带有 Spring Data Mongo 聚合的光标

Question

有没有办法用spring data的mongodb聚合返回游标？

Aggregation agg = newAggregation(
            match(Criteria.where("_id").is(objId)),
            unwind("taskResultContent"),
            project("taskResultContent.executionUUID","taskResultContent.returnContent","taskResultContent.sequency").and("resultID").previousOperation(),
            match(Criteria.where("executionUUID").is(executionUUID)),
            sort(DESC,"sequency")
        ).withOptions(Aggregation.newOptions().cursor(cursor).build());

Answer 1

Solution 在此引用：

从 spring-data-mongo 版本 2.0.0.M4 开始 (AFAIK) MongoTemplate 得到了一个 aggregateStream 方法。

因此您可以执行以下操作：

 AggregationOptions aggregationOptions = Aggregation.newAggregationOptions()
    // this is very important: if you do not set the batch size, 
    // you'll get all the objects at once and you might run out of memory
    // if the returning data set is too large
    .cursorBatchSize(mongoCursorBatchSize)
    .build();

data = mongoTemplate.aggregateStream(Aggregation.newAggregation(
       Aggregation.group("person_id")
                  .count()
                  .as("count"))
                  .withOptions(aggregationOptions), collectionName, YourClazz.class);

Answer 2

mongodb 的 Spring 数据在聚合时不支持使用游标。必须改用 MongoDB java 驱动程序。