TheR1sing3un commented on code in PR #8187: URL: https://github.com/apache/paimon/pull/8187#discussion_r3392968985
########## paimon-python/pypaimon/casting/data_type_casts.py: ########## @@ -0,0 +1,167 @@ +# 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. + +"""Type-cast support rules used to validate ``update column type`` schema +changes. + +The rules mirror the engine-wide cast specification so a type change accepted +here is one the read path can also materialize: an *implicit* cast is a safe +widening (e.g. INT -> BIGINT, any numeric -> DECIMAL/DOUBLE), while an +*explicit* cast covers the broader, possibly lossy conversions a user opts into +(e.g. DOUBLE -> INT truncation, anything -> STRING). Read-time execution then +applies the conversion leniently. +""" + +from pypaimon.schema.data_types import (ArrayType, AtomicType, MapType, + MultisetType, RowType, VectorType) + +# ---- Type roots -------------------------------------------------------------- + +CHAR = "CHAR" +VARCHAR = "VARCHAR" +BOOLEAN = "BOOLEAN" +BINARY = "BINARY" +VARBINARY = "VARBINARY" +DECIMAL = "DECIMAL" +TINYINT = "TINYINT" +SMALLINT = "SMALLINT" +INTEGER = "INTEGER" +BIGINT = "BIGINT" +FLOAT = "FLOAT" +DOUBLE = "DOUBLE" +DATE = "DATE" +TIME = "TIME" +TIMESTAMP = "TIMESTAMP" +TIMESTAMP_LTZ = "TIMESTAMP_LTZ" +ARRAY = "ARRAY" +MAP = "MAP" +MULTISET = "MULTISET" +ROW = "ROW" +VECTOR = "VECTOR" +VARIANT = "VARIANT" +BLOB = "BLOB" + +# ---- Families ---------------------------------------------------------------- + +CHARACTER_STRING = {CHAR, VARCHAR} +BINARY_STRING = {BINARY, VARBINARY} +INTEGER_NUMERIC = {TINYINT, SMALLINT, INTEGER, BIGINT} +NUMERIC = INTEGER_NUMERIC | {FLOAT, DOUBLE, DECIMAL} +TIMESTAMP_FAMILY = {TIMESTAMP, TIMESTAMP_LTZ} +TIME_FAMILY = {TIME} +DATETIME = {DATE, TIME, TIMESTAMP, TIMESTAMP_LTZ} +PREDEFINED = { + CHAR, VARCHAR, BOOLEAN, BINARY, VARBINARY, DECIMAL, + TINYINT, SMALLINT, INTEGER, BIGINT, FLOAT, DOUBLE, + DATE, TIME, TIMESTAMP, TIMESTAMP_LTZ, +} +CONSTRUCTED = {ARRAY, MAP, MULTISET, ROW, VECTOR} + + +def _root(data_type) -> str: + if isinstance(data_type, RowType): + return ROW + if isinstance(data_type, ArrayType): + return ARRAY + if isinstance(data_type, MapType): + return MAP + if isinstance(data_type, MultisetType): + return MULTISET + if isinstance(data_type, VectorType): + return VECTOR + if isinstance(data_type, AtomicType): + t = data_type.type.upper() + if t.startswith("DECIMAL") or t.startswith("NUMERIC") or t.startswith("DEC"): + return DECIMAL + if t in ("INT", "INTEGER"): + return INTEGER + if t in (TINYINT, SMALLINT, BIGINT, FLOAT, DOUBLE, BOOLEAN, DATE): + return t + if t == "STRING" or t.startswith("VARCHAR"): + return VARCHAR + if t.startswith("CHAR"): + return CHAR + if t == "BYTES" or t.startswith("VARBINARY"): + return VARBINARY + if t.startswith("BINARY"): + return BINARY + if t == "BLOB": + return BLOB + if t.startswith("TIMESTAMP_LTZ"): + return TIMESTAMP_LTZ + if t.startswith("TIMESTAMP"): + return TIMESTAMP + if t.startswith("TIME"): + return TIME + if t == "VARIANT": + return VARIANT + return None + + +def _build_rules(): + implicit = {} + explicit = {} + # Identity cast for every root. + for root in (PREDEFINED | CONSTRUCTED | {VARIANT, BLOB}): + implicit[root] = {root} + explicit[root] = set() + + def rule(target, implicit_from=None, explicit_from=None): + implicit[target] |= set(implicit_from or set()) + explicit[target] |= set(explicit_from or set()) + + rule(CHAR, {CHAR}, PREDEFINED | CONSTRUCTED) + rule(VARCHAR, CHARACTER_STRING, PREDEFINED | CONSTRUCTED) Review Comment: > This allows constructed types to be changed to STRING, but the read-time cast cannot materialize those conversions. For example, create a table with `mv ROW<a INT>` (or ARRAY/MAP), write one file, then `update_column_type("mv", STRING)`: the alter succeeds because `supports_cast` returns true here, but reading the old file fails in `DataFileBatchReader._align_array_by_id` with `ArrowNotImplementedError: Unsupported cast from struct/list/map ... to utf8`. Please either reject constructed-type -> STRING here, or add an explicit serialization conversion in the read path and cover it with a round-trip test. Nice catch! Thank you! Fixed~ -- 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]
