NEDB 查询在数组上使用 $nin 返回误报

Question

我在使用 NEDB find() 查询结构时遇到问题。

下面的 find() 查询应该 return 所有新消息：发送到指定的 email 或 All 组并且尚未被阅读或发送的email 指定。

但是，它是 returning 误报。例如，尽管 email IS 的数组中的 email IS 属性正在评估中。我正在使用 $nin 运算符，但我无法弄清楚我做错了什么？欢迎所有建议:)

var email = 'anotheraddress@gmail.com';
var message_query = [];
    message_query.push({$and: [{to: 'All'}, {'data.readBy': {$nin: [email]}}]});
    message_query.push({$and: [{to: email}, {'data.read': {$exists: false}}]});

    message
        .find({
            $and: [
                {$not: {from: email}},
                {$or: message_query}
            ]
        })
        .exec(function (err, results) {

        });

这是平面文件的片段。这两个不应该 returned，但它们是 :/

...

{ 
  to: 'All',
  toname: 'Some Name',
  from: 'someaddress@gmail.com',
  fromname: 'Some other Name',
  message: 'A message for all...',
  timestamp: 1502473320,
  imtype: 'msg',
  _id: 'K66iP3dZHbYTfGgK',
  data:
   { readBy:
      [ 'someotheraddress@gmail.com',
        'anotheraddress@gmail.com' ] } 
},
{ 
  to: 'All',
  toname: 'Some Name',
  from: 'someoneelse@gmail.com',
  fromname: 'Some other Name',
  message: 'A message for all...',
  timestamp: 1502473420,
  imtype: 'msg',
  _id: 'K66iP3dZNyNxfGgK',
  data:
   { readBy:
      [ 'someotheraddress@gmail.com',
        'anotheraddress@gmail.com' ] } 
}

...

提前致谢

Answer 1

问题出在 $nin 运算符 - 它不像在 mongo 中那样工作。

NEDB 的 $in 运算符的工作方式不同：只有一个操作数可以是数组。查看数组的 $in ($nin is just a negation of $in after all). When it checks if things are equal 定义，它确保只有一项是数组，即 a 或 b[i] 都不能是数组。如果是，则 return 为假。 $nin 因此 return 是正确的 - 解释了结果中两个文档的存在。

您可以按如下方式验证这一点：尝试将 [email] 更改为 ["someotheraddress@gmail.com", "anotheraddress@gmail.com", "foo@bar.com"] 之类的内容，您会注意到这两个结果消失了 - 证明它不会检查 data.readBy 不在我们提供的列表中，但请检查整个 data.readBy 是否存在于我们提供的列表中。

解决方法 使用 { $not: { elemMatch }

您可以通过将查询更改为以下内容来解决此问题：

message_query.push({
  $and: [{ to: "All" }, { $not: { "data.readBy": { $elemMatch: email } } }]
});

验证代码如下：

const Datastore = require("nedb");

const db = new Datastore({
  inMemoryOnly: true,
  autoload: false
});

db.insert(
  [
    {
      to: "All",
      toname: "Some Name",
      from: "someaddress@gmail.com",
      fromname: "Some other Name",
      message: "A message for all...",
      timestamp: 1502473320,
      imtype: "msg",
      data: {
        readBy: ["someotheraddress@gmail.com", "anotheraddress@gmail.com"]
      }
    },
    {
      to: "All",
      toname: "Some Name",
      from: "someoneelse@gmail.com",
      fromname: "Some other Name",
      message: "A message for all...",
      timestamp: 1502473420,
      imtype: "msg",
      data: {
        readBy: ["someotheraddress@gmail.com", "anotheraddress@gmail.com"]
      }
    },
    {
      to: "All",
      toname: "Some Name",
      from: "someoneelse@gmail.com",
      fromname: "Some other Name",
      message: "A message for all...",
      timestamp: 1502473420,
      imtype: "msg",
      data: {
        readBy: ["someotheraddress@gmail.com" ]
      }
    },
    {
      to: "foo@bar.com",
      toname: "Some Name",
      from: "someoneelse@gmail.com",
      fromname: "Some other Name",
      message: "A message for all...",
      timestamp: 1502473420,
      imtype: "msg",
      data: {
        readBy: ["someotheraddress@gmail.com", "anotheraddress@gmail.com"]
      }
    },
    {
      to: "anotheraddress@gmail.com",
      toname: "Some Name",
      from: "someoneelse@gmail.com",
      fromname: "Some other Name",
      message: "A message for all...",
      timestamp: 1502473420,
      imtype: "msg",
      data: {
        read: true
      }
    },
    {
      to: "anotheraddress@gmail.com",
      toname: "Some Name",
      from: "someoneelse@gmail.com",
      fromname: "Some other Name",
      message: "A message for all...",
      timestamp: 1502473420,
      imtype: "msg",
      data: {
      }
    }
  ],
  (...args) => {
    var email = "anotheraddress@gmail.com";

    var _list = ["someotheraddress@gmail.com", "anotheraddress@gmail.com", "foo@bar.com"];

    var message_query = [];

    message_query.push({
      $and: [{ to: "All" }, { $not: { "data.readBy": { $elemMatch: email } } }]
    });

    // message_query.push({
    //   $and: [{ to: "All" }, { "data.readBy": { $nin: [email] } }]
    // });

    // message_query.push({
    //   $and: [{ to: "All" }, { "data.readBy": { $nin: _list } }]
    // });

    message_query.push({
      $and: [{ to: email }, { "data.read": { $exists: false } }]
    });

    db.find({
      $and: [ { $not: { from: email } }, { $or: message_query } ]
    }).exec(function(err, results) {
      console.log(JSON.stringify(results, null, 2));
    });

  }
);

NEDB 查询在数组上使用 $nin 返回误报

NEDB Query returning false positives with $nin on array

javascript

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node.js

nedb