如何在使用mongodb $和$ lookup条件将其应用于管道中的存储数据时修复“无法识别的表达式$ round" [英] How to fix 'Unrecognized expression $round' while applying it to stored data in pipeline using mongodb $and condition with $lookup

问题描述

在使用Angular 7在浏览器中查看数据时，我已经对来自DB的数据应用了精度.
前端:Angular 7
后端:Java和Mongodb

I have applied precision to the data coming from DB, while viewing it in browser using Angular 7.
Front End: Angular 7
Back End: Java and Mongodb

精度前(以db为单位): 100.9999
对用户可见的精度(小数点后2位): 101.00

before precision (in db): 100.9999
after precision visible to user(2 after decimal): 101.00

UI上具有搜索功能，用户可以在其中输入任何金额范围.
方案1:
用户输入 t:100至100
结果:未找到任何记录(预期)

There is a search functionality on UI in which a user can write any amount range.
Scenario 1:
User input: 100 to 100
Result: no records found (expected)

方案2:
用户输入:101至101
结果:未找到记录(应根据用户(101)找到1条记录，但是由于实际值为100.9999，因此不会返回任何记录)

Scenario 2:
User input: 101 to 101
Result: no records found (should have found 1 record according to user(101), but since the actual value is 100.9999, it won't return any)

解决方案，我试图在甚至在查询中应用搜索条件之前就应用精度.
解决方案之前的代码:

Solution, I am trying to apply precision before even applying the search criteria in query.
Code before the solution:

 "$pipeline": [{
        "$match": {
            "$expr": {
               "$and": [{
                          "$eq": ["$column1", "$valueForColumn1"]
                        },
                        {
                          "$gte": ["$amount", "$minValue"]
                        },
                        {
                          "$lte": ["$amount", "$maxValue"]
                        }]
                      }
                    }
                  }]

SQL等效项是:

Select * from table_name where minVale >= ROUND(amount) <= maxValue;

我尝试了以下代码，但给出了错误.
应用解决方案后的代码:

I tried the following code, but it gives the error.
Code after applying the solution:

  "$pipeline": [{
        "$match": {
            "$expr": {
               "$and": [{
                          "$eq": ["$column1", "$valueForColumn1"]
                        },
                        {
                          "$gte": [{"$round": ["$amount", 2]}, "$minValue"]
                        },
                        {
                          "$lte": [{"$round": ["$amount", 2]}, "$maxValue"]
                        }]
                      }
                    }
                  }]

在$ and和$ gte/$ lte下使用"$ round"时，出现以下错误

I get the following error while using "$round" under $and and $gte/$lte

Assert: command failed {
    ok: 0,
    errmsg: Unrecognised expression "$round"
    code: 168
    codeName: InvalidPipeline Operator

任何人都可以告诉我，我在做什么错，我应该怎么做.

Can anyone tell, what am I doing wrong and how should I do it.

注意::我也在查询中使用$ lookup，可能就是为什么它无法识别"$ round".

NOTE: I am also using $lookup in the query, may be that is why it is not able to recognise "$round".

推荐答案

我看到的原因之一是您使用的mongodb版本不支持$ round运算符.在版本4.2和更高版本中引入了$ round运算符. 根据 Mongodb文档

One of the reason i can see is the version of mongodb you are using is not supporting $round operator. $round operator was introduced in version 4.2... and above. according to do Mongodb doc

升级您的mongodb版本并尝试.

Upgrade your mongodb version and try.

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