Read partitioned tables with source field missing from schema #2367
Conversation
| source_field = schema.find_field(field.source_id) | ||
| result_type = field.transform.result_type(source_field.field_type) | ||
| nested_fields.append(NestedField(field.field_id, field.name, result_type, required=source_field.required)) | ||
| else: |
There was a problem hiding this comment.
Wanted to get some opinions for just allowing this for VoidTransforms fields, as as of now we can drop columns without dropping the partition first
There was a problem hiding this comment.
Unfortunally, dropping is not an option. The V1 tables do not have field-IDs encoded in the struct, and is purely positional based. See the spec for details. Dropping a field, would change the position, potentially resulting in data integrity issues.
There was a problem hiding this comment.
I was referring more to that if the field's transform is not VoidTransform then we should potentially fail here. Java does not allow dropping a schema column if there is an non-void partition referencing that field, but here it is not guaranteed that if there is no source-field for a partition then the partition will be void.
Rationale for this change
Following with the Java solution implementation on how to read partition specs when a source field was dropped.
Are these changes tested?
Yes, added one integration tests, and one unit test
Are there any user-facing changes?
No