How to implement distributed transactions and cross-table queries in MySQL?

How to implement distributed transactions and cross-table queries in MySQL?

Introduction:
As the scale of applications continues to expand, the demand for distributed systems is becoming more and more urgent. In distributed systems, database transaction processing and cross-table queries have become an important technical challenge. This article will introduce how to implement distributed transactions and cross-table queries in MySQL to cope with the needs of distributed systems.

1. Distributed transactions
Distributed transactions are transactions when operations involving multiple databases must be committed or rolled back as a whole. MySQL's distributed transactions can be implemented in two ways: distributed transactions based on the XA protocol and distributed transactions based on two-phase commit (2PC).

1. Distributed transactions based on XA protocol
   XA protocol is a global transaction protocol participated by multiple database management systems. It consists of two phases: preparation phase and submission phase. In the preparation phase, each database will send a prepare request to the coordinator to tell the coordinator the preparation status of the transaction. The coordinator will wait for all databases to be ready before sending a commit request to all participants, telling them to commit the transaction. If there is a problem with any participant, the coordinator will send a rollback request to all participants, telling them to roll back the transaction.
   The following is a sample code that uses the XA protocol to implement distributed transactions:

Connection conn1 = null;
Connection conn2 = null;
try {
   // 获取数据库连接1
   conn1 = dataSource1.getConnection();
   conn1.setAutoCommit(false);
   // 获取数据库连接2
   conn2 = dataSource2.getConnection();
   conn2.setAutoCommit(false);

   // 在数据库1上执行操作
   // ...

   // 在数据库2上执行操作
   // ...
   
   // 提交分布式事务
   conn1.commit();
   conn2.commit();
} catch (SQLException e) {
   // 回滚分布式事务
   if (conn1 != null) {
       conn1.rollback();
   }
   if (conn2 != null) {
       conn2.rollback();
   }
} finally {
   // 关闭数据库连接
   if (conn1 != null) {
       conn1.close();
   }
   if (conn2 != null) {
       conn2.close();
   }
}

2. Distributed transactions based on two-phase commit (2PC)
   Two-phase commit is a A method to ensure the consistency of transactions through agreements between the coordinator and participants. It contains two phases: voting phase and submission phase. During the voting phase, the coordinator sends a message to the participants asking them if they are ready to commit the transaction. If all participants are ready, the coordinator sends a commit message to all participants, asking them to commit the transaction. If any participant is not ready or the votes received by the coordinator are inconsistent, the coordinator sends an abort message to all participants, asking them to roll back the transaction.
   The following is a sample code that uses two-phase commit to implement distributed transactions:

Connection conn1 = null;
Connection conn2 = null;
try {
   // 获取数据库连接1
   conn1 = dataSource1.getConnection();
   conn1.setAutoCommit(false);
   // 获取数据库连接2
   conn2 = dataSource2.getConnection();
   conn2.setAutoCommit(false);

   // 在数据库1上执行操作
   // ...

   // 在数据库2上执行操作
   // ...
   
   // 第一阶段：询问所有参与者是否准备好提交事务
   conn1.prepare();
   conn2.prepare();
   
   // 第二阶段：提交或回滚事务
   if (conn1.isReady() && conn2.isReady()) {
       conn1.commit();
       conn2.commit();
   } else {
       conn1.rollback();
       conn2.rollback();
   }
} catch (SQLException e) {
   // 回滚分布式事务
   if (conn1 != null) {
       conn1.rollback();
   }
   if (conn2 != null) {
       conn2.rollback();
   }
} finally {
   // 关闭数据库连接
   if (conn1 != null) {
       conn1.close();
   }
   if (conn2 != null) {
       conn2.close();
   }
}

2. Cross-table query
Cross-table query refers to involving multiple queries at the same time in one query statement Table query operations. In MySQL, cross-table queries can be implemented through the following methods: subqueries, join queries, full-text indexes, and partitioned tables.

1. Subquery
   Subquery is a query method based on the query result as another query condition. It can be nested in SELECT statements, FROM statements, WHERE statements and other statements to obtain relevant data. The following is a sample code that uses subqueries to implement cross-table queries:

SELECT * FROM table1 WHERE id IN (SELECT id FROM table2 WHERE condition);

2. Join query
   A join query is a method that combines data in two or more tables according to related Field matching and correlation query methods. Through join queries, multiple tables can be involved in one query at the same time, and relevant data can be obtained based on the association conditions between fields. The following is a sample code that uses join queries to implement cross-table queries:

SELECT * FROM table1 JOIN table2 ON table1.column = table2.column WHERE condition;

3. Full-text index
   Full-text index is an indexing method based on text content rather than just keywords. By creating a full-text index, you can perform fuzzy matching using keywords in cross-table queries to obtain relevant results. The following is a sample code that uses a full-text index to implement cross-table query:

SELECT * FROM table1 WHERE MATCH(column) AGAINST('keyword');

4. Partitioned table
   A partitioned table is divided into several small tables according to certain rules. Ways to improve query performance and maintainability. By creating partitions in a partitioned table, only relevant partitions can be queried in cross-table queries, reducing query time. The following is a sample code that uses partitioned tables to implement cross-table queries:

SELECT * FROM partitioned_table WHERE condition;

Conclusion:
In distributed systems, MySQL's distributed transactions and cross-table queries are two important technologies challenge. Transaction consistency between multiple databases can be guaranteed by using distributed transactions based on the XA protocol or distributed transactions based on two-phase commit. In cross-table queries, you can use subqueries, join queries, full-text indexes, and partition tables to implement multi-table query operations. Through reasonable selection and use of technical means, the needs of distributed systems can be better met.

Reference:

• O'Reilly. (2014). High Performance MySQL. O'Reilly Media, Inc.

The above is the detailed content of How to implement distributed transactions and cross-table queries in MySQL?. For more information, please follow other related articles on the PHP Chinese website!