假设我的JSON如下:
{ "id":0,"keywords":"amount,debited,account,ticket,not,generated,now" }
{ "id":1,"keywords":"how,safe,gocash" }
{ "id":2,"keywords":"how,referral,program,gocash,works" }
如果我的数组就像
array =["how","safe","gocash"];
然后我如何得到第一次检查时的计数; count应该为零,第二个为三,第二个为第二个。 (这意味着字符串中存在多少个数组元素)
我应该采用什么方法或采用什么方法?
答案 0 :(得分:0)
解决此问题的一种方法是,需要对模式进行某种形式的修改,方法是在数组中添加一个包含keywords
的额外字段。运行聚合管道以返回与原始字符串匹配的所需元素数时,此字段变得非常方便。
要添加其他字段,您需要 Bulk API 操作来更新集合,如下所示:
var bulk = db.collection.initializeOrderedBulkOp(),
count = 0;
db.collection.find({"keywords": { "$exists": true, "$type": 2 }}).forEach(function(doc) {
var keywordsArray = doc.keywords.split(',');
bulk.find({ "_id": doc._id }).updateOne({
"$set": { "keywordsArray": keywordsArray }
});
count++;
if (count % 100 == 0) {
bulk.execute();
bulk = db.collection.initializeUnorderedBulkOp();
}
});
if (count % 100 != 0) { bulk.execute(); }
上面创建了一个额外的字段"keywordsArray"
,它是将keywords
字符串拆分为数组的结果。
操作完成后,您的样本集将包含以下文档:
/* 0 */
{
"_id" : ObjectId("561e24e9ba53a16c763eaab4"),
"id" : 0,
"keywords" : "amount,debited,account,ticket,not,generated,now",
"keywordsArray" : [
"amount",
"debited",
"account",
"ticket",
"not",
"generated",
"now"
]
}
/* 1 */
{
"_id" : ObjectId("561e24e9ba53a16c763eaab5"),
"id" : 1,
"keywords" : "how,safe,gocash",
"keywordsArray" : [
"how",
"safe",
"gocash"
]
}
/* 2 */
{
"_id" : ObjectId("561e24e9ba53a16c763eaab6"),
"id" : 2,
"keywords" : "how,referral,program,gocash,works",
"keywordsArray" : [
"how",
"referral",
"program",
"gocash",
"works"
]
}
进入下一阶段,聚合框架管道,运行以下管道操作,该操作使用 $let
, $size
和 $setIntersection
运算符计算出所需的计数结果:
var array = ["how","safe","gocash"];
db.collection.aggregate([
{
"$project": {
"id": 1, "keywords": 1,
"count": {
"$let": {
"vars": {
"commonToBoth": { "$setIntersection": [ "$keywordsArray", array ] }
},
"in": { "$size": "$$commonToBoth" }
}
}
}
}
])
示例输出:
/* 0 */
{
"result" : [
{
"_id" : ObjectId("561e24e9ba53a16c763eaab4"),
"id" : 0,
"keywords" : "amount,debited,account,ticket,not,generated,now",
"count" : 0
},
{
"_id" : ObjectId("561e24e9ba53a16c763eaab5"),
"id" : 1,
"keywords" : "how,safe,gocash",
"count" : 3
},
{
"_id" : ObjectId("561e24e9ba53a16c763eaab6"),
"id" : 2,
"keywords" : "how,referral,program,gocash,works",
"count" : 2
}
],
"ok" : 1
}