[GitHub] [iceberg] jun-he commented on a diff in pull request #5030: [Python] add truncate transform

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

jun-he commented on code in PR #5030:
URL: https://github.com/apache/iceberg/pull/5030#discussion_r906929059


##########
python/src/iceberg/utils/decimal.py:
##########
@@ -75,3 +75,16 @@ def decimal_to_bytes(value: Decimal) -> bytes:
     """
     unscaled_value = decimal_to_unscaled(value)
     return unscaled_value.to_bytes(bytes_required(unscaled_value), byteorder="big", signed=True)
+
+
+def truncate_decimal(value: Decimal, width: int) -> Decimal:
+    """Get a truncated Decimal value given a decimal value and a width
+    Args:
+        value (Decimal): a decimal value
+        width (int): A width for the returned Decimal instance
+    Returns:
+        Decimal: A truncated Decimal instance
+    """
+    unscaled_value = decimal_to_unscaled(value)
+    applied_value = unscaled_value - (((unscaled_value % width) + width) % width)
+    return Decimal(f"{applied_value}e{value.as_tuple().exponent}")

Review Comment:
   changed it to use `unscaled_to_decimal(applied_value, -value.as_tuple().exponent)`



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