Bug #75390 IMPROVE FILESORT MEMCMP BY USING GLIBC MEMCMP FOR LONG KEYS

• Submitted: 2 Jan 2015 12:56
• Modified: 9 Jan 2015 16:06
• Reporter: Tor Didriksen
• Status: Closed
• Category: MySQL Server: Optimizer
• Severity: S3 (Non-critical)
• Version: 5.7
• OS: Any
• CPU Architecture: Any

[2 Jan 2015 12:56] Tor Didriksen

Description:
Switch from my_qsort to std::sort, and re-use compare functions implemented by patch for
Bug#14635144 IMPROVE FILESORT MEMCMP BY USING GLIBC MEMCMP FOR LONG KEYS
That patch fixed memcmp for the case where we use std::stable_sort

Using glibc memcmp improves the sysbench 'order-by-range' test
with 5 - 10 % depending on range size.

How to repeat:
Read the code, run sysbench.

Suggested fix:
See description

[9 Jan 2015 16:06] Paul DuBois

Noted in 5.7.6 changelog.

Overhead was reduced for queries such as tested by the sysbench
"order-by-range" test.