Multiple cardinality property or edge

Multiple cardinality allows a property to stored multiple values within a single key, or multiple edges with the same edge label to connect two vertices.

Multiple cardinality property

Create schema for a multiple cardinality property item_mult and create two vertices, each of which has two items listed for the defined property:

schema.propertyKey('item_mult').Text().multiple().ifNotExists().create()
schema.vertexLabel('fridgeItem_multiple').properties('item_mult').ifNotExists().create()
graph.addVertex(label,'fridgeItem_multiple','name', 'item1','item_mult', ['cheese', 'cheddar cheese'])
graph.addVertex(label, 'fridgeItem_multiple','name', 'item2', 'item_mult',['yogurt','Greek yogurt'], 'item_mult', ['key lime yogurt'])
g.V().hasLabel('fridgeItem_multiple').valueMap()

Because item_mult is defined with multiple cardinality, any number of key value insertions can be made, even using two lists to insert the values. Note that all values are stored in a single list.

==>{item_mult=[cheddar cheese, cheese], name=[item1]}
==>{item_mult=[Greek yogurt, key lime yogurt, yogurt], name=[item2]}

Explore the inserted data further:
```
g.V().has('fridgeItem_multiple', 'name', 'item2').values('item_mult')
```
```
==>Greek yogurt
==>key lime yogurt
==>yogurt
```
This output makes it clear that each entry in the list is a separately stored value.

Check for a single list item, specifying a particular value:

g.V().hasLabel('fridgeItem_multiple').has('item_mult', 'Greek yogurt').valueMap()

==>{item_mult=[Greek yogurt, key lime yogurt, yogurt], name=[item2]}

Multiple cardinality edge

Create schema for a multiple cardinality edge:

// SCHEMA
// PROPERTIES
schema.propertyKey('author').Text().single().create()
schema.propertyKey('city').Text().single().create()
schema.propertyKey('dateStart').Text().single().create()
schema.propertyKey('dateEnd').Text().single().create()
// VERTEX LABELS
schema.vertexLabel('author').properties('author').create()
schema.vertexLabel('city').properties('city').create()
// EDGE LABELS
schema.edgeLabel('livedIn').multiple().connection('author','city').create()
schema.edgeLabel('livedIn').properties('dateStart', 'dateEnd').add()
// INDEXES
schema.vertexLabel('author').index('byAuthor').materialized().by('author').add()
schema.vertexLabel('city').index('byCity').materialized().by('city').add()
schema.vertexLabel('author').index('byStartDate').outE('livedIn').by('dateStart').add()

Note that the edge label livedIn is defined with multi-cardinality. The sample data loaded with graphloader is:

author|city|dateStart|dateEnd
Julia Child|Paris|1961-01-01|1967-02-10
Julia Child|New York|1970-06-06|1971-09-23
Julia Child|Chicago|1980-04-05|1981-01-01
Julia Child|Paris|1990-01-01|1991-01-01
Simone Beck|Paris|1960-01-01|1962-09-23

This data includes two different periods of time in which Julia Child lived in Paris (fictiously), and edges will be multiple because of the multi-cardinality.

With this data loaded, the resulting graph shows the multi-cardinal edges exist:

multiCard1

Multiple cardinality property or edge

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