SQL - MOVE VERTEX

Moves one or more vertices into a different class or cluster.

Following the move, the vertices use a different Record ID. The command updates all edges to use the moved vertices. When using a distributed database, if you specify a cluster, it moves the vertices to the server owner of the target cluster.

Syntax

  1. MOVE VERTEX <source> TO <destination> [SET [<field>=<value>]* [,]] [MERGE <JSON>] 
  2. [BATCH <batch-size>]
  • <source> Defines the vertex you want to move. It supports the following values,
    • Vertex Using the Record ID of a single vertex.
    • Array Using an array of record ID’s for vertices you want to move.
  • <destination> Defines where you want to move the vertex to. It supports the following values,
    • Class Using CLASS:<class> with the class you want to move the vertex into.
    • Cluster Using CLUSTER:<cluster> with the cluster you want to move the vertex into.
  • SET Clause to set values on fields during the transition.
  • MERGE Clause to set values on fields during the transition, through JSON.
  • BATCH Defines the batch size, allowing you to execute the command in smaller blocks to avoid memory problems when moving a large number of vertices.
WARNING WARNING: This command updates all connected edges, but not the links. When using the Graph API, it is recommend that you always use edges connected to vertices and never links.

Examples

  • Move a single vertex from its current position to the class Provider:

    1. orientdb> MOVE VERTEX #34:232 TO CLASS:Provider

  • Move an array of vertices by their record ID’s to the class Provider:

    1. orientdb> MOVE VERTEX [#34:232,#34:444] TO CLASS:Provider

  • Move a set of vertices to the class Provider, defining those you want to move with a subquery:

    1. orientdb> MOVE VERTEX (SELECT FROM V WHERE city = 'Rome') TO CLASS:Provider

  • Move a vertex from its current position to the European cluster

    1. orientdb> MOVE VERTEX #3:33 TO CLUSTER:providers_europe

    You may find this useful when using a distributed database, where you can move vertices onto different servers.

  • Move a set of vertices to the class Provider, while doing so update the property movedOn to the current date:

    1. orientdb> MOVE VERTEX (SELECT FROM V WHERE type = 'provider') TO CLASS:Provider 
    2.           SET movedOn = Date()

    Note the similarities this syntax has with the UPDATE command.

  • Move the vertex using a subquery, using JSON update the properties during the transition:

    1. orientdb> MOVE VERTEX (SELECT FROM User) TO CLUSTER:users_europe BATCH 50

  • Move the same vertices as above using only one transaction:

    1. orientdb> MOVE VERTEX (SELECT FROM User) TO CLUSTER:users_europe BATCH -1

For more information, see

Use Cases

Refactoring Graphs through Sub-types

It’s a very common situation where you begin modeling your domain one way, but find later that you need more flexibility.

For instance, say that you start out with a vertex class called Person. After using the database for several months, populating it with new vertices, you decide that you need to split these vertices into two new classes, or sub-types, called Customer and Provider, (rendering Person into an abstract class).

  • Create the new classes for your sub-types:

    1. orientdb> CREATE CLASS Customer EXTENDS Person
    2. orientdb> CREATE CLASS Provider EXTENDS Person

  • Move the providers and customers from Person into their respective sub-types:

    1. orientdb> MOVE VERTEX (SELECT FROM Person WHERE type = 'Customer') TO 
    2.           CLASS:Customer
    3. orientdb> MOVE VERTEX (SELECT FROM Person WHERE type = 'Provider') TO 
    4.           CLASS:Provider

  • Make the class Person an abstract class:

    1. orientdb> ALTER CLASS Person ABSTRACT TRUE

Moving Vertices onto Different Servers

With OrientDB, you can scale your infrastructure up by adding new servers. When you add a new server, OrientDB automatically creates a new cluster with the name of the class plus the node name. For instance, customer_europe.

The best practice when you need to scale up is partitioning, especially on writes. If you have a graph with Customer vertices and you want to move some of these onto a different server, you can move them to the cluster owned by the server.

For instance, move all customers that live in Italy, Germany or the United Kingdom onto the cluster customer_europe, which is assigned to the node Europe. This means that access to European customers is faster with applications connected to the European node.

  1. orientdb> MOVE VERTEX (SELECT FROM Customer WHERE ['Italy', 'Germany', 'UK'] IN 
  2.           out('city').out('country') ) TO CLUSTER:customer_europe

History

2.0

  • Initial implementation of the feature.