Merge pull request #190 from Shopify/cursor_delete

Add Cursor.Delete()

cursor.go

@@ -111,6 +111,25 @@ func (c *Cursor) Seek(seek []byte) (key []byte, value []byte) {
 	return k, v
 }
 
+// Delete removes the current key/value under the cursor from the bucket.
+// Delete fails if current key/value is a bucket or if the transaction is not writable.
+func (c *Cursor) Delete() error {
+	if c.bucket.tx.db == nil {
+		return ErrTxClosed
+	} else if !c.bucket.Writable() {
+		return ErrTxNotWritable
+	}
+
+	key, _, flags := c.keyValue()
+	// Return an error if current value is a bucket.
+	if (flags & bucketLeafFlag) != 0 {
+		return ErrIncompatibleValue
+	}
+	c.node().del(key)
+
+	return nil
+}
+
 // seek moves the cursor to a given key and returns it.
 // If the key does not exist then the next key is used.
 func (c *Cursor) seek(seek []byte) (key []byte, value []byte, flags uint32) {

cursor_test.go

@@ -1,6 +1,7 @@
 package bolt
 
 import (
+	"bytes"
 	"encoding/binary"
 	"sort"
 	"testing"
@@ -67,6 +68,45 @@ func TestCursor_Seek(t *testing.T) {
 	})
 }
 
+func TestCursor_Delete(t *testing.T) {
+	withOpenDB(func(db *DB, path string) {
+		var count = 1000
+
+		// Insert every other key between 0 and $count.
+		db.Update(func(tx *Tx) error {
+			b, _ := tx.CreateBucket([]byte("widgets"))
+			for i := 0; i < count; i += 1 {
+				k := make([]byte, 8)
+				binary.BigEndian.PutUint64(k, uint64(i))
+				b.Put(k, make([]byte, 100))
+			}
+			b.CreateBucket([]byte("sub"))
+			return nil
+		})
+
+		db.Update(func(tx *Tx) error {
+			c := tx.Bucket([]byte("widgets")).Cursor()
+			bound := make([]byte, 8)
+			binary.BigEndian.PutUint64(bound, uint64(count/2))
+			for key, _ := c.First(); bytes.Compare(key, bound) < 0; key, _ = c.Next() {
+				if err := c.Delete(); err != nil {
+					return err
+				}
+			}
+			c.Seek([]byte("sub"))
+			err := c.Delete()
+			assert.Equal(t, err, ErrIncompatibleValue)
+			return nil
+		})
+
+		db.View(func(tx *Tx) error {
+			b := tx.Bucket([]byte("widgets"))
+			assert.Equal(t, b.Stats().KeyN, count/2+1)
+			return nil
+		})
+	})
+}
+
 // Ensure that a Tx cursor can seek to the appropriate keys when there are a
 // large number of keys. This test also checks that seek will always move
 // forward to the next key.