[jira] [Commented] (PARQUET-407) Incorrect delta-encoding example

["Sergio Peña (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PARQUET-407?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15086519#comment-15086519 ] 

Sergio Peña commented on PARQUET-407:
-------------------------------------

[~julienledem] I cannot assign [~woo cheol] to this ticket (it does not find the username). 
Do you know why?

> Incorrect delta-encoding example
> --------------------------------
>
>                 Key: PARQUET-407
>                 URL: https://issues.apache.org/jira/browse/PARQUET-407
>             Project: Parquet
>          Issue Type: Improvement
>          Components: parquet-format
>            Reporter: choi woo cheol
>            Priority: Trivial
>             Fix For: format-2.4.0
>
>
> The minimum and the number of bits are incorrect at delta encoding Example 2 In {{Encodings.md}}.
> In the example, 
> {code}
> Example 2
> 7, 5, 3, 1, 2, 3, 4, 5, the deltas would be
> -2, -2, -2, 1, 1, 1, 1
> The minimum is -2, so the relative deltas are:
> 0, 0, 0, 3, 3, 3, 3
> The encoded data is
> header: 8 (block size), 1 (miniblock count), 8 (value count), 7 (first value)
> block 0 (minimum delta), 2 (bitwidth), 000000111111b (0,0,0,3,3,3 packed on 2 bits)
> {code}
> The minimum is -2 and the relative deltas are 0, 0, 0, 3, 3, 3, 3. So, this should be corrected as below:
> {code}
> block -2 (minimum delta), 2 (bitwidth), 00000011111111b (0,0,0,3,3,3,3 packed on 2 bits)
> {code}



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