Read, while MySQL's default isolation level is Read Committed.

Summary:

Data consistency and isolation level are very important concepts in the database system. Both MySQL and TiDB can ensure data consistency by using transactions and supporting multiple isolation levels. However, TiDB provides more flexible and reliable data consistency by using MVCC and snapshots. I hope this article will help you understand the data consistency and isolation levels of MySQL and TiDB.

(The code example is only for illustration, please adjust it according to the actual situation when using it)

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