Node Properties
The Neo4j Graph Data Science Library is capable of augmenting nodes with additional properties.
These properties can be loaded from the database when the graph is projected.
Many algorithms can also persist their result as one or more node properties when they are run using the mutate
mode.
1. Supported types
The Neo4j Graph Data Science library does not support all property types that are supported by the Neo4j database. Every supported type also defines a fallback value, which is used to indicate that the value of this property is not set.
The following table lists the supported property types, as well as their corresponding fallback values.
-
Long
-Long.MIN_VALUE
-
Double
-NaN
-
Long Array
-null
-
Float Array
-null
-
Double Array
-null
2. Defining the type of a node property
When creating a graph projection that specifies a set of node properties, the type of these properties is automatically determined using the first property value that is read by the loader for any specified property.
All integral numerical types are interpreted as Long
values, all floating point values are interpreted as Double
values.
Array values are explicitly defined by the type of the values that the array contains, i.e. a conversion of, for example, an Integer Array
into a Long Array
is not supported.
Arrays with mixed content types are not supported.
3. Automatic type conversion
Most algorithms that are capable of using node properties require a specific property type. In cases of a mismatch between the type of the provided property and the required type, the library will try to convert the property value into the required type.
The automatic conversion only happens when the conversion is loss-less. Hence, we check the following:
-
Long
toDouble
: The Long value does not exceed the supported range of the Double type. -
Double
toLong
: The Double value does not have any decimal places. -
Double[]
toFloat[]
: The Double values do not exceed the supported range of the Float type for any of the elements in the array.
The algorithm computation will fail if any of these conditions are not satisfied for any node property value.
The automatic conversion is computationally more expensive and should therefore be avoided in performance critical applications. |
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