[jira] [Created] (PARQUET-575) Different RLE Encoding Specification

["Fabrizio Milo (JIRA)" <ji...@apache.org>]

Fabrizio Milo created PARQUET-575:
-------------------------------------

             Summary: Different RLE Encoding Specification 
                 Key: PARQUET-575
                 URL: https://issues.apache.org/jira/browse/PARQUET-575
             Project: Parquet
          Issue Type: Improvement
            Reporter: Fabrizio Milo
            Priority: Trivial


In the parquet-format specification https://github.com/Parquet/parquet-format/blob/master/Encodings.md#run-length-encoding--bit-packing-hybrid-rle--3
 is written that the RLE encoding starts with 
```
rle-bit-packed-hybrid: <length> <encoded-data>
length := length of the <encoded-data> in bytes stored as 4 bytes little endian
```

while in the cpp implementation there is this description https://github.com/apache/parquet-cpp/blob/master/src/parquet/util/rle-encoding.h#L42 and the implementation seems to follow that specification
which  does not include the initial <length> <encoded-data>
https://github.com/apache/parquet-cpp/blob/master/src/parquet/util/rle-encoding.h#L272

So which one is the correct? seems that the parquet-format is the wrong one.
DataPage.definitionLevels uses RLE and none of the example format files seem to have that initial <length> <encoded-data> 

Also the use of both names `literal` and `bit-encoding` is confusing.






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