Add temporary DB and prefix methods to Storage

database/leveldb.go

@@ -4,6 +4,9 @@ package database
 import (
 	"bytes"
 	"errors"
+	"io/ioutil"
+	"os"
+
 	"github.com/syndtr/goleveldb/leveldb"
 	"github.com/syndtr/goleveldb/leveldb/filter"
 	"github.com/syndtr/goleveldb/leveldb/opt"
@@ -16,11 +19,17 @@ var (
 	ErrNotFound = errors.New("key not found")
 )
 
+// StorageProcessor is a function to process one single storage entry
+type StorageProcessor func(key []byte, value []byte) error
+
 // Storage is an interface to KV storage
 type Storage interface {
+	CreateTemporary() (Storage, error)
 	Get(key []byte) ([]byte, error)
 	Put(key []byte, value []byte) error
 	Delete(key []byte) error
+	HasPrefix(prefix []byte) bool
+	ProcessByPrefix(prefix []byte, proc StorageProcessor) error
 	KeysByPrefix(prefix []byte) [][]byte
 	FetchByPrefix(prefix []byte) [][]byte
 	Close() error
@@ -28,6 +37,7 @@ type Storage interface {
 	StartBatch()
 	FinishBatch() error
 	CompactDB() error
+	Drop() error
 }
 
 type levelDB struct {
@@ -77,6 +87,16 @@ func RecoverDB(path string) error {
 	return nil
 }
 
+// CreateTemporary creates new DB of the same type in temp dir
+func (l *levelDB) CreateTemporary() (Storage, error) {
+	tempdir, err := ioutil.TempDir("", "aptly")
+	if err != nil {
+		return nil, err
+	}
+
+	return OpenDB(tempdir)
+}
+
 // Get key value from database
 func (l *levelDB) Get(key []byte) ([]byte, error) {
 	value, err := l.db.Get(key, nil)
@@ -152,6 +172,29 @@ func (l *levelDB) FetchByPrefix(prefix []byte) [][]byte {
 	return result
 }
 
+// HasPrefix checks whether it can find any key with given prefix and returns true if one exists
+func (l *levelDB) HasPrefix(prefix []byte) bool {
+	iterator := l.db.NewIterator(nil, nil)
+	defer iterator.Release()
+	return iterator.Seek(prefix) && bytes.HasPrefix(iterator.Key(), prefix)
+}
+
+// ProcessByPrefix iterates through all entries where key starts with prefix and calls
+// StorageProcessor on key value pair
+func (l *levelDB) ProcessByPrefix(prefix []byte, proc StorageProcessor) error {
+	iterator := l.db.NewIterator(nil, nil)
+	defer iterator.Release()
+
+	for ok := iterator.Seek(prefix); ok && bytes.HasPrefix(iterator.Key(), prefix); ok = iterator.Next() {
+		err := proc(iterator.Key(), iterator.Value())
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 // Close finishes DB work
 func (l *levelDB) Close() error {
 	if l.db == nil {
@@ -197,3 +240,12 @@ func (l *levelDB) FinishBatch() error {
 func (l *levelDB) CompactDB() error {
 	return l.db.CompactRange(util.Range{})
 }
+
+// Drop removes all the DB files (DANGEROUS!)
+func (l *levelDB) Drop() error {
+	if l.db != nil {
+		return errors.New("DB is still open")
+	}
+
+	return os.RemoveAll(l.path)
+}

database/leveldb_test.go

@@ -71,6 +71,29 @@ func (s *LevelDBSuite) TestGetPut(c *C) {
 	c.Assert(result, DeepEquals, value)
 }
 
+func (s *LevelDBSuite) TestTemporaryDelete(c *C) {
+	var (
+		key   = []byte("key")
+		value = []byte("value")
+	)
+
+	err := s.db.Put(key, value)
+	c.Assert(err, IsNil)
+
+	temp, err := s.db.CreateTemporary()
+	c.Assert(err, IsNil)
+
+	c.Check(s.db.HasPrefix([]byte(nil)), Equals, true)
+	c.Check(temp.HasPrefix([]byte(nil)), Equals, false)
+
+	err = temp.Put(key, value)
+	c.Assert(err, IsNil)
+	c.Check(temp.HasPrefix([]byte(nil)), Equals, true)
+
+	c.Assert(temp.Close(), IsNil)
+	c.Assert(temp.Drop(), IsNil)
+}
+
 func (s *LevelDBSuite) TestDelete(c *C) {
 	var (
 		key   = []byte("key")
@@ -107,10 +130,41 @@ func (s *LevelDBSuite) TestByPrefix(c *C) {
 	c.Check(s.db.FetchByPrefix([]byte{0x80}), DeepEquals, [][]byte{{0x01}, {0x02}, {0x03}})
 	c.Check(s.db.KeysByPrefix([]byte{0x80}), DeepEquals, [][]byte{{0x80, 0x01}, {0x80, 0x02}, {0x80, 0x03}})
 
+	keys := [][]byte{}
+	values := [][]byte{}
+
+	c.Check(s.db.ProcessByPrefix([]byte{0x80}, func(k, v []byte) error {
+		keys = append(keys, append([]byte(nil), k...))
+		values = append(values, append([]byte(nil), v...))
+		return nil
+	}), IsNil)
+
+	c.Check(values, DeepEquals, [][]byte{{0x01}, {0x02}, {0x03}})
+	c.Check(keys, DeepEquals, [][]byte{{0x80, 0x01}, {0x80, 0x02}, {0x80, 0x03}})
+
+	c.Check(s.db.ProcessByPrefix([]byte{0x80}, func(k, v []byte) error {
+		return ErrNotFound
+	}), Equals, ErrNotFound)
+
+	c.Check(s.db.ProcessByPrefix([]byte{0xa0}, func(k, v []byte) error {
+		return ErrNotFound
+	}), IsNil)
+
 	c.Check(s.db.FetchByPrefix([]byte{0xa0}), DeepEquals, [][]byte{})
 	c.Check(s.db.KeysByPrefix([]byte{0xa0}), DeepEquals, [][]byte{})
 }
 
+func (s *LevelDBSuite) TestHasPrefix(c *C) {
+	c.Check(s.db.HasPrefix([]byte(nil)), Equals, false)
+	c.Check(s.db.HasPrefix([]byte{0x80}), Equals, false)
+
+	s.db.Put([]byte{0x80, 0x01}, []byte{0x01})
+
+	c.Check(s.db.HasPrefix([]byte(nil)), Equals, true)
+	c.Check(s.db.HasPrefix([]byte{0x80}), Equals, true)
+	c.Check(s.db.HasPrefix([]byte{0x79}), Equals, false)
+}
+
 func (s *LevelDBSuite) TestBatch(c *C) {
 	var (
 		key    = []byte("key")