Add transactional support to leveldb datastore.

.gx/lastpubver

@@ -1 +1 @@
-1.1.2: QmPnXsHj9W8WpDDwj2iogRcnVL6d5ANtK9SAJLgKpeBMq8
+1.2.0: QmcxDvw8NnJsfdEcfrypwHkLeVxZY2rT8iiWsUuBnw93gb

datastore.go

@@ -9,16 +9,21 @@ import (
 	"github.com/jbenet/goprocess"
 	"github.com/syndtr/goleveldb/leveldb"
 	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/iterator"
 	"github.com/syndtr/goleveldb/leveldb/opt"
 	"github.com/syndtr/goleveldb/leveldb/storage"
 	"github.com/syndtr/goleveldb/leveldb/util"
 )
 
 type datastore struct {
+	*accessor
 	DB   *leveldb.DB
 	path string
 }
 
+var _ ds.Datastore = (*datastore)(nil)
+var _ ds.TxnDatastore = (*datastore)(nil)
+
 // Options is an alias of syndtr/goleveldb/opt.Options which might be extended
 // in the future.
 type Options opt.Options
@@ -49,21 +54,34 @@ func NewDatastore(path string, opts *Options) (*datastore, error) {
 	}
 
 	return &datastore{
-		DB:   db,
-		path: path,
+		accessor: &accessor{ldb: db},
+		DB:       db,
+		path:     path,
 	}, nil
 }
 
-// Returns ErrInvalidType if value is not of type []byte.
+// An extraction of the common interface between LevelDB Transactions and the DB itself.
 //
-// Note: using sync = false.
-// see http://godoc.org/github.com/syndtr/goleveldb/leveldb/opt#WriteOptions
-func (d *datastore) Put(key ds.Key, value []byte) (err error) {
-	return d.DB.Put(key.Bytes(), value, nil)
+// It allows to plug in either inside the `accessor`.
+type levelDbOps interface {
+	Put(key, value []byte, wo *opt.WriteOptions) error
+	Get(key []byte, ro *opt.ReadOptions) (value []byte, err error)
+	Has(key []byte, ro *opt.ReadOptions) (ret bool, err error)
+	Delete(key []byte, wo *opt.WriteOptions) error
+	NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator
+}
+
+// Datastore operations using either the DB or a transaction as the backend.
+type accessor struct {
+	ldb levelDbOps
+}
+
+func (a *accessor) Put(key ds.Key, value []byte) (err error) {
+	return a.ldb.Put(key.Bytes(), value, nil)
 }
 
-func (d *datastore) Get(key ds.Key) (value []byte, err error) {
-	val, err := d.DB.Get(key.Bytes(), nil)
+func (a *accessor) Get(key ds.Key) (value []byte, err error) {
+	val, err := a.ldb.Get(key.Bytes(), nil)
 	if err != nil {
 		if err == leveldb.ErrNotFound {
 			return nil, ds.ErrNotFound
@@ -73,40 +91,40 @@ func (d *datastore) Get(key ds.Key) (value []byte, err error) {
 	return val, nil
 }
 
-func (d *datastore) Has(key ds.Key) (exists bool, err error) {
-	return d.DB.Has(key.Bytes(), nil)
+func (a *accessor) Has(key ds.Key) (exists bool, err error) {
+	return a.ldb.Has(key.Bytes(), nil)
 }
 
-func (d *datastore) Delete(key ds.Key) (err error) {
+func (a *accessor) Delete(key ds.Key) (err error) {
 	// leveldb Delete will not return an error if the key doesn't
 	// exist (see https://github.com/syndtr/goleveldb/issues/109),
 	// so check that the key exists first and if not return an
 	// error
-	exists, err := d.DB.Has(key.Bytes(), nil)
+	exists, err := a.ldb.Has(key.Bytes(), nil)
 	if !exists {
 		return ds.ErrNotFound
 	} else if err != nil {
 		return err
 	}
-	return d.DB.Delete(key.Bytes(), nil)
+	return a.ldb.Delete(key.Bytes(), nil)
 }
 
-func (d *datastore) Query(q dsq.Query) (dsq.Results, error) {
-	return d.QueryNew(q)
+func (a *accessor) Query(q dsq.Query) (dsq.Results, error) {
+	return a.queryNew(q)
 }
 
-func (d *datastore) QueryNew(q dsq.Query) (dsq.Results, error) {
+func (a *accessor) queryNew(q dsq.Query) (dsq.Results, error) {
 	if len(q.Filters) > 0 ||
 		len(q.Orders) > 0 ||
 		q.Limit > 0 ||
 		q.Offset > 0 {
-		return d.QueryOrig(q)
+		return a.queryOrig(q)
 	}
 	var rnge *util.Range
 	if q.Prefix != "" {
 		rnge = util.BytesPrefix([]byte(q.Prefix))
 	}
-	i := d.DB.NewIterator(rnge, nil)
+	i := a.ldb.NewIterator(rnge, nil)
 	return dsq.ResultsFromIterator(q, dsq.Iterator{
 		Next: func() (dsq.Result, bool) {
 			ok := i.Next()
@@ -130,7 +148,7 @@ func (d *datastore) QueryNew(q dsq.Query) (dsq.Results, error) {
 	}), nil
 }
 
-func (d *datastore) QueryOrig(q dsq.Query) (dsq.Results, error) {
+func (a *accessor) queryOrig(q dsq.Query) (dsq.Results, error) {
 	// we can use multiple iterators concurrently. see:
 	// https://godoc.org/github.com/syndtr/goleveldb/leveldb#DB.NewIterator
 	// advance the iterator only if the reader reads
@@ -140,7 +158,7 @@ func (d *datastore) QueryOrig(q dsq.Query) (dsq.Results, error) {
 	// that resources should be reclaimed.
 	qrb := dsq.NewResultBuilder(q)
 	qrb.Process.Go(func(worker goprocess.Process) {
-		d.runQuery(worker, qrb)
+		a.runQuery(worker, qrb)
 	})
 
 	// go wait on the worker (without signaling close)
@@ -157,13 +175,12 @@ func (d *datastore) QueryOrig(q dsq.Query) (dsq.Results, error) {
 	return qr, nil
 }
 
-func (d *datastore) runQuery(worker goprocess.Process, qrb *dsq.ResultBuilder) {
-
+func (a *accessor) runQuery(worker goprocess.Process, qrb *dsq.ResultBuilder) {
 	var rnge *util.Range
 	if qrb.Query.Prefix != "" {
 		rnge = util.BytesPrefix([]byte(qrb.Query.Prefix))
 	}
-	i := d.DB.NewIterator(rnge, nil)
+	i := a.ldb.NewIterator(rnge, nil)
 	defer i.Release()
 
 	// advance iterator for offset
@@ -261,3 +278,26 @@ func (b *leveldbBatch) Delete(key ds.Key) error {
 	b.b.Delete(key.Bytes())
 	return nil
 }
+
+// A leveldb transaction embedding the accessor backed by the transaction.
+type transaction struct {
+	*accessor
+	tx *leveldb.Transaction
+}
+
+func (t *transaction) Commit() error {
+	return t.tx.Commit()
+}
+
+func (t *transaction) Discard() {
+	t.tx.Discard()
+}
+
+func (d *datastore) NewTransaction(readOnly bool) (ds.Txn, error) {
+	tx, err := d.DB.OpenTransaction()
+	if err != nil {
+		return nil, err
+	}
+	accessor := &accessor{tx}
+	return &transaction{accessor, tx}, nil
+}

ds_test.go

@@ -1,6 +1,8 @@
 package leveldb
 
 import (
+	"bytes"
+	"fmt"
 	"io/ioutil"
 	"os"
 	"testing"
@@ -223,3 +225,98 @@ func TestDiskUsageInMem(t *testing.T) {
 		t.Fatal("inmem dbs have 0 disk usage")
 	}
 }
+
+func TestTransactionCommit(t *testing.T) {
+	key := ds.NewKey("/test/key1")
+
+	d, done := newDS(t)
+	defer done()
+
+	txn, err := d.NewTransaction(false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer txn.Discard()
+
+	if err := txn.Put(key, []byte("hello")); err != nil {
+		t.Fatal(err)
+	}
+	if val, err := d.Get(key); err != ds.ErrNotFound {
+		t.Fatalf("expected ErrNotFound, got err: %v, value: %v", err, val)
+	}
+	if err := txn.Commit(); err != nil {
+		t.Fatal(err)
+	}
+	if val, err := d.Get(key); err != nil || !bytes.Equal(val, []byte("hello")) {
+		t.Fatalf("expected entry present after commit, got err: %v, value: %v", err, val)
+	}
+}
+
+func TestTransactionDiscard(t *testing.T) {
+	key := ds.NewKey("/test/key1")
+
+	d, done := newDS(t)
+	defer done()
+
+	txn, err := d.NewTransaction(false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer txn.Discard()
+
+	if err := txn.Put(key, []byte("hello")); err != nil {
+		t.Fatal(err)
+	}
+	if val, err := d.Get(key); err != ds.ErrNotFound {
+		t.Fatalf("expected ErrNotFound, got err: %v, value: %v", err, val)
+	}
+	if txn.Discard(); err != nil {
+		t.Fatal(err)
+	}
+	if val, err := d.Get(key); err != ds.ErrNotFound {
+		t.Fatalf("expected ErrNotFound, got err: %v, value: %v", err, val)
+	}
+}
+
+func TestTransactionManyOperations(t *testing.T) {
+	keys := []ds.Key{ds.NewKey("/test/key1"), ds.NewKey("/test/key2"), ds.NewKey("/test/key3"), ds.NewKey("/test/key4"), ds.NewKey("/test/key5")}
+
+	d, done := newDS(t)
+	defer done()
+
+	txn, err := d.NewTransaction(false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer txn.Discard()
+
+	// Insert all entries.
+	for i := 0; i < 5; i++ {
+		if err := txn.Put(keys[i], []byte(fmt.Sprintf("hello%d", i))); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	// Remove the third entry.
+	if err := txn.Delete(keys[2]); err != nil {
+		t.Fatal(err)
+	}
+
+	// Check existences.
+	if has, err := txn.Has(keys[1]); err != nil || !has {
+		t.Fatalf("expected key[1] to be present, err: %v, has: %v", err, has)
+	}
+	if has, err := txn.Has(keys[2]); err != nil || has {
+		t.Fatalf("expected key[2] to be absent, err: %v, has: %v", err, has)
+	}
+
+	var res dsq.Results
+	if res, err = txn.Query(dsq.Query{Prefix: "/test"}); err != nil {
+		t.Fatalf("query failed, err: %v", err)
+	}
+	if entries, err := res.Rest(); err != nil || len(entries) != 4 {
+		t.Fatalf("query failed or contained unexpected number of entries, err: %v, results: %v", err, entries)
+	}
+
+	txn.Discard()
+}

package.json

@@ -21,16 +21,16 @@
     },
     {
       "author": "jbenet",
-      "hash": "QmUyz7JTJzgegC6tiJrfby3mPhzcdswVtG4x58TQ6pq8jV",
+      "hash": "QmbQshXLNcCPRUGZv4sBGxnZNAHREA6MKeomkwihNXPZWP",
       "name": "go-datastore",
-      "version": "3.2.0"
+      "version": "3.3.0"
     }
   ],
   "gxVersion": "0.8.0",
   "language": "go",
   "license": "",
   "name": "go-ds-leveldb",
   "releaseCmd": "git commit -a -m \"gx publish $VERSION\"",
-  "version": "1.1.2"
+  "version": "1.2.0"
 }