[PARQUET-2108] Specification for RLEDictionary encoding is incorrect.

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Unassigned
• Reporter: Balaji K
• Created: 10/Dec/21 20:53
• Updated: 23/Jun/24 03:32

Description

The spec for RLE Dictionary 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.

I'm proposing the spec be updated to state the above clearly.

see discussion here:

https://lists.apache.org/thread/p45tpjd5r03qbswtpr7xfy072josnjxs