[PARQUET-407] Incorrect delta-encoding example

• Type: Improvement
• Status: Resolved
• Priority: Trivial
• Resolution: Fixed
• Fix Version/s: format-2.4.0
• Component/s: parquet-format
• Assignee: Unassigned
• Reporter: choi woo cheol
• Created: 15/Dec/15 01:52
• Updated: 3 days ago 03:27
• Resolved: 06/Jan/16 23:51

Description

The minimum and the number of bits are incorrect at delta encoding Example 2 In Encodings.md.

In the example,

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)

The minimum is -2 and the relative deltas are 0, 0, 0, 3, 3, 3, 3. So, this should be corrected as below:

block -2 (minimum delta), 2 (bitwidth), 00000011111111b (0,0,0,3,3,3,3 packed on 2 bits)