當查詢的數據來自多個數據源，有哪些好的分頁策略？

時間 2020-03-17

標籤當查數據來自多個哪些好的分頁策略简体版

原文原文鏈接

概述

在業務系統開發中，尤爲是後臺管理系統，列表頁展現的數據來自多個數據源，列表頁須要支持分頁，怎麼解決？數據庫

問題

如上圖，數據源可能來自不一樣 DB 數據庫，可能來自不一樣 API 接口，也可能來自 DB 和 API 的組合。json

我這也沒有太好的解決方案，接到這樣的需求，確定首先和需求方溝通，這樣分頁是否合理。數組

無非就兩種方案：bash

數據按期同步，首先將查詢的數據彙總到一個地方，而後再進行查詢分頁。
內存中分頁，首先將查詢的數據存放到內存，而後再進行查詢分頁。

若是以某一數據源進行分頁，其餘字段去其餘數據源獲取，這樣還好處理一些。less

若是以多個數據源融合後再分頁的話，就數據按期同步或內存中分頁吧。學習

數據按期同步方案能夠根據實際狀況去設計同步頻率，至於同步到 ES/MySQL/MongoDB 本身決定便可。ui

關於內存中分頁方案，下面分享兩個小方法，供參考。spa

PHP 方法

$data = [
    0 => ['name' => "姓名1", 'age' => "年齡1"],
    1 => ['name' => "姓名2", 'age' => "年齡2"],
    2 => ['name' => "姓名3", 'age' => "年齡3"],
    3 => ['name' => "姓名4", 'age' => "年齡4"],
    4 => ['name' => "姓名5", 'age' => "年齡5"],
    5 => ['name' => "姓名6", 'age' => "年齡6"],
    6 => ['name' => "姓名7", 'age' => "年齡7"],
    7 => ['name' => "姓名8", 'age' => "年齡8"],
    8 => ['name' => "姓名9", 'age' => "年齡9"],
    9 => ['name' => "姓名10", 'age' => "年齡10"],
];

/**
 * 數組分頁
 * @param array $arrayData 數組數據
 * @param int   $page      第幾頁
 * @param int   $pageSize  每頁展現條數
 * @return array
 */
function arrayToPageData($arrayData = [], $page = 1, $pageSize = 10)
{
    $arrayData = array_values((array)$arrayData);
    $pageData['list'] = array_slice($arrayData, ($page - 1) * $pageSize, $pageSize);
    $pageData['pagination']['total'] = count($arrayData);
    $pageData['pagination']['currentPage'] = $page;
    $pageData['pagination']['prePageCount'] = $pageSize;
    return $pageData;
}

echo json_encode(arrayToPageData($data, 2, 3));
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輸出：設計

{
    "list": [
        {
            "name": "姓名4",
            "age": "年齡4"
        },
        {
            "name": "姓名5",
            "age": "年齡5"
        },
        {
            "name": "姓名6",
            "age": "年齡6"
        }
    ],
    "pagination": {
        "total": 10,
        "currentPage": 2,
        "prePageCount": 3
    }
}
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Go 方法

package main

import (
	"encoding/json"
	"fmt"
)

type User []struct {
	Name string `json:"name"`
	Age  string `json:"age"`
}

type Pagination struct {
	Total        int `json:"total"`
	CurrentPage  int `json:"currentPage"`
	PrePageCount int `json:"prePageCount"`
}

type ListPageData struct {
	List       User `json:"list"`
	Pagination Pagination `json:"pagination"`
}

func main() {
	jsonStr := `[{"name": "姓名1","age": "年齡1"},
		{"name": "姓名2","age": "年齡2"},
		{"name": "姓名3","age": "年齡3"},
		{"name": "姓名4","age": "年齡4"},
		{"name": "姓名5","age": "年齡5"},
		{"name": "姓名6","age": "年齡6"},
		{"name": "姓名7","age": "年齡7"},
		{"name": "姓名8","age": "年齡8"},
		{"name": "姓名9","age": "年齡9"},
		{"name": "姓名10","age": "年齡10"}
	]`

	var user User
	err := json.Unmarshal([]byte(jsonStr), &user)
	if err != nil {
		fmt.Println(err.Error())
	}

	page := 2
	pageSize := 3
	pageData := ArraySlice(user, page, pageSize)

	listPageData := ListPageData{}
	listPageData.List = pageData
	listPageData.Pagination.Total = len(user)
	listPageData.Pagination.CurrentPage = page
	listPageData.Pagination.PrePageCount = pageSize

	jsonData, _ := JsonEncode(listPageData)
	fmt.Println(jsonData)
}

func JsonEncode(v interface{}) (string, error) {
	bytes, err := json.Marshal(v)
	if err != nil {
		return "", err
	}
	return string(bytes), nil
}

func ArraySlice(u User, page int, pageSize int) User {
	offset := (page - 1) * pageSize
	if offset > int(len(u)) {
		panic("offset: the offset is less than the length of u")
	}
	end := offset + pageSize
	if end < int(len(u)) {
		return u[offset:end]
	}
	return u[offset:]
}
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輸出：code

{
    "list": [
        {
            "name": "姓名4",
            "age": "年齡4"
        },
        {
            "name": "姓名5",
            "age": "年齡5"
        },
        {
            "name": "姓名6",
            "age": "年齡6"
        }
    ],
    "pagination": {
        "total": 10,
        "currentPage": 2,
        "prePageCount": 3
    }
}
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