Balaji K created PARQUET-2108:
---------------------------------
Summary: Specification for RLEDictionary encoding is incorrect.
Key: PARQUET-2108
URL: https://issues.apache.org/jira/browse/PARQUET-2108
Project: Parquet
Issue Type: Bug
Reporter: Balaji K
The [spec for RLE
Dictionary|[https://github.com/apache/parquet-format/blob/master/Encodings.md#dictionary-encoding-plain_dictionary--2-and-rle_dictionary--8]]
encoding says the "length of the encoded-data" is placed before the
"encoded-data". Reproducing the first 3 lines here:
```
rle-bit-packed-hybrid: <length> <encoded-data>
length := length of the <encoded-data> in bytes stored as 4 bytes little endian
(unsigned int32)
encoded-data := <run>*
```
However, this is not true. Parquet-MR implementation does not encode the length
in front of the data. It encodes bitWidth as 1 byte. See
[implementation|[https://github.com/apache/parquet-mr/blob/01a5d074829ad4cf4de1f662d54fe7bceb4bef63/parquet-column/src/main/java/org/apache/parquet/column/values/dictionary/DictionaryValuesWriter.java#L173]].
I'm proposing the spec be updated to state the above clearly.
see discussion here:
[https://lists.apache.org/thread/p45tpjd5r03qbswtpr7xfy072josnjxs]
--
This message was sent by Atlassian Jira
(v8.20.1#820001)
