alamb commented on code in PR #6990:
URL: https://github.com/apache/arrow-rs/pull/6990#discussion_r1920729763
##########
parquet/src/arrow/arrow_writer/mod.rs:
##########
@@ -3409,4 +3409,30 @@ mod tests {
"Arrow: Incompatible type. Field 'temperature' has type Float64,
array has type Int32"
);
}
+
+ #[test]
+ // https://github.com/apache/arrow-rs/issues/6988
+ fn test_roundtrip_empty_schema() {
+ // create empty record batch with empty schema
+ let empty_fields: Vec<Field> = vec![];
+ let empty_schema = Arc::new(Schema::new(empty_fields));
+ let empty_batch = RecordBatch::try_new_with_options(
+ empty_schema,
+ vec![],
+ &RecordBatchOptions::default().with_row_count(Some(0)),
+ )
+ .unwrap();
+
+ // write to parquet
+ let mut parquet_bytes: Vec<u8> = Vec::new();
+ let mut writer =
+ ArrowWriter::try_new(&mut parquet_bytes, empty_batch.schema(),
None).unwrap();
+ writer.write(&empty_batch).unwrap();
+ writer.close().unwrap();
+
+ // read from parquet
+ let bytes = Bytes::from(parquet_bytes);
+ let result = ParquetRecordBatchReaderBuilder::try_new(bytes);
+ result.unwrap();
Review Comment:
I think we should also
1. check that the schema is correctly read back
2. Verify that the reader works correctly (reading back no batches)
For example, something like:
```suggestion
// read from parquet
let bytes = Bytes::from(parquet_bytes);
let reader =
ParquetRecordBatchReaderBuilder::try_new(bytes).unwrap();
assert_eq!(reader.schema(), &empty_batch.schema());
let batches: Vec<_> =
reader.build().unwrap().collect::<ArrowResult<Vec<_>>>().unwrap();
assert_eq!(batches.len(), 0);
```
(I ran this locally and it passed so I think we could also make these
changes as a follow on PR)
##########
parquet/src/arrow/arrow_writer/mod.rs:
##########
@@ -3409,4 +3409,30 @@ mod tests {
"Arrow: Incompatible type. Field 'temperature' has type Float64,
array has type Int32"
);
}
+
+ #[test]
+ // https://github.com/apache/arrow-rs/issues/6988
+ fn test_roundtrip_empty_schema() {
+ // create empty record batch with empty schema
+ let empty_fields: Vec<Field> = vec![];
+ let empty_schema = Arc::new(Schema::new(empty_fields));
Review Comment:
Very minor: you can use `Schema::empty` as well:
```suggestion
let empty_schema = Arc::new(Schema::new(empty_fields));
```
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