mongodb - 如何通过一个字段匹配、分组和排序进行聚合

Question

我正在使用 MongoDB。这是我的文件。集合名称是测试

{"group_id":"111","image":"x1.jpg",create_time:129}
{"group_id":"111","image":"x2.jpg",create_time:94}
{"group_id":"222","image":"x3.jpg",create_time:129}
{"group_id":"222","image":"x4.jpg",create_time:101}

预期输出的示例

{"group_id":"111","count":2,"image":["x1.jpg","x2.jpg"]}
{"group_id":"222","count":2,"image":["x3.jpg","x4.jpg"]}

然后我尝试

db.test.aggregate([{"$group":{"_id":{"group_id":"$group_id"},"count":{"$sum":1},"image":{"$push":"$image"}}},{"$sort":{"count":1}}],{allowDiskUse:true})

但我想得到图像按create_time排序的结果。像这样：

{"group_id":"111","count":2,"image":["x2.jpg","x1.jpg"]}
{"group_id":"222","count":2,"image":["x4.jpg","x3.jpg"]}

任何人都可以指导我正确组合分组和排序吗？

标签： mongodb

Answer 1

再使用一种

{'$sort' : {"group_id" : 1,"image" : 1}}

在聚合管道的开头

db.test.aggregate([
    {'$sort' : {"group_id" : 1,"image" : 1}},
    {"$group":{"_id":{"group_id":"$group_id"},"count":{"$sum":1},"image":{"$push":"$image"}}},
    {"$sort":{"count":1}}],
{allowDiskUse:true})

希望你会得到预期的结果