Fokko commented on code in PR #6437:
URL: https://github.com/apache/iceberg/pull/6437#discussion_r1052611597
##########
python/pyiceberg/io/pyarrow.py:
##########
@@ -437,3 +459,120 @@ def visit_or(self, left_result: pc.Expression,
right_result: pc.Expression) -> p
def expression_to_pyarrow(expr: BooleanExpression) -> pc.Expression:
return boolean_expression_visit(expr, _ConvertToArrowExpression())
+
+
+class _ConstructFinalSchema(SchemaVisitor[pa.ChunkedArray]):
+ file_schema: Schema
+ table: pa.Table
+
+ def __init__(self, file_schema: Schema, table: pa.Table):
+ self.file_schema = file_schema
+ self.table = table
+
+ def schema(self, schema: Schema, struct_result: List[pa.ChunkedArray]) ->
pa.Table:
+ return pa.table(struct_result, schema=schema_to_pyarrow(schema))
+
+ def struct(self, _: StructType, field_results: List[pa.ChunkedArray]) ->
List[pa.ChunkedArray]:
+ return field_results
+
+ def field(self, field: NestedField, _: pa.ChunkedArray) -> pa.ChunkedArray:
+ column_name = self.file_schema.find_column_name(field.field_id)
+
+ if column_name:
+ column_idx = self.table.schema.get_field_index(column_name)
+ else:
+ column_idx = -1
+
+ expected_arrow_type = schema_to_pyarrow(field.field_type)
+
+ # The idx will be -1 when the column can't be found
+ if column_idx >= 0:
+ column_field: pa.Field = self.table.schema[column_idx]
+ column_arrow_type: pa.DataType = column_field.type
+ column_data: pa.ChunkedArray = self.table[column_idx]
+ file_type = self.file_schema.find_type(field.field_id)
+
+ # In case of schema evolution
+ if column_arrow_type != expected_arrow_type:
+ # To check if the promotion is allowed
+ _ = promote(file_type, field.field_type)
+ column_data = column_data.cast(expected_arrow_type)
+ else:
+ import numpy as np
+
+ column_data = pa.array(np.full(shape=len(self.table),
fill_value=None), type=expected_arrow_type)
Review Comment:
Nice!
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