def valid_snapshot_target(self, relation: BaseRelation) -> None:
"""Ensure that the target relation is valid, by making sure it has the
expected columns.
:param Relation relation: The relation to check
:raises CompilationException: If the columns are
incorrect.
"""
if not isinstance(relation, self.Relation):
invalid_type_error(method_name='valid_snapshot_target',
arg_name='relation',
got_value=relation,
expected_type=self.Relation)
columns = self.get_columns_in_relation(relation)
names = set(c.name.lower() for c in columns)
expanded_keys = ('scd_id', 'valid_from', 'valid_to')
extra = []
missing = []
for legacy in expanded_keys:
desired = 'dbt_' + legacy
if desired not in names:
missing.append(desired)
if legacy in names:
extra.append(legacy)
if missing:
if extra:
msg = ('Snapshot target has ("{}") but not ("{}") - is it an '
'unmigrated previous version archive?'.format(
'", "'.join(extra), '", "'.join(missing)))
else:
msg = ('Snapshot target is not a snapshot table (missing "{}")'
.format('", "'.join(missing)))
raise_compiler_error(msg)
def get_missing_columns(self, from_relation: BaseRelation,
to_relation: BaseRelation) -> List[BaseColumn]:
"""Returns a list of Columns in from_relation that are missing from
to_relation.
"""
if not isinstance(from_relation, self.Relation):
invalid_type_error(method_name='get_missing_columns',
arg_name='from_relation',
got_value=from_relation,
expected_type=self.Relation)
if not isinstance(to_relation, self.Relation):
invalid_type_error(method_name='get_missing_columns',
arg_name='to_relation',
got_value=to_relation,
expected_type=self.Relation)
from_columns = {
col.name: col
for col in self.get_columns_in_relation(from_relation)
}
to_columns = {
col.name: col
for col in self.get_columns_in_relation(to_relation)
}
missing_columns = set(from_columns.keys()) - set(to_columns.keys())
return [
col for (col_name, col) in from_columns.items()
if col_name in missing_columns
]
def expand_target_column_types(self, from_relation: BaseRelation,
to_relation: BaseRelation) -> None:
if not isinstance(from_relation, self.Relation):
invalid_type_error(method_name='expand_target_column_types',
arg_name='from_relation',
got_value=from_relation,
expected_type=self.Relation)
if not isinstance(to_relation, self.Relation):
invalid_type_error(method_name='expand_target_column_types',
arg_name='to_relation',
got_value=to_relation,
expected_type=self.Relation)
self.expand_column_types(from_relation, to_relation)