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$currentDate

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$currentDate

The $currentDate operator sets the value of a field to the current date, either as a Date or a timestamp. The default type is Date.

The $currentDate operator has the form:

{ $currentDate: { <field1>: <typeSpecification1>, ... } }

<typeSpecification> can be either:

  • a boolean true to set the field value to the current date as a Date, or

  • a document { $type: "timestamp" } or { $type: "date" } which explicitly specifies the type. The operator is case-sensitive and accepts only the lowercase "timestamp" or the lowercase "date".

To specify a <field> in an embedded document or in an array, use dot notation.

Starting in MongoDB 5.0, update operators process document fields with string-based names in lexicographic order. Fields with numeric names are processed in numeric order. See Update Operators Behavior for details.

$currentDate sets the specified field to the date when $currentDate was run.

If the field does not exist, $currentDate adds the field to a document.

Starting in MongoDB 5.0, mongod no longer raises an error when you use an update operator like $currentDate with an empty operand expression ( { } ). An empty update results in no changes and no oplog entry is created (meaning that the operation is a no-op).

Create a sample collection customers with the following document:

db.customers.insertOne(
{ _id: 1, status: "a", lastModified: ISODate("2013-10-02T01:11:18.965Z") }
)

The following operation updates the lastModified field to the current date, the "cancellation.date" field to the current timestamp as well as updating the status field to "D" and the "cancellation.reason" to "user request".

db.customers.updateOne(
{ _id: 1 },
{
$currentDate: {
lastModified: true,
"cancellation.date": { $type: "timestamp" }
},
$set: {
"cancellation.reason": "user request",
status: "D"
}
}
)

$currentDate sets the specified field to the date when $currentDate was run.

To verify the update:

db.customers.find()

The updated document resembles:

{
"_id" : 1,
"status" : "D",
"lastModified" : ISODate("2020-01-22T21:21:41.052Z"),
"cancellation" : {
"date" : Timestamp(1579728101, 1),
"reason" : "user request"
}
}

The lastModified field is set to the date when $currentDate was run in the update example shown earlier.

Starting in version 4.2, update methods can accept an aggregation pipeline. As such, the previous example can be rewritten as the following using the aggregation stage $set and the aggregation variables NOW (for the current datetime) and CLUSTER_TIME (for the current timestamp):

Tip

  • To access aggregation variables, prefix the variable with double dollar signs $$ and enclose in quotes.

  • CLUSTER_TIME is available only on replica sets and sharded clusters.

  • The NOW and CLUSTER_TIME values remain the same throughout the pipeline.

db.customers.updateOne(
{ _id: 1 },
[
{ $set: { lastModified: "$$NOW", cancellation: {date: "$$CLUSTER_TIME", reason: "user request"}, status: "D" } }
]
)

After the operation, you can query the collection to verify the update:

db.customers.find().pretty()

The query should return the following document:

{
"_id" : 1,
"status" : "D",
"lastModified" : ISODate("2020-01-22T21:02:18.994Z"),
"cancellation" : {
"date" : Timestamp(1579726934, 2),
"reason" : "user request"
}
}

Tip

See also:

←  Field Update Operators$inc →
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