tustvold commented on code in PR #2097:
URL: https://github.com/apache/arrow-rs/pull/2097#discussion_r923621973
##########
parquet/src/arrow/array_reader/byte_array_dictionary.rs:
##########
@@ -459,7 +481,75 @@ mod tests {
None,
Some("1"),
Some("2"),
- None
+ None,
+ ]
+ )
+ }
+
+ #[test]
+ fn test_dictionary_preservation_skip() {
+ let data_type = utf8_dictionary();
+
+ let data: Vec<_> = vec!["0", "1", "0", "1", "2", "1", "2"]
+ .into_iter()
+ .map(ByteArray::from)
+ .collect();
+ let (dict, encoded) = encode_dictionary(&data);
+
+ let column_desc = utf8_column();
+ let mut decoder = DictionaryDecoder::<i32, i32>::new(&column_desc);
+
+ decoder
+ .set_dict(dict, 3, Encoding::RLE_DICTIONARY, false)
+ .unwrap();
+
+ decoder
+ .set_data(Encoding::RLE_DICTIONARY, encoded, 14, Some(data.len()))
+ .unwrap();
+
+ let mut output = DictionaryBuffer::<i32, i32>::default();
+ assert_eq!(decoder.skip_values(1).unwrap(), 1);
+ assert_eq!(decoder.read(&mut output, 0..2).unwrap(), 2);
+
+ let mut valid = vec![false, false, false, true, false, true];
+ let valid_buffer = Buffer::from_iter(valid.iter().cloned());
+ output.pad_nulls(0, 2, valid.len(), valid_buffer.as_slice());
+
+ assert!(matches!(output, DictionaryBuffer::Dict { .. }));
+
+ assert_eq!(decoder.skip_values(1).unwrap(), 1);
+ assert_eq!(decoder.read(&mut output, 0..3).unwrap(), 3);
Review Comment:
I think it should be 2..5 if anything, you've only read 2 values
##########
parquet/src/arrow/array_reader/byte_array_dictionary.rs:
##########
@@ -368,16 +368,38 @@ where
dict_offsets,
dict_values,
)?;
-
+ *max_remaining_values -= len;
Ok(len)
}
}
}
}
}
- fn skip_values(&mut self, _num_values: usize) -> Result<usize> {
- Err(nyi_err!("https://github.com/apache/arrow-rs/issues/1792";))
+ fn skip_values(&mut self, num_values: usize) -> Result<usize> {
+ match self.decoder.as_mut().expect("decoder not set in
DictionaryDecoder.") {
+ MaybeDictionaryDecoder::Fallback(decoder) => {
+ decoder.skip_without_dict(num_values)
+ }
+ MaybeDictionaryDecoder::Dict {
+ decoder,
+ max_remaining_values, } => {
+ let to_skip = num_values.min(*max_remaining_values);
+
+ let dict = self
+ .dict
+ .as_ref()
+ .ok_or_else(|| general_err!("missing dictionary page for
column"))?;
+
+ if dict.is_empty() {
Review Comment:
I'm not sure why this check is necessary, removing the corresponding check
from read, doesn't seem to fail any tests
##########
parquet/src/arrow/array_reader/byte_array_dictionary.rs:
##########
@@ -459,7 +481,75 @@ mod tests {
None,
Some("1"),
Some("2"),
- None
+ None,
+ ]
+ )
+ }
+
+ #[test]
+ fn test_dictionary_preservation_skip() {
+ let data_type = utf8_dictionary();
+
+ let data: Vec<_> = vec!["0", "1", "0", "1", "2", "1", "2"]
+ .into_iter()
+ .map(ByteArray::from)
+ .collect();
+ let (dict, encoded) = encode_dictionary(&data);
+
+ let column_desc = utf8_column();
+ let mut decoder = DictionaryDecoder::<i32, i32>::new(&column_desc);
+
+ decoder
+ .set_dict(dict, 3, Encoding::RLE_DICTIONARY, false)
+ .unwrap();
+
+ decoder
+ .set_data(Encoding::RLE_DICTIONARY, encoded, 14, Some(data.len()))
+ .unwrap();
+
+ let mut output = DictionaryBuffer::<i32, i32>::default();
+ assert_eq!(decoder.skip_values(1).unwrap(), 1);
+ assert_eq!(decoder.read(&mut output, 0..2).unwrap(), 2);
+
+ let mut valid = vec![false, false, false, true, false, true];
+ let valid_buffer = Buffer::from_iter(valid.iter().cloned());
+ output.pad_nulls(0, 2, valid.len(), valid_buffer.as_slice());
+
+ assert!(matches!(output, DictionaryBuffer::Dict { .. }));
+
+ assert_eq!(decoder.skip_values(1).unwrap(), 1);
+ assert_eq!(decoder.read(&mut output, 0..3).unwrap(), 3);
+
+ valid.extend_from_slice(&[false, false, false, true, false, true,
true, false]);
Review Comment:
I think these tests would be easier to follow if they didn't include the
null padding logic, which seems unnecessary for testing the skip behaviour
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