manifest: simplify VirtualBackings interface

This commit adapts the VirtualBackings type, replacing its ForEach and Backings
methods with an All method that returns an iter.Seq of table backings.
Additionally, use maps.Keys and slices.Collect where applicable.

Author: jbowens

checkpoint.go

@@ -198,9 +198,9 @@ func (d *DB) Checkpoint(
 	optionsFileNum := d.optionsFileNum
 
 	virtualBackingFiles := make(map[base.DiskFileNum]struct{})
-	d.mu.versions.latest.virtualBackings.ForEach(func(backing *manifest.TableBacking) {
+	for backing := range d.mu.versions.latest.virtualBackings.All() {
 		virtualBackingFiles[backing.DiskFileNum] = struct{}{}
-	})
+	}
 	versionBlobFiles := d.mu.versions.latest.blobFiles.Metadatas()
 
 	// Acquire the logs while holding mutexes to ensure we don't race with a

internal/manifest/virtual_backings.go

@@ -9,6 +9,7 @@ import (
 	stdcmp "cmp"
 	"container/heap"
 	"fmt"
+	"iter"
 	"maps"
 	"slices"
 
@@ -274,30 +275,20 @@ func (bv *VirtualBackings) Get(n base.DiskFileNum) (_ *TableBacking, ok bool) {
 }
 
 // ForEach calls fn on each backing, in unspecified order.
-func (bv *VirtualBackings) ForEach(fn func(backing *TableBacking)) {
-	for _, v := range bv.m {
-		fn(v.backing)
+func (bv *VirtualBackings) All() iter.Seq[*TableBacking] {
+	return func(yield func(*TableBacking) bool) {
+		for _, v := range bv.m {
+			if !yield(v.backing) {
+				return
+			}
+		}
 	}
 }
 
 // DiskFileNums returns disk file nums of all the backing in the set, in sorted
 // order.
 func (bv *VirtualBackings) DiskFileNums() []base.DiskFileNum {
-	res := make([]base.DiskFileNum, 0, len(bv.m))
-	for n := range bv.m {
-		res = append(res, n)
-	}
-	slices.Sort(res)
-	return res
-}
-
-// Backings returns all backings in the set, in unspecified order.
-func (bv *VirtualBackings) Backings() []*TableBacking {
-	res := make([]*TableBacking, 0, len(bv.m))
-	for _, v := range bv.m {
-		res = append(res, v.backing)
-	}
-	return res
+	return slices.Sorted(maps.Keys(bv.m))
 }
 
 // ReplacementCandidate returns the backing with the lowest ratio of data

version_set.go

@@ -7,6 +7,7 @@ package pebble
 import (
 	"fmt"
 	"io"
+	"slices"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -369,13 +370,13 @@ func (vs *versionSet) load(
 			}
 		}
 	}
-	vs.latest.virtualBackings.ForEach(func(backing *manifest.TableBacking) {
+	for backing := range vs.latest.virtualBackings.All() {
 		isLocal, localSize := sizeIfLocal(backing, vs.provider)
 		vs.metrics.Table.Local.LiveSize = uint64(int64(vs.metrics.Table.Local.LiveSize) + localSize)
 		if isLocal {
 			vs.metrics.Table.Local.LiveCount++
 		}
-	})
+	}
 
 	vs.setCompactionPicker(newCompactionPickerByScore(newVersion, &vs.latest, vs.opts, nil))
 	return nil
@@ -578,7 +579,7 @@ func (vs *versionSet) UpdateVersionLocked(
 		// We want the virtual backings *before* applying the version edit, because
 		// the new manifest will contain the pre-apply version plus the last version
 		// edit.
-		newManifestVirtualBackings = vs.latest.virtualBackings.Backings()
+		newManifestVirtualBackings = slices.Collect(vs.latest.virtualBackings.All())
 	}
 
 	// Grab certain values before releasing vs.mu, in case createManifest() needs
@@ -1174,9 +1175,9 @@ func (vs *versionSet) addLiveFileNums(m map[base.DiskFileNum]struct{}) {
 	// are not but are still alive because of the protection mechanism (see
 	// manifset.VirtualBackings). This loop ensures the latter get added to the
 	// map.
-	vs.latest.virtualBackings.ForEach(func(b *manifest.TableBacking) {
+	for b := range vs.latest.virtualBackings.All() {
 		m[b.DiskFileNum] = struct{}{}
-	})
+	}
 }
 
 // addObsoleteLocked will add the fileInfo associated with obsolete backing