从另一个数组中删除数组元素

Question

我有一个MongoDB对象，比如：

{
"courseName": "ML",
"user": ObjectId("6087dc4c2ba7a828363c9fca"),
"questions": [  
{
"topics": [
"a","b"
],
},
{
"topics": [
"a","b","d"
],
}
]
}

我想将具有courseName和user的问题查找为问题，我想删除与输入主题匹配的主题。

我该怎么做？

如果我的输入是["a"]，那么更新输出应该看起来像：

{
"courseName": "ML",
"user": ObjectId("6087dc4c2ba7a828363c9fca"),
"questions": [  
{
"topics": [
"b"
],
},
{
"topics": [
"b","d"
],
}
]
}

Answer 1

• questions中所有元素的$[]位置和$in运算符的检查条件

db.collection.updateMany(
{ 
"courseName": "ML",
"user": ObjectId("6087dc4c2ba7a828363c9fca"),
"questions.topics": { $in: ["a"] } 
},
{
$pull: {
"questions.$[].topics": { $in: ["a"] }
}
}
)

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