Verifying Data with Custom Scripts

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Comparing Documents

Comparing Indexes
Comparing Metadata
Comparing Shard Keys

You can write a script to query your source cluster and compare the documents, indexes, collections, metadata, and views with the destination cluster.

Comparing Documents

You can verify sync by comparing documents on the source and destination clusters.

Before you can verify data transfer with this method, mongosync must be in the COMMITTED state.

Comparing Indexes

To verify the transfer of indexes, run db.collection.getIndexes() on the source and destination clusters and compare the results.

Comparing Metadata

To verify the transfer of metadata, run db.getCollectionInfos() on the source and destination clusters and compare the results.

Comparing Shard Keys

To verify the transfer of shard keys to a synced collection, run a query on the config.collections collection to find a document whose _id value is the namespace of the target collection. Compare the key value of this document in the source and destination clusters.

For example, for a collection named pets in the records database, you can verify the shard key using the following query in mongosh:

db.getSiblingDB("config").collections.find({ _id : "records.pets" })

{
 "_id" : "records.pets",
 "lastmod" : ISODate("2021-07-21T15:48:15.193Z"),
 "timestamp": Timestamp(1626882495, 1),
    "key" : {
    "_id" : 1
    },
 "unique" : false,
 "lastmodEpoch" : ObjectId("5078407bd58b175c5c225fdc"),
 "uuid" :  UUID("f8669e52-5c1b-4ea2-bbdc-a00189b341da")
 }

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