[ARROW-1800] [C++] Fix and simplify random_decimals

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.7.1
• Fix Version/s: 0.8.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/17797
• Assignee: Phillip Cloud
• Reporter: Phillip Cloud
• Created: 11/Nov/17 19:30
• Updated: 11/Jan/23 07:17
• Resolved: 11/Nov/17 23:58

Description

UniformDecimalDistribution currently generates values outside the range specified for the given precision in cases where the number of bytes required to represent a decimal value was less than or equal to 8.

For example, for a 1 byte value the range is -128, 127 for the low bits and -1, 0 for the high bits. In cases where the low bits generated a negative number and the high bits generated a zero value the number can end up being much larger than desired.

It's much easier to just generate N random bytes and sign extend based on the sign bit of the last byte.

Issue Links

• links to: GitHub Pull Request #1306