tustvold commented on code in PR #2076:
URL: https://github.com/apache/arrow-rs/pull/2076#discussion_r922305417
##########
parquet/src/arrow/array_reader/byte_array.rs:
##########
@@ -589,6 +680,38 @@ impl ByteArrayDecoderDictionary {
}
Ok(values_read)
}
+
+ fn skip<I: OffsetSizeTrait + ScalarValue>(
+ &mut self,
+ dict: &OffsetBuffer<I>,
+ to_skip: usize,
+ ) -> Result<usize> {
+ let to_skip = to_skip.min(self.max_remaining_values);
+ // All data must be NULL
+ if dict.is_empty() {
+ return Ok(0);
+ }
+
+ let mut values_skip = 0;
+ while values_skip < to_skip {
+ if self.index_offset == self.index_buf_len {
+ let read = self.decoder.get_batch(self.index_buf.as_mut())?;
Review Comment:
Possibly something for a follow up PR, but it would be nice if we could
avoid decoding values only to dump them on the floor
##########
parquet/src/arrow/array_reader/byte_array.rs:
##########
@@ -653,6 +776,57 @@ mod tests {
}
}
+ #[test]
+ fn test_byte_array_decoder_skip() {
+ let (pages, encoded_dictionary) =
+ byte_array_all_encodings(vec!["hello", "world", "a", "b"]);
+
+ let column_desc = utf8_column();
+ let mut decoder = ByteArrayColumnValueDecoder::new(&column_desc);
+
+ decoder
+ .set_dict(encoded_dictionary, 4, Encoding::RLE_DICTIONARY, false)
+ .unwrap();
+
+ for (encoding, page) in pages {
+ let mut output = OffsetBuffer::<i32>::default();
+ decoder.set_data(encoding, page, 4, Some(4)).unwrap();
+
+ assert_eq!(decoder.read(&mut output, 0..1).unwrap(), 1);
+
+ assert_eq!(output.values.as_slice(), "hello".as_bytes());
+ assert_eq!(output.offsets.as_slice(), &[0, 5]);
+
+ assert_eq!(decoder.skip_values(1).unwrap(), 1);
+ assert_eq!(decoder.skip_values(1).unwrap(), 1);
+
+ assert_eq!(decoder.read(&mut output, 0..1).unwrap(), 1);
Review Comment:
```suggestion
assert_eq!(decoder.read(&mut output, 1..2).unwrap(), 1);
```
The decoder doesn't actually care, as it keeps track of the number of read
values, but this is technically more correct
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