mongoTemplate查询效率对比

前言：经常苦恼mongoTemplate的查询效率太慢，想找出最快的查询方法，测试如下：

1.四个查询方法比较

    @ApiOperation("test")
    @GetMapping("/test")
    public void test() {

        Query query = new Query();
        query.addCriteria(Criteria.where("_id").is(1181511074567032832L).and("tenant_id").is(1178574081264586752L));

        long t1 = System.currentTimeMillis();
        mongoTemplate.find(query, FormData.class, "formData");

        long t2 = System.currentTimeMillis();
        mongoTemplate.findOne(query, FormData.class, "formData");

        long t3 = System.currentTimeMillis();
        mongoTemplate.findAll(FormData.class, "formData");

        long t4 = System.currentTimeMillis();
        mongoTemplate.findById(1181511074567032832L, FormData.class, "formData");

        long t5 = System.currentTimeMillis();
        System.out.println("查询带collectionName");
        System.out.println("find()的询时间是：" + (t2 - t1));
        System.out.println("findOne()的询时间是：" + (t3 - t2));
        System.out.println("findAll()的询时间是：" + (t4 - t3));
        System.out.println("findById()的询时间是：" + (t5 - t4));
    }

4次查询统计结果

查询带collectionName
find()的询时间是：27
findOne()的询时间是：29
findAll()的询时间是：4022
findById()的询时间是：30

2.查询时，不带collectionName参数

    @ApiOperation("test2")
    @GetMapping("/test2")
    public void test2() {

        Query query = new Query();
        query.addCriteria(Criteria.where("_id").is(1181511074567032832L).and("tenant_id").is(1178574081264586752L));

        long t1 = System.currentTimeMillis();
        mongoTemplate.find(query, FormData.class);

        long t2 = System.currentTimeMillis();
        mongoTemplate.findOne(query, FormData.class);

        long t3 = System.currentTimeMillis();
        mongoTemplate.findAll(FormData.class);

        long t4 = System.currentTimeMillis();
        mongoTemplate.findById(1181511074567032832L, FormData.class);

        long t5 = System.currentTimeMillis();
        System.out.println("查询不带collectionName");
        System.out.println("find()的询时间是：" + (t2 - t1));
        System.out.println("findOne()的询时间是：" + (t3 - t2));
        System.out.println("findAll()的询时间是：" + (t4 - t3));
        System.out.println("findById()的询时间是：" + (t5 - t4));
    }

4次查询统计结果

查询不带collectionName
find()的询时间是：27
findOne()的询时间是：27
findAll()的询时间是：4154
findById()的询时间是：34

3.结论

find()最快;
findAll()最慢；
带collectionName的查询快于不带的，同时能避免各种子类引发的问题。

4.看源码

find();

    public  List find(Query query, Class entityClass, String collectionName) {
        Assert.notNull(query, "Query must not be null!");
        Assert.notNull(collectionName, "CollectionName must not be null!");
        Assert.notNull(entityClass, "EntityClass must not be null!");
        return this.doFind(collectionName, query.getQueryObject(), query.getFieldsObject(), entityClass, new MongoTemplate.QueryCursorPreparer(query, entityClass));
    }

findOne();

    @Nullable
    public  T findOne(Query query, Class entityClass, String collectionName) {
        Assert.notNull(query, "Query must not be null!");
        Assert.notNull(entityClass, "EntityClass must not be null!");
        Assert.notNull(collectionName, "CollectionName must not be null!");
        if (ObjectUtils.isEmpty(query.getSortObject()) && !query.getCollation().isPresent()) {
            return this.doFindOne(collectionName, query.getQueryObject(), query.getFieldsObject(), entityClass);
        } else {
            query.limit(1);
            List results = this.find(query, entityClass, collectionName);
            return results.isEmpty() ? null : results.get(0);
        }
    }

发现，findOne()源码中调用了find()，所以findOne()慢于find();
findById();

    @Nullable
    public  T findById(Object id, Class entityClass, String collectionName) {
        Assert.notNull(id, "Id must not be null!");
        Assert.notNull(entityClass, "EntityClass must not be null!");
        Assert.notNull(collectionName, "CollectionName must not be null!");
        MongoPersistentEntity persistentEntity = (MongoPersistentEntity)this.mappingContext.getPersistentEntity(entityClass);
        String idKey = "_id";
        if (persistentEntity != null && persistentEntity.getIdProperty() != null) {
            idKey = ((MongoPersistentProperty)persistentEntity.getIdProperty()).getName();
        }

        return this.doFindOne(collectionName, new Document(idKey, id), new Document(), entityClass);
    }

findAll();

    public  List findAll(Class entityClass, String collectionName) {
        return this.executeFindMultiInternal(new MongoTemplate.FindCallback(new Document(), new Document()), (CursorPreparer)null, new MongoTemplate.ReadDocumentCallback(this.mongoConverter, entityClass, collectionName), collectionName);
    }