Fokko commented on code in PR #6515:
URL: https://github.com/apache/iceberg/pull/6515#discussion_r1060905337
##########
python/pyiceberg/schema.py:
##########
@@ -1350,3 +1349,98 @@ def _(file_type: DecimalType, read_type: IcebergType) ->
IcebergType:
raise ResolveError(f"Cannot reduce precision from {file_type} to
{read_type}")
else:
raise ResolveError(f"Cannot promote an decimal to {read_type}")
+
+
+def check_schema_compatibility(requested_schema: Schema, file_schema: Schema)
-> Schema:
+ return visit_with_partner(requested_schema, file_schema,
_RequiredFieldVisitor(), _PartnerSchemaAccessor(file_schema))
+
+
+class _RequiredFieldVisitor(SchemaWithPartnerVisitor[Union[Schema,
IcebergType], Union[Schema, IcebergType]]):
+ def schema(
+ self, schema: Schema, schema_partner: Optional[Union[Schema,
IcebergType]], struct_result: Union[Schema, IcebergType]
+ ) -> Union[Schema, IcebergType]:
+ return schema
+
+ def struct(
+ self,
+ struct: StructType,
+ struct_partner: Optional[Union[Schema, IcebergType]],
+ field_results: List[Union[Schema, IcebergType]],
+ ) -> Union[Schema, IcebergType]:
+ assert len(struct.fields) == len(field_results)
+
+ if struct_partner is not None:
+ if isinstance(struct_partner, Schema):
+ struct_partner = struct_partner.as_struct()
+ if not isinstance(struct_partner, StructType):
+ raise ValueError(f"Expected StructType, got: {struct_partner}")
+ struct_partner_ids = {field.field_id for field in
struct_partner.fields}
+ for field in field_results:
+ assert isinstance(field, NestedField)
+ # The field does not exist in the partner_struct
+ if field.field_id not in struct_partner_ids and field.required:
+ raise ResolveError(f"Field is required, and could not be
found in the file: {field}")
+
+ return struct
+
+ def field(
+ self, field: NestedField, field_partner: Optional[Union[Schema,
IcebergType]], field_result: Union[Schema, IcebergType]
+ ) -> Union[Schema, IcebergType]:
+ return field
+
+ def list(
+ self, list_type: ListType, list_partner: Optional[Union[Schema,
IcebergType]], element_result: Union[Schema, IcebergType]
+ ) -> Union[Schema, IcebergType]:
+ if list_partner is not None and not isinstance(list_partner, ListType):
+ raise ValueError(f"Expected ListType, got: {list_partner}")
+
+ return list_type
+
+ def map(
+ self,
+ map_type: MapType,
+ map_partner: Optional[Union[Schema, IcebergType]],
+ key_result: Union[Schema, IcebergType],
+ value_result: Union[Schema, IcebergType],
+ ) -> Union[Schema, IcebergType]:
+ if map_type is not None and not isinstance(map_type, MapType):
+ raise ValueError(f"Expected MapType, got: {map_type}")
+
+ return map_type
+
+ def primitive(
+ self, primitive: PrimitiveType, primitive_partner:
Optional[Union[Schema, IcebergType]]
+ ) -> Union[Schema, IcebergType]:
+ if primitive_partner and primitive_partner != primitive:
+ return promote(primitive_partner, primitive)
+ else:
+ return primitive
+
+
+class _PartnerSchemaAccessor(PartnerAccessor[Union[Schema, IcebergType]]):
+ partner_schema: Schema
+
+ def __init__(self, partner_schema: Schema) -> None:
+ self.partner_schema = partner_schema
+
+ def schema_partner(self, partner: Optional[Union[Schema, IcebergType]]) ->
Optional[Union[Schema, IcebergType]]:
+ return partner
+
+ def field_partner(
+ self, partner_struct: Optional[Union[Schema, IcebergType]], field_id:
int, _: str
+ ) -> Optional[Union[Schema, IcebergType]]:
+ if partner_struct is not None:
+ try:
+ return self.partner_schema.find_field(field_id).field_type
Review Comment:
Ah, great catch!
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