![](/img/trans.png)
[英]Translate mongodb aggregate query into Java/Kotlin Spring Data
[英]Mongodb Aggregate (Java/Spring) query to fetch last subelement
我有以下结构名称“讨论”。 我想获取用户讨论中的最后一条消息。 我尝试遵循不完整的Spring MongoDB查询,能否让我知道如何在每个讨论中仅获取一条消息(按lastmodifieddate排序),或在用户是对话中最后一条消息的接收者的位置找到讨论。
Aggregation aggr = newAggregation(
match(Criteria.where("participants").regex(Pattern.compile(userid))),
unwind("messages"),
match(new Criteria().orOperator(Criteria.where("messages.touserId").is(userid),Criteria.where("messages.fromuserId").is(userid))),
sort(Direction.DESC, "messages.lastModifiedDate"),
group("_id").push("messages").as("messages"),
project("_id","messages")
);
{
"_id": {
"$oid": "57c2d7c8e4b0bcf181b7db0a"
},
"_class": "xxxxx",
"participants": [
"56893b22e4b0e8d1c6a25783",
"56893bb6e4b0e8d1c6a25785",
"577c2f6ee4b09ccb44d14415"
],
"messages": [
{
"_id": {
"$oid": "57c2d7c8e4b0bcf181b7db08"
},
"fromuserId": "577c2f6ee4b09ccb44d14415",
"fromuser": "xxxx",
"touserId": "56893b22e4b0e8d1c6a25783",
"touser": "Bloreshop1",
"message": "Check Product Price",
"isMute": false,
"index": 1,
"createDate": {
"$date": "2016-08-28T12:23:36.037Z"
},
"lastModifiedDate": {
"$date": "2016-08-28T12:23:36.037Z"
},
"createdBy": "xxxx",
"lastModifiedBy": "xxxxx"
},
{
"_id": {
"$oid": "57c2d7c8e4b0bcf181b7db09"
},
"fromuserId": "577c2f6ee4b09ccb44d14415",
"fromuser": "xxxxxx",
"touserId": "56893bb6e4b0e8d1c6a25785",
"touser": "Bloreshop2",
"message": "Check Product Price",
"isMute": false,
"index": 2,
"createDate": {
"$date": "2016-08-28T12:23:36.302Z"
},
"lastModifiedDate": {
"$date": "2016-08-28T12:23:36.302Z"
},
"createdBy": "xxxxx",
"lastModifiedBy": "xxx"
}
],
"discussionTopic": "Check Product Price",
"messageCount": 2,
"createDate": {
"$date": "2016-08-28T12:23:36.318Z"
},
"lastModifiedDate": {
"$date": "2016-08-28T12:23:36.318Z"
},
"createdBy": "xxxx",
"lastModifiedBy": "xxxxx"
}
您正在寻找$ slice(aggregation) 。 当前版本1.9.5不支持slice。
Aggregation aggr = newAggregation(
match(Criteria.where("participants").regex(Pattern.compile(userid))),
unwind("messages"),
match(new Criteria().orOperator(Criteria.where("messages.touserId").is(userid), Criteria.where("messages.fromuserId").is(userid))),
sort(Direction.DESC, "messages.lastModifiedDate"),
group("_id").push("messages").as("messages"),
project("_id").and("messages").project("slice", 1));
未发行版本(2.x)支持切片
Aggregation aggr = newAggregation(
match(Criteria.where("participants").regex(Pattern.compile(userid))),
unwind("messages"),
match(new Criteria().orOperator(Criteria.where("messages.touserId").is(userid), Criteria.where("messages.fromuserId").is(userid))),
sort(Direction.DESC, "messages.lastModifiedDate"),
group("_id").push("messages").as("messages"),
project("_id").and("messages").slice(1));
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.