Data consistency capability: Which is better, MySQL or TiDB?

Data consistency capability: Which one is better, MySQL or TiDB?

Introduction:
Data consistency has always been one of the core issues of distributed databases. In actual application scenarios, it is very important for distributed databases to ensure data consistency. This article will focus on comparing the data consistency capabilities of MySQL and TiDB, and demonstrate their specific implementation methods through code examples.

1. MySQL's data consistency capability
MySQL is a relational database, and its common data consistency mechanisms include "atomicity" and "isolation".

1. Atomicity
   Atomicity means that all transaction operations are either successful or all fail and are rolled back. MySQL ensures atomicity by introducing transactions. Transaction ensures that a set of database operations are either successfully submitted or rolled back if they fail. The following is a simple transaction example:

START TRANSACTION;
UPDATE table1 SET column1 = 'value1' WHERE id = 1;
INSERT INTO table2 (column2) VALUES ('value2');
COMMIT;

In the above example, by using START TRANSACTION and COMMIT to mark the beginning and end of the transaction, it is guaranteed that both operations in the transaction will either succeed, Or all fail and rollback.

2. Isolation
   Isolation means that in multiple transactions executed concurrently, each transaction cannot feel the existence of other transactions, and each transaction is isolated from each other, thereby ensuring the integrity of the data. consistency. MySQL achieves isolation through the MVCC (Multiple Version Concurrency Control) mechanism. In MVCC, each transaction obtains a snapshot when reading data instead of directly reading the data in the database, thus avoiding the problem of data update during the reading process. The following is a simple MVCC example:

SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
START TRANSACTION;
SELECT * FROM table1 WHERE column1 = 'value1';
COMMIT;

In the above example, the isolation level is set to READ COMMITTED through SET TRANSACTION ISOLATION LEVEL, ensuring that each transaction can obtain the data when reading the data. A snapshot to ensure data consistency.

2. TiDB’s data consistency capability
TiDB is a distributed NewSQL database that ensures data consistency through replica synchronization and Raft consistency protocol.

1. Replica Synchronization
   In TiDB, each table will be divided into multiple Regions, and each Region will have multiple Replica. When performing data operations, the replica synchronization mechanism ensures that write operations are synchronized among multiple Replicas. Once the write operation is successfully completed synchronously on multiple Replicas, data consistency can be guaranteed.
2. Raft Consistency Protocol
   In TiDB, the Raft consistency protocol is used to ensure data synchronization and consistency between multiple TiKV nodes. The Raft protocol divides each Region into multiple Raft groups and ensures data consistency through mechanisms such as leader selection, Leader and Follower. Once the write operation is successfully agreed on multiple Raft groups, data consistency can be guaranteed.

3. MySQL vs. TiDB
From the above introduction to the data consistency capabilities of MySQL and TiDB, it can be seen that MySQL and TiDB have certain differences in ensuring data consistency. .

MySQL ensures data consistency through transaction atomicity and multi-version concurrency control (MVCC) mechanism, which is suitable for stand-alone scenarios and small-scale applications.

TiDB ensures data consistency through replica synchronization and Raft consistency protocol, which is suitable for distributed scenarios and large-scale applications.

It is critical to choose a suitable database based on actual application requirements and scenarios.

Conclusion:
MySQL and TiDB both have certain data consistency capabilities, but their respective advantages are different in different application scenarios. When choosing a database, you need to decide which database to use based on actual needs.

(Note: This article introduces the differences between MySQL and TiDB in terms of data consistency capabilities, and provides relevant code examples. Specific database selection also needs to be comprehensively considered based on actual needs and scenarios.)

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