SPARK-25132 adds support for case-insensitive field resolution when reading from Parquet files. We found ORC files have similar issues, but not identical to Parquet. Spark has two OrcFileFormat.
SPARK-2883, Spark supports ORC inside sql/hive module with Hive dependency. This hive OrcFileFormat always do case-insensitive field resolution regardless of case sensitivity mode. When there is ambiguity, hive OrcFileFormat always returns the first matched field, rather than failing the reading operation. SPARK-20682adds a new ORC data source inside sql/core. This native OrcFileFormat supports case-insensitive field resolution, however it cannot handle duplicate fields.
Besides data source tables, hive serde tables also have issues. If ORC data file has more fields than table schema, we just can't read hive serde tables. If ORC data file does not have more fields, hive serde tables always do field resolution by ordinal, rather than by name.
Both ORC data source hive impl and hive serde table rely on the hive orc InputFormat/SerDe to read table. I'm not sure whether we can change underlying hive classes to make all orc read behaviors consistent.
This ticket aims to make read behavior of ORC data source native impl consistent with Parquet data source.
SPARK-20901 Feature parity for ORC with Parquet
- relates to
SPARK-25132 Case-insensitive field resolution when reading from Parquet
- links to