Using MySQL to manage metadata in Go language

With the advent of the big data era, data management has become more and more important. When performing data processing, metadata management is an essential part. Metadata is data that describes data and is mainly used for data management, maintenance and query. As an open source relational database system, MySQL has a wide range of application scenarios. In the Go language, it is also very convenient to use MySQL to manage metadata.

This article will introduce how to use MySQL in Go language to implement metadata management.

1. Install the MySQL driver

When using MySQL, we need to install the corresponding Go driver. Currently, the more commonly used MySQL drivers in the Go language arego-sql-driver/mysql and mysql-connector-go. In this article we will use go-sql-driver/mysql as the MySQL driver.

The installation method is as follows:

go get github.com/go-sql-driver/mysql

2. Connect to MySQL database

You need to use the database/sql package and go-sql to connect to the MySQL database -driver/mysqldriver. The following is an example of connecting to a MySQL database:

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

func main() {
    db, err := sql.Open("mysql", "用户名:密码@tcp(地址:端口)/数据库名")
    if err != nil {
        // 错误处理
    }
    defer db.Close()
}

In the above example, we use the sql.Open() method to connect to the MySQL database, where mysql is the MySQL driver name . We need to specify the username, password, address, port and database name to connect to the database. The db object returned by the sql.Open() method can be used for subsequent operations.

3. Create a table

In MySQL, we can use the CREATE TABLE statement to create a table. The following is an example of creating a metadata table:

func createMetadataTable(db *sql.DB) error {
    _, err := db.Exec(`CREATE TABLE IF NOT EXISTS metadata (
        id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
        name VARCHAR(20) NOT NULL,
        type VARCHAR(20) NOT NULL,
        size INT NOT NULL,
        create_time TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
        update_time TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
    )ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`)
    if err != nil {
        return err
    }
    return nil
}

In the above code, we use the CREATE TABLE statement to create a table named metadata. The table contains 5 fields: id, name, type, size, create_time and update_time. Among them, id is an auto-increment field, name represents the name, type represents the type, size represents the size, create_time Indicates the creation time, update_time indicates the update time. The table engine is InnoDB and the character set is utf8mb4.

4. Insert data

To insert new data into the metadata table, you can use the db.Exec() method. The following is an example of inserting data into the metadata table:

func insertMetadata(db *sql.DB, name string, type string, size int) error {
    _, err := db.Exec(`INSERT INTO metadata (name, type, size) VALUES (?, ?, ?)`, name, type, size)
    if err != nil {
        return err
    }
    return nil
}

In the above code, we use the db.Exec() method to insert a piece of data into the metadata table. Use ? to represent placeholders, name, type and size will replace ? in turn.

5. Query data

You can use the db.Query() and db.QueryRow() methods to query data from the metadata table. The following is an example of querying data from the metadata table:

func selectMetadata(db *sql.DB, id int) (*Metadata, error) {
    var metadata Metadata
    err := db.QueryRow(`SELECT * FROM metadata WHERE id=?`, id).Scan(&metadata.id, &metadata.name, &metadata.typ, &metadata.size, &metadata.createTime, &metadata.updateTime)
    if err != nil {
        if err == sql.ErrNoRows {
            return nil, nil
        }
        return nil, err
    }
    return &metadata, nil
}

In the above code, we use the db.QueryRow() method to query a piece of data from the metadata table. Use the Scan() method to map the query results into a structure.

6. Update data

To update data in the metadata table, you can use the db.Exec() method. The following is an example of updating data:

func updateMetadata(db *sql.DB, id int, name string, typ string, size int) error {
    _, err := db.Exec(`UPDATE metadata SET name=?, type=?, size=? WHERE id=?`, name, typ, size, id)
    if err != nil {
        return err
    }
    return nil
}

In the above code, we use the db.Exec() method to update a piece of data in the metadata table.

7. Delete data

You can use the db.Exec() method to delete data from the metadata table. The following is an example of deleting data:

func deleteMetadata(db *sql.DB, id int) error {
    _, err := db.Exec(`DELETE FROM metadata WHERE id=?`, id)
    if err != nil {
        return err
    }
    return nil
}

In the above code, we use the db.Exec() method to delete a piece of data in the metadata table.

Summary

This article introduces the method of using MySQL to implement metadata management in Go language. We use the database/sql package and the go-sql-driver/mysql driver to connect to the MySQL database, and use SQL statements to create metadata tables, insert, query, update and delete data . These methods can be used in various data management scenarios to make data management easier and more efficient.

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