How to check pagination in golang

This article will introduce how to implement paging query in Golang.

When performing paging queries, we need to understand three key parameters:

1. The number of records per page, that is, the maximum number of records displayed on each page.
2. The current page number is used to specify which page of query results we need to display.
3. The total number of records, that is, the total number of records in the entire query result.

In Golang, you can use different methods to implement paging queries. This article will introduce two implementation methods.

Method 1: Use the LIMIT and OFFSET clauses of the database

In Golang, we can use the LIMIT and OFFSET clauses in the SQL statement to query the data in the database in pages. For the MySQL database, we can do this:

func getPageData(pageSize int, pageNum int) ([]*Record, error) {
  offset := (pageNum - 1) * pageSize
  rows, err := db.Query("SELECT * FROM my_table LIMIT ? OFFSET ?", pageSize, offset)
  if err != nil {
    return nil, err
  }
  defer rows.Close()

  var records []*Record
  for rows.Next() {
    record := new(Record)
    if err := rows.Scan(&record.Field1, &record.Field2, &record.Field3); err != nil {
      return nil, err
    }
    records = append(records, record)
  }

  if err := rows.Err(); err != nil {
    return nil, err
  }
  return records, nil
}

In the getPageData function, we pass in the number of records per page pageSize and the number of pages to be displayed pageNum. Then we calculate the offset offset based on pageNum and pageSize, and use the LIMIT and OFFSET clauses to obtain the data record corresponding to the page number from the database.

It should be noted that we need to close the rows object of the database query at the end of the function and handle the error.

Method 2: Use Golang’s built-in slices and arrays for paging

In addition to using the LIMIT and OFFSET clauses of the database, we can also use Golang’s built-in slices and arrays for paging. First we need to get all the query results, and then paginate according to the parameters passed in.

func getPageData(data []*Record, pageSize int, pageNum int) ([]*Record, error) {
  // 计算起始和结束下标
  start := (pageNum - 1) * pageSize
  end := start + pageSize

  // 处理边界情况，确保不越界
  if start > len(data)-1 {
    return nil, errors.New("Page not found")
  }
  if end > len(data) {
    end = len(data)
  }

  // 截取数据切片
  result := data[start:end]

  return result, nil
}

In the getPageData function, we pass in all the query result data, the number of records per page pageSize and the number of pages to be displayed pageNum. Then we calculate the starting and ending subscripts of the data to be intercepted based on pageSize and pageNum, and then use Golang's built-in slice to paginate the query results.

It should be noted that we need to handle boundary situations to ensure that we do not cross the boundary.

Summary

This article introduces two methods to implement paging queries in Golang: using the LIMIT and OFFSET clauses of the database and using Golang's built-in slice and array for paging. Both methods have their own advantages and disadvantages. Which method to use depends on the actual needs of the project.

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