我有以下查询:
match := bson.D{{"$match", bson.D{{"venue", venueID}}}}
group := bson.D{{"$lookup", bson.M{
"from": "labels",
"localField": "label_ids",
"foreignField": "_id",
"as": "labels",
}}, {"$graphLookup", bson.M{
"from": "menus",
"startWith": "$child_ids",
"connectFromField": "child_ids",
"connectToField": "_id",
"as": "children",
"maxDepth": 5,
"depthField": "level",
}}}
cur, err := m.collection.Aggregate(ctx, mongo.Pipeline{group, match})
我有两个相关的字段,其中一个是图形结构(菜单),每个父元素都有一个ID数组,用于每个子元素。
第二个字段,标签,只是一对多的查询。标签和菜单应该是可重用的,因此不能嵌入单个父实体中。上面概述的查询对我来说很有意义,但是出现以下错误:
A pipeline stage specification object must contain exactly one field.
谢谢!
答案 0 :(得分:1)
MongoDB管道中的每个元素都必须是单个阶段,例如$match
,$group
等
您的group
元素包含两个阶段:$lookup
和$graphLookup
。
将它们拆分并单独列出:
match := bson.D{{"$match", bson.D{{"venue", venueID}}}}
group := bson.D{{"$lookup", bson.M{
"from": "labels",
"localField": "label_ids",
"foreignField": "_id",
"as": "labels",
}}}
graphLookup := bson.D{{"$graphLookup", bson.M{
"from": "menus",
"startWith": "$child_ids",
"connectFromField": "child_ids",
"connectToField": "_id",
"as": "children",
"maxDepth": 5,
"depthField": "level",
}}}
cur, err := m.collection.Aggregate(ctx, mongo.Pipeline{group, graphLookup, match})