Golang implements paging

With the development of Internet technology and the increasing amount of data, paging queries for data are becoming more and more common. In golang, paging query is not too troublesome, and the efficiency of paging can be improved through some optimizations.

1. Basic paging

In golang, the most basic way of paging query is to use the limit clause in the sql statement. For example:

SELECT * FROM table LIMIT offset, limit;

Among them, offset represents the offset and limit represents the number of records returned. For example, if 10 pieces of data are displayed on each page, then the sql statement on page 1 is:

SELECT * FROM table LIMIT 0, 10;

The sql statement on page 2 is:

SELECT * FROM table LIMIT 10, 10;

This method requires manual calculation of the offset of each page. Measuring and recording quantities is cumbersome and error-prone. Therefore, we can use some libraries to simplify the implementation of paginated queries.

2. Use the gorm library to implement paging

gorm is a commonly used golang orm library, which provides a very convenient paging query method. We can use its built-in Limit and Offset methods to implement paging queries. For example:

db.Limit(10).Offset(0).Find(&users)

Among them, the Limit method represents the number of records returned, the Offset method represents the offset, and the Find method is used to execute the query.

The following is a simple example to demonstrate how to use the gorm library to implement paging query:

package main

import (
    "fmt"
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/mysql"
)

type User struct {
    Id   int
    Name string
    Age  int
}

func main() {
    db, _ := gorm.Open("mysql", "root:123456@/test?charset=utf8mb4&parseTime=True&loc=Local")

    defer db.Close()

    // 创建表
    db.AutoMigrate(&User{})

    // 添加测试数据
    for i := 0; i < 100; i++ {
        user := User{Id: i + 1, Name: fmt.Sprintf("user%d", i+1), Age: i%20 + 10}
        db.Create(&user)
    }

    // 分页查询
    page := 5       // 第5页
    pageSize := 10   // 每页10条记录
    offset := (page - 1) * pageSize // 计算偏移量
    var users []User

    // 查询第5页的记录
    db.Limit(pageSize).Offset(offset).Find(&users)

    // 输出结果
    for _, user := range users {
        fmt.Printf("ID: %d, Name: %s, Age: %d
", user.Id, user.Name, user.Age)
    }
}

Run the above code, the output result is:

ID: 41, Name: user41, Age: 10
ID: 42, Name: user42, Age: 11
ID: 43, Name: user43, Age: 12
ID: 44, Name: user44, Age: 13
ID: 45, Name: user45, Age: 14
ID: 46, Name: user46, Age: 15
ID: 47, Name: user47, Age: 16
ID: 48, Name: user48, Age: 17
ID: 49, Name: user49, Age: 18
ID: 50, Name: user50, Age: 19

3. Use the paging library Implementing paging

In addition to using gorm's built-in paging method, we can also use some third-party paging libraries to implement paging. For example:

1. paginator

paginator is a lightweight golang paging library that supports mysql, postgres, sqlite3 and other databases. It is very simple to use, just specify the current page number, number of records per page and total number of records. The following is an example:

package main

import (
    "fmt"
    "github.com/biezhi/gorm-paginator/pagination"
    _ "github.com/jinzhu/gorm/dialects/mysql"
    "github.com/jinzhu/gorm"
)

type User struct {
    Id   uint `gorm:"primary_key"`
    Name string
    Age  uint
}

func main() {
    db,_ := gorm.Open("mysql", "root:123456@/test?charset=utf8mb4&parseTime=True&loc=Local")

    var users []User
    pagination.Paging(&pagination.Param{
        DB:      db,
        Page:    5,
        Limit:   10,
        OrderBy: []string{"id desc"},
        ShowSQL: true,
    }, &users)

    for _, user := range users {
        fmt.Printf("ID: %d, Name: %s, Age: %d
", user.Id, user.Name, user.Age)
    }
}

2. go-paginator

go-paginator is another lightweight golang paging library that does not rely on any database and is very convenient to use. The following is an example:

package main

import (
    "fmt"
    "github.com/liyuliang/go-paginator"
)

type User struct {
    Id   uint
    Name string
    Age  uint
}

func main() {
    var users []User
    pageSize := 10                                    // 每页记录数
    page, _ := paginator.New(paginator.Config{        // 初始化分页器
        CurrentPage: 5,                               // 当前页码
        PageSize:    pageSize,                         // 每页记录数
        Total:       100,                              // 总记录数
    })

    records := make([]interface{}, 100)                // 模拟100条记录
    for i := 0; i < 100; i++ {
        user := User{Id: uint(i + 1), Name: fmt.Sprintf("user%d", i+1), Age: uint(i%20 + 10)}
        records[i] = user
    }

    pageData := page.Data(records)                     // 获取分页数据
    offset := (page.CurrentPage - 1) * pageSize         // 计算偏移量
    users = pageData[offset : offset+pageSize].([]User) // 获取当前页的记录

    for _, user := range users {
        fmt.Printf("ID: %d, Name: %s, Age: %d
", user.Id, user.Name, user.Age)
    }
}

However, it should be noted that paging libraries usually require us to manually calculate the total number of records, which may affect query efficiency. Therefore, if the total number of records is not very large, we can not use the paging library, but use gorm's built-in paging method.

4. Paging optimization

In practical applications, paging queries may face some performance problems, especially when the amount of data is large. In order to improve query efficiency, the following optimization methods can be used:

1. Use caching

If the data does not need to be updated in real time, the query results can be cached in the memory for next time Obtain data directly from the cache during access to avoid frequent access to the database.

2. Reduce the number of fields returned

If the queried record contains a large number of fields, you can only return some fields to avoid querying a large amount of unnecessary data.

3. Use indexes

Adding indexes to frequently queried fields can greatly improve query efficiency.

4. Batch query

When the amount of data is large, batch query can be used to query a batch of data at a time to avoid querying too much data at once. causing inefficiency.

In general, it is very simple to implement paging query in golang. Through the built-in gorm library and third-party paging library, we can easily implement the paging function, and can improve query efficiency through some optimizations.

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