问题描述

项目中一个复杂的接口耗时过高，查询的表数据量大，该接口使用了PageHelper进行查询结果进行分页，且该查询sql进行了 联表查询 。通过查看日志，将sql提出，发现是PageHelper组件在进行count计数的时候慢，而这个接口查询因为是分页且走了索引，反而并不慢。

PageHelper.startPage(searchRecordPosition.getPage(), searchRecordPosition.getSize());
List<positionRecordVO> result = positionRecordMapper.getRecordPositionList(searchRecordPosition);

这个是写的sql

<select id="getRecordPositionList" resultType="com.hengtiansoft.hzrc.dal.vo.positionRecordVO">
        SELECT p.id AS positionId,p.NAME AS positionName,p.education_id AS
        educationId,p.working_years_id AS workYearsId,p.recruit_number AS recruitNumber,
        p.high_tech as highTech,p.urgently_hired as urgentlyHired,r.id as recruitmentId,c.id as companyId,
        r.way as positionSource,r.name as recruitmentName,r.status as status,c.name as companyName,
        c.credit_code as creditCode,p.create_ts as releaseTs,
        p.tag_id AS tagId,p.s_region_id AS sRegionId,p.property as property,p.salary_lower as salaryLower,
        p.salary_max as salaryMax,p.contact as contact,p.contact_number as contactNumber,p.update_by as updateBy,r.id as
        recruitmentId
        FROM position_record p
        LEFT JOIN recruitment r ON p.recruitment_id = r.id
        LEFT JOIN company c ON p.company_id = c.id
        <where>
            <if test="null != searchPosition.educationId and searchPosition.educationId != ''">
                AND p.education_id = #{
    
    searchPosition.educationId}
            </if>
            <if test="searchPosition.companyId != null  and searchPosition.companyId != ''">
                and p.company_id = #{
    
    searchPosition.companyId}
            </if>
            <if test="searchPosition.positionName != null and searchPosition.positionName != ''">
                and p.name LIKE CONCAT('%',#{
    
    searchPosition.positionName},'%')
            </if>
            <if test="searchPosition.companyName != null and searchPosition.companyName != ''">
                and c.name LIKE CONCAT('%',#{
    
    searchPosition.companyName},'%')
            </if>
            <if test="searchPosition.startTime != null and searchPosition.endTime != null">
                and p.release_ts<![CDATA[>=]]> #{
    
    searchPosition.startTime}
                and p.release_ts <![CDATA[<=]]> #{
    
    searchPosition.endTime}
                and p.status != '1'
            </if>
            <if test="searchPosition.createStartTs !=null ">
                and p.create_ts <![CDATA[>=]]> #{
    
    searchPosition.createStartTs}
            </if>
            <if test="searchPosition.createEndTs !=null ">
                and p.create_ts <![CDATA[<=]]> #{
    
    searchPosition.createEndTs}
            </if>
            <if test="searchPosition.property !=null and searchPosition.property != ''">
                and p.property = #{
    
    searchPosition.property}
            </if>
            <if test="searchPosition.salaryMax !=null and searchPosition.salaryMax != ''">
                and p.salary_max <![CDATA[<=]]> #{
    
    searchPosition.salaryMax}
            </if>
            <if test="searchPosition.salaryLower !=null and searchPosition.salaryLower != ''">
                and p.salary_lower <![CDATA[>=]]> #{
    
    searchPosition.salaryLower}
            </if>
            <if test="searchPosition.workingYearsId !=null and searchPosition.workingYearsId != ''">
                and p.working_years_id = #{
    
    searchPosition.workingYearsId}
            </if>
            <if test="searchPosition.sRegionId !=null and searchPosition.sRegionId != ''">
                and p.s_region_id = #{
    
    searchPosition.sRegionId}
            </if>
            <if test="searchPosition.urgentlyHired !=null and searchPosition.urgentlyHired != ''">
                and p.urgently_hired = #{
    
    searchPosition.urgentlyHired}
            </if>
            <if test="searchPosition.tagId != null and searchPosition.tagId != ''">
                and p.tag_id = #{
    
    searchPosition.tagId}
            </if>
            <if test="searchPosition.recruitmentName != null and searchPosition.recruitmentName != ''">
                and r.name LIKE CONCAT('%',#{
    
    searchPosition.recruitmentName},'%')
            </if>
            <if test="searchPosition.positionSource !=null and searchPosition.positionSource != ''">
                and r.way = #{
    
    searchPosition.positionSource}
            </if>
            <if test="searchPosition.status !=null and searchPosition.status != ''">
                and r.status = #{
    
    searchPosition.status}
            </if>
        </where>
        order by p.create_ts desc
    </select>

解决方案

问题出在count上，而count慢其实是因为联表，所以我选择重写count，利用if标签，避免联表，做条件查询的时候，由于做了筛选，数据量会小很多，所以不慢

<select id="getRecordPositionList_COUNT" resultType="Long">
        SELECT count(*)
        FROM position_record p
        <if test="searchPosition.recruitmentName != null and searchPosition.recruitmentName != '' and searchPosition.positionSource !=null and searchPosition.positionSource != '' and searchPosition.status !=null and searchPosition.status != ''">
            LEFT JOIN recruitment r ON p.recruitment_id = r.id
        </if>
        <if test="null != searchPosition.companyName and searchPosition.companyName != ''">
            LEFT JOIN company c ON p.company_id = c.id
        </if>
        <where>
            <if test="null != searchPosition.educationId and searchPosition.educationId != ''">
                AND p.education_id = #{
    
    searchPosition.educationId}
            </if>
            <if test="searchPosition.companyId != null  and searchPosition.companyId != ''">
                and p.company_id = #{
    
    searchPosition.companyId}
            </if>
            <if test="searchPosition.positionName != null and searchPosition.positionName != ''">
                and p.name LIKE CONCAT('%',#{
    
    searchPosition.positionName},'%')
            </if>
            <if test="searchPosition.companyName != null and searchPosition.companyName != ''">
                and c.name LIKE CONCAT('%',#{
    
    searchPosition.companyName},'%')
            </if>
            <if test="searchPosition.startTime != null and searchPosition.endTime != null">
                and p.release_ts<![CDATA[>=]]> #{
    
    searchPosition.startTime}
                and p.release_ts <![CDATA[<=]]> #{
    
    searchPosition.endTime}
                and p.status != '1'
            </if>
            <if test="searchPosition.createStartTs !=null ">
                and p.create_ts <![CDATA[>=]]> #{
    
    searchPosition.createStartTs}
            </if>
            <if test="searchPosition.createEndTs !=null ">
                and p.create_ts <![CDATA[<=]]> #{
    
    searchPosition.createEndTs}
            </if>
            <if test="searchPosition.property !=null and searchPosition.property != ''">
                and p.property = #{
    
    searchPosition.property}
            </if>
            <if test="searchPosition.salaryMax !=null and searchPosition.salaryMax != ''">
                and p.salary_max <![CDATA[<=]]> #{
    
    searchPosition.salaryMax}
            </if>
            <if test="searchPosition.salaryLower !=null and searchPosition.salaryLower != ''">
                and p.salary_lower <![CDATA[>=]]> #{
    
    searchPosition.salaryLower}
            </if>
            <if test="searchPosition.workingYearsId !=null and searchPosition.workingYearsId != ''">
                and p.working_years_id = #{
    
    searchPosition.workingYearsId}
            </if>
            <if test="searchPosition.sRegionId !=null and searchPosition.sRegionId != ''">
                and p.s_region_id = #{
    
    searchPosition.sRegionId}
            </if>
            <if test="searchPosition.urgentlyHired !=null and searchPosition.urgentlyHired != ''">
                and p.urgently_hired = #{
    
    searchPosition.urgentlyHired}
            </if>
            <if test="searchPosition.tagId != null and searchPosition.tagId != ''">
                and p.tag_id = #{
    
    searchPosition.tagId}
            </if>
            <if test="searchPosition.recruitmentName != null and searchPosition.recruitmentName != ''">
                and r.name LIKE CONCAT('%',#{
    
    searchPosition.recruitmentName},'%')
            </if>
            <if test="searchPosition.positionSource !=null and searchPosition.positionSource != ''">
                and r.way = #{
    
    searchPosition.positionSource}
            </if>
            <if test="searchPosition.status !=null and searchPosition.status != ''">
                and r.status = #{
    
    searchPosition.status}
            </if>
        </where>
    </select>

使用方式

原有的代码不需要动，只需要在mybatis的xml文件里添加一个count查询
这里注意以下三点即可：

1.id和对应的查询语句保持一致，并且以 _COUNT 结尾，注意大小写
2.入参和对应的查询语句保持一致
3.出参为 resultType=“Long”
4.PageHelper的版本一定要在 5.0.5 以上