[GitHub] [iceberg] rdblue commented on a diff in pull request #3450: [Python] support iceberg transforms in python

[GitBox <gi...@apache.org>]

rdblue commented on code in PR #3450:
URL: https://github.com/apache/iceberg/pull/3450#discussion_r841281813


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python/src/iceberg/transforms.py:
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@@ -0,0 +1,567 @@
+# 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.
+
+import re
+import struct
+from decimal import Decimal
+from enum import Enum
+from typing import Callable, Optional
+from uuid import UUID
+
+import mmh3  # type: ignore
+
+from iceberg.types import (
+    BinaryType,
+    DateType,
+    DecimalType,
+    FixedType,
+    IcebergType,
+    IntegerType,
+    LongType,
+    StringType,
+    TimestampType,
+    TimestamptzType,
+    TimeType,
+    Truncatable,
+    UUIDType,
+)
+from iceberg.utils import transform_util
+
+
+class Transform:
+    """Transform base class for concrete transforms.
+
+    A base class to transform values and project predicates on partition values.
+    This class is not used directly. Instead, use one of module method to create the child classes.
+
+    Args:
+        transform_string (str): name of the transform type
+        repr_string (str): string representation of a transform instance
+    """
+
+    def __init__(self, transform_string: str, repr_string: str):
+        self._transform_string = transform_string
+        self._repr_string = repr_string
+
+    def __repr__(self):
+        return self._repr_string
+
+    def __str__(self):
+        return self._transform_string
+
+    def __call__(self, value):
+        return self.apply(value)
+
+    def apply(self, value):
+        raise NotImplementedError()
+
+    def can_transform(self, target: IcebergType) -> bool:
+        return False
+
+    def result_type(self, source: IcebergType) -> IcebergType:
+        return source
+
+    def preserves_order(self) -> bool:
+        return False
+
+    def satisfies_order_of(self, other) -> bool:
+        return self == other
+
+    def to_human_string(self, value) -> str:
+        if value is None:
+            return "null"
+        return str(value)
+
+    def dedup_name(self) -> str:
+        return self._transform_string
+
+
+class BaseBucketTransform(Transform):
+    """Base Transform class to transform a value into a bucket partition value
+
+    Transforms are parameterized by a number of buckets. Bucket partition transforms use a 32-bit
+    hash of the source value to produce a positive value by mod the bucket number.
+
+    Args:
+      source_type (Type): An Iceberg Type of IntegerType, LongType, DecimalType, DateType, TimeType,
+      TimestampType, TimestamptzType, StringType, BinaryType, FixedType, UUIDType.
+      num_buckets (int): The number of buckets.
+    """
+
+    def __init__(self, source_type: IcebergType, num_buckets: int):
+        super().__init__(
+            f"bucket[{num_buckets}]",
+            f"transforms.bucket(source_type={repr(source_type)}, num_buckets={num_buckets})",
+        )
+        self._num_buckets = num_buckets
+
+    @property
+    def num_buckets(self) -> int:
+        return self._num_buckets
+
+    def hash(self, value) -> int:
+        raise NotImplementedError()
+
+    def apply(self, value) -> Optional[int]:
+        if value is None:
+            return None
+
+        return (self.hash(value) & IntegerType.max) % self._num_buckets
+
+    def can_transform(self, target: IcebergType) -> bool:
+        raise NotImplementedError()
+
+    def result_type(self, source: IcebergType) -> IcebergType:
+        return IntegerType()
+
+
+class BucketIntegerTransform(BaseBucketTransform):
+    """Transforms a value of IntegerType or DateType into a bucket partition value
+
+    Example:
+        >>> transform = BucketIntegerTransform(100)
+        >>> transform.apply(34)
+        79
+    """
+
+    def can_transform(self, target: IcebergType) -> bool:
+        return type(target) in {IntegerType, DateType}
+
+    def hash(self, value) -> int:
+        return mmh3.hash(struct.pack("q", value))
+
+
+class BucketLongTransform(BaseBucketTransform):
+    """Transforms a value of LongType, TimeType, TimestampType, or TimestamptzType
+    into a bucket partition value
+
+    Example:
+        >>> transform = BucketLongTransform(100)
+        >>> transform.apply(81068000000)
+        59
+    """
+
+    def can_transform(self, target: IcebergType) -> bool:
+        return type(target) in {LongType, TimeType, TimestampType, TimestamptzType}
+
+    def hash(self, value) -> int:
+        return mmh3.hash(struct.pack("q", value))
+
+
+class BucketDoubleTransform(BaseBucketTransform):
+    """Transforms a value of FloatType or DoubleType into a bucket partition value.
+
+    Note that bucketing by Double is not allowed by the spec, but this has the hash implementation.
+
+    Example:
+        >>> transform = BucketDoubleTransform(8)
+        >>> transform.hash(1.0)
+        -142385009
+    """
+
+    def hash(self, value) -> int:
+        return mmh3.hash(struct.pack("d", value))
+
+
+class BucketDecimalTransform(BaseBucketTransform):
+    """Transforms a value of DecimalType into a bucket partition value.
+
+    Example:
+        >>> transform = BucketDecimalTransform(100)
+        >>> transform.apply(Decimal("14.20"))
+        59
+    """
+
+    def can_transform(self, target: IcebergType) -> bool:
+        return isinstance(target, DecimalType)
+
+    def hash(self, value: Decimal) -> int:
+        return mmh3.hash(transform_util.decimal_to_bytes(value))
+
+
+class BucketStringTransform(BaseBucketTransform):
+    """Transforms a value of StringType into a bucket partition value.
+
+    Example:
+        >>> transform = BucketStringTransform(100)
+        >>> transform.apply("iceberg")
+        89
+    """
+
+    def can_transform(self, target: IcebergType) -> bool:
+        return isinstance(target, StringType)
+
+    def hash(self, value: str) -> int:
+        return mmh3.hash(value)
+
+
+class BucketFixedTransform(BaseBucketTransform):
+    """Transforms a value of FixedType into a bucket partition value.
+
+    Example:
+        >>> transform = BucketFixedTransform(128)
+        >>> transform.apply(b"foo")
+        32
+    """
+
+    def can_transform(self, target: IcebergType) -> bool:
+        return isinstance(target, FixedType)
+
+    def hash(self, value: bytearray) -> int:
+        return mmh3.hash(value)
+
+
+class BucketBinaryTransform(BaseBucketTransform):
+    """Transforms a value of BinaryType into a bucket partition value.
+
+    Example:
+        >>> transform = BucketBinaryTransform(128)
+        >>> transform.apply(b"\x00\x01\x02\x03")
+        57
+    """
+
+    def can_transform(self, target: IcebergType) -> bool:
+        return isinstance(target, BinaryType)
+
+    def hash(self, value: bytes) -> int:
+        return mmh3.hash(value)
+
+
+class BucketUUIDTransform(BaseBucketTransform):
+    """Transforms a value of UUIDType into a bucket partition value.
+
+    Example:
+        >>> transform = BucketUUIDTransform(100)
+        >>> transform.apply(UUID("f79c3e09-677c-4bbd-a479-3f349cb785e7"))
+        40
+    """
+
+    def can_transform(self, target: IcebergType) -> bool:
+        return isinstance(target, UUIDType)
+
+    def hash(self, value: UUID) -> int:
+        return mmh3.hash(
+            struct.pack(
+                ">QQ",
+                (value.int >> 64) & 0xFFFFFFFFFFFFFFFF,
+                value.int & 0xFFFFFFFFFFFFFFFF,
+            )
+        )
+
+
+class DateTimeTransform(Transform):

Review Comment:
   @jun-he I merged the bucketing PR, so maybe date/time transforms in the next one?
   
   I also opened #4480 with some common util packages to make this a bit easier.



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