Graph vertex data source wrap a Cassandra data source It's used internally by DseGraphFrame to handle vertices stored in C*
VertexSourceRelation return DF for one vertex label only It returns DF with all graph vertex properties by default.
The class is capable to generate local properties id only.
The class is capable to generate local properties id only. It should be able to generate the same vertex id as VertexIdAssignerRandomImpl in the future
VertexSourceRelation return DF for one vertex label only It returns DF with all graph vertex properties by default. It is done to simplify UNION of different vertexes. Unavailable vertex properties are returned as null. spark cassandra connector mapping is used to map C* type to DF types. mutli vertices are returned as array of values: ArrayType[DataType] if property definition has table, following struct will be returned StructType[value: FieldType, metaFields*]
multi-meta property will be: ArrayType[StructType[value: FieldType, meta...]]
Example of the schema: |member_id|community_id|skill| name|startTime|location|endTime|since| for one vertex it will return |member_id|community_id|NULL | name|NULL |location|NULL |NULL | if user defines columns with select("skill", "name", "startTime", "location") call, C* source will be asked for: |~~property-key-id| all vertex meta properties|idcolumns*|name|location| the source will return all requested properties (with meta struct if defined by schema). |NULL|name|null|location