golang transaction query

With the continuous development of the Internet and mobile Internet, data processing has become an important part of enterprises' business operations. In order to ensure data integrity and consistency, many companies use transaction technology to manage data operations. In this article, we will explore how to implement transaction queries in Golang.

1. What is transaction query

In the database, a transaction refers to a series of operations, which are regarded as a whole. These operations either all execute successfully or all fail. , there is no alternate execution of success and failure. Transactions are to ensure the integrity and consistency of the database.

Transactions contain four basic attributes (ACID):

1. Atomicity: All operations in a transaction either succeed or fail, with no intermediate state.

2. Consistency: Before and after transaction execution, the integrity and consistency of the database are guaranteed, and the constraints of the data (such as primary keys, foreign keys, etc.) are maintained.

3. Isolation: When accessing transactions concurrently, each transaction should be independent and should not interfere with each other.

4. Durability: Once the transaction is committed, the changes will be permanently saved in the database and will not be lost even if there is a system failure or downtime.

2. Golang transaction query

In Golang, use the database driver to implement transaction query. Golang supports a variety of database drivers, including MySQL, PostgreSQL, Oracle, etc.

Let’s take MySQL as an example to introduce how to implement transaction query in Golang.

1. Connect to the database

First, we need to establish a database connection. In Golang, we can use the database/sql package to connect to the MySQL database as follows:

import (
    "database/sql"
    _ "github.com/go-sql-driver/mysql"
)

func main() {
    db, err := sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/dbname")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()
}

Here, we use the sql.Open() function Open a MySQL connection. The sql.Open() function receives two parameters: the first parameter is the MySQL driver name (in this case mysql), and the second parameter is the MySQL connection string, where Including the database user name, password, host address and port number, and database name.

2. Create a transaction

In MySQL, you can use the BEGIN statement to start a transaction. In order to use MySQL transactions in Golang, we need to use the db.Begin() function to start a transaction.

tx, err := db.Begin()
if err != nil {
    log.Fatal(err)
}

Here, the db.Begin() function will return a transaction object. If an error occurs, an error is returned.

3. Perform transaction operations

Executing SQL statements in a transaction is the same as executing SQL statements individually. It is important to note that every SQL statement executed within a transaction will be affected by the transaction.

// 执行事务操作
_, err = tx.Exec("UPDATE users SET name = ? WHERE id = ?", "Alice", 1)
if err != nil {
    tx.Rollback()
    log.Fatal(err)
}

// 提交事务
err = tx.Commit()
if err != nil {
    log.Fatal(err)
}

Here, we use the tx.Exec() function to execute the SQL statement. If an error occurs, use the tx.Rollback() function to undo the transaction. If all operations are performed successfully, the transaction is committed using the tx.Commit() function.

4. Handling concurrent access

In a transaction, if multiple users access the same data table at the same time, race conditions may occur. To avoid this situation, we need to use MySQL's lock mechanism to handle concurrent access.

MySQL provides two types of locks: Shared Lock and Exclusive Lock. Shared locks allow multiple users to view data at the same time, but do not allow them to modify the data. An exclusive lock allows a user to have exclusive access to data during the lock period, and other users cannot read or modify the data.

In Golang, we can use the tx.Exec() function to add FOR SHARE or FOR when executing the SELECT statement UPDATE option to set the lock type.

// 查询数据并设置共享锁
rows, err := tx.Query("SELECT * FROM users WHERE id = ? FOR SHARE", 1)
if err != nil {
    tx.Rollback()
    log.Fatal(err)
}
defer rows.Close()

// 查询数据并设置排它锁
rows, err := tx.Query("SELECT * FROM users WHERE id = ? FOR UPDATE", 1)
if err != nil {
    tx.Rollback()
    log.Fatal(err)
}
defer rows.Close()

Here, we use the tx.Query() function to execute the SELECT statement and set the lock type. Note that the tx.Query() function must be used when executing query statements in a transaction. (If you use the db.Query() function, the query results will not be affected by the transaction)

5. Transaction rollback

If an error occurs in the transaction, we need Use the tx.Rollback() function to undo a transaction and roll back to the state before starting the transaction.

// 执行事务操作
_, err = tx.Exec("UPDATE users SET name = ? WHERE id = ?", "Alice", 1)
if err != nil {
    tx.Rollback()
    log.Fatal(err)
}

// 提交事务
err = tx.Commit()
if err != nil {
    log.Fatal(err)
}

Here, if the tx.Exec() function returns an error, the tx.Rollack() function is used to roll back the transaction.

6. Complete code example

import (
    "database/sql"
    "log"
    _ "github.com/go-sql-driver/mysql"
)

func main() {
    // 建立数据库连接
    db, err := sql.Open("mysql", "user:password@tcp(127.0.0.1:3306)/dbname")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    // 开始事务
    tx, err := db.Begin()
    if err != nil {
        log.Fatal(err)
    }

    // 查询数据并设置锁类型
    rows, err := tx.Query("SELECT * FROM users WHERE id = ? FOR UPDATE", 1)
    if err != nil {
        tx.Rollback()
        log.Fatal(err)
    }
    defer rows.Close()

    // 执行事务操作
    _, err = tx.Exec("UPDATE users SET name = ? WHERE id = ?", "Alice", 1)
    if err != nil {
        tx.Rollback()
        log.Fatal(err)
    }

    // 提交事务
    err = tx.Commit()
    if err != nil {
        log.Fatal(err)
    }
}

The above is how to implement transaction query in Golang. The use of transaction technology can effectively ensure the integrity and consistency of data, which is very important for enterprises to process data operations.

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