java – Spring – mongodb – aggregation – ‘cursor’选项是必需的

执行以下聚合管道：

public void getMostLikedItems () {
        UnwindOperation unwind = Aggregation.unwind("favoriteItems");
        GroupOperation group = Aggregation.group("favoriteItems").count().as("likes");
        SortOperation sort = Aggregation.sort(Sort.Direction.DESC,"likes");

        Aggregation aggregation = newAggregation(unwind,group,sort);
        DBObject result = mongoTemplate.aggregate(aggregation,"users",LikedItem.class).getRawResults();
}

抛出以下异常：

com.mongodb.MongoCommandException: Command Failed with error 9: 'The 'cursor' option is required,except for aggregate with the explain argument' on server localhost:27017. The full response is { "ok" : 0.0,"errmsg" : "The 'cursor' option is required,except for aggregate with the explain argument","code" : 9,"codeName" : "FailedToParse" }

我不明白这里的光标选项是什么意思.应该在哪里配置此选项？

编辑这是一个示例用户文档

{
  "_id": "5a6df13552f42a34dcca9aa6","username": "user1","password": "$2a$10$p0OXq5PPa41j1e4iPcGZHuWjoKJ983sieS/ovFI.cVX5Whwj21WYi","favoriteItems": [
    {
      "_id": "5a0c6b2dfd3eb67969316d6d","name": "item1","city": "Rabat"
    },{
      "_id": "5a0c680afd3eb67969316d0b","name": "item2","city": "Rabat"
    }
  ]
}

最佳答案

来自文档.

MongoDB 3.4 deprecates the use of aggregate command without the cursor
option,unless the pipeline includes the explain option. When
returning aggregation results inline using the aggregate command,
specify the cursor option using the default batch size cursor: {} or
specify the batch size in the cursor option cursor: { batchSize:
}.

您可以在Spring Mongo 2.x版本中使用Aggregationoptions传递batchSize

Aggregation aggregation = newAggregation(unwind,group).withOptions(newAggregationoptions().cursorBatchSize(100).build());

使用默认批量大小

Aggregation aggregation = newAggregation(unwind,group).withOptions(newAggregationoptions().cursor(new Document()).build());