How to Check for Entity Changes

• The session's advanced property has_changed indicates whether the specified entity was added, modified, or deleted within the session.

• Note: The has_changed property is cleared (reset to False) after calling save_changes.

with store.open_session() as session:
    # Store a new entity within the session
    # =====================================

    employee = Employee(first_name="John", last_name="Doe")
    session.store(employee, "employees/1-A")

    # 'has_changed' will be True
    self.assertTrue(session.advanced.has_changed(employee))

    # 'has_changed' will reset to False after saving changes
    session.save_changes()
    self.assertFalse(session.advanced.has_changed(employee))

    # Load & modify entity within the session
    # =======================================

    employee = session.load("employees/1-A", Employee)
    self.assertFalse(session.advanced.has_changed(employee))  # False

    employee.last_name = "Brown"
    self.assertTrue(session.advanced.has_changed(employee))  # True

    session.save_changes()
    self.assertFalse(session.advanced.has_changed(employee))  # False

• Use the advanced session what_changed method to get all changes made to the specified entity
  within the session.

• Details will include:

  • The name and path of the changed field
  • Its old and new values
  • The type of change

• Note: what_changed reports changes made prior to calling save_changes.
  Calling it immediately after save_changes will return no results, since all changes are cleared at that point.

Example I

with store.open_session() as session:
    # Store (add) a new entity, it will be tracked by the session
    employee = Employee(first_name="John", last_name="Doe")
    session.store(employee, "employees/1-A")

    # Get the changes for the entity in the session
    # Call 'what_changed', pass the document id as a key to a resulting dict
    changes = session.advanced.what_changed()
    changes_for_employee = changes["employees/1-A"]

    self.assertEquals(1, len(changes_for_employee))  # a single change for this entity (adding)

    # Get the change type
    change_type = changes_for_employee[0].change
    self.assertEquals(DocumentsChanges.ChangeType.DOCUMENT_ADDED, change_type)

    session.save_changes()

Example II

with store.open_session() as session:
    # Load the entity, it will be tracked by the session
    employee = session.load("employees/1-A", Employee)

    # Modify the entity
    employee.first_name = "Jim"
    employee.last_name = "Brown"

    # Get the changes for the entity in the session
    # Call 'what_changed', pass the document id as a key to a resulting dict
    changes = session.advanced.what_changed()
    changes_for_employee = changes["employees/1-A"]

    self.assertEquals("FirstName", changes_for_employee[0].field_name)  # Field name
    self.assertEquals("Jim", changes_for_employee[0].field_new_value)  # New value
    self.assertEquals(
        changes_for_employee[0].change, DocumentsChanges.ChangeType.FIELD_CHANGED
    )  # Change type

    self.assertEquals("LastName", changes_for_employee[1].field_name)  # Field name
    self.assertEquals("Brown", changes_for_employee[1].field_new_value)  # New value
    self.assertEquals(
        changes_for_employee[1].change, DocumentsChanges.ChangeType.FIELD_CHANGED
    )  # Change type

    session.save_changes()

# has_changed
def has_changed(self, entity: object) -> bool: ...

# what_changed
def what_changed(self) -> Dict[str, List[DocumentsChanges]]: ...

class DocumentsChanges:

    def __init__(
        self,
        field_old_value: object,
        field_new_value: object,
        change: DocumentsChanges.ChangeType,
        field_name: str = None,
        field_path: str = None,
    ): ...

    class ChangeType(Enum):
        DOCUMENT_DELETED = "DocumentDeleted"
        DOCUMENT_ADDED = "DocumentAdded"
        FIELD_CHANGED = "FieldChanged"
        NEW_FIELD = "NewField"
        REMOVED_FIELD = "RemovedField"
        ARRAY_VALUE_CHANGED = "ArrayValueChanged"
        ARRAY_VALUE_ADDED = "ArrayValueAdded"
        ARRAY_VALUE_REMOVED = "ArrayValueRemoved"