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db.copyDatabase()

Definition

db.copyDatabase(fromdb, todb, fromhost, username, password, mechanism)

Deprecated since version 4.0: MongoDB deprecates copydb and its helper db.copyDatabase(). For information on alternatives, see copydb and clone Commands.

Copies a database either from one mongod instance to the current mongod instance or within the current mongod. The mongo shell method db.copyDatabase() wraps the copydb command and takes the following arguments:

Parameter Type Description
fromdb string Name of the source database.
todb string Name of the target database.
fromhost string Optional. The hostname of the source mongod instance. Omit to copy databases within the same mongod instance.
username string

Optional. The name of the user on the fromhost MongoDB instance. The user authenticates to the fromdb.

For more information, see Authentication to Source mongod Instance.

password string

Optional. The password on the fromhost for authentication. The method does not transmit the password in plaintext.

For more information, see Authentication to Source mongod Instance.

mechanism string

Optional. The authentication mechanism on the fromhost.

The fromhost credentials must use SCRAM-SHA-1.

Changed in version 4.0: copyDatabase() no longer supports MONGODB-CR to authenticate to the fromhost.

Behavior

Feature Compatibility Version

You cannot copy data between a MongoDB 4.0 mongod instance with featureCompatibilityVersion (FCV) 4.0 and a MongoDB version 3.6 mongod instance.

Note

You cannot copy data between a MongoDB 4.0 mongod instance (regardless of the FCV value) and a MongoDB 3.4 and earlier mongod instance.

For example:

Instance 1 Instance 2  
Version 4.0 mongod with FCV 4.0 Version 4.0 mongod with FCV 4.0 Can copy data.
Version 4.0 mongod with FCV 4.0 Version 4.0 mongod with FCV 3.6 Can copy data.
Version 4.0 mongod with FCV 4.0 Version 3.6 mongod with FCV 3.6 Cannot copy data. Instance 2 must be a MongoDB version 4.0
Version 4.0 mongod with FCV 3.6 Version 3.6 mongod with FCV 3.6 Can copy data.
Version 4.0 mongod with FCV 3.6 Version 3.6 mongod with FCV 3.4 Can copy data.

In general, if the mongod instance has its featureCompatibilityVersion (FCV) set to its MongoDB version, you cannot copy data between that instance and a mongod instance of an earlier MongoDB version.

Operations that copy data include:

Destination

  • Run db.copyDatabase() in the admin database of the destination mongod instance, i.e. the instance receiving the copied data.
  • db.copyDatabase() creates the target database if it does not exist.
  • If the target database exists and no collection from the source database exists in the target database, db.copyDatabase() copies the collections from the source database to the target database. If any collection from the source database exists in the target database, db.copyDatabase() errors out and does not copy any remaining collections from the source database.
  • db.copyDatabase() requires enough free disk space on the host instance for the copied database. Use the db.stats() operation to check the size of the database on the source mongod instance.

Authentication to Source mongod Instance

  • If copying from another mongod instance (fromhost) that enforces access control, then you must authenticate to the fromhost instance by specifying the username, password, and optionally mechanism. The method does not transmit the password in plaintext.

  • db.copyDatabase() uses the fromdb as the authentication database for the specified user.

  • Changed in version 4.0: db.copyDatabase() only supports SCRAM to authenticate to the fromhost.

For more information on required access and authentication, see Required Access.

Concurrency

  • db.copyDatabase() and clone do not produce point-in-time snapshots of the source database. Write traffic to the source or destination database during the copy process will result in divergent data sets.
  • db.copyDatabase() does not lock the destination server during its operation, so the copy will occasionally yield to allow other operations to complete.

Indexes

MongoDB performs foreground builds of indexes on databases copied via db.copyDatabase(). Foreground index builds lock the database and prevent all other operations on that database until the foreground build completes. There may also be a performance impact on other databases while the indexes build.

You can keep track of ongoing index creation operations with the db.currentOp() command.

Sharded Clusters

Required Access

Source Database (fromdb)

If the mongod instance of the source database (fromdb) enforces access control, you must have proper authorization for the source database.

If you are copying from a different mongod instance that enforces access control, you must authenticate to the fromhost instance as a user with the appropriate authorization:

Source is non-admin Database

Changed in version 3.0.

If the source database is a non-admin database, you must have privileges that specify find, listCollections, and listIndexes actions on the source database, and find action on the system.js collection in the source database.

{ resource: { db: "mySourceDB", collection: "" }, actions: [ "find", "listCollections", "listIndexes" ] },
{ resource: { db: "mySourceDB", collection: "system.js" }, actions: [ "find" ] },

Source is admin Database

Changed in version 3.0.

If the source database is the admin database, you must have privileges that specify find, listCollections, and listIndexes actions on the admin database, and find action on the system.js, system.users, system.roles, and system.version collections in the admin database. For example:

{ resource: { db: "admin", collection: "" }, actions: [ "find",  "listCollections", "listIndexes" ] },
{ resource: { db: "admin", collection: "system.js" }, actions: [ "find" ] },
{ resource: { db: "admin", collection: "system.users" }, actions: [ "find" ] },
{ resource: { db: "admin", collection: "system.roles" }, actions: [ "find" ] },
{ resource: { db: "admin", collection: "system.version" }, actions: [ "find" ] }

Target Database (todb)

If the mongod instance of the target database (todb) enforces access control, you must have proper authorization for the target database.

Copy from non-admin Database

If the source database is not the admin database, you must have privileges that specify insert and createIndex actions on the target database, and insert action on the system.js collection in the target database. For example:

{ resource: { db: "myTargetDB", collection: "" }, actions: [ "insert", "createIndex" ] },
{ resource: { db: "myTargetDB", collection: "system.js" }, actions: [ "insert" ] }

Copy from admin Database

If the source database is the admin database, you must have privileges that specify insert and createIndex actions on the target database, and insert action on the system.js, system.users, system.roles, and system.version collections in the target database. For example:

{ resource: { db: "myTargetDB", collection: "" }, actions: [ "insert", "createIndex" ] },
{ resource: { db: "myTargetDB", collection: "system.js" }, actions: [ "insert" ] },
{ resource: { db: "myTargetDB", collection: "system.users" }, actions: [ "insert" ] },
{ resource: { db: "myTargetDB", collection: "system.roles" }, actions: [ "insert" ] },
{ resource: { db: "myTargetDB", collection: "system.version" }, actions: [ "insert" ] }

Example

Copy from the Same mongod Instance

To copy within the same mongod instance, omit the fromhost.

The following operation copies a database named records into a database named archive_records:

db.copyDatabase('records', 'archive_records')

Copy Database from a mongod Instances that Enforce Authentication

The following operation copies a database named reporting from a mongod instance that runs on example.net and enforces access control and uses SCRAM-SHA-1 authentication mechanism.

 db.copyDatabase(
   "reporting",       // from database
   "reporting_copy",  // to database
   "example.net",     // from host
   "reportUser",      // user on from database
   "abc123",          // password for user
   "SCRAM-SHA-1"      // mechanism for user
)

See also

clone