猫鼬聚合，不能动态添加someField:{$ not;空值 } [英] Mongoose aggregate, can't dynamically add someField: { $not; null }

问题描述

我正在根据用户输入的条件生成查询.用户可以通过选择来设置自定义过滤.

I am generating a query based on user's input as to conditions. User can set custom filtering by making selections.

到目前为止，一切都还好.例如，这有效:

All is okay, so far. For example, this works:

exports.getJoinedTransactions = function(firmId, page, pageSize, billerId, matterId, words, billingStatus, cb) {

    let firmIdToObjId = new mongoose.Types.ObjectId(global.user.firmId);
    let query = { firmId: firmIdToObjId };

    if ( typeof billerId === "object" ) {
        billerId = new mongoose.Types.ObjectId(billerId);
        query.contactId = billerId;
    }

    if ( typeof matterId === "object" ) {
        matterId = new mongoose.Types.ObjectId(matterId);
        query.matterId = matterId;
    }

    ....

    myAggregate = [
        { $sort: { date: -1 } },
        {
            $match: query
        },

    ....

    Transactions.aggregate(myAggregate).exec( function(err, transactions) {

        if (err) {
            console.log(err);
        }

        someVar = transactions.length;

    ....

这可以很好地构建查询并运行良好.但是，现在我有一点不同的要求要添加到列表中.我还想包括一个可能为null或不为null的查询.像这样:

This builds the query nicely and runs well. Now, however, I have a slightly different requirement to add to the list. I want to also include a possible query for null or not null. Something like this:

if (typeof billingStatus === "string" && billingStatus != "") {

    if (billingStatus === "billed") {
        query.billId = { $not: null } ;          <-- This does not work.
    } else if (billingStatus === "unbilled") {
        query.billId = null;                     <-- This works!
    }
}

当我运行此代码时，将状态设置为开帐单"，则不会引发任何错误.但是，也不会返回事务".引发错误:无法读取未定义的属性'length'."

When I run this code setting the status to "billed," no error is thrown. However, no "transactions" are returned, either. An error is thrown: "Cannot read property 'length' of undefined."

如何修复损坏的部分?

顺便说一句，总共有5条记录，并且有1条记帐.当它起作用时，我应该收到1条记录.

By the way, there are 5 records total, and 1 is billed. When it works, I should receive the 1 record.

推荐答案

有一个特殊的 $ type 运算符，可用于检查属性类型.因此，如果您的集合中有明确的null，它们的类型将为10.类型代码的完整列表在此处.因此，要检查属性是否不等于null，可以使用以下查询.

There's a special $type operator which allows you to check property type. So if you have explicit nulls in your collection, they will be of type 10. Full list of type codes here. So to check if a property is not equal to null you can use following query.

db.transactions.aggregate([
    {
        $match: {
            billId: {  $not: { $type: 10 } }  
        }
    }
])

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