albertlockett commented on code in PR #8069:
URL: https://github.com/apache/arrow-rs/pull/8069#discussion_r2310030616
##########
parquet/src/arrow/arrow_writer/mod.rs:
##########
@@ -4293,4 +4304,50 @@ mod tests {
assert_eq!(get_dict_page_size(col0_meta), 1024 * 1024);
assert_eq!(get_dict_page_size(col1_meta), 1024 * 1024 * 4);
}
+
+ #[test]
+ fn arrow_writer_run_end_encoded() {
+ // Create a run array of strings
+ let mut builder = StringRunBuilder::<Int16Type>::new();
+ builder.extend(
+ vec![Some("alpha"); 1000]
+ .into_iter()
+ .chain(vec![Some("beta"); 1000]),
+ );
+ let run_array: RunArray<Int16Type> = builder.finish();
+ println!("run_array type: {:?}", run_array.data_type());
+ let schema = Arc::new(Schema::new(vec![Field::new(
+ "ree",
+ run_array.data_type().clone(),
+ run_array.is_nullable(),
+ )]));
+
+ // Write to parquet
+ let mut parquet_bytes: Vec<u8> = Vec::new();
+ let mut writer = ArrowWriter::try_new(&mut parquet_bytes,
schema.clone(), None).unwrap();
+ let batch = RecordBatch::try_new(schema.clone(),
vec![Arc::new(run_array)]).unwrap();
+ writer.write(&batch).unwrap();
+ writer.close().unwrap();
+
+ // Schema of output is plain, not dictionary or REE encoded!!
Review Comment:
> It makes sense to add the reader implementation in this PR as well, right?
Sure, if you have time!
If you don't have time to add in this PR maybe we could maybe add it as a
followup (I'd be happy to help with this as well, if needed).
The temporary workaround to get the Parquet column to decode to the correct
Arrow type would be to decode the column to the native Arrow type, and then
convert to a `RunArray` by casting. This is less efficient because we
materialize a full length array before encoding it to REE.
For non-byte types (numberic types), this would already be happening. We
follow this branch when creating the reader:
https://github.com/apache/arrow-rs/blob/1dacecba8e11cac307eea5d1a0f10c22d7f4a8b7/parquet/src/arrow/array_reader/builder.rs#L354-L358
And then in the `PrimitiveArrayReader` we do the cast here:
https://github.com/apache/arrow-rs/blob/1dacecba8e11cac307eea5d1a0f10c22d7f4a8b7/parquet/src/arrow/array_reader/primitive_array.rs#L484
For byte types (String, Binary, etc), we'd need to do something like this:
https://github.com/albertlockett/arrow-rs/commit/f3d072f5684ff2749e9a961eb8e9662a629cbc2b
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