Fokko commented on code in PR #921:
URL: https://github.com/apache/iceberg-python/pull/921#discussion_r1677184500
##########
pyiceberg/schema.py:
##########
@@ -1616,3 +1621,145 @@ def _(file_type: FixedType, read_type: IcebergType) ->
IcebergType:
return read_type
else:
raise ResolveError(f"Cannot promote {file_type} to {read_type}")
+
+
+def _check_schema_compatible(requested_schema: Schema, provided_schema:
Schema) -> None:
+ """
+ Check if the `provided_schema` is compatible with `requested_schema`.
+
+ Both Schemas must have valid IDs and share the same ID for the same field
names.
+
+ Two schemas are considered compatible when:
+ 1. All `required` fields in `requested_schema` are present and are also
`required` in the `provided_schema`
+ 2. Field Types are consistent for fields that are present in both schemas.
I.e. the field type
+ in the `provided_schema` can be promoted to the field type of the same
field ID in `requested_schema`
+
+ Raises:
+ ValueError: If the schemas are not compatible.
+ """
+ visit(requested_schema, _SchemaCompatibilityVisitor(provided_schema))
+
+ # from rich.console import Console
+ # from rich.table import Table as RichTable
+
+ # console = Console(record=True)
+
+ # rich_table = RichTable(show_header=True, header_style="bold")
+ # rich_table.add_column("")
+ # rich_table.add_column("Table field")
+ # rich_table.add_column("Dataframe field")
+
+ # is_compatible = True
+
+ # for field_id in requested_schema.field_ids:
+ # lhs = requested_schema.find_field(field_id)
+ # try:
+ # rhs = provided_schema.find_field(field_id)
+ # except ValueError:
+ # if lhs.required:
+ # rich_table.add_row("❌", str(lhs), "Missing")
+ # is_compatible = False
+ # else:
+ # rich_table.add_row("✅", str(lhs), "Missing")
+ # continue
+
+ # if lhs.required and not rhs.required:
+ # rich_table.add_row("❌", str(lhs), "Missing")
+ # is_compatible = False
+
+ # if lhs.field_type == rhs.field_type:
+ # rich_table.add_row("✅", str(lhs), str(rhs))
+ # continue
+ # elif any(
+ # (isinstance(lhs.field_type, container_type) and
isinstance(rhs.field_type, container_type))
+ # for container_type in {StructType, MapType, ListType}
+ # ):
+ # rich_table.add_row("✅", str(lhs), str(rhs))
+ # continue
+ # else:
+ # try:
+ # promote(rhs.field_type, lhs.field_type)
+ # rich_table.add_row("✅", str(lhs), str(rhs))
+ # except ResolveError:
+ # rich_table.add_row("❌", str(lhs), str(rhs))
+ # is_compatible = False
+
+ # if not is_compatible:
+ # console.print(rich_table)
+ # raise ValueError(f"Mismatch in fields:\n{console.export_text()}")
+
+
+class _SchemaCompatibilityVisitor(SchemaVisitor[bool]):
Review Comment:
Yes, I think pre-order makes sense here 👍
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