Node.js 如何在 mongoDB 中用值 0 填充缺失的文档

也许是这样的:

db.collection.aggregate([
{
 $group: {
   _id: null,
   ar: {
    $push: "$$ROOT"
   },
   mind: {
    "$min": "$midNightTimeStamp"
   },
   maxd: {
    "$max": "$midNightTimeStamp"
   }
  }
 },
 {
  $project: {
  ar: {
    $map: {
      input: {
        $range: [
          "$mind",
          {
            "$sum": [
              "$maxd",
              86400
            ]
          },
          86400
        ]
      },
      as: "dateInRange",
      in: {
        $let: {
          vars: {
            dateIndex: {
              "$indexOfArray": [
                "$ar.midNightTimeStamp",
                "$$dateInRange"
              ]
            }
          },
          in: {
            $cond: {
              if: {
                $ne: [
                  "$$dateIndex",
                  -1
                ]
              },
              then: {
                $arrayElemAt: [
                  "$ar",
                  "$$dateIndex"
                ]
              },
              else: {
                midNightTimeStamp: "$$dateInRange",
                "waterDispensed": NumberInt(0)
              }
            }
          }
        }
       }
      }
     }
    }
  },
  {
   $unwind: "$ar"
  },
  {
   $project: {
    _id: 0,
    "waterDispensed": "$ar.waterDispensed",
    midNightTimeStamp: "$ar.midNightTimeStamp",
    "Date": {
      $toDate: {
         "$multiply": [
         "$ar.midNightTimeStamp",
         1000
       ]
      }
    }
   }
  }
])

解释:

1. $将文档分组以查找max&；时间戳的最小值和$push名为"ar"的临时数组中的所有元素
2. $project数组$mapping，其中包含一个在max&；最小值为1x天步长(86400)，用waterDispanced:0填充空元素
3. $展开数组$ar
4. $project仅用于最终输出中所需的字段.

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