Spring-mongodb-聚合-需要'cursor'选项

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?

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"

}

]

}

回答:

从文档。

MongoDB

3.4不建议使用不带游标选项的聚合命令,除非管道包括解释选项。使用聚合命令以内联方式返回聚合结果时,请使用默认批处理大小游标:{}指定游标选项,或在游标选项游标:{batchSize:}中指定批处理大小。

你可以通过batchSizeAggregationOptions在spring蒙戈2.x版

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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