Sharding data with the copy command

This section provides an example of how to use neo4j-admin database copy to filter out data for creating shards.

The copy command can be used to filter out data when creating database copies. In the following example, a sample database is separated into 3 shards.

Example 1. Use the copy command to filter out data

The sample database contains the following data:

(p1 :Person :S2 {id:123, name: "Ava"})
(p2 :Person :S2 {id:124, name: "Bob"})
(p3 :Person :S3 {id:125, name: "Cat", age: 54})
(p4 :Person :S3 {id:126, name: "Dan"})
(t1 :Team :S1 :SAll {id:1, name: "Foo", mascot: "Pink Panther"})
(t2 :Team :S1 :SAll {id:2, name: "Bar", mascot: "Cookie Monster"})
(d1 :Division :SAll {name: "Marketing"})

The data has been prepared using queries to add the labels :S1,:S2, :S3, and :SAll, which denotes the target shard. Shard 1 contains the team data. Shard 2 and Shard 3 contain person data.

  1. Create Shard 1 with:

    $neo4j-home> bin/neo4j-admin database copy neo4j shard1 \
       --copy-only-nodes-with-labels=S1,SAll \ (1)
       --skip-labels=S1,S2,S3,SAll (2)
    1 The --copy-only-node-with-labels property is used to filter out everything that does not have the label :S1 or :SAll.
    2 The --skip-labels property is used to exclude the temporary labels you created for the sharding process.

    The resulting shard contains the following:

    (t1 :Team {id:1, name: "Foo", mascot: "Pink Panther"})
    (t2 :Team {id:2, name: "Bar", mascot: "Cookie Monster"})
    (d1 :Division {name: "Marketing"})
  2. Create Shard 2:

    $neo4j-home> bin/neo4j-admin database copy neo4j shard2 \
       --copy-only-nodes-with-labels=S2,SAll \
       --skip-labels=S1,S2,S3,SAll \

    In Shard 2, you want to keep the :Team nodes as proxy nodes, to be able to link together information from the separate shards. The nodes will be included since they have the label :SAll, but you specify --copy-only-node-properties so as to not duplicate the team information from Shard 1.

    (p1 :Person {id:123, name: "Ava"})
    (p2 :Person {id:124, name: "Bob"})
    (t1 :Team {id:1})
    (t2 :Team {id:2})
    (d1 :Division {name: "Marketing"})

    Observe that --copy-only-node-properties did not filter out since the :Person label was not mentioned in the filter.

  3. Create Shard 3, but with the filter --skip-node-properties, instead of --copy-only-node-properties.

    $neo4j-home> bin/neo4j-admin database copy neo4j shard3 \
       --copy-only-nodes-with-labels=S3,SAll \
       --skip-labels=S1,S2,S3,SAll \,Team.mascot

    The result is:

    (p3 :Person {id:125, name: "Cat", age: 54})
    (p4 :Person {id:126, name: "Dan"})
    (t1 :Team {id:1})
    (t2 :Team {id:2})
    (d1 :Division {name: "Marketing"})

    As demonstrated, you can achieve the same result with both --skip-node-properties and --copy-only-node-properties. In this example, it is easier to use --copy-only-node-properties because only one property should be kept. The relationship property filters works in the same way.