How to implement query paging in golang

Go language is one of the very popular programming languages ​​​​in recent years. With its advantages of high efficiency and strong scalability, it is widely used by more and more developers in various fields. Among them, golang's query paging function is widely used and is a common functional requirement in many enterprise-level applications. This article will introduce in detail the implementation methods and examples of golang query paging.

1. How to implement golang query paging

1. Using the ORM framework

ORM (Object-Relation Mapping) is a mapping between objects and relational databases Programming technology is also a programming idea. The ORM framework is a relatively mature technology. For example, GORM in golang is an open source ORM framework. It can map structures and database tables, and convert CRUD operations into database query statements, thus achieving Data storage and reading.

GORM is one of the most popular ORM frameworks in golang. It provides very simple API operations that even beginners can easily get started. Using GORM, we can easily implement paging queries based on SQL. The specific implementation code is as follows:

func FindPage(pageNum int, pageSize int) (users []User, total int64, err error) {
    tx := db.Model(&User{})
    tx.Count(&total)
    err = tx.Offset((pageNum - 1)*pageSize).Limit(pageSize).Find(&users).Error
    if err != nil && err != gorm.ErrRecordNotFound {
        return nil, 0, err
    }
    return
}

In the above code, we define a function named FindPage to implement paging queries. First, we obtain the User model through the db.Model() method, then call the Count() method to count the total number of queried records; then, use the Offset and Limit methods to implement paging, and finally call the Find() method to store the query results in in the users variable. In addition, during the query process, special attention needs to be paid to error handling to ensure the safety and reliability of function calls.

2. Customized paging query function

In actual applications, you can also define your own paging query function to better meet business needs. The specific implementation method is as follows:

func CustomFindPage(pageNum int, pageSize int, query string) (users []User, total int64, err error) {
    sql := "SELECT * FROM users WHERE 1 = 1 " + query + " ORDER BY created_at DESC LIMIT ? OFFSET ?"
    err = db.Raw(sql, pageSize, (pageNum-1)*pageSize).Scan(&users).Error
    if err != nil && err != gorm.ErrRecordNotFound {
        return nil, 0, err
    }
    err = db.Model(&User{}).Where(query).Count(&total).Error
    if err != nil {
        return nil, 0, err
    }
    return
}

Unlike the ORM framework, this method uses native SQL statements to implement, and query conditions and query statements can be freely defined to better meet business needs.

2. Golang query paging example

1.ORM framework implements paging query

Refer to the following code:

type User struct {
    gorm.Model
    Name string `gorm:"column:name" json:"name"`
    Age  int    `gorm:"column:age" json:"age"`
}

func main() {
    db, err := gorm.Open("mysql", "user:password@tcp(127.0.0.1:3306)/demo_golang?charset=utf8mb4&parseTime=True&loc=Local")
    if err != nil {
        panic(err)
    }
    defer db.Close()

    var (
        pageNum  = 1
        pageSize = 10
        users    []User
        total    int64
    )
    if users, total, err = FindPage(pageNum, pageSize); err != nil {
        fmt.Printf("查询用户列表失败：%v\n", err)
        return
    }
    fmt.Printf("查询到的用户列表如下：\n%+v\n总记录数：%d\n", users, total)
}

The above code implements the ORM framework based on paging query function. Among them, you need to define the User model first and construct the database through GORM. Then, define a query function named FindPage(), which contains two parameters, pageNum and pageSize, to query the data of the specified page number and the number of records displayed on each page. The function returns two values, one is the queried user list, and the other is the total number of records in the list. Finally, call the FindPage() function in the main function to query and output the paging query results.

2. Custom function to implement paging query

Refer to the following code:

type User struct {
    Name      string `gorm:"column:name" json:"name"`
    Age       int    `gorm:"column:age" json:"age"`
    CreatedAt int64  `gorm:"column:created_at" json:"created_at"`
}

func main() {
    db, err := gorm.Open("mysql", "user:password@tcp(127.0.0.1:3306)/demo_golang?charset=utf8mb4&parseTime=True&loc=Local")
    if err != nil {
        panic(err)
    }
    defer db.Close()

    var (
        pageNum  = 1
        pageSize = 10
        order    = "DESC"
        field    = "created_at"
        query    = ""
        users    []User
        total    int64
    )
    if users, total, err = CustomFindPage(pageNum, pageSize, query, field, order); err != nil {
        fmt.Printf("查询用户列表失败：%v\n", err)
        return
    }
    fmt.Printf("查询到的用户列表如下：\n%+v\n总记录数：%d\n", users, total)
}

The above code implements the query paging function based on the custom paging query function. Among them, you need to define the User model first, set the query parameters (pageNum, pageSize, field, order, query) in the main function, and then call the CustomFindPage() function to implement paging query. It should be noted that in the custom query function, you need to manually splice the SQL statement and query conditions, and use the native SQL statement to query. In addition, we can further modify the custom paging query function according to specific needs to achieve more flexible queries.

3. Summary

This article introduces the implementation methods and examples of golang query paging, from the basic use of ORM framework to custom paging query functions, covering common query methods in practical applications. Whether you are a beginner or an experienced Golang developer, you can learn the specific implementation methods and further understand the features and technologies of the Golang language.

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