hzuo commented on code in PR #5554:
URL: https://github.com/apache/arrow-rs/pull/5554#discussion_r1538388341
##########
arrow-ipc/src/writer.rs:
##########
@@ -2234,4 +2270,124 @@ mod tests {
let in_batch = RecordBatch::try_new(schema, vec![values]).unwrap();
roundtrip_ensure_sliced_smaller(in_batch, 1000);
}
+
+ #[test]
+ fn test_decimal128_alignment16() {
+ const IPC_ALIGNMENT: u8 = 16;
+
+ for num_cols in 1..100 {
+ let num_rows = (num_cols * 7 + 11) % 100; // Deterministic swizzle
+
+ let mut fields = Vec::new();
+ let mut arrays = Vec::new();
+ for i in 0..num_cols {
+ let field = Field::new(&format!("col_{}", i),
DataType::Decimal128(38, 10), true);
+ let array = Decimal128Array::from(vec![num_cols as i128;
num_rows]);
+ fields.push(field);
+ arrays.push(Arc::new(array) as Arc<dyn Array>);
+ }
+ let schema = Schema::new(fields);
+ let batch = RecordBatch::try_new(Arc::new(schema),
arrays).unwrap();
+
+ let mut writer = FileWriter::try_new_with_options(
+ Vec::new(),
+ batch.schema_ref(),
+ IpcWriteOptions::try_new(IPC_ALIGNMENT, false,
MetadataVersion::V5).unwrap(),
+ )
+ .unwrap();
+ writer.write(&batch).unwrap();
+ writer.finish().unwrap();
+
+ let out: Vec<u8> = writer.into_inner().unwrap();
+
+ let buffer = Buffer::from_vec(out);
+ let trailer_start = buffer.len() - 10;
+ let footer_len =
+
read_footer_length(buffer[trailer_start..].try_into().unwrap()).unwrap();
+ let footer =
+ root_as_footer(&buffer[trailer_start -
footer_len..trailer_start]).unwrap();
+
+ let schema = fb_to_schema(footer.schema().unwrap());
+ assert_eq!(&schema, batch.schema().as_ref());
+
+ let decoder =
+ FileDecoder::new(Arc::new(schema),
footer.version()).with_enforce_zero_copy(true);
+
+ assert_eq!(footer.dictionaries().unwrap().len(), 0);
+
+ let batches = footer.recordBatches().unwrap();
+ assert_eq!(batches.len(), 1);
+
+ let block = batches.get(0);
+ let block_len = block.bodyLength() as usize +
block.metaDataLength() as usize;
+ let data = buffer.slice_with_length(block.offset() as _,
block_len);
+
+ let batch2 = decoder.read_record_batch(block,
&data).unwrap().unwrap();
+
+ assert_eq!(batch, batch2);
+ }
+ }
+
+ #[test]
+ fn test_decimal128_alignment8_is_unaligned() {
+ const IPC_ALIGNMENT: u8 = 8;
Review Comment:
This test is equivalent to the current behavior without the changes in this
PR, it's equivalent to using `pad_to_8` everywhere.
Because the Decimal128Array is insufficiently aligned, this prevents readers
from doing a _true_ zero-copy read (e.g. mmapping), because they need to copy
the block into a more-aligned buffer.
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