[ORC-1137] [C++] Improve float/double conversion in DoubleColumnReader::next()

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.8.0
• Fix Version/s: 1.8.0
• Component/s: C++
• Assignee: Quanlong Huang
• Reporter: Quanlong Huang
• Created: 28/Mar/22 05:06
• Updated: 03/Sep/22 22:43
• Resolved: 01/Apr/22 02:11

Description

DoubleColumnReader::next() takes a portion of time when reading doubles from a tpch-lineitem ORC file.

I can see the loop in readDouble is unrolled. But it still have redundant checks. We can manually unroll it to save some instructions.

Furthermode, in little-endian machines, the layout of the DATA stream of the DOUBLE column matches the memory layout of the output array. We can use std::memcpy to copy the data directly.

Issue Links

• links to: GitHub Pull Request #1071