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MySQL深分頁問題原理與三種解決方案

更新時(shí)間：2023年05月04日 08:44:40 作者：JAVA前線

本文主要介紹了MySql深分頁問題原理與解決方案，文中通過示例代碼介紹的非常詳細(xì)，對大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值，需要的朋友們下面隨著小編來一起學(xué)習(xí)學(xué)習(xí)吧

1 深分頁問題

1.1 創(chuàng)建表

CREATE TABLE `player` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主鍵',
  `player_id` varchar(256) NOT NULL COMMENT '運(yùn)動(dòng)員編號',
  `player_name` varchar(256) NOT NULL COMMENT '運(yùn)動(dòng)員名稱',
  `height` int(11) NOT NULL COMMENT '身高',
  `weight` int(11) NOT NULL COMMENT '體重',
  `game_performance` text COMMENT '最近一場比賽表現(xiàn)',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8

1.2 新增100萬條數(shù)據(jù)

@SpringBootTest(classes = TestApplication.class)
@RunWith(SpringJUnit4ClassRunner.class)
public class PlayerServiceTest {

    @Resource
    private PlayerRepository playerRepository;

    @Test
    public void initBigData() {
        for (int i = 0; i < 1000000; i++) {
            PlayerEntity entity = new PlayerEntity();
            entity.setPlayerId(UUID.randomUUID().toString());
            entity.setPlayerName("球員_" + System.currentTimeMillis());
            entity.setWeight(150);
            entity.setHeight(188);
            entity.setGamePerformance("{\"runDistance\":8900.0,\"passSuccess\":80.12,\"scoreNum\":3}");
            playerRepository.insert(entity);
        }
    }
}

1.3 深分頁語句

select * from player limit 990000,5

1.4 結(jié)果分析

查詢耗時(shí)：1.233秒
本語句目標(biāo)查詢[990001-990005]五條數(shù)據(jù)
但是執(zhí)行時(shí)需要排序[1-990005]數(shù)據(jù)
最終丟棄[1-990000]只返回[990001-990005]數(shù)據(jù)

2 深分頁優(yōu)化方案

2.1 方案一

我們可以從業(yè)務(wù)形態(tài)維度去解決，可以參考搜索引擎解決方案。因?yàn)镋S也存在深分頁問題，搜索引擎解決方案是在業(yè)務(wù)上會(huì)限制查詢頁數(shù)。因?yàn)轫摂?shù)越大，內(nèi)容相關(guān)度越低，所以頁數(shù)太大對業(yè)務(wù)價(jià)值不高。MySQL可以類比處理：

限制查詢頁數(shù)
限制全量導(dǎo)出
查詢時(shí)要求帶必要條件（時(shí)間范圍、userId）

2.2 方案二

2.2.1 優(yōu)化語句

select * from player a, (select id as tmpId from player limit 990000,5) b WHERE a.id = b.tmpId

2.2.2 執(zhí)行計(jì)劃

(1) 查看計(jì)劃

explain select * from player a, (select id as tmpId from player limit 990000,5) b WHERE a.id = b.tmpId

(2) 執(zhí)行順序

id越大執(zhí)行順序越靠前
id相同則按照行數(shù)從上到下執(zhí)行
本語句執(zhí)行順序如下圖：

第一步和第二步表示執(zhí)行子查詢
第三步表示player表與子查詢關(guān)聯(lián)

(3) explain type

訪問類型是重要分析指標(biāo)：

(4) explain Extra

Extra表示執(zhí)行計(jì)劃擴(kuò)展信息重點(diǎn)關(guān)注三個(gè)：

2.2.3 結(jié)果分析

查詢耗時(shí)：0.5秒
原因是覆蓋索引提升分頁查詢效率（只查詢ID列）
覆蓋索引含義是查詢時(shí)索引列完全包含查詢列
using index表示使用覆蓋索引，性能提升

2.3 方案三

2.3.1 優(yōu)化語句

select * from player where id > 990000 LIMIT 5

2.3.2 執(zhí)行計(jì)劃

(1) 查看計(jì)劃

explain select * from player where id > 990000 LIMIT 5

(2) 結(jié)果分析

查詢耗時(shí)：0.001秒
range表示索引范圍搜索性能尚可

(3) 適用場景

不適用跳頁場景
只適用【上一頁】【下一頁】場景

3 MyBatis

<mapper namespace="com.test.java.front.test.mysql.deep.page.repository.PlayerRepository">

	<resultMap id="BaseResultMap" type="com.test.java.front.test.mysql.deep.page.entity.PlayerEntity">
		<id column="id" jdbcType="BIGINT" property="id" />
		<result column="player_id" jdbcType="VARCHAR" property="playerId" />
		<result column="player_name" jdbcType="VARCHAR" property="playerName" />
		<result column="height" jdbcType="INTEGER" property="height" />
		<result column="weight" jdbcType="INTEGER" property="weight" />
		<result column="game_performance" jdbcType="LONGVARCHAR" property="gamePerformance" />
	</resultMap>

	<sql id="Base_Column_List">
		id, player_id, player_name, height, weight, game_performance
	</sql>

	<sql id="conditions">
		<where>
			<if test="playerId != null">
				and player_id = #{playerId,jdbcType=VARCHAR}
			</if>
		</where>
	</sql>

	<sql id="pager">
		<if test="skip != null and limit != null">
			limit #{skip}, #{limit}
		</if>
	</sql>

	<!-- 查詢條數(shù) -->
	<select id="selectPageCount" parameterType="com.test.java.front.test.mysql.deep.page.param.biz.PlayerQueryParam" resultType="java.lang.Long">
		select count(*) from player
		<include refid="conditions" />
	</select>

	<!-- 分頁方式1：普通分頁存在深分頁問題 -->
	<!-- select * from player limit 990000,5 -->
	<select id="selectPager1" parameterType="com.test.java.front.test.mysql.deep.page.param.biz.PlayerQueryParam" resultMap="BaseResultMap">
		select
		<include refid="Base_Column_List" />
		from player
		<include refid="conditions" />
		<include refid="pager" />
	</select>

	<!-- 分頁方式2：覆蓋索引優(yōu)化深分頁問題 -->
	<!-- select * from player a, (select id as tmpId from player limit 990000,5) b where a.id = b.tmpId -->
	<select id="selectPager2" parameterType="com.test.java.front.test.mysql.deep.page.param.biz.PlayerQueryParam" resultMap="BaseResultMap">
		select
		<include refid="Base_Column_List" />
		from player a,
		(
		select id as tmpId from player
		<include refid="conditions" />
		<include refid="pager" />
		) b
		where a.id = b.tmpId
	</select>

	<!-- 分頁方式3：Id分頁不支持跳頁 -->
	<!-- select * from player where id > 990000 limit 5 -->
	<select id="selectPager3" parameterType="com.test.java.front.test.mysql.deep.page.param.biz.PlayerQueryIdParam" resultMap="BaseResultMap">
		select
		<include refid="Base_Column_List" />
		<include refid="conditions" />
		from player where id > #{startId} limit #{pageSize}
	</select>
</mapper>