Deprecate Sortable

CHANGELOG.md

@@ -12,6 +12,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - Drop support for [Go 1.20]. (#4967)
 
+### Deprecated
+
+- Deprecate `go.opentelemetry.io/otel/attribute.Sortable` and methods that use it. (#4734)
+
 ## [1.24.0/0.46.0/0.0.1-alpha] 2024-02-23
 
 This release is the last to support [Go 1.20].

attribute/set.go

@@ -4,10 +4,11 @@
 package attribute // import "go.opentelemetry.io/otel/attribute"
 
 import (
+	"cmp"
 	"encoding/json"
 	"reflect"
+	"slices"
 	"sort"
-	"sync"
 )
 
 type (
@@ -28,10 +29,9 @@ type (
 		iface interface{}
 	}
 
-	// Sortable implements sort.Interface, used for sorting KeyValue. This is
-	// an exported type to support a memory optimization. A pointer to one of
-	// these is needed for the call to sort.Stable(), which the caller may
-	// provide in order to avoid an allocation. See NewSetWithSortable().
+	// Sortable implements sort.Interface, used for sorting KeyValue.
+	//
+	// Deprecated: no longer needed.
 	Sortable []KeyValue
 )
 
@@ -45,12 +45,6 @@ var (
 			iface: [0]KeyValue{},
 		},
 	}
-
-	// sortables is a pool of Sortables used to create Sets with a user does
-	// not provide one.
-	sortables = sync.Pool{
-		New: func() interface{} { return new(Sortable) },
-	}
 )
 
 // EmptySet returns a reference to a Set with no elements.
@@ -180,22 +174,21 @@ func NewSet(kvs ...KeyValue) Set {
 	if len(kvs) == 0 {
 		return empty()
 	}
-	srt := sortables.Get().(*Sortable)
-	s, _ := NewSetWithSortableFiltered(kvs, srt, nil)
-	sortables.Put(srt)
+	s, _ := NewSetWithSortableFiltered(kvs, nil, nil)
 	return s
 }
 
 // NewSetWithSortable returns a new Set. See the documentation for
 // NewSetWithSortableFiltered for more details.
 //
 // This call includes a Sortable option as a memory optimization.
-func NewSetWithSortable(kvs []KeyValue, tmp *Sortable) Set {
+// Deprecated: NewSet.
+func NewSetWithSortable(kvs []KeyValue, _ *Sortable) Set {
 	// Check for empty set.
 	if len(kvs) == 0 {
 		return empty()
 	}
-	s, _ := NewSetWithSortableFiltered(kvs, tmp, nil)
+	s, _ := NewSetWithSortableFiltered(kvs, nil, nil)
 	return s
 }
 
@@ -209,9 +202,7 @@ func NewSetWithFiltered(kvs []KeyValue, filter Filter) (Set, []KeyValue) {
 	if len(kvs) == 0 {
 		return empty(), nil
 	}
-	srt := sortables.Get().(*Sortable)
-	s, filtered := NewSetWithSortableFiltered(kvs, srt, filter)
-	sortables.Put(srt)
+	s, filtered := NewSetWithSortableFiltered(kvs, nil, filter)
 	return s, filtered
 }
 
@@ -238,19 +229,18 @@ func NewSetWithFiltered(kvs []KeyValue, filter Filter) (Set, []KeyValue) {
 //
 // The second []KeyValue return value is a list of attributes that were
 // excluded by the Filter (if non-nil).
-func NewSetWithSortableFiltered(kvs []KeyValue, tmp *Sortable, filter Filter) (Set, []KeyValue) {
+// Deprecated: use NewSetWithFiltered.
+func NewSetWithSortableFiltered(kvs []KeyValue, _ *Sortable, filter Filter) (Set, []KeyValue) {
 	// Check for empty set.
 	if len(kvs) == 0 {
 		return empty(), nil
 	}
 
-	*tmp = kvs
-
 	// Stable sort so the following de-duplication can implement
 	// last-value-wins semantics.
-	sort.Stable(tmp)
-
-	*tmp = nil
+	slices.SortStableFunc(kvs, func(a, b KeyValue) int {
+		return cmp.Compare(a.Key, b.Key)
+	})
 
 	position := len(kvs) - 1
 	offset := position - 1