Specification for RLEDictionary encoding is incorrect.

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 := length of the in bytes stored as 4 bytes little endian (unsigned int32)

encoded-data := \*

```

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:

**Reporter**: [Balaji K](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=gamaken)

_{**Note**: *This issue was originally created as [PARQUET-2108](https://issues.apache.org/jira/browse/PARQUET-2108). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Inizia con la sezione RLE Dictionary in Encodings.md e confrontane la formulazione con DictionaryValuesWriter.java nell’implementazione collegata. Controlla la discussione collegata per l’interpretazione prevista, quindi aggiorna la specifica in modo che il layout dei byte documentato corrisponda all’implementazione e verifica che la descrizione circostante della codifica rimanga coerente.

Scritto dal modello di indicizzazione a partire dal testo della issue.