多表联查如何提高效率

Posted 2023-04-08

1. 确保连接的字段有索引
2. 尽可能把限制条件写在前面（取尽可能少的行）
3. 每次只取必须的数据列（取尽可能少的列）追问

我现在是做左连接，是要把两表连接on条件对应的字段做索引吗？

追答

最好是这样。

追问

条件字段需要做索引吗？

追答

如果可能，加上。

参考技术A 多表联查如何提高效率？
1. 确保连接的字段有索引
2. 尽可能把限制条件写在前面（取尽可能少的行）
3. 每次只取必须的数据列（取尽可能少的列）

mongoDB多表联查以及MongoTemplate的表联查API使用

一对一联查

结构

//多表联查
db.TABLE_NAME.aggregate([
    
        $lookup://连表
            from:'table0',    //被关联的表名
            localField:'localField',    //关联标识符    主动关联的表
            foreignField:'foreignField',    //关联标识符    被关联的表
            as:'table0'        //被关联的表的别名，下面涉及到被关联的表的操作，都用这个
        
    ,
    
        $unwind:'$table0'//扁平化,将数组数据拆分    被关联的表
    ,
    
        $match:<query>//正常查询
        $match:'or':[<query>,<query>]//多条件查询    或
    ,
    
        $project:                //要显示的字段
            '_id':0,    //_id
            'F1':'$table.f1',//取别称    主动关联的表的数据
            'F2':'$table0.f2',    被关联的表的数据
            'F3'://case when
                $cond:if:$gte:['$f3',30],then:0,else:50
            
        
    ,
]).forEach(function(item))    //遍历    对多表联查出来的数据做操作    一般创建新表
    db.aaaa.insert(item);    //创建新表

案例

db.risk_group_info.aggregate([
    
        '$lookup':
            'from':'person',
            'localField':'person_id',
            'foreignField':'_id',
            'as':'person'
        
    ,
    '$unwind':'$person',
    
        '$project':
            'name':'$person.name'
         
     
])

结果

java代码

    Aggregation aggregation = Aggregation.newAggregation(
    Aggregation.lookup(MongoColConfig.COL_PERSON, "person_id", "_id", "person"),
    Aggregation.unwind("person", true),
    Aggregation.project("person.name").and("person.name").as("name"));
    AggregationResults<JSONObject> aggregate = MongoTemplate.aggregate(aggregation, MongoColConfig.COL_RISK_GROUP_INFO, JSONObject.class);
    if (!ObjectUtils.isEmpty(aggregate) && MyCollectionUtil.isNotEmpty(aggregate.getMappedResults())) 
        List<JSONObject> mappedResults = aggregate.getMappedResults();
    

一对多联查

主表一条数据对应联查的副表的多条数据，主表对象中的集合存放副表的多条数据

mongo接收实体

@Data
public class SendAssistBaseJointQuery 
    private String id;

    private String primaryId;

    private String taskId;

    private String taskType;

    private String riskPersonType;

    private String caseId;

    private String caseName;

    private String pointPositionId;

    private String sitePointPositionName;

    private String pointPositionType;

    private String assistDataInfoId;

    private String cancelReason;

    private String backReason;

    private String backTime;

    private String dataSource;

    private String updateTime;

    // 任务表字段
    private String createTime;
    private String dealUsername;
    private String taskStatus;
    String sendAssistTaskStatus;
    String receiveFeedbackTaskStatus;

    private List<AssistDataInfo> assistDataInfos;


    @Data
    // assist_data_info表中字段
    public class AssistDataInfo 
        private String type;
        private String assistLetterName;
        private Integer sendCount;
        private Integer feedbackCount;
        private List<String> assistDataAnnexes;
    

java代码

        Criteria criteria = new Criteria();
        List<AggregationOperation> aggregationOperation = new ArrayList<>();

        aggregationOperation.add(Aggregation.match(criteria));
        // 主表一对一，关联task表
        aggregationOperation.add(Aggregation.lookup(MongoColConfig.COL_TASK, "task_id", "_id", "task"));
        aggregationOperation.add(Aggregation.unwind("task", true));
        // 主表一对多，关联assist_data_info表
        aggregationOperation.add(Aggregation.lookup(MongoColConfig.ASSIST_DATA_INFO, "task_id", "task_id", "assist_data_info"));
        aggregationOperation.add(Aggregation.unwind("assist_data_info", true));
        aggregationOperation.add(Aggregation.project("_id")
                .and("_id").as("primary_id")
                .and("site_point_position_name").as("site_point_position_name")
                .and("task_id").as("task_id").and("task_type").as("task_type")
                .and("risk_person_type").as("risk_person_type").and("case_id").as("case_id")
                .and("case_name").as("case_name").and("point_position_id").as("point_position_id")
                .and("site_point_position_name").as("site_point_position_name").and("point_position_type").as("point_position_type")
                .and("assist_data_info_id").as("assist_data_info_id").and("cancel_reason").as("cancel_reason")
                .and("back_time").as("back_time")
                .and("data_source").as("data_source").and("update_time").as("update_time")
                .and("task.deal_username").as("deal_username").and("task.create_time").as("create_time")
                .and("task.task_status").as("task_status")
                .and("task.send_assist_task_status").as("send_assist_task_status")
                .and("task.receive_feedback_task_status").as("receive_feedback_task_status")
                .and("task.cancel_reason").as("cancel_reason")
                .and("task.back_reason").as("back_reason")
                .and("assist_data_info.type").as("type")
                .and("assist_data_info.assist_data_annexes").as("assist_data_annexes").and("assist_data_info.feedback_count").as("feedback_count")
                .and("assist_data_info.assist_letter_name").as("assist_letter_name").and("assist_data_info.send_count").as("send_count"));


        Aggregation aggregationPage = Aggregation.newAggregation(aggregationOperation);

        // 这些被basicDBObject.append的字段为assist_data_info表中字段。使用list集合接收
        BasicDBObject basicDBObject = new BasicDBObject();
        basicDBObject.append("type", "$type");
        basicDBObject.append("assist_data_annexes", "$assist_data_annexes");
        basicDBObject.append("assist_letter_name", "$assist_letter_name");
        basicDBObject.append("feedback_count", "$feedback_count");
        basicDBObject.append("send_count", "$send_count");
        // 根据task_id字段聚合，取每个字段第一个字段附别名。（这些是主字段）
        aggregationPage.getPipeline().add(Aggregation.group("task_id")
                .first("primary_id").as("primary_id")
                .first("site_point_position_name").as("site_point_position_name")
                .first("task_id").as("task_id").first("task_type").as("task_type")
                .first("risk_person_type").as("risk_person_type").first("case_id").as("case_id")
                .first("case_name").as("case_name").first("point_position_id").as("point_position_id")
                .first("site_point_position_name").as("site_point_position_name").first("point_position_type").as("point_position_type")
                .first("assist_data_info_id").as("assist_data_info_id").first("cancel_reason").as("cancel_reason")
                .first("back_reason").as("back_reason").first("back_time").as("back_time")
                .first("data_source").as("data_source").first("update_time").as("update_time")
                .first("deal_username").as("deal_username").first("create_time").as("create_time")
                .first("cancel_reason").as("cancel_reason")
                .first("task_status").as("task_status")
                .first("send_assist_task_status").as("send_assist_task_status")
                .first("receive_feedback_task_status").as("receive_feedback_task_status")
                // 需要和实体中assistDataInfos对应，集合名接收关联assist_data_info表中数据
                .addToSet(basicDBObject).as("assist_data_infos"));

        // 分页
        int skip = (pageReq.getPage() - 1) * pageReq.getPageSize();
        aggregationPage.getPipeline().add(Aggregation.sort(Sort.Direction.DESC, "create_time"));
        aggregationPage.getPipeline().add(Aggregation.skip((long) skip));
        aggregationPage.getPipeline().add(Aggregation.limit(ret.getPageSize()));

        aggregationPage = aggregationPage.withOptions(AggregationOptions.builder().allowDiskUse(true).build());
        AggregationResults<SendAssistBaseJointQuery> aggregatePage = MongoTemplate.aggregate(aggregationPage, MongoColConfig.SEND_ASSIST_BASE, SendAssistBaseJointQuery.class);
        if (!ObjectUtils.isEmpty(aggregatePage) && MyCollectionUtil.isNotEmpty(aggregatePage.getMappedResults())) 
            List<SendAssistBaseJointQuery> mappedResults = aggregatePage.getMappedResults();
        
        // 总数
        aggregationTotal.getPipeline().add(Aggregation.group("task_id").count().as("count"));
        aggregationPage = aggregationPage.withOptions(AggregationOptions.builder().allowDiskUse(true).build());
        aggregationTotal = aggregationTotal.withOptions(AggregationOptions.builder().allowDiskUse(true).build());
        AggregationResults<JSONObject> aggregateTotal = MongoTemplate.aggregate(aggregationTotal, MongoColConfig.SEND_ASSIST_BASE, JSONObject.class);
        if (!ObjectUtils.isEmpty(aggregateTotal) && MyCollectionUtil.isNotEmpty(aggregateTotal.getMappedResults())) 
            aggregateTotal.getMappedResults().size();