From 488a368e5b8ee85dafc5726021d9cafa308660e7 Mon Sep 17 00:00:00 2001
From: Alex Sharov <AskAlexSharov@gmail.com>
Date: Sat, 27 Jun 2020 15:27:06 +0700
Subject: [PATCH] remove "k,v,err" fields in kv_bolt, they are useful only in
 badger (#690)

---
 ethdb/kv_bolt.go | 76 +++++++++++++++++++++++-------------------------
 1 file changed, 36 insertions(+), 40 deletions(-)

diff --git a/ethdb/kv_bolt.go b/ethdb/kv_bolt.go
index e2574b2a9..8bc337c1e 100644
--- a/ethdb/kv_bolt.go
+++ b/ethdb/kv_bolt.go
@@ -122,10 +122,6 @@ type boltCursor struct {
 	prefix []byte
 
 	bolt *bolt.Cursor
-
-	k   []byte
-	v   []byte
-	err error
 }
 
 type noValuesBoltCursor struct {
@@ -412,9 +408,6 @@ func (b boltBucket) Cursor() Cursor {
 	c.ctx = b.tx.ctx
 	c.bucket = b
 	c.prefix = nil
-	c.k = nil
-	c.v = nil
-	c.err = nil
 	c.bolt = b.bolt.Cursor()
 	// add to auto-close on end of transactions
 	if b.tx.cursors == nil {
@@ -424,64 +417,64 @@ func (b boltBucket) Cursor() Cursor {
 	return c
 }
 
-func (c *boltCursor) First() ([]byte, []byte, error) {
+func (c *boltCursor) First() (k, v []byte, err error) {
 	if len(c.prefix) == 0 {
-		c.k, c.v = c.bolt.First()
-		return c.k, c.v, nil
+		k, v = c.bolt.First()
+		return k, v, nil
 	}
-	c.k, c.v = c.bolt.Seek(c.prefix)
-	if !bytes.HasPrefix(c.k, c.prefix) {
+	k, v = c.bolt.Seek(c.prefix)
+	if !bytes.HasPrefix(k, c.prefix) {
 		return nil, nil, nil
 	}
-	return c.k, c.v, nil
+	return k, v, nil
 }
 
-func (c *boltCursor) Seek(seek []byte) ([]byte, []byte, error) {
+func (c *boltCursor) Seek(seek []byte) (k, v []byte, err error) {
 	select {
 	case <-c.ctx.Done():
 		return []byte{}, nil, c.ctx.Err()
 	default:
 	}
 
-	c.k, c.v = c.bolt.Seek(seek)
+	k, v = c.bolt.Seek(seek)
 	if c.prefix != nil {
-		if !bytes.HasPrefix(c.k, c.prefix) {
+		if !bytes.HasPrefix(k, c.prefix) {
 			return nil, nil, nil
 		}
 	}
-	return c.k, c.v, nil
+	return k, v, nil
 }
 
-func (c *boltCursor) SeekTo(seek []byte) ([]byte, []byte, error) {
+func (c *boltCursor) SeekTo(seek []byte) (k, v []byte, err error) {
 	select {
 	case <-c.ctx.Done():
 		return []byte{}, nil, c.ctx.Err()
 	default:
 	}
 
-	c.k, c.v = c.bolt.SeekTo(seek)
+	k, v = c.bolt.SeekTo(seek)
 	if c.prefix != nil {
-		if !bytes.HasPrefix(c.k, c.prefix) {
+		if !bytes.HasPrefix(k, c.prefix) {
 			return nil, nil, nil
 		}
 	}
-	return c.k, c.v, nil
+	return k, v, nil
 }
 
-func (c *boltCursor) Next() ([]byte, []byte, error) {
+func (c *boltCursor) Next() (k, v []byte, err error) {
 	select {
 	case <-c.ctx.Done():
 		return []byte{}, nil, c.ctx.Err()
 	default:
 	}
 
-	c.k, c.v = c.bolt.Next()
+	k, v = c.bolt.Next()
 	if c.prefix != nil {
-		if !bytes.HasPrefix(c.k, c.prefix) {
-			c.k, c.v = nil, nil
+		if !bytes.HasPrefix(k, c.prefix) {
+			k, v = nil, nil
 		}
 	}
-	return c.k, c.v, nil
+	return k, v, nil
 }
 
 func (c *boltCursor) Delete(key []byte) error {
@@ -540,47 +533,50 @@ func (c *noValuesBoltCursor) Walk(walker func(k []byte, vSize uint32) (bool, err
 	return nil
 }
 
-func (c *noValuesBoltCursor) First() ([]byte, uint32, error) {
+func (c *noValuesBoltCursor) First() (k []byte, vSize uint32, err error) {
+	var v []byte
 	if len(c.prefix) == 0 {
-		c.k, c.v = c.bolt.First()
-		return c.k, uint32(len(c.v)), nil
+		k, v = c.bolt.First()
+		return k, uint32(len(v)), nil
 	}
 
-	c.k, c.v = c.bolt.Seek(c.prefix)
-	if !bytes.HasPrefix(c.k, c.prefix) {
+	k, v = c.bolt.Seek(c.prefix)
+	if !bytes.HasPrefix(k, c.prefix) {
 		return nil, 0, nil
 	}
-	return c.k, uint32(len(c.v)), nil
+	return k, uint32(len(v)), nil
 }
 
-func (c *noValuesBoltCursor) Seek(seek []byte) ([]byte, uint32, error) {
+func (c *noValuesBoltCursor) Seek(seek []byte) (k []byte, vSize uint32, err error) {
 	select {
 	case <-c.ctx.Done():
 		return []byte{}, 0, c.ctx.Err() // on error key should be != nil
 	default:
 	}
 
-	c.k, c.v = c.bolt.Seek(seek)
+	var v []byte
+	k, v = c.bolt.Seek(seek)
 	if c.prefix != nil {
-		if !bytes.HasPrefix(c.k, c.prefix) {
+		if !bytes.HasPrefix(k, c.prefix) {
 			return nil, 0, nil
 		}
 	}
-	return c.k, uint32(len(c.v)), nil
+	return k, uint32(len(v)), nil
 }
 
-func (c *noValuesBoltCursor) Next() ([]byte, uint32, error) {
+func (c *noValuesBoltCursor) Next() (k []byte, vSize uint32, err error) {
 	select {
 	case <-c.ctx.Done():
 		return []byte{}, 0, c.ctx.Err()
 	default:
 	}
 
-	c.k, c.v = c.bolt.Next()
+	var v []byte
+	k, v = c.bolt.Next()
 	if c.prefix != nil {
-		if !bytes.HasPrefix(c.k, c.prefix) {
+		if !bytes.HasPrefix(k, c.prefix) {
 			return nil, 0, nil
 		}
 	}
-	return c.k, uint32(len(c.v)), nil
+	return k, uint32(len(v)), nil
 }