Fokko commented on code in PR #921:
URL: https://github.com/apache/iceberg-python/pull/921#discussion_r1678314538
##########
pyiceberg/schema.py:
##########
@@ -1616,3 +1616,103 @@ 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.
+ """
+ pre_order_visit(requested_schema,
_SchemaCompatibilityVisitor(provided_schema))
+
+
+class _SchemaCompatibilityVisitor(PreOrderSchemaVisitor[bool]):
+ provided_schema: Schema
+
+ def __init__(self, provided_schema: Schema):
+ from rich.console import Console
+ from rich.table import Table as RichTable
+
+ self.provided_schema = provided_schema
+ self.rich_table = RichTable(show_header=True, header_style="bold")
+ self.rich_table.add_column("")
+ self.rich_table.add_column("Table field")
+ self.rich_table.add_column("Dataframe field")
+ self.console = Console(record=True)
+
+ def _is_field_compatible(self, lhs: NestedField) -> bool:
+ # Validate nullability first.
+ # An optional field can be missing in the provided schema
+ # But a required field must exist as a required field
+ try:
+ rhs = self.provided_schema.find_field(lhs.field_id)
+ except ValueError:
+ if lhs.required:
+ self.rich_table.add_row("❌", str(lhs), "Missing")
+ return False
+ else:
+ self.rich_table.add_row("✅", str(lhs), "Missing")
+ return True
+
+ if lhs.required and not rhs.required:
+ self.rich_table.add_row("❌", str(lhs), str(rhs))
+ return False
+
+ # Check type compatibility
+ if lhs.field_type == rhs.field_type:
+ self.rich_table.add_row("✅", str(lhs), str(rhs))
+ return True
+ # We only check that the parent node is also of the same type.
+ # We check the type of the child nodes when we traverse them later.
+ elif any(
+ (isinstance(lhs.field_type, container_type) and
isinstance(rhs.field_type, container_type))
+ for container_type in {StructType, MapType, ListType}
+ ):
Review Comment:
Ah, yes I see
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