如何在 pymongo 中进行条件搜索? [英] how can I do a conditional search in pymongo?

问题描述

我正在尝试进行条件查询.我想在整个集合中搜索那些符合 25% 价格范围的文档，并且如果文档有特定字段(在本例中为audiPrice")，我将使用此字段进行搜索，如果该文档具有'不是字段，我将使用'价格'字段

I am trying to make a conditional query. I want to search in the whole collection those documents that fit in range of prices of 25% and if the documents has a particular field(in this case 'audiPrice') I will use this field to do my search, and if this document hasn't the field, I will use a 'price' field

我在 mongodb 文档(https://docs.mongodb.com/manual/reference/operator/aggregation/cond/) 并找到操作符 $cond 并且我尝试进行查询，如您所见

I have search in the mongodb documentation(https://docs.mongodb.com/manual/reference/operator/aggregation/cond/) and found the operator $cond and I have try to make a the query as you can see

pipeline = [
    {
        '$cond': {
            'if': {'audiPrice': {'$exists': True}}, 'then': {'$match':
                {'audiPrice': {
                    '$lte': price * 1.75, '$gte': price * 0.25
            }
                }
            },'else': {'$match': {
                'price': {
                    '$lte': price * 1.75, '$gte': price * 0.25
            }
            }


        }

    }
    }

]

我收到了这个错误信息

pymongo.errors.OperationFailure: Unrecognized pipeline stage name: '$cond'

你知道我怎样才能实现我的目标吗?

Do you know how could I achieve my goal?

我正在使用 python 和 pymongo.

I am using python and pymongo.

谢谢

推荐答案

你可以在 $project 中使用 cond 或在 $match 阶段使用 $expr 作为:

You can use cond in $project or $expr in $match stage as:

collectionName.aggregate([
  {
    $match: {
      $expr: {
        $cond: {
          if: {
            $gt: [
              "$audiPrice",
              null
            ]
          },
          then: {
            $and: [
              {
                $gte: [
                  "$audiPrice",
                  price * 0.25
                ]
              },
              {
                $lte: [
                  "$audiPrice",
                  price * 1.75
                ]
              }
            ]
          },
          else: {
            $and: [
              {
                $gte: [
                  "$price",
                  price * 0.25
                ]
              },
              {
                $lte: [
                  "$price",
                  price * 1.75
                ]
              }
            ]
          }
        }
      }
    }
  }
])

在这里，您首先检查字段 audiPrice 是否不为空，然后对该键执行匹配，否则对价格键执行匹配.

Here you first check if field audiPrice is not null then perform the match on that key else on price key.

这篇关于如何在 pymongo 中进行条件搜索?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！