How do I implement cursor-based pagination in Go?

Cursor-based pagination allows you to efficiently load pages of data by using a reference to the last item of the previous page. This avoids issues with changes in dataset size or order, providing a more consistent experience while navigating through large datasets. Here's how you can implement it in Go:


package main

import (
    "database/sql"
    "fmt"
    "net/http"

    _ "github.com/lib/pq"
)

const pageSize = 10

type Item struct {
    ID   int
    Name string
}

func getItems(db *sql.DB, cursor string) ([]Item, string, error) {
    query := "SELECT id, name FROM items"
    if cursor != "" {
        query += " WHERE id > " + cursor
    }
    query += " ORDER BY id ASC LIMIT $1"

    rows, err := db.Query(query, pageSize)
    if err != nil {
        return nil, "", err
    }
    defer rows.Close()

    var items []Item
    var nextCursor string
    
    for rows.Next() {
        var item Item
        if err := rows.Scan(&item.ID, &item.Name); err != nil {
            return nil, "", err
        }
        items = append(items, item)
        nextCursor = fmt.Sprintf("%d", item.ID) // Set nextCursor to the last item's ID
    }

    return items, nextCursor, nil
}

func itemsHandler(w http.ResponseWriter, r *http.Request, db *sql.DB) {
    cursor := r.URL.Query().Get("cursor")
    items, nextCursor, err := getItems(db, cursor)
    if err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }

    // Here you would typically marshal items to JSON and respond
}

func main() {
    connStr := "user=username dbname=dbname sslmode=disable"
    db, err := sql.Open("postgres", connStr)
    if err != nil {
        panic(err)
    }
    defer db.Close()

    http.HandleFunc("/items", func(w http.ResponseWriter, r *http.Request) {
        itemsHandler(w, r, db)
    })

    http.ListenAndServe(":8080", nil)
}

How do I implement cursor-based pagination in Go?

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How do I implement cursor-based pagination in Go?

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