Add Timestamp while insertMany() in mongoDB - php

Question

Hi I am MySQL user and new to mongoDB.
I get data from my IOT devices as following:
$body={
"key": "121239",
"secrete": "Your_Device_Secrete",
"data": [
{
"Temperature":50,
"Humidity":30,
"Vibration":100,
"Time":"2020-1-26 00:00:01"
},
{
"Temperature":55,
"Humidity":34,
"Vibration":50,
"Time":"2020-1-26 00:00:02"
}
]
}
I am inserting it into mongoDB using PHP CodeIgnitor as following:
$this->mongo->batch_insert($body["key"],$body["data"]);
data is getting inserted in collection named as given key as following:
{
"Temperature": 50,
"Humidity": 30,
"Vibration": 100,
"Time": "2020-1-26 00:00:01",
"_id": {
"$id": "5e330be3f7577f640d2a0922"
}
},
{
"Temperature": 55,
"Humidity": 34,
"Vibration": 50,
"Time": "2020-1-26 00:00:02",
"_id": {
"$id": "5e330be3f7577f640d2a0923"
}
}
Now I want to add timestamp to every row getting inserted. I want data getting inserted as following :
{
"Temperature": 50,
"Humidity": 30,
"Vibration": 100,
"Time": "2020-1-26 00:00:01",
"_id": {
"$id": "5e330be3f7577f640d2a0922"
},
timestamp:<CURRUNT TIME>
},
{
"Temperature": 55,
"Humidity": 34,
"Vibration": 50,
"Time": "2020-1-26 00:00:02",
"_id": {
"$id": "5e330be3f7577f640d2a0923"
},
timestamp:<CURRUNT TIME>
}
is there any way to make mongoDB add current timestamp auto like MySQL?

Answer 1

First of all you should not store date/time values as string! It will just generate trouble at later times. Better use
"Time": ISODate("2020-01-26T00:00:02Z")
"Time": new Date("2020-01-26 00:00:02") may also work
Then in general you don't need to insert a timestamp. Every document gets an internal _id identifier which contains also the time when it was inserted. You can try like this:
db.collection.aggregate([
{
$project: {
timestamp: {
$toDate: "$_id"
},
key: 1,
secrete: 1,
data: 1,
_id: 0
}
}
])
Result:
{
"data": [
{
"Humidity": 30,
"Temperature": 50,
"Time": "2018-02-26 01:00:00",
"Vibration": 100
},
{
"Humidity": 34,
"Temperature": 55,
"Time": "2018-02-26 01:00:00",
"Vibration": 50
}
],
"key": "121239",
"secrete": "Your_Device_Secrete",
"timestamp": ISODate("2018-02-26T00:00:00Z")
}
You can also query for it, e.g.
db.collection.find({
$expr: {
$gte: [ {"$toDate": "$_id"}, ISODate("2020-01-03T11:00:00Z") ]
}
})
However, if you like to insert timestamp explicitly then simply do it like this.
{
"Temperature": 50,
"Humidity": 30,
"Vibration": 100,
"_id": {
"$id": "5e330be3f7577f640d2a0923"
},
"timestamp": new Date()
}
Or "timestamp": ISODate() should also work
Another note, this embedded document "_id": {"$id": "5e330be3f7577f640d2a0923"} looks really strange. I assume this is a bug. The string look like a ObjectId object used for _id. Somehow you scratched it.
Update
I really recommend to use proper data types. In PHP the insert could look like this:
$mongo->db->collection->insertOne([
"timestamp" => new MongoDB\BSON\UTCDateTime(NULL),
"key" => "121239",
"secrete" => "Your_Device_Secrete",
"data" => [
[
"Temperature" => 50,
"Humidity" => 30,
"Vibration" => 100,
"Time" => new MongoDB\BSON\UTCDateTime(new DateTime("2020-1-26 00:00:01"))
],
[
"Temperature" => 55,
"Humidity" => 34,
"Vibration" => 50,
"Time" => new MongoDB\BSON\UTCDateTime(new DateTime("2020-1-26 00:00:02"))
]
]
]);

Answer 2

I also had similar requirements as yours while reading sensor values from DHT11 sensor in my IoT class. I was able to insert all the temperature and humidity readings into MongoDB but later while plotting the graph I realized that I would need the timestamps as well. After researching for a while, I came up with this query. However, it will create a new collection in the database.
Here, the new collection name is dht11-sensor-readings.
Please also refer to https://docs.mongodb.com/manual/reference/operator/aggregation/out/ for more.
db.collection.aggregate([
{
$addFields:{timestamp:{$toDate:"$_id"}
}
},
{ $out:"dht11-sensor-readings"
}
])