From 5ffcadcdf47d6d5a474fd6c78470987ff4480058 Mon Sep 17 00:00:00 2001
From: Pavel Kalinnikov <pavel@cockroachlabs.com>
Date: Tue, 27 Feb 2024 21:51:52 +0000
Subject: [PATCH] tracker,quorum: use native Sort

The insertion sort is no longer needed, since Go 1.21 introduced a
generic slices.Sort algorithm which achieves the same effect: it doesn't
incur allocations, and uses insertion sort for slices up to 16 elements.

Signed-off-by: Pavel Kalinnikov <pavel@cockroachlabs.com>
---
 quorum/majority.go | 15 ++-------------
 tracker/tracker.go | 12 ++----------
 2 files changed, 4 insertions(+), 23 deletions(-)

diff --git a/quorum/majority.go b/quorum/majority.go
index 12766137..0c9c24ee 100644
--- a/quorum/majority.go
+++ b/quorum/majority.go
@@ -17,6 +17,7 @@ package quorum
 import (
 	"fmt"
 	"math"
+	"slices"
 	"sort"
 	"strings"
 )
@@ -112,15 +113,6 @@ func (c MajorityConfig) Slice() []uint64 {
 	return sl
 }
 
-func insertionSort(sl []uint64) {
-	a, b := 0, len(sl)
-	for i := a + 1; i < b; i++ {
-		for j := i; j > a && sl[j] < sl[j-1]; j-- {
-			sl[j], sl[j-1] = sl[j-1], sl[j]
-		}
-	}
-}
-
 // CommittedIndex computes the committed index from those supplied via the
 // provided AckedIndexer (for the active config).
 func (c MajorityConfig) CommittedIndex(l AckedIndexer) Index {
@@ -159,10 +151,7 @@ func (c MajorityConfig) CommittedIndex(l AckedIndexer) Index {
 			}
 		}
 	}
-
-	// Sort by index. Use a bespoke algorithm (copied from the stdlib's sort
-	// package) to keep srt on the stack.
-	insertionSort(srt)
+	slices.Sort(srt)
 
 	// The smallest index into the array for which the value is acked by a
 	// quorum. In other words, from the end of the slice, move n/2+1 to the
diff --git a/tracker/tracker.go b/tracker/tracker.go
index 2710a7a4..5c4e14ce 100644
--- a/tracker/tracker.go
+++ b/tracker/tracker.go
@@ -16,6 +16,7 @@ package tracker
 
 import (
 	"fmt"
+	"slices"
 	"sort"
 	"strings"
 
@@ -180,15 +181,6 @@ func (p *ProgressTracker) Committed() uint64 {
 	return uint64(p.Voters.CommittedIndex(matchAckIndexer(p.Progress)))
 }
 
-func insertionSort(sl []uint64) {
-	a, b := 0, len(sl)
-	for i := a + 1; i < b; i++ {
-		for j := i; j > a && sl[j] < sl[j-1]; j-- {
-			sl[j], sl[j-1] = sl[j-1], sl[j]
-		}
-	}
-}
-
 // Visit invokes the supplied closure for all tracked progresses in stable order.
 func (p *ProgressTracker) Visit(f func(id uint64, pr *Progress)) {
 	n := len(p.Progress)
@@ -206,7 +198,7 @@ func (p *ProgressTracker) Visit(f func(id uint64, pr *Progress)) {
 		n--
 		ids[n] = id
 	}
-	insertionSort(ids)
+	slices.Sort(ids)
 	for _, id := range ids {
 		f(id, p.Progress[id])
 	}