Merge pull request #590 from benbjohnson/vincent-petithory-compact-db

Compaction Command

bucket.go

@@ -329,6 +329,28 @@ func (b *Bucket) Delete(key []byte) error {
 	return nil
 }
 
+// Sequence returns the current integer for the bucket without incrementing it.
+func (b *Bucket) Sequence() uint64 { return b.bucket.sequence }
+
+// SetSequence updates the sequence number for the bucket.
+func (b *Bucket) SetSequence(v uint64) error {
+	if b.tx.db == nil {
+		return ErrTxClosed
+	} else if !b.Writable() {
+		return ErrTxNotWritable
+	}
+
+	// Materialize the root node if it hasn't been already so that the
+	// bucket will be saved during commit.
+	if b.rootNode == nil {
+		_ = b.node(b.root, nil)
+	}
+
+	// Increment and return the sequence.
+	b.bucket.sequence = v
+	return nil
+}
+
 // NextSequence returns an autoincrementing integer for the bucket.
 func (b *Bucket) NextSequence() (uint64, error) {
 	if b.tx.db == nil {

bucket_test.go

@@ -782,6 +782,48 @@ func TestBucket_DeleteBucket_IncompatibleValue(t *testing.T) {
 	}
 }
 
+// Ensure bucket can set and update its sequence number.
+func TestBucket_Sequence(t *testing.T) {
+	db := MustOpenDB()
+	defer db.MustClose()
+
+	if err := db.Update(func(tx *bolt.Tx) error {
+		bkt, err := tx.CreateBucket([]byte("0"))
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		// Retrieve sequence.
+		if v := bkt.Sequence(); v != 0 {
+			t.Fatalf("unexpected sequence: %d", v)
+		}
+
+		// Update sequence.
+		if err := bkt.SetSequence(1000); err != nil {
+			t.Fatal(err)
+		}
+
+		// Read sequence again.
+		if v := bkt.Sequence(); v != 1000 {
+			t.Fatalf("unexpected sequence: %d", v)
+		}
+
+		return nil
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	// Verify sequence in separate transaction.
+	if err := db.View(func(tx *bolt.Tx) error {
+		if v := tx.Bucket([]byte("0")).Sequence(); v != 1000 {
+			t.Fatalf("unexpected sequence: %d", v)
+		}
+		return nil
+	}); err != nil {
+		t.Fatal(err)
+	}
+}
+
 // Ensure that a bucket can return an autoincrementing sequence.
 func TestBucket_NextSequence(t *testing.T) {
 	db := MustOpenDB()

cmd/bolt/main.go

@@ -102,6 +102,8 @@ func (m *Main) Run(args ...string) error {
 		return newBenchCommand(m).Run(args[1:]...)
 	case "check":
 		return newCheckCommand(m).Run(args[1:]...)
+	case "compact":
+		return newCompactCommand(m).Run(args[1:]...)
 	case "dump":
 		return newDumpCommand(m).Run(args[1:]...)
 	case "info":
@@ -130,6 +132,7 @@ The commands are:
 
     bench       run synthetic benchmark against bolt
     check       verifies integrity of bolt database
+    compact     copies a bolt database, compacting it in the process
     info        print basic info
     help        print this screen
     pages       print list of pages with their types
@@ -1530,3 +1533,208 @@ func (n *leafPageElement) value() []byte {
 	buf := (*[maxAllocSize]byte)(unsafe.Pointer(n))
 	return buf[n.pos+n.ksize : n.pos+n.ksize+n.vsize]
 }
+
+// CompactCommand represents the "compact" command execution.
+type CompactCommand struct {
+	Stdin  io.Reader
+	Stdout io.Writer
+	Stderr io.Writer
+
+	SrcPath   string
+	DstPath   string
+	TxMaxSize int64
+}
+
+// newCompactCommand returns a CompactCommand.
+func newCompactCommand(m *Main) *CompactCommand {
+	return &CompactCommand{
+		Stdin:  m.Stdin,
+		Stdout: m.Stdout,
+		Stderr: m.Stderr,
+	}
+}
+
+// Run executes the command.
+func (cmd *CompactCommand) Run(args ...string) (err error) {
+	// Parse flags.
+	fs := flag.NewFlagSet("", flag.ContinueOnError)
+	fs.SetOutput(ioutil.Discard)
+	fs.StringVar(&cmd.DstPath, "o", "", "")
+	fs.Int64Var(&cmd.TxMaxSize, "tx-max-size", 65536, "")
+	if err := fs.Parse(args); err == flag.ErrHelp {
+		fmt.Fprintln(cmd.Stderr, cmd.Usage())
+		return ErrUsage
+	} else if err != nil {
+		return err
+	} else if cmd.DstPath == "" {
+		return fmt.Errorf("output file required")
+	}
+
+	// Require database paths.
+	cmd.SrcPath = fs.Arg(0)
+	if cmd.SrcPath == "" {
+		return ErrPathRequired
+	}
+
+	// Ensure source file exists.
+	fi, err := os.Stat(cmd.SrcPath)
+	if os.IsNotExist(err) {
+		return ErrFileNotFound
+	} else if err != nil {
+		return err
+	}
+	initialSize := fi.Size()
+
+	// Open source database.
+	src, err := bolt.Open(cmd.SrcPath, 0444, nil)
+	if err != nil {
+		return err
+	}
+	defer src.Close()
+
+	// Open destination database.
+	dst, err := bolt.Open(cmd.DstPath, fi.Mode(), nil)
+	if err != nil {
+		return err
+	}
+	defer dst.Close()
+
+	// Run compaction.
+	if err := cmd.compact(dst, src); err != nil {
+		return err
+	}
+
+	// Report stats on new size.
+	fi, err = os.Stat(cmd.DstPath)
+	if err != nil {
+		return err
+	} else if fi.Size() == 0 {
+		return fmt.Errorf("zero db size")
+	}
+	fmt.Fprintf(cmd.Stdout, "%d -> %d bytes (gain=%.2fx)\n", initialSize, fi.Size(), float64(initialSize)/float64(fi.Size()))
+
+	return nil
+}
+
+func (cmd *CompactCommand) compact(dst, src *bolt.DB) error {
+	// commit regularly, or we'll run out of memory for large datasets if using one transaction.
+	var size int64
+	tx, err := dst.Begin(true)
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+
+	if err := cmd.walk(src, func(keys [][]byte, k, v []byte, seq uint64) error {
+		// On each key/value, check if we have exceeded tx size.
+		sz := int64(len(k) + len(v))
+		if size+sz > cmd.TxMaxSize && cmd.TxMaxSize != 0 {
+			// Commit previous transaction.
+			if err := tx.Commit(); err != nil {
+				return err
+			}
+
+			// Start new transaction.
+			tx, err = dst.Begin(true)
+			if err != nil {
+				return err
+			}
+			size = 0
+		}
+		size += sz
+
+		// Create bucket on the root transaction if this is the first level.
+		nk := len(keys)
+		if nk == 0 {
+			bkt, err := tx.CreateBucket(k)
+			if err != nil {
+				return err
+			}
+			if err := bkt.SetSequence(seq); err != nil {
+				return err
+			}
+			return nil
+		}
+
+		// Create buckets on subsequent levels, if necessary.
+		b := tx.Bucket(keys[0])
+		if nk > 1 {
+			for _, k := range keys[1:] {
+				b = b.Bucket(k)
+			}
+		}
+
+		// If there is no value then this is a bucket call.
+		if v == nil {
+			bkt, err := b.CreateBucket(k)
+			if err != nil {
+				return err
+			}
+			if err := bkt.SetSequence(seq); err != nil {
+				return err
+			}
+			return nil
+		}
+
+		// Otherwise treat it as a key/value pair.
+		return b.Put(k, v)
+	}); err != nil {
+		return err
+	}
+
+	return tx.Commit()
+}
+
+// walkFunc is the type of the function called for keys (buckets and "normal"
+// values) discovered by Walk. keys is the list of keys to descend to the bucket
+// owning the discovered key/value pair k/v.
+type walkFunc func(keys [][]byte, k, v []byte, seq uint64) error
+
+// walk walks recursively the bolt database db, calling walkFn for each key it finds.
+func (cmd *CompactCommand) walk(db *bolt.DB, walkFn walkFunc) error {
+	return db.View(func(tx *bolt.Tx) error {
+		return tx.ForEach(func(name []byte, b *bolt.Bucket) error {
+			return cmd.walkBucket(b, nil, name, nil, b.Sequence(), walkFn)
+		})
+	})
+}
+
+func (cmd *CompactCommand) walkBucket(b *bolt.Bucket, keypath [][]byte, k, v []byte, seq uint64, fn walkFunc) error {
+	// Execute callback.
+	if err := fn(keypath, k, v, seq); err != nil {
+		return err
+	}
+
+	// If this is not a bucket then stop.
+	if v != nil {
+		return nil
+	}
+
+	// Iterate over each child key/value.
+	keypath = append(keypath, k)
+	return b.ForEach(func(k, v []byte) error {
+		if v == nil {
+			bkt := b.Bucket(k)
+			return cmd.walkBucket(bkt, keypath, k, nil, bkt.Sequence(), fn)
+		}
+		return cmd.walkBucket(b, keypath, k, v, b.Sequence(), fn)
+	})
+}
+
+// Usage returns the help message.
+func (cmd *CompactCommand) Usage() string {
+	return strings.TrimLeft(`
+usage: bolt compact [options] -o DST SRC
+
+Compact opens a database at SRC path and walks it recursively, copying keys
+as they are found from all buckets, to a newly created database at DST path.
+
+The original database is left untouched.
+
+Additional options include:
+
+	-tx-max-size NUM
+		Specifies the maximum size of individual transactions.
+		Defaults to 64KB.
+`, "\n")
+}

cmd/bolt/main_test.go

@@ -2,7 +2,12 @@ package main_test
 
 import (
 	"bytes"
+	crypto "crypto/rand"
+	"encoding/binary"
+	"fmt"
+	"io"
 	"io/ioutil"
+	"math/rand"
 	"os"
 	"strconv"
 	"testing"
@@ -183,3 +188,169 @@ func (db *DB) Close() error {
 	defer os.Remove(db.Path)
 	return db.DB.Close()
 }
+
+func TestCompactCommand_Run(t *testing.T) {
+	var s int64
+	if err := binary.Read(crypto.Reader, binary.BigEndian, &s); err != nil {
+		t.Fatal(err)
+	}
+	rand.Seed(s)
+
+	dstdb := MustOpen(0666, nil)
+	dstdb.Close()
+
+	// fill the db
+	db := MustOpen(0666, nil)
+	if err := db.Update(func(tx *bolt.Tx) error {
+		n := 2 + rand.Intn(5)
+		for i := 0; i < n; i++ {
+			k := []byte(fmt.Sprintf("b%d", i))
+			b, err := tx.CreateBucketIfNotExists(k)
+			if err != nil {
+				return err
+			}
+			if err := b.SetSequence(uint64(i)); err != nil {
+				return err
+			}
+			if err := fillBucket(b, append(k, '.')); err != nil {
+				return err
+			}
+		}
+		return nil
+	}); err != nil {
+		db.Close()
+		t.Fatal(err)
+	}
+
+	// make the db grow by adding large values, and delete them.
+	if err := db.Update(func(tx *bolt.Tx) error {
+		b, err := tx.CreateBucketIfNotExists([]byte("large_vals"))
+		if err != nil {
+			return err
+		}
+		n := 5 + rand.Intn(5)
+		for i := 0; i < n; i++ {
+			v := make([]byte, 1000*1000*(1+rand.Intn(5)))
+			_, err := crypto.Read(v)
+			if err != nil {
+				return err
+			}
+			if err := b.Put([]byte(fmt.Sprintf("l%d", i)), v); err != nil {
+				return err
+			}
+		}
+		return nil
+	}); err != nil {
+		db.Close()
+		t.Fatal(err)
+	}
+	if err := db.Update(func(tx *bolt.Tx) error {
+		c := tx.Bucket([]byte("large_vals")).Cursor()
+		for k, _ := c.First(); k != nil; k, _ = c.Next() {
+			if err := c.Delete(); err != nil {
+				return err
+			}
+		}
+		return tx.DeleteBucket([]byte("large_vals"))
+	}); err != nil {
+		db.Close()
+		t.Fatal(err)
+	}
+	db.DB.Close()
+	defer db.Close()
+	defer dstdb.Close()
+
+	dbChk, err := chkdb(db.Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	m := NewMain()
+	if err := m.Run("compact", "-o", dstdb.Path, db.Path); err != nil {
+		t.Fatal(err)
+	}
+
+	dbChkAfterCompact, err := chkdb(db.Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	dstdbChk, err := chkdb(dstdb.Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !bytes.Equal(dbChk, dbChkAfterCompact) {
+		t.Error("the original db has been touched")
+	}
+	if !bytes.Equal(dbChk, dstdbChk) {
+		t.Error("the compacted db data isn't the same than the original db")
+	}
+}
+
+func fillBucket(b *bolt.Bucket, prefix []byte) error {
+	n := 10 + rand.Intn(50)
+	for i := 0; i < n; i++ {
+		v := make([]byte, 10*(1+rand.Intn(4)))
+		_, err := crypto.Read(v)
+		if err != nil {
+			return err
+		}
+		k := append(prefix, []byte(fmt.Sprintf("k%d", i))...)
+		if err := b.Put(k, v); err != nil {
+			return err
+		}
+	}
+	// limit depth of subbuckets
+	s := 2 + rand.Intn(4)
+	if len(prefix) > (2*s + 1) {
+		return nil
+	}
+	n = 1 + rand.Intn(3)
+	for i := 0; i < n; i++ {
+		k := append(prefix, []byte(fmt.Sprintf("b%d", i))...)
+		sb, err := b.CreateBucket(k)
+		if err != nil {
+			return err
+		}
+		if err := fillBucket(sb, append(k, '.')); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func chkdb(path string) ([]byte, error) {
+	db, err := bolt.Open(path, 0666, nil)
+	if err != nil {
+		return nil, err
+	}
+	defer db.Close()
+	var buf bytes.Buffer
+	err = db.View(func(tx *bolt.Tx) error {
+		return tx.ForEach(func(name []byte, b *bolt.Bucket) error {
+			return walkBucket(b, name, nil, &buf)
+		})
+	})
+	if err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+func walkBucket(parent *bolt.Bucket, k []byte, v []byte, w io.Writer) error {
+	if _, err := fmt.Fprintf(w, "%d:%x=%x\n", parent.Sequence(), k, v); err != nil {
+		return err
+	}
+
+	// not a bucket, exit.
+	if v != nil {
+		return nil
+	}
+	return parent.ForEach(func(k, v []byte) error {
+		if v == nil {
+			return walkBucket(parent.Bucket(k), k, nil, w)
+		}
+		return walkBucket(parent, k, v, w)
+	})
+}