rdblue commented on code in PR #6997:
URL: https://github.com/apache/iceberg/pull/6997#discussion_r1168052211
##########
python/pyiceberg/io/pyarrow.py:
##########
@@ -476,6 +483,202 @@ def expression_to_pyarrow(expr: BooleanExpression) ->
pc.Expression:
return boolean_expression_visit(expr, _ConvertToArrowExpression())
+def pyarrow_to_schema(schema: pa.Schema) -> Schema:
+ visitor = _ConvertToIceberg()
+ struct_results = []
+ for i in range(len(schema.names)):
+ field = schema.field(i)
+ visitor.before_field(field)
+ struct_result = visit_pyarrow(field.type, visitor)
+ visitor.after_field(field)
+ struct_results.append(struct_result)
+ return visitor.schema(schema, struct_results)
+
+
+@singledispatch
+def visit_pyarrow(obj: pa.DataType, visitor: PyarrowSchemaVisitor[T]) -> T:
+ """A generic function for applying a pyarrow schema visitor to any point
within a schema
+
+ The function traverses the schema in post-order fashion
+
+ Args:
+ obj(Schema | IcebergType): An instance of a Schema or an IcebergType
+ visitor (PyarrowSchemaVisitor[T]): An instance of an implementation of
the generic PyarrowSchemaVisitor base class
+
+ Raises:
+ NotImplementedError: If attempting to visit an unrecognized object type
+ """
+ raise NotImplementedError("Cannot visit non-type: %s" % obj)
+
+
+@visit_pyarrow.register(pa.StructType)
+def _(obj: pa.StructType, visitor: PyarrowSchemaVisitor[T]) -> T:
+ struct_results = []
+ for field in obj:
+ visitor.before_field(field)
+ struct_result = visit_pyarrow(field.type, visitor)
+ visitor.after_field(field)
+ struct_results.append(struct_result)
+
+ return visitor.struct(obj, struct_results)
+
+
+@visit_pyarrow.register(pa.ListType)
+def _(obj: pa.ListType, visitor: PyarrowSchemaVisitor[T]) -> T:
+ visitor.before_list_element(obj.value_field)
+ list_result = visit_pyarrow(obj.value_field.type, visitor)
+ visitor.after_list_element(obj.value_field)
+ return visitor.list(obj, list_result)
+
+
+@visit_pyarrow.register(pa.MapType)
+def _(obj: pa.MapType, visitor: PyarrowSchemaVisitor[T]) -> T:
+ visitor.before_map_key(obj.key_field)
+ key_result = visit_pyarrow(obj.key_field.type, visitor)
+ visitor.after_map_key(obj.key_field)
+ visitor.before_map_value(obj.item_field)
+ value_result = visit_pyarrow(obj.item_field.type, visitor)
+ visitor.after_map_value(obj.item_field)
+ return visitor.map(obj, key_result, value_result)
+
+
+@visit_pyarrow.register(pa.DataType)
+def _(obj: pa.DataType, visitor: PyarrowSchemaVisitor[T]) -> T:
+ if pa.types.is_nested(obj):
+ raise TypeError(f"Expected primitive type, got {type(obj)}")
+ return visitor.primitive(obj)
+
+
+class PyarrowSchemaVisitor(Generic[T], ABC):
+ def before_field(self, field: pa.Field) -> None:
+ """Override this method to perform an action immediately before
visiting a field."""
+
+ def after_field(self, field: pa.Field) -> None:
+ """Override this method to perform an action immediately after
visiting a field."""
+
+ def before_list_element(self, element: pa.Field) -> None:
+ """Override this method to perform an action immediately before
visiting a list element."""
+
+ def after_list_element(self, element: pa.Field) -> None:
+ """Override this method to perform an action immediately after
visiting a list element."""
+
+ def before_map_key(self, key: pa.Field) -> None:
+ """Override this method to perform an action immediately before
visiting a map key."""
+
+ def after_map_key(self, key: pa.Field) -> None:
+ """Override this method to perform an action immediately after
visiting a map key."""
+
+ def before_map_value(self, value: pa.Field) -> None:
+ """Override this method to perform an action immediately before
visiting a map value."""
+
+ def after_map_value(self, value: pa.Field) -> None:
+ """Override this method to perform an action immediately after
visiting a map value."""
+
+ @abstractmethod
+ def schema(self, schema: pa.Schema, field_results: List[T]) -> Schema:
+ """visit a schema"""
+
+ @abstractmethod
+ def struct(self, struct: pa.StructType, field_results: List[T]) -> T:
+ """visit a struct"""
+
+ @abstractmethod
+ def list(self, list_type: pa.ListType, element_result: T) -> T:
+ """visit a list"""
+
+ @abstractmethod
+ def map(self, map_type: pa.MapType, key_result: T, value_result: T) -> T:
+ """visit a map"""
+
+ @abstractmethod
+ def primitive(self, primitive: pa.DataType) -> T:
+ """visit a primitive type"""
+
+
+def _get_field_id(field: pa.Field) -> int:
+ if field.metadata is not None:
+ field_metadata = {k.decode(): v.decode() for k, v in
field.metadata.items()}
+ if field_id := field_metadata.get("PARQUET:field_id"):
+ return int(field_id)
+ raise ValueError(f"Field {field.name} does not have a field_id")
+
+
+class _ConvertToIceberg(PyarrowSchemaVisitor[IcebergType], ABC):
+ def schema(self, schema: pa.Schema, field_results: List[IcebergType]) ->
Schema:
+ fields = []
+ for i in range(len(schema.names)):
+ field = schema.field(i)
+ field_id = _get_field_id(field)
+ field_type = field_results[i]
+ if field_type is not None:
+ fields.append(NestedField(field_id, field.name, field_type,
required=not field.nullable))
+ return Schema(*fields)
+
+ def struct(self, struct: pa.StructType, field_results: List[IcebergType])
-> IcebergType:
+ fields = []
+ for i in range(struct.num_fields):
+ field = struct[i]
+ field_id = _get_field_id(field)
+ # may need to check doc strings
+ field_type = field_results[i]
+ if field_type is not None:
+ fields.append(NestedField(field_id, field.name, field_type,
required=not field.nullable))
+ return StructType(*fields)
+
+ def list(self, list_type: pa.ListType, element_result: IcebergType) ->
IcebergType:
+ element_field = list_type.value_field
+ element_id = _get_field_id(element_field)
+ if element_result is not None:
+ return ListType(element_id, element_result, element_required=not
element_field.nullable)
+ raise ValueError(f"List type must have element field: {list_type}")
+
+ def map(self, map_type: pa.MapType, key_result: IcebergType, value_result:
IcebergType) -> IcebergType:
+ key_field = map_type.key_field
+ key_id = _get_field_id(key_field)
+ value_field = map_type.item_field
+ value_id = _get_field_id(value_field)
+ if key_result is not None and value_result is not None:
+ return MapType(key_id, key_result, value_id, value_result,
value_required=not value_field.nullable)
+ raise ValueError(f"Map type must have key and value fields:
{map_type}")
+
+ def primitive(self, primitive: pa.DataType) -> IcebergType:
+ if pa.types.is_boolean(primitive):
+ return BooleanType()
+ elif pa.types.is_int32(primitive) or pa.types.is_uint32(primitive):
+ return IntegerType()
+ elif pa.types.is_int64(primitive) or pa.types.is_uint64(primitive):
+ return LongType()
+ elif pa.types.is_float32(primitive):
+ return FloatType()
+ elif pa.types.is_float64(primitive):
+ return DoubleType()
+ elif pa.types.is_decimal(primitive):
+ if isinstance(primitive, pa.Decimal256Type):
+ primitive = cast(pa.Decimal256Type, primitive)
+ else:
+ primitive = cast(pa.Decimal128Type, primitive)
+ return DecimalType(primitive.precision, primitive.scale)
+ elif pa.types.is_string(primitive):
+ return StringType()
+ elif pa.types.is_date(primitive):
+ return DateType()
+ elif pa.types.is_time(primitive):
Review Comment:
This still seems suspicious to me. While it's now correct, how does PyArrow
read Python files that have other time or timestamp representations?
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