Fokko commented on code in PR #5116: URL: https://github.com/apache/iceberg/pull/5116#discussion_r908953001
########## python/src/iceberg/avro/resolver.py: ########## @@ -0,0 +1,150 @@ +# Licensed to the Apache Software Foundation (ASF) under one +# or more contributor license agreements. See the NOTICE file +# distributed with this work for additional information +# regarding copyright ownership. The ASF licenses this file +# to you under the Apache License, Version 2.0 (the +# "License"); you may not use this file except in compliance +# with the License. You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, +# software distributed under the License is distributed on an +# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +# KIND, either express or implied. See the License for the +# specific language governing permissions and limitations +# under the License. +from functools import singledispatch +from typing import ( + Dict, + List, + Optional, + Set, + Tuple, + Type, +) + +from iceberg.avro.reader import ( + ConstructReader, + ListReader, + MapReader, + NoneReader, + OptionReader, + Reader, + StructReader, + primitive_reader, +) +from iceberg.schema import Schema, visit +from iceberg.types import ( + BinaryType, + IcebergType, + IntegerType, + ListType, + LongType, + MapType, + PrimitiveType, + StringType, + StructType, +) + + +class ResolveException(Exception): + pass + + +@singledispatch +def resolve(write_schema, read_schema) -> Reader: + """This resolves the write and read schema + + The function traverses the schema in post-order fashion + + Args: + write_schema (Schema | IcebergType): The write schema of the Avro file + read_schema (Schema | IcebergType): The requested read schema which is equal or a subset of the write schema + + Raises: + NotImplementedError: If attempting to resolve an unrecognized object type + """ + raise NotImplementedError("Cannot resolve non-type: %s" % write_schema) + + [email protected](Schema) +def _(write_schema: Schema, read_schema: Schema) -> Reader: + """Visit a Schema and starts resolving it by converting it to a struct""" + return resolve(write_schema.as_struct(), read_schema.as_struct()) + + [email protected](StructType) +def _(write_struct: StructType, read_struct: StructType) -> Reader: + """Iterates over the write schema, and checks if the field is in the read schema""" + results: List[Tuple[Optional[int], Reader]] = [] + + read_fields = {field.name: (pos, field) for pos, field in enumerate(read_struct.fields)} + + for write_field in write_struct.fields: + if write_field.name in read_fields: + read_pos, read_field = read_fields[write_field.name] + result_reader = resolve(write_field.field_type, read_field.field_type) + else: + read_pos = None + result_reader = visit(write_field.field_type, ConstructReader()) + result_reader = result_reader if write_field.required else OptionReader(result_reader) + results.append((read_pos, result_reader)) + + write_fields = {field.name: field for field in write_struct.fields} + for pos, read_field in enumerate(read_struct.fields): + if read_field.name not in write_fields: + if read_field.required: + raise ResolveException(f"{read_field} is in not in the write schema, and is required") + # Just set the new field to None + results.append((pos, NoneReader())) + + return StructReader(tuple(results)) + + [email protected](ListType) +def _(write_list: ListType, read_list: ListType) -> Reader: + if not isinstance(read_list, ListType): + raise ResolveException(f"Cannot change {write_list} into {read_list}") + element_reader = resolve(write_list.element.field_type, read_list.element.field_type) + return ListReader(element_reader) + + [email protected](MapType) +def _(write_map: MapType, read_map: MapType) -> Reader: + if not isinstance(read_map, MapType): + raise ResolveException(f"Cannot change {write_map} into {read_map}") + key_reader = resolve(write_map.key.field_type, read_map.key.field_type) + value_reader = resolve(write_map.value.field_type, read_map.value.field_type) + + return MapReader(key_reader, value_reader) + + +ALLOWED_PROMOTIONS: Dict[Type[PrimitiveType], Set[Type[PrimitiveType]]] = { + # For now we only support the binary compatible ones + IntegerType: {LongType}, + StringType: {BinaryType}, + BinaryType: {StringType}, Review Comment: I've created a PR here to add string/binary conversion to the Spec: https://github.com/apache/iceberg/pull/5151 > I also want to note that the type promotions that we care about are the promotions that are allowed in Iceberg, not Avro. While we're using Avro files, Avro is more permissive in these cases than Iceberg allows. Good point, I was focussing on the Avro ones here (since it is in the Avro package), but we can also make this pluggable by providing different promotion dictionaries for Avro and Iceberg. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
