Java实现MongoDB分页查询以及优化方案设计_mongotemplate查询大数据量分页 优化

点击这里 > mongoTemplate结合Criteria实现分页、模糊、二级嵌套和时间范围查询等
自带分页api
pageNum：当前页，pageSize：页大小
query.skip((pageNum - 1) * pageSize);
query.limit(pageSize);
当数据量大的时候查询效率降低，所以进行优化设计

自定义分页
1、实现Pageable接口

import lombok.AllArgsConstructor;
import lombok.NoArgsConstructor;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;

import javax.validation.constraints.Min;

/**
 * 自定义分页实现
 */
@NoArgsConstructor
@AllArgsConstructor
public class SpringDataPageable implements Pageable {

	/** 当前页 */
    @Min(1)
    private int pageNumber;
    /** 页大小*/
    @Min(1)
    private int pageSize;
	/** 排序设置 */
    private Sort sort;

    public void setPageNumber(int pageNumber) {
        this.pageNumber = pageNumber;
    }

    @Override
    public int getPageNumber() {
        return this.pageNumber;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    @Override
    public int getPageSize() {
        return this.pageSize;
    }

    @Override
    public long getOffset() {
        return (getPageNumber() - 1) * getPageSize();
    }

    public void setSort(Sort sort) {
        this.sort = sort;
    }

    @Override
    public Sort getSort() {
        return this.sort;
    }

    @Override
    public Pageable next() {
        return null;
    }

    @Override
    public Pageable previousOrFirst() {
        return null;
    }

    @Override
    public Pageable first() {
        return null;
    }

    @Override
    public Pageable withPage(int i) {
        return null;
    }

    @Override
    public boolean hasPrevious() {
        return false;
    }
}
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2、使用自定义分页

	@Transactional
    public Result<PageResult<SubjectInfo>> list(SubjectInfoDTO subjectInfoDTO){
        Criteria criteria = new Criteria();
        // 模糊查询
        if (ObjectUtils.isNotEmpty(subjectInfoDTO.getTitle())) {
            criteria.and("title").regex(subjectInfoDTO.getTitle());
        }
        // 设置排序
        Sort sort = Sort.by(Sort.Direction.ASC,"sort");
        Query query = new Query(criteria).with(sort);
        // 总数
        long count = subjectInfoDao.count(query);
        // 分页条件
        SpringDataPageable pageable = new SpringDataPageable();
        pageable.setPageNumber(subjectInfoDTO.getPageNum());
        pageable.setPageSize(subjectInfoDTO.getPageSize());
        pageable.setSort(sort);
        List<SubjectInfo> list = subjectInfoDao.list(query.with(pageable));
        PageResult<SubjectInfo> pageResult = new PageResult<>();
        pageResult.setTotal((int)count);
        pageResult.setList(list);
        return new Result<PageResult<SubjectInfo>>().ok(pageResult);
    }
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优化方案：
使用情况：在_id自增或者自定义生成的_id有序的情况下

	public Result<Map<String, Object>> list(Map<String, Object> params) {
		// 查询条件
        String name = MapUtils.getString(params, "name");
        Criteria criteria = new Criteria();
        if (ObjectUtils.isNotEmpty(name)){
            criteria.and("name").regex(name);
        }
        Query query = new Query(criteria).with(Sort.by(Sort.Direction.DESC,"_id"));
        long count = personDao.count(query);
        getPage(params, query);
        List<Person> list = personDao.list(query);
        Map<String, Object> result = new HashMap<>();
        result.put("total", (int)count);
        result.put("list", list);
        return new Result<Map<String, Object>>().ok(result);
    }

    // 优化
    private void getPage(Map<String, Object> params, Query query) {
        int pageNum = MapUtils.getInteger(params, "pageNum");
        int pageSize = MapUtils.getInteger(params, "pageSize");
        // 查询优化
        if (pageNum > 1) {
            // number参数是为了取上一页的最后一条数据
            int number = (pageNum - 1) * pageSize;
            query.limit(number);
            List<Person> lists = personDao.list(query);
            // 取出最后一条数据
            Person person = lists.get(lists.size() - 1);
            // 取出id当作条件查询后面的数据
            String id = person.getId();
            // 从上一页最后一条开始查（小于不包括当前条）
            query.addCriteria(Criteria.where("_id").lt(id));
        }
        query.limit(pageSize);
    }
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