Implement multiget

db.go

@@ -5,6 +5,7 @@ package gorocksdb
 import "C"
 import (
 	"errors"
+	"fmt"
 	"unsafe"
 )
 
@@ -263,6 +264,49 @@ func (db *DB) GetCF(opts *ReadOptions, cf *ColumnFamilyHandle, key []byte) (*Sli
 	return NewSlice(cValue, cValLen), nil
 }
 
+// Get returns the data associated with the key from the database.
+func (db *DB) MultiGet(opts *ReadOptions, keys ...[]byte) (Slices, error) {
+	cKeys, cKeySizes := bytesSliceToArray(keys)
+	defer freeCharsArray(cKeys, len(keys))
+	vals, cVals := emptyCharSlice(len(keys))
+	rocksErrs, cRocksErrs := emptyCharSlice(len(keys))
+	valSizes, cValSizes := emptySizetSlice(len(keys))
+	_ = vals
+	_ = valSizes
+
+	C.rocksdb_multi_get(
+		db.c,
+		opts.c,
+		C.size_t(len(keys)),
+		cKeys,
+		cKeySizes,
+		cVals,
+		cValSizes,
+		cRocksErrs,
+	)
+
+	var errs []error
+
+	for i, rocksErr := range rocksErrs {
+		if rocksErr != nil {
+			defer C.free(unsafe.Pointer(rocksErr))
+			err := fmt.Errorf("getting %q failed: %v", string(keys[i]), C.GoString(rocksErr))
+			errs = append(errs, err)
+		}
+	}
+
+	if len(errs) > 0 {
+		return nil, fmt.Errorf("failed to get %d keys, first error: %v", len(errs), errs[0])
+	}
+
+	slices := make(Slices, len(keys))
+	for i, val := range vals {
+		slices[i] = NewSlice(val, valSizes[i])
+	}
+
+	return slices, nil
+}
+
 // Put writes data associated with a key to the database.
 func (db *DB) Put(opts *WriteOptions, key, value []byte) error {
 	var (

db_test.go

@@ -140,3 +140,35 @@ func newTestDBPathNames(t *testing.T, name string, names []string, target_sizes
 
 	return db
 }
+
+func TestDBMultiGet(t *testing.T) {
+	db := newTestDB(t, "TestDBMultiGet", nil)
+	defer db.Close()
+
+	var (
+		givenKey1 = []byte("hello1")
+		givenKey2 = []byte("hello2")
+		givenKey3 = []byte("hello3")
+		givenVal1 = []byte("world1")
+		givenVal2 = []byte("world2")
+		givenVal3 = []byte("world3")
+		wo        = NewDefaultWriteOptions()
+		ro        = NewDefaultReadOptions()
+	)
+
+	// create
+	ensure.Nil(t, db.Put(wo, givenKey1, givenVal1))
+	ensure.Nil(t, db.Put(wo, givenKey2, givenVal2))
+	ensure.Nil(t, db.Put(wo, givenKey3, givenVal3))
+
+	// retrieve
+	values, err := db.MultiGet(ro, []byte("noexist"), givenKey1, givenKey2, givenKey3)
+	defer values.Destroy()
+	ensure.Nil(t, err)
+	ensure.DeepEqual(t, len(values), 4)
+
+	ensure.DeepEqual(t, values[0].Data(), []byte(nil))
+	ensure.DeepEqual(t, values[1].Data(), givenVal1)
+	ensure.DeepEqual(t, values[2].Data(), givenVal2)
+	ensure.DeepEqual(t, values[3].Data(), givenVal3)
+}

slice.go

@@ -11,6 +11,14 @@ type Slice struct {
 	freed bool
 }
 
+type Slices []*Slice
+
+func (slices Slices) Destroy() {
+	for _, s := range slices {
+		s.Free()
+	}
+}
+
 // NewSlice returns a slice with the given data.
 func NewSlice(data *C.char, size C.size_t) *Slice {
 	return &Slice{data, size, false}