我已将我的第一步移至MongoDB，但我在编写复杂查询时遇到了困难。
我的收藏中有几个这样的项目：
{
"_id" : "sku001",
"deposits" : [
{
"deposit_id" : "deposit01",
"total" : "3",
"sizes" : [
{
"size" : "36",
"stock" : "2"
},
{
"size" : "38",
"stock" : "0"
},
{
"size" : "40",
"stock" : "0"
},
{
"size" : "42",
"stock" : "0"
},
{
"size" : "44",
"stock" : "0"
},
{
"size" : "46",
"stock" : "1"
},
{
"size" : "48",
"stock" : "0"
},
{
"size" : "50",
"stock" : "0"
},
{
"size" : "52",
"stock" : "0"
}
]
},
{
"deposit_id" : "deposit02",
"total" : "5",
"sizes" : [
{
"size" : "36",
"stock" : "1"
},
{
"size" : "38",
"stock" : "1"
},
{
"size" : "40",
"stock" : "0"
},
{
"size" : "42",
"stock" : "1"
},
{
"size" : "44",
"stock" : "0"
},
{
"size" : "46",
"stock" : "1"
},
{
"size" : "48",
"stock" : "1"
},
{
"size" : "50",
"stock" : "0"
},
{
"size" : "52",
"stock" : "0"
}
]
},
{
"deposit_id" : "deposit03",
"total" : "2",
"sizes" : [
{
"size" : "36",
"stock" : "1"
},
{
"size" : "38",
"stock" : "0"
},
{
"size" : "40",
"stock" : "0"
},
{
"size" : "42",
"stock" : "1"
},
{
"size" : "44",
"stock" : "0"
},
{
"size" : "46",
"stock" : "0"
},
{
"size" : "48",
"stock" : "0"
},
{
"size" : "50",
"stock" : "0"
},
{
"size" : "52",
"stock" : "0"
}
]
},
{
"deposit_id" : "deposit04",
"total" : "0",
"sizes" : [
{
"size" : "36",
"stock" : "0"
},
{
"size" : "38",
"stock" : "0"
},
{
"size" : "40",
"stock" : "0"
},
{
"size" : "42",
"stock" : "0"
},
{
"size" : "44",
"stock" : "0"
},
{
"size" : "46",
"stock" : "0"
},
{
"size" : "48",
"stock" : "0"
},
{
"size" : "50",
"stock" : "0"
},
{
"size" : "52",
"stock" : "0"
}
]
}
]
}
并且想编写一个查询来输出这个结果文档：
{
"_id" : "sku001",
"total": 10,
"sizes" [
{
"size" : "36",
"stock" : "4"
},
{
"size" : "38",
"stock" : "1"
},
{
"size" : "40",
"stock" : "0"
},
{
"size" : "42",
"stock" : "2"
},
{
"size" : "44",
"stock" : "0"
},
{
"size" : "46",
"stock" : "2"
},
{
"size" : "48",
"stock" : "1"
},
{
"size" : "50",
"stock" : "0"
},
{
"size" : "52",
"stock" : "0"
}
]
}
这样：
我知道我需要将ObjectMapper mapper = new ObjectMapper();
Foo response = mapper.readValue("{\"some_key\": {\"a\": 1, \"b\": \"text\"}}", Foo.class);
与aggregate()，$unwind和$group一起使用，但我不了解如何以及以何种顺序。< / p>
你能帮帮我吗？我使用MongoDB版本3.4.3
答案 0 :(得分：0)
在将聚合框架中的运算符应用于生成所需报告之前，您可能希望先更改架构，即需要将字符串值解析为数字，然后运行聚合操作。
要更改架构，您需要迭代集合，并为集合中的每个文档更新需要将字符串值解析为数字的键。如果无法更改原始集合架构，您可能希望使用更新的架构创建临时集合。 对于前者，请考虑运行以下更新操作（对于相对较小的集合）：
db.collection.find({}).snapshot()
.forEach(function(doc) {
var query = { "_id": doc._id },
update = { "$set": {} };
for (var i=0; i<doc.deposits.length; i++) {
update["$set"]["deposits."+i+".total"] = parseInt(doc.deposits[i].total);
for (var j=0; j<doc.deposits[i].sizes.length; j++) {
update["$set"]["deposits."+i+".sizes."+j+".stock"] = parseInt(doc.deposits[i].sizes[j].stock);
}
}
printjson(query);
printjson(update);
db.collection.updateOne( query, update );
});
拥有正确的架构将允许您在以下聚合操作中运行管道，该操作应该为您提供所需的报告：
db.collection.aggregate([
{ "$unwind": "$deposits" },
{ "$unwind": "$deposits.sizes" },
{
"$group": {
"_id": {
"id": "$_id",
"size": "$deposits.sizes.size"
},
"total_stock": { "$sum": "$deposits.sizes.stock" },
"deposits": {
"$push": {
"deposit_id": "$deposits.deposit_id",
"total": "$deposits.total"
}
}
}
},
{ "$unwind": "$deposits" },
{
"$group": {
"_id": {
"id": "$_id.id",
"deposit_id": "$deposits.deposit_id"
},
"sizes": {
"$push": {
"size": "$_id.size",
"stock": "$total_stock"
}
},
"total": { "$first": "$deposits.total" }
}
},
{
"$group": {
"_id": "$_id.id",
"total": { "$sum": "$total" },
"sizes": { "$first": "$sizes" }
}
}
])