如何解决Amazon Document DB中的Mongodb聚合功能 插入文档查询输出
我在运行于Amazon document DB的mongodb中有以下文档,即mongodb 3.6
{"item":"journal","instock":[{"warehouse":"A","qty":[2,4,5] },{"warehouse":"C","qty":[8,5,2] },{"warehouse":"F","qty":[3] },{"warehouse":"K",8] },{"warehouse":"P","qty":[3,7,9] } ] }
使用此数据,我只想提取数量为5的库存对象。 我在本地mongodb(4.2)上运行的查询如下:
db.inventory.aggregate({$match:{"item": "journal"}},{$project:{instock: {$filter: {input: "$instock",cond: {$in: [5,"$$this.qty"] } } } }})
给出预期结果:
{ "_id" : ObjectId("5f59a6bd85a366711c35fc7b"),"instock" : [ { "warehouse" : "A","qty" : [ 2,5 ] },{ "warehouse" : "C","qty" : [ 8,2 ] } ] }
但是问题是当我在DocumentDB中运行相同的查询时,如果给出错误: “ errmsg”:“ $ in需要一个数组作为第二个参数,找到:string”,
根据mongodb文档,自版本3.2起就有$ filter操作。所以我不太确定这是什么问题。有什么想法吗?
解决方法
我正在研究为什么此查询无法针对Amazon DocumentDB使用。同时,这是一个重写的查询,可在Amazon DocumentDB上运行,并且应执行原始查询试图执行的操作:
插入文档
db.coll.insert({
"item": "journal","instock": [{
"warehouse": "A","qty": [2,4,5]
},{
"warehouse": "C","qty": [8,5,2]
},{
"warehouse": "F","qty": [3]
},{
"warehouse": "K",8]
},{
"warehouse": "P","qty": [3,7,9]
}]
});
查询
db.coll.aggregate([
{ $match: { "item": "journal" } },{ $unwind: "$instock" },{ $match: { "instock.qty": 5 } },{
"$group": {
"_id": { "id": "$id","item": "$item" },"instock": {
"$push": {
"warehouse": "$instock.warehouse","qty": "$instock.qty"
}
}
}
}]).pretty()
输出
{
"_id" : {
"item" : "journal"
},"instock" : [
{
"warehouse" : "A","qty" : [
2.0,4.0,5.0
]
},{
"warehouse" : "C","qty" : [
8.0,5.0,2.0
]
}
]
}