Node operations

This section details the operations available over node-properties stored in projected graphs within the Neo4j Graph Data Science library.

The graphs in the Neo4j Graph Data Science Library support properties for nodes. We provide multiple operations to work with the stored node-properties in projected graphs. Node properties are either created during the graph creation or when using the mutate mode of our graph algorithms.

To inspect stored values, the gds.graph.streamNodeProperties procedure can be used. This is useful if we ran multiple algorithms in mutate mode and want to retrieve some or all of the results.

To persist the values in a Neo4j database, we can use gds.graph.writeNodeProperties. Similar to streaming node properties, it is also possible to write those back to Neo4j. This is similar to what an algorithm write execution mode does, but allows more fine-grained control over the operations.

We can also remove node properties from a named graph in the catalog. This is useful to free up main memory or to remove accidentally created node properties.

1. Syntax

Syntax descriptions of the different operations over node properties

CALL gds.graph.streamNodeProperty(
    graphName: String,
    nodeProperties: String,
    nodeLabels: String or List of Strings,
    configuration: Map
)
YIELD
    nodeId: Integer,
    propertyValue: Integer or Float or List of Integer or List of Float

Table 1. Parameters
Name	Type	Optional	Description
graphName	String	no	The name under which the graph is stored in the catalog.
nodeProperties	String	no	The node property in the graph to stream.
nodeLabels	String or List of Strings	yes	The node labels to stream the node properties for graph.
configuration	Map	yes	Additional parameters to configure streamNodeProperties.

Table 2. Configuration
Name	Type	Default	Description
concurrency	Integer	4	The number of concurrent threads. Note, this procedure is always running single-threaded.

Table 3. Results
Name	Type	Description
nodeId	Integer	The id of the node.
propertyValue	Integer Float List of Integer List of Float	The stored property value.

CALL gds.graph.streamNodeProperties(
    graphName: String,
    nodeProperties: String or List of Strings,
    nodeLabels: String or List of Strings,
    configuration: Map
)
YIELD
    nodeId: Integer,
    nodeProperty: String,
    propertyValue: Integer or Float or List of Integer or List of Float

Table 4. Parameters
Name	Type	Optional	Description
graphName	String	no	The name under which the graph is stored in the catalog.
nodeProperties	String or List of Strings	no	The node properties in the graph to stream.
nodeLabels	String or List of Strings	yes	The node labels to stream the node properties for graph.
configuration	Map	yes	Additional parameters to configure streamNodeProperties.

Table 5. Configuration
Name	Type	Default	Description
concurrency	Integer	4	The number of concurrent threads. Note, this procedure is always running single-threaded.

Table 6. Results
Name	Type	Description
nodeId	Integer	The id of the node.
nodeProperty	String	The name of the node property.
propertyValue	Integer Float List of Integer List of Float	The stored property value.

CALL gds.graph.writeNodeProperties(
    graphName: String,
    nodeProperties: String or List of Strings,
    nodeLabels: String or List of Strings,
    configuration: Map
)
YIELD
    writeMillis: Integer,
    propertiesWritten: Integer,
    graphName: String,
    nodeProperties: String or List of String

Table 7. Parameters
Name	Type	Optional	Description
graphName	String	no	The name under which the graph is stored in the catalog.
nodeProperties	String or List of Strings	no	The node properties in the graph to write back.
nodeLabels	String or List of Strings	yes	The node labels to write back their node properties.
configuration	Map	yes	Additional parameters to configure writeNodeProperties.

Table 8. Configuration
Name	Type	Default	Description
concurrency	Integer	4	The number of concurrent threads used for running the procedure. Also provides the default value for `writeConcurrency`
writeConcurrency	Integer	'concurrency'	The number of concurrent threads used for writing the node properties.

Table 9. Results
Name	Type	Description
writeMillis	Integer	Milliseconds for writing result data back to Neo4j.
propertiesWritten	Integer	Number of properties written.
graphName	String	The name of a graph stored in the catalog.
nodeProperties	String or List of String	The written node properties.

CALL gds.graph.removeNodeProperties(
    graphName: String,
    nodeProperties: String or List of Strings,
    nodeLabels: String or List of Strings,
    configuration: Map
)
YIELD
    propertiesRemoved: Integer,
    graphName: String,
    nodeProperties: String or List of String

Table 10. Parameters
Name	Type	Optional	Description
graphName	String	no	The name under which the graph is stored in the catalog.
nodeProperties	String or List of Strings	no	The node properties in the graph to remove.
nodeLabels	String or List of Strings	yes	The node labels to remove the node properties from.
configuration	Map	yes	Additional parameters to configure removeNodeProperties.

Table 11. Configuration
Name	Type	Default	Description
concurrency	Integer	4	The number of concurrent threads. Note, this procedure is always running single-threaded.

Table 12. Results
Name	Type	Description
propertiesRemoved	Integer	Number of properties removed.
graphName	String	The name of a graph stored in the catalog.
nodeProperties	String or List of String	The removed node properties.

2. Examples

In order to demonstrate the GDS capabilities over node properties, we are going to create a small social network graph in Neo4j and project it into our graph catalog.

The following Cypher statement will create the example graph in the Neo4j database:

CREATE
  (florentin:Person { name: 'Florentin', age: 16 }),
  (adam:Person { name: 'Adam', age: 18 }),
  (veselin:Person { name: 'Veselin', age: 20 }),
  (hobbit:Book { name: 'The Hobbit', numberOfPages: 310 }),
  (florentin)-[:KNOWS { since: 2010 }]->(adam),
  (florentin)-[:KNOWS { since: 2018 }]->(veselin),
  (adam)-[:READ]->(hobbit)

Project the small social network graph:

CALL gds.graph.create(
  'socialGraph',
  {
    Person: {properties: "age"},
    Book: {}
  },
  ['KNOWS', 'READ']
)

Compute the Degree Centrality in our social graph:

CALL gds.degree.mutate('socialGraph', {mutateProperty: 'score'})

2.1. Stream

We can stream node properties stored in a named in-memory graph back to the user. This is useful if we ran multiple algorithms in mutate mode and want to retrieve some or all of the results. This is similar to what an algorithm stream execution mode does, but allows more fine-grained control over the operations.

2.1.1. Single property

In the following, we stream the previously computed scores score.

Stream the score node property:

CALL gds.graph.streamNodeProperty('socialGraph', 'score')
YIELD nodeId, propertyValue
RETURN gds.util.asNode(nodeId).name AS name, propertyValue AS score
ORDER BY score DESC

Table 13. Results
name	score
"Florentin"	2.0
"Adam"	1.0
"Veselin"	0.0
"The Hobbit"	0.0

The above example requires all given properties to be present on at least one node projection, and the properties will be streamed for all such projections.

2.1.2. NodeLabels

The procedure can be configured to stream just the properties for specific node labels.

Stream the score property for Person nodes:

CALL gds.graph.streamNodeProperty('socialGraph', 'score', ['Person'])
YIELD nodeId, propertyValue
RETURN gds.util.asNode(nodeId).name AS name, propertyValue AS score
ORDER BY score DESC

Table 14. Results
name	score
"Florentin"	2.0
"Adam"	1.0
"Veselin"	0.0

It is required, that all specified node labels have the node property.

2.1.3. Multiple Properties

We can also stream several properties at once.

Stream multiple node properties:

CALL gds.graph.streamNodeProperties('socialGraph', ['score', 'age'])
YIELD nodeId, nodeProperty, propertyValue
RETURN gds.util.asNode(nodeId).name AS name, nodeProperty, propertyValue
ORDER BY name, nodeProperty

Table 15. Results
name	nodeProperty	propertyValue
"Adam"	"age"	18
"Adam"	"score"	1.0
"Florentin"	"age"	16
"Florentin"	"score"	2.0
"Veselin"	"age"	20
"Veselin"	"score"	0.0

When streaming multiple node properties, the name of each property is included in the result. This adds with some overhead, as each property name must be repeated for each node in the result, but is necessary in order to distinguish properties.

2.2. Write

To write the 'score' property for all node labels in the social graph, we use the following query:

Write the score property back to Neo4j:

CALL gds.graph.writeNodeProperties('socialGraph', ['score'])
YIELD propertiesWritten

Table 16. Results
propertiesWritten
4

The above example requires the score property to be present on at least one projected node label, and the properties will be written for all such labels.

2.2.1. NodeLabels

The procedure can be configured to write just the properties for some specific node labels. In the following example, we will only write back the scores of the Person nodes.

Write node properties of a specific projected node label to Neo4j:

CALL gds.graph.writeNodeProperties('socialGraph', ['score'], ['Person'])
YIELD propertiesWritten

Table 17. Results
propertiesWritten
3

If the nodeLabels parameter is specified, it is required that all given node labels have all of the given properties.

2.3. Remove

Remove the score property from all projected nodes in the socialGraph:

CALL gds.graph.removeNodeProperties('socialGraph', ['score'])
YIELD propertiesRemoved

Table 18. Results
propertiesRemoved
4

The above example requires all given properties to be present on at least one projected node label.

2.3.1. NodeLabels

Consider we compute the Degree Centrality only for a subset of the graph.

Compute the Degree Centrality for only the Book nodes in our social graph:

CALL gds.degree.mutate('socialGraph', {nodeLabels: ['Book'], mutateProperty: 'degree'})

The procedure can be configured to remove just the properties for s. In the following example, we will only remove the scores from the Book nodes.

Remove the degree property from the projected Book nodes:

CALL gds.graph.removeNodeProperties('socialGraph', ['degree'], ['Book'])
YIELD propertiesRemoved

Table 19. Results
propertiesRemoved
1

If the nodeLabels parameter is specified, it is required that all given node labels have all of the given properties.

3. Utility functions

Utility functions allow accessing specific nodes of in-memory graphs directly from a Cypher query.

Table 20. Catalog Functions
Name	Description
`gds.util.nodeProperty`	Allows accessing a node property stored in a named graph.

3.1. Syntax

Name Description

Name	Description
`gds.util.nodeProperty(graphName: STRING, nodeId: INTEGER, propertyKey: STRING, nodeLabel: STRING?)`	Named graph in the catalog, Neo4j node id, node property key and optional node label present in the named-graph.

gds.util.nodeProperty(graphName: STRING, nodeId: INTEGER, propertyKey: STRING, nodeLabel: STRING?)

Named graph in the catalog, Neo4j node id, node property key and optional node label present in the named-graph.

If a node label is given, the property value for the corresponding projection and the given node is returned. If no label or '*' is given, the property value is retrieved and returned from an arbitrary projection that contains the given propertyKey. If the property value is missing for the given node, null is returned.

3.2. Examples

We use the socialGraph with the property score introduced above.

Access a property node property for Florentin:

MATCH (florentin:Person {name: 'Florentin'})
RETURN
  florentin.name AS name,
  gds.util.nodeProperty('socialGraph', id(florentin), 'score') AS score

Table 21. Results
name	score
"Florentin"	2.0

We can also specifically return the score property from the Person projection in case other projections also have a score property as follows.

Access a property node property from Person for Florentin:

MATCH (florentin:Person {name: 'Florentin'})
RETURN
  florentin.name AS name,
  gds.util.nodeProperty('socialGraph', id(florentin), 'score', 'Person') AS score

Table 22. Results
name	score
"Florentin"	2.0

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