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property Hierarchy.virtual : bool | None

Whether the hierarchy is virtual or not. A virtual hierarchy does not store in memory the list of its members. Hierarchies with large cardinality are good candidates for being virtual. By default, a given hierarchy is automatically set as virtual if and only if it comes from an ExternalTable and one of the following conditions is met:
  • The hierarchy has a cardinality of 10000 or more;
  • The activeviam.experimental.forceVirtualHierarchies property is set to true.
As its name suggests, activeviam.experimental.forceVirtualHierarchies is an experimental/temporary property which may change in future bugfix releases.

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Example

>>> from atoti_directquery_clickhouse import ConnectionConfig, TableConfig
>>> connection_config = ConnectionConfig(
...     url=f"clickhouse:http://localhost:{clickhouse_server_port}/{schema_name}",
... )
>>> table_config = TableConfig(keys={"id"})
  • Without activeviam.experimental.forceVirtualHierarchies: 
    >>> session = tt.Session.start()
>>> external_database = session.connect_to_external_database(
...     connection_config
... )
>>> sales_table = session.add_external_table(
...     external_database.tables["sales"], config=table_config
... )
>>> cube = session.create_cube(sales_table)
>>> cube.hierarchies["product"].virtual
False
  • With activeviam.experimental.forceVirtualHierarchies: 
    >>> session_config = tt.SessionConfig(
...     java_options=["-Dactiveviam.experimental.forceVirtualHierarchies=true"]
... )
>>> session = tt.Session.start(session_config)
>>> external_database = session.connect_to_external_database(
...     connection_config
... )
>>> sales_table = session.add_external_table(
...     external_database.tables["sales"], config=table_config
... )
>>> cube = session.create_cube(sales_table)
>>> cube.hierarchies["product"].virtual
True