How to run a query inside an array in mongodb

Question

I have a Database in Mongo. I need to find all the samples within a particular time.

[
  {
    deviceid: 1,
    bucketSize: 4,
    first: 1573833152,
    last: 1573833155,
    samples: [
      {
        val: 10,
        time: 1573833152
      },
      {
        val: 15,
        time: 1573833153
      },
      {
        val: 14,
        time: 1573833154
      },
      {
        val: 20,
        time: 1573833155
      }
    ]
  },
  {
    deviceid: 1,
    bucketSize: 4,
    first: 1573833156,
    last: 1573833160,
    samples: [
      {
        val: 10,
        time: 1573833156
      },
      {
        val: 15,
        time: 1573833157
      },
      {
        val: 14,
        time: 1573833158
      },
      {
        val: 20,
        time: 1573833159
      },
      {
        val: 20,
        time: 1573833160
      }
    ]
  },
  {
    deviceid: 1,
    bucketSize: 4,
    first: 1573833161,
    last: 1573833165,
    samples: [
      {
        val: 10,
        time: 1573833161
      },
      {
        val: 15,
        time: 1573833162
      },
      {
        val: 14,
        time: 1573833163
      },
      {
        val: 20,
        time: 1573833164
      }
    ]
  }
]

Eg: samples between 1573833152 and 1573833156

should yield

samples: [
      {
        val: 10,
        time: 1573833152
      },
{
        val: 15,
        time: 1573833153
      },
   {
        val: 14,
        time: 1573833154
      },
      {
        val: 20,
        time: 1573833155
      },      {
        val: 10,
        time: 1573833156
      }

I tried all methods but failed to extract the required results. Thank You So much in advance.I tried using $or, $elemMatch. But as I am new to Mongo I failed. If someone can please help

Joe · Accepted Answer · 2020-04-18 09:11:56Z

1

You'll need to use aggregation for that.

First match the timestamps against the samples array so you only consider documents that contain at least one sample you care about
unwind samples so each document contains only 1 sample
match the timestamps again to eliminate the extraneous samples
sort by timestamp, if desired
group by _null, pushing each sample onto an array

db.collection.aggregate([
    {$match: { "samples.time": { $gte: 1573833152, $lte: 1573833156 }}},
    {$unwind: "$samples"},
    {$match: { "samples.time": { $gte: 1573833152, $lte: 1573833156 }}},
    {$sort: { "samples.time": 1}},
    {$group: { _id:null, samples:{$push:"$samples"}}}
])

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answered Apr 18, 2020 at 9:11

Joe

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Comments

Samim Hakimi · Accepted Answer · 2020-04-18 09:27:57Z

0

Try this one:

 samples.find({
     $elemMatch: {
         $gte: 1573833152,
         $lte: 1573833156
     }
 })

edited Apr 18, 2020 at 9:27

answered Apr 18, 2020 at 8:57

Samim Hakimi

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1 Comment

Yatin Pandit Over a year ago

It does work, but it returns those samples too which are not needed. Like 1573833157 which is in second document

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