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Restore Archived Data

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You can restore archived data to your Atlas cluster. You can use the alternate syntax that Data Lake provides for the $merge pipeline stage to move the data back into the same or different Atlas cluster, database, or collection within the same Atlas project.

This page describes how to restore using the $merge pipeline stage.

1

See Pause and Resume Archiving for more information.

2

See Connect to Online Archive for more information.

3

To learn more about the $merge pipeline stage syntax and usage for moving data back into your Atlas cluster, see the $merge pipeline stage.

Example

Consider the following documents in an S3 archive:

{
"_id" : 1,
"item": "cucumber",
"source": "nepal",
"released": ISODate("2016-05-18T16:00:00Z")
}
{
"_id" : 2,
"item": "miso",
"source": "canada",
"released": ISODate("2016-05-18T16:00:00Z")
}
{
"_id" : 3,
"item": "oyster",
"source": "luxembourg",
"released": ISODate("2016-05-18T16:00:00Z")
}
{
"_id" : 4,
"item": "mushroom",
"source": "ghana",
"released": ISODate("2016-05-18T16:00:00Z")
}

Suppose the $merge syntax for restoring these documents into the Atlas cluster identifies documents based on the item and source fields during the $merge stage.

db.<collection>.aggregate([
{
"$merge": {
"into": {
"atlas": {
"clusterName": "<atlas-cluster-name>",
"db": "<db-name>",
"coll": "<collection-name>"
}
},
"on": [ "item", "source" ],
"whenMatched": "keepExisting",
"whenNotMatched": "insert"
}
}
])

In this example, when an archived document matches a document on the Atlas cluster on those two fields, Atlas keeps the existing document in the cluster because the copy of the document on the Atlas cluster is more recent than the copy of the document in the archive. When an archived document doesn't match any document in the Atlas cluster, Atlas inserts the document into the specified collection on the Atlas cluster.

When restoring data back into the Atlas cluster, the archived data might have duplicate _id fields. For this example, we can include a $sort stage for sorting on the _id and released fields before the $merge stage to ensure that Atlas chooses the documents with the recent date if there are duplicates to resolve.

db.<collection>.aggregate([
{
$sort: {
"_id": 1,
"released": 1,
}
},
{
"$merge": {
"into": {
"atlas": {
"clusterName": "<atlas-cluster-name>",
"db": "<db-name>",
"coll": "<collection-name>"
}
},
"on": [ "item", "source" ],
"whenMatched": "keepExisting",
"whenNotMatched": "insert"
}
}
])

To learn more about resolving duplicate fields, see the $merge considerations.

4

See Delete an Online Archive for more information.

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