remove check for schema before reading column orders

Author: etseidl

parquet/src/file/metadata/thrift_gen.rs

@@ -1182,9 +1182,6 @@ pub(crate) fn parquet_metadata_from_bytes(buf: &[u8]) -> Result<ParquetMetaData>
                 created_by = Some(<&str>::read_thrift(&mut prot)?);
             }
             7 => {
-                if schema_descr.is_none() {
-                    return Err(general_err!("Required field schema is missing"));
-                }
                 let val = read_thrift_vec::<ColumnOrder, ThriftSliceInputProtocol>(&mut prot)?;
                 column_orders = Some(val);
             }

parquet/src/file/serialized_reader.rs

@@ -1896,7 +1896,7 @@ mod tests {
         let ret = SerializedFileReader::new(Bytes::copy_from_slice(&data));
         assert_eq!(
             ret.err().unwrap().to_string(),
-            "Parquet error: Required field schema is missing"
+            "Parquet error: Received empty union from remote ColumnOrder"
         );
     }