Add streaming check.

This commit changes Tx.Check() to return a channel through which check errors are returned. This allows
errors to be found before checking the entire data file.

5 files changed, 46 insertions, 62 deletions

diff --git a/cmd/bolt/check.go b/cmd/bolt/check.go
index 1436aba..1466fd7 100644
--- a/cmd/bolt/check.go
+++ b/cmd/bolt/check.go
@@ -21,19 +21,27 @@ func Check(path string) {
 	defer db.Close()
 
 	// Perform consistency check.
-	err = db.View(func(tx *bolt.Tx) error {
-		return tx.Check()
-	})
-
-	// Print out any errors that occur.
-	if err != nil {
-		if errors, ok := err.(bolt.ErrorList); ok {
-			for _, err := range errors {
+	_ = db.View(func(tx *bolt.Tx) error {
+		var count int
+		ch := tx.Check()
+	loop:
+		for {
+			select {
+			case err, ok := <-ch:
+				if !ok {
+					break loop
+				}
 				println(err)
+				count++
 			}
 		}
-		fatalln(err)
-		return
-	}
-	println("OK")
+
+		// Print summary of errors.
+		if count > 0 {
+			fatalf("%d errors found")
+		} else {
+			println("OK")
+		}
+		return nil
+	})
 }
diff --git a/db.go b/db.go
index 7b17086..d759b1b 100644
--- a/db.go
+++ b/db.go
@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"hash/fnv"
 	"os"
-	"strings"
 	"sync"
 	"syscall"
 	"unsafe"
@@ -632,23 +631,6 @@ func (m *meta) sum64() uint64 {
 	return h.Sum64()
 }
 
-// ErrorList represents a slice of errors.
-type ErrorList []error
-
-// Error returns a readable count of the errors in the list.
-func (l ErrorList) Error() string {
-	return fmt.Sprintf("%d errors occurred", len(l))
-}
-
-// join returns a error messages joined by a string.
-func (l ErrorList) join(sep string) string {
-	var a []string
-	for _, e := range l {
-		a = append(a, e.Error())
-	}
-	return strings.Join(a, sep)
-}
-
 // _assert will panic with a given formatted message if the given condition is false.
 func _assert(condition bool, msg string, v ...interface{}) {
 	if !condition {
diff --git a/db_test.go b/db_test.go
index 06accd3..e1c4aaa 100644
--- a/db_test.go
+++ b/db_test.go
@@ -53,12 +53,12 @@ func TestOpen_Check(t *testing.T) {
 	withTempPath(func(path string) {
 		db, err := Open(path, 0666)
 		assert.NoError(t, err)
-		assert.NoError(t, db.View(func(tx *Tx) error { return tx.Check() }))
+		assert.NoError(t, db.View(func(tx *Tx) error { return <-tx.Check() }))
 		db.Close()
 
 		db, err = Open(path, 0666)
 		assert.NoError(t, err)
-		assert.NoError(t, db.View(func(tx *Tx) error { return tx.Check() }))
+		assert.NoError(t, db.View(func(tx *Tx) error { return <-tx.Check() }))
 		db.Close()
 	})
 }
@@ -464,20 +464,13 @@ func withOpenDB(fn func(*DB, string)) {
 // mustCheck runs a consistency check on the database and panics if any errors are found.
 func mustCheck(db *DB) {
 	err := db.Update(func(tx *Tx) error {
-		return tx.Check()
+		return <-tx.Check()
 	})
 	if err != nil {
 		// Copy db off first.
 		var path = tempfile()
 		db.View(func(tx *Tx) error { return tx.CopyFile(path, 0600) })
-
-		if errors, ok := err.(ErrorList); ok {
-			for _, err := range errors {
-				warn(err)
-			}
-		}
-		warn(err)
-		panic("check failure: " + path)
+		panic("check failure: " + err.Error() + ": " + path)
 	}
 }
 
diff --git a/tx.go b/tx.go
index a0ae5bd..6ebe04e 100644
--- a/tx.go
+++ b/tx.go
@@ -184,10 +184,10 @@ func (tx *Tx) Commit() error {
 	}
 
 	// If strict mode is enabled then perform a consistency check.
+	// Only the first consistency error is reported in the panic.
 	if tx.db.StrictMode {
-		if err := tx.Check(); err != nil {
-			err := err.(ErrorList)
-			panic("check fail: " + err.Error() + ": " + err.join("; "))
+		if err, ok := <-tx.Check(); ok {
+			panic("check fail: " + err.Error())
 		}
 	}
 
@@ -291,14 +291,18 @@ func (tx *Tx) CopyFile(path string, mode os.FileMode) error {
 // because of caching. This overhead can be removed if running on a read-only
 // transaction, however, it is not safe to execute other writer transactions at
 // the same time.
-func (tx *Tx) Check() error {
-	var errors ErrorList
+func (tx *Tx) Check() <-chan error {
+	ch := make(chan error)
+	go tx.check(ch)
+	return ch
+}
 
+func (tx *Tx) check(ch chan error) {
 	// Check if any pages are double freed.
 	freed := make(map[pgid]bool)
 	for _, id := range tx.db.freelist.all() {
 		if freed[id] {
-			errors = append(errors, fmt.Errorf("page %d: already freed", id))
+			ch <- fmt.Errorf("page %d: already freed", id)
 		}
 		freed[id] = true
 	}
@@ -312,26 +316,23 @@ func (tx *Tx) Check() error {
 	}
 
 	// Recursively check buckets.
-	tx.checkBucket(&tx.root, reachable, &errors)
+	tx.checkBucket(&tx.root, reachable, 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] {
-			errors = append(errors, fmt.Errorf("page %d: unreachable unfreed", int(i)))
+			ch <- fmt.Errorf("page %d: unreachable unfreed", int(i))
 		} else if isReachable && freed[i] {
-			errors = append(errors, fmt.Errorf("page %d: reachable freed", int(i)))
+			ch <- fmt.Errorf("page %d: reachable freed", int(i))
 		}
 	}
 
-	if len(errors) > 0 {
-		return errors
-	}
-
-	return nil
+	// Close the channel to signal completion.
+	close(ch)
 }
 
-func (tx *Tx) checkBucket(b *Bucket, reachable map[pgid]*page, errors *ErrorList) {
+func (tx *Tx) checkBucket(b *Bucket, reachable map[pgid]*page, ch chan error) {
 	// Ignore inline buckets.
 	if b.root == 0 {
 		return
@@ -343,7 +344,7 @@ func (tx *Tx) checkBucket(b *Bucket, reachable map[pgid]*page, errors *ErrorList
 		for i := pgid(0); i <= pgid(p.overflow); i++ {
 			var id = p.id + i
 			if _, ok := reachable[id]; ok {
-				*errors = append(*errors, fmt.Errorf("page %d: multiple references", int(id)))
+				ch <- fmt.Errorf("page %d: multiple references", int(id))
 			}
 			reachable[id] = p
 		}
@@ -351,18 +352,18 @@ func (tx *Tx) checkBucket(b *Bucket, reachable map[pgid]*page, errors *ErrorList
 		// Retrieve page info.
 		info, err := b.tx.Page(int(p.id))
 		if err != nil {
-			*errors = append(*errors, err)
+			ch <- err
 		} else if info == nil {
-			*errors = append(*errors, fmt.Errorf("page %d: out of bounds: %d", int(p.id), int(b.tx.meta.pgid)))
+			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" {
-			*errors = append(*errors, fmt.Errorf("page %d: invalid type: %s", int(p.id), info.Type))
+			ch <- fmt.Errorf("page %d: invalid type: %s", int(p.id), info.Type)
 		}
 	})
 
 	// Check each bucket within this bucket.
 	_ = b.ForEach(func(k, v []byte) error {
 		if child := b.Bucket(k); child != nil {
-			tx.checkBucket(child, reachable, errors)
+			tx.checkBucket(child, reachable, ch)
 		}
 		return nil
 	})
diff --git a/tx_test.go b/tx_test.go
index f6ee3d3..dd04ae6 100644
--- a/tx_test.go
+++ b/tx_test.go
@@ -310,7 +310,7 @@ func TestTx_Check_Corrupt(t *testing.T) {
 		})
 	}()
 
-	assert.Equal(t, "check fail: 1 errors occurred: page 3: already freed", msg)
+	assert.Equal(t, "check fail: page 3: already freed", msg)
 }
 
 // Ensure that the database can be copied to a file path.