rdblue commented on a change in pull request #4263: URL: https://github.com/apache/iceberg/pull/4263#discussion_r839108425
########## File path: python/src/iceberg/conversions.py ########## @@ -0,0 +1,319 @@ +# 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. +"""Utility module for various conversions around PrimitiveType implementations + +This module enables: + - Converting partition strings to built-in python objects + - Converting a value to a byte buffer + - Converting a byte buffer to a value + +Note: + Conversion logic varies based on the PrimitiveType implementation. Therefore conversion functions + are defined here as generic functions using the @singledispatch decorator. For each PrimitiveType + implementation, a concrete function is registered for each generic conversion function. For PrimitiveType + implementations that share the same conversion logic, registrations can be stacked. +""" +import struct +import uuid +from decimal import Decimal +from functools import singledispatch +from typing import Union + +from iceberg.types import ( + BinaryType, + BooleanType, + DateType, + DecimalType, + DoubleType, + FixedType, + FloatType, + IntegerType, + LongType, + PrimitiveType, + StringType, + TimestampType, + TimestamptzType, + TimeType, + UUIDType, +) + + +def handle_none(func): + """A decorator function to handle cases where partition values are `None` or "__HIVE_DEFAULT_PARTITION__" + + Args: + func (Callable): A function registered to the singledispatch function `partition_to_py` + """ + + def wrapper(primitive_type, value_str): + if value_str is None: + return None + elif value_str == "__HIVE_DEFAULT_PARTITION__": + return None + return func(primitive_type, value_str) + + return wrapper + + +def decimal_to_unscaled(value: Decimal) -> int: + """Get an unscaled value given a Decimal value + + Args: + value (Decimal): A Decimal instance + + Returns: + int: The unscaled value + """ + sign, digits, _ = value.as_tuple() + return int(Decimal((sign, digits, 0)).to_integral_value()) + + +def unscaled_to_decimal(unscaled: int, scale: int) -> Decimal: + """Get a scaled Decimal value given an unscaled value and a scale + + Args: + unscaled (int): An unscaled value + scale (int): A scale to set for the returned Decimal instance + + Returns: + Decimal: A scaled Decimal instance + """ + sign, digits, _ = Decimal(unscaled).as_tuple() + return Decimal((sign, digits, -scale)) + + +@singledispatch +def partition_to_py(primitive_type, value_str: str): + """A generic function which converts a partition string to a python built-in + + Args: + primitive_type(PrimitiveType): An implementation of the PrimitiveType base class + value_str(str): A string representation of a partition value + """ + raise TypeError(f"Cannot convert '{value_str}' to unsupported type: {primitive_type}") + + +@partition_to_py.register(BooleanType) +@handle_none +def _(primitive_type, value_str: str) -> Union[int, float, str, uuid.UUID]: + return value_str.lower() == "true" + + +@partition_to_py.register(IntegerType) +@partition_to_py.register(LongType) +@partition_to_py.register(DateType) +@partition_to_py.register(TimeType) +@partition_to_py.register(TimestampType) +@partition_to_py.register(TimestamptzType) +@handle_none +def _(primitive_type, value_str: str) -> int: + """ + Raises: + ValueError: If the scale/exponent is not 0 + """ + _, digits, exponent = Decimal(value_str).as_tuple() + if exponent != 0: # Raise if there are digits to the right of the decimal + raise ValueError(f"Cannot convert partition value, value cannot have fractional digits for {primitive_type} partition") + return int(float(value_str)) + + +@partition_to_py.register(FloatType) +@partition_to_py.register(DoubleType) +@handle_none +def _(primitive_type, value_str: str) -> float: + return float(value_str) + + +@partition_to_py.register(StringType) +@handle_none +def _(primitive_type, value_str: str) -> str: + return value_str + + +@partition_to_py.register(UUIDType) +@handle_none +def _(primitive_type, value_str: str) -> uuid.UUID: + return uuid.UUID(value_str) + + +@partition_to_py.register(FixedType) +@partition_to_py.register(BinaryType) +@handle_none +def _(primitive_type, value_str: str) -> bytes: + return bytes(value_str, "UTF-8") + + +@partition_to_py.register(DecimalType) +@handle_none +def _(primitive_type, value_str: str) -> Decimal: + return Decimal(value_str) + + +@singledispatch +def to_bytes(primitive_type: PrimitiveType, value: Union[bool, bytes, Decimal, float, int, str, uuid.UUID]) -> bytes: + """A generic function which converts a built-in python value to bytes + + This conversion follows the serialization scheme for storing single values as individual binary values defined in the Iceberg specification that + can be found at https://iceberg.apache.org/spec/#appendix-d-single-value-serialization + + Args: + primitive_type(PrimitiveType): An implementation of the PrimitiveType base class + value: The value to convert to bytes (The type of this value depends on which dispatched function is + used--check dispatchable functions for typehints) + """ + raise TypeError(f"scale does not match {primitive_type}") + + +@to_bytes.register(BooleanType) +def _(primitive_type, value: bool) -> bytes: + return struct.pack("<?", 1 if value else 0) + + +@to_bytes.register(IntegerType) +@to_bytes.register(DateType) +def _(primitive_type, value: int) -> bytes: + return struct.pack("<i", value) + + +@to_bytes.register(LongType) +@to_bytes.register(TimeType) +@to_bytes.register(TimestampType) +@to_bytes.register(TimestamptzType) +def _(primitive_type, value: int) -> bytes: + return struct.pack("<q", value) + + +@to_bytes.register(FloatType) +def _(primitive_type, value: float) -> bytes: + """ + Note: float in python is implemented using a double in C. Therefore this involves a conversion of a 32-bit (single precision) + float to a 64-bit (double precision) float which introduces some imprecision. + """ + return struct.pack("<f", value) + + +@to_bytes.register(DoubleType) +def _(primitive_type, value: float) -> bytes: + return struct.pack("<d", value) + + +@to_bytes.register(StringType) +def _(primitive_type, value: str) -> bytes: + return value.encode("UTF-8") + + +@to_bytes.register(UUIDType) +def _(primitive_type, value: uuid.UUID) -> bytes: + return struct.pack(">QQ", (value.int >> 64) & 0xFFFFFFFFFFFFFFFF, value.int & 0xFFFFFFFFFFFFFFFF) + + +@to_bytes.register(BinaryType) +@to_bytes.register(FixedType) +def _(primitive_type, value: bytes) -> bytes: + return value + + +@to_bytes.register(DecimalType) +def _(primitive_type, value: Decimal) -> bytes: + """Convert a Decimal value to bytes given a DecimalType instance with defined precision and scale + + Args: + primitive_type (Decimal): A DecimalType instance with precision and scale + value (Decimal): A Decimal instance + + Raises: + ValueError: If either the precision or scale of `value` does not match that defined in the DecimalType instance + + + Returns: + bytes: The byte representation of `value` + """ + sign, digits, exponent = value.as_tuple() + + if -exponent != primitive_type.scale: + raise ValueError(f"Cannot serialize value, scale of value does not match type {primitive_type}: {-exponent}") + elif len(digits) > primitive_type.precision: + raise ValueError( + f"Cannot serialize value, precision of value is greater than precision of type {primitive_type}: {len(digits)}" + ) + + unscaled_value = decimal_to_unscaled(value=Decimal((sign, digits, 0))) Review comment: Minor: this could pass `value` now that `decimal_to_unscaled` is fixed. -- This is an automated message from the Apache Git Service. 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