[ORC-595] Optimize Decimal64 scale calculation

• Type: Improvement
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 1.7.0
• Fix Version/s: 1.7.0
• Component/s: encoding
• Flags: Important
• Assignee: Panagiotis Garefalakis
• Reporter: Panagiotis Garefalakis
• Created: 10/Feb/20 20:50
• Updated: 27/Feb/24 22:23
• Resolved: 02/Mar/20 20:02

Description

Currently Decimal64 is using an inner loop to apply the correct scale to each read Long value https://github.com/apache/orc/blob/master/java/core/src/java/org/apache/orc/impl/TreeReaderFactory.java#L1294

A more efficient way would be to apply the scale using a single array access and by multiplying by 10 in the power of (scale - scratchScaleVector[r]).

An extra optimization would be to keep all powers of 10 (up to 18) in a static array and reuse it across runtime instead of calculating each time.

cc: rameshkumar gopalv

Issue Links

• links to: GitHub Pull Request #482