Optimize Tx.Check().

This commit removes several memory allocations occurring on every page and also caches the freelist map used when iterating over the pages. This results in significantly better performance.

cmd/bolt/check.go

@@ -38,7 +38,7 @@ func Check(path string) {
 
 		// Print summary of errors.
 		if count > 0 {
-			fatalf("%d errors found")
+			fatalf("%d errors found", count)
 		} else {
 			println("OK")
 		}

cmd/bolt/main.go

@@ -10,11 +10,13 @@ import (
 
 	"github.com/boltdb/bolt"
 	"github.com/codegangsta/cli"
+	// "github.com/davecheney/profile"
 )
 
 var branch, commit string
 
 func main() {
+	// defer profile.Start(&profile.Config{CPUProfile: true, MemProfile: true}).Stop()
 	log.SetFlags(0)
 	NewApp().Run(os.Args)
 }

tx.go

@@ -316,15 +316,13 @@ func (tx *Tx) check(ch chan error) {
 	}
 
 	// Recursively check buckets.
-	tx.checkBucket(&tx.root, reachable, ch)
+	tx.checkBucket(&tx.root, reachable, freed, ch)
 
 	// Ensure all pages below high water mark are either reachable or freed.
 	for i := pgid(0); i < tx.meta.pgid; i++ {
 		_, isReachable := reachable[i]
 		if !isReachable && !freed[i] {
 			ch <- fmt.Errorf("page %d: unreachable unfreed", int(i))
-		} else if isReachable && freed[i] {
-			ch <- fmt.Errorf("page %d: reachable freed", int(i))
 		}
 	}
 
@@ -332,7 +330,7 @@ func (tx *Tx) check(ch chan error) {
 	close(ch)
 }
 
-func (tx *Tx) checkBucket(b *Bucket, reachable map[pgid]*page, ch chan error) {
+func (tx *Tx) checkBucket(b *Bucket, reachable map[pgid]*page, freed map[pgid]bool, ch chan error) {
 	// Ignore inline buckets.
 	if b.root == 0 {
 		return
@@ -340,6 +338,10 @@ func (tx *Tx) checkBucket(b *Bucket, reachable map[pgid]*page, ch chan error) {
 
 	// Check every page used by this bucket.
 	b.tx.forEachPage(b.root, 0, func(p *page, _ int) {
+		if p.id > tx.meta.pgid {
+			ch <- fmt.Errorf("page %d: out of bounds: %d", int(p.id), int(b.tx.meta.pgid))
+		}
+
 		// Ensure each page is only referenced once.
 		for i := pgid(0); i <= pgid(p.overflow); i++ {
 			var id = p.id + i
@@ -349,21 +351,18 @@ func (tx *Tx) checkBucket(b *Bucket, reachable map[pgid]*page, ch chan error) {
 			reachable[id] = p
 		}
 
-		// Retrieve page info.
-		info, err := b.tx.Page(int(p.id))
-		if err != nil {
-			ch <- err
-		} else if info == nil {
-			ch <- fmt.Errorf("page %d: out of bounds: %d", int(p.id), int(b.tx.meta.pgid))
-		} else if info.Type != "branch" && info.Type != "leaf" {
-			ch <- fmt.Errorf("page %d: invalid type: %s", int(p.id), info.Type)
+		// We should only encounter un-freed leaf and branch pages.
+		if freed[p.id] {
+			ch <- fmt.Errorf("page %d: reachable freed", int(p.id))
+		} else if (p.flags&branchPageFlag) == 0 && (p.flags&leafPageFlag) == 0 {
+			ch <- fmt.Errorf("page %d: invalid type: %s", int(p.id), p.typ())
 		}
 	})
 
 	// Check each bucket within this bucket.
 	_ = b.ForEach(func(k, v []byte) error {
 		if child := b.Bucket(k); child != nil {
-			tx.checkBucket(child, reachable, ch)
+			tx.checkBucket(child, reachable, freed, ch)
 		}
 		return nil
 	})