春季-mongodb-聚合-需要'cursor'选项 [英] Spring - mongodb - aggregation - The 'cursor' option is required

问题描述

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();
}

引发以下异常:

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.该选项应在哪里配置?

I don't understand what is meant by cursor option here. Where should this option be configured?

编辑这是一个示例用户文档

EDIT Here is a sample user document

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

推荐答案

从文档开始.

MongoDB 3.4不建议使用不带游标的聚合命令 选项，除非管道包含解释选项.什么时候 使用Aggregation命令内联返回聚合结果， 使用默认的批量大小游标指定游标选项:{}或 在光标选项游标中指定批量大小:{batchSize: }.

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版本中将batchSize与AggregationOptions一起传递

You can pass batchSize with AggregationOptions in Spring Mongo 2.x version

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

使用默认批次大小

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

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