Copy a database store

This section describes how to copy the data store of an existing offline database to a new database.

A user database or backup can be copied to a Neo4j instance using the copy command of neo4j-admin.

neo4j-admin copy is not supported for use on the system database.

In Fabric deployments, neo4j-admin copy cannot be applied to the Fabric virtual database. It must be run directly on the databases that are part of the Fabric setup.

It is important to note that neo4j-admin copy is an IOPS-intensive process. Using this process for upgrading or migration purposes can have significant performance implications, depending on your disc specification. It is therefore not appropriate for all use cases.

Estimating the processing time

Estimations for how long the neo4j-admin copy command will take can be made based upon the following:

  • Neo4j, like many other databases, do IO in 8K pages.

  • Your disc manufacturer will have a value for the maximum IOPS it can process.

For example, if your disc manufacturer has provided a maximum of 5000 IOPS, you can reasonably expect up to 5000 such page operations a second. Therefore, the maximal theoretical throughput you can expect is 40MB/s (or 144 GB/hour) on that disc. You may then assume that the best-case scenario for running neo4j-admin copy on that 5000 IOPS disc is that it will take at least 1 hour to process a 144 GB database. [1]

However, it is important to remember that the process must read 144 GB from the source database, and must also write to the target store (assuming the target store is of comparable size). Additionally, there are internal processes during the copy that will read/modify/write the store multiple times. Therefore, with an additional 144 GB of both read and write, the best-case scenario for running neo4j-admin copy on a 5000 IOPS disc is that it will take at least 3 hours to process a 144 GB database.

Finally, it is also important to consider that in almost all Cloud environments, the published IOPS value may not be the same as the actual value, or be able to continuously maintain the maximum possible IOPS. The real processing time for this example could be well above that estimation of 3 hours.

For detailed information about supported methods of upgrade and migration, see the Neo4j Upgrade and Migration Guide.

1. Command

neo4j-admin copy copies the data store of an existing offline database to a new database.

1.1. Usage

The neo4j-admin copy command can be used to clean up database inconsistencies, compact stores, and do a direct migration from Neo4j 3.5 to any 4.x version. It can process an optional set of filters, which you can use to remove any unwanted data before copying the database. The command also reclaims the unused space of a database and creates a defragmented copy of that database or backup in the destination Neo4j instance.

neo4j-admin copy copies the data store without the schema (indexes and constraints). However, if the database has a schema defined, the command will output Cypher statements, which you can run to recreate the indexes and constraints.

For a detailed example of how to reclaim unused space, see Reclaim unused space.
For a detailed example of how to back up a 3.5 database and use the neo4j-admin copy command to compact its store and migrate it to a 4.x Neo4j standalone instance, see Upgrade and Migration Guide → Tutorial: Back up and copy a database in a standalone instance.

neo4j-admin copy preserves the node IDs; however, the relationships get new IDs.

1.2. Syntax

neo4j-admin copy  [--verbose]
                  [--from-database=<database>]
                  [--from-path=<path>]
                  [--from-path-tx=<path>]
                   --to-database=<database>
                  [--neo4j-home-directory=<path>]
                  [--force]
                  [--compact-node-store]
                  [--to-format=<format>]
                  [--delete-nodes-with-labels=<label>[,<label>...]]
                  [--keep-only-node-properties=<label.property>[,<label.property>...]]
                  [--keep-only-nodes-with-labels=<label>[,<label>...]]
                  [--keep-only-relationship-properties=<relationship.property>[,<relationship.property>...]]
                  [--skip-labels=<label>[,<label>...]]
                  [--skip-node-properties=<label.property>[,<label.property>...]]
                  [--skip-properties=<property>[,<property>...]]
                  [--skip-relationship-properties=<relationship.property>[,<relationship.property>...]]
                  [--skip-relationships=<relationship>[,<relationship>...]]
                  [--from-pagecache=<size>]
                  [--to-pagecache=<size>]

1.3. Options

Option Description

--verbose

Enable verbose output.

--from-database

The database name to copy from.

--from-path

The path to the database to copy from.

It can be used to target databases outside of the installation, e.g., backups.

--from-path-tx

The path to the transaction log files. Use if the command cannot determine where they are located.

--to-database

The destination database name.

--neo4j-home-directory=<path>

Path to the home directory for the copied database.

Default: The same as the database copied from.

--force

Force the command to proceed even if the integrity of the database can not be verified.

--compact-node-store

Enforce node store compaction.

By default, the node store is not compacted on copy since it changes the node IDs.

--to-format

Set the format for the new database.

Valid values are same, standard, high_limit, and aligned. The high_limit format is only available in Enterprise Edition. If you go from high_limit to standard, there is no validation that the data will fit.

Default: The format of the source database.

--delete-nodes-with-labels

A comma-separated list of labels.

All nodes that have ANY of the specified labels will be deleted. Any node matching any of the labels will be ignored during copy.

--keep-only-node-properties

A list of property keys to keep for nodes with the specified label.

Any labels not explicitly mentioned will keep their properties. Cannot be combined with --skip-properties or --skip-node-properties.

--keep-only-nodes-with-labels

A list of labels.

All nodes that have any of the specified labels will be kept. Cannot be combined with --delete-nodes-with-labels.

--keep-only-relationship-properties

A list of property keys to keep for relationships with the specified type.

Any relationship types not explicitly mentioned will keep their properties.

Cannot be combined with --skip-properties or --skip-relationship-properties.

--skip-labels

A comma-separated list of labels to ignore during the copy.

--skip-node-properties

A list of property keys to ignore for nodes with the specified label.

Cannot be combined with --skip-properties or --keep-only-node-properties.

--skip-properties

A comma-separated list of property keys to ignore during the copy.

Cannot be combined with --skip-node-properties, --keep-only-node-properties, --skip-relationship-properties, and --keep-only-relationship-properties.

--skip-relationships

A comma-separated list of relationship types to ignore during the copy.

--skip-relationship-properties

A list of property keys to ignore for relationships with the specified type.

Cannot be combined with --skip-properties or --keep-only-relationship-properties.

--from-pagecache

The size of the page cache to use for reading.

--to-pagecache

The size of the page cache to use for writing.

You can use the --from-pagecache and --to-pagecache options to speed up the copy operation by specifying how much cache to allocate when reading the source and writing the destination. As a rule of thumb, --to-pagecache should be around 1-2GB since it mostly does sequential writes. The --from-pagecache should then be assigned whatever memory you can spare since Neo4j does random reads from the source.

2. Examples

Example 1. Use neo4j-admin copy to copy the data store of the database neo4j.

  1. Stop the database named neo4j:

    STOP DATABASE neo4j

  2. Copy the data store from neo4j to a new database called copy:

    bin/neo4j-admin copy --from-database=neo4j --to-database=copy

  3. Run the following command to verify that database has been successfully copied.

    ls -al ../data/databases
    Copying a database does not automatically create it. Therefore, it will not be visible if you do SHOW DATABASES at this point.

  4. Create the copied database.

    CREATE DATABASE copy

  5. Verify that the copy database is online.

    SHOW DATABASES

  6. If your original database has a schema defined, change your active database to copy and recreate the schema using the neo4j-admin copy output.

    The console output is saved to logs/neo4j-admin-copy-<timestamp>.log.
Example 2. Use neo4j-admin copy to filter the data you want to copy.

The command can perform some basic forms of processing. You can filter the data that you want to copy by removing nodes, labels, properties, and relationships.

bin/neo4j-admin copy --from-database=neo4j --to-database=copy --delete-nodes-with-labels="Cat,Dog"

The command creates a copy of the database neo4j but without the nodes with the labels :Cat and :Dog.

Labels are processed independently, i.e., the filter deletes any node with a label :Cat, :Dog, or both.

For a detailed example of how to use neo4j-admin copy to filter out data for a Fabric installation, see Sharding data with the copy command.
1. The calculations are based on MB/s = (IOPS * B) ÷ 10^6, where B is the block size in bytes; in the case of Neo4j, this is 8000. GB/hour can then be calculated from (MB/s * 3600) ÷ 1000.