add prefix check in NewIter

Author: zhangchiqing

storage/operation/badgerimpl/reader.go

@@ -1,7 +1,9 @@
 package badgerimpl
 
 import (
+	"bytes"
 	"errors"
+	"fmt"
 	"io"
 
 	"github.com/dgraph-io/badger/v2"
@@ -54,8 +56,13 @@ func (b dbReader) Get(key []byte) ([]byte, io.Closer, error) {
 //   - have a prefix equal to the endPrefix OR
 //   - have a prefix that is lexicographically between startPrefix and endPrefix
 //
+// it returns error if the startPrefix key is greater than the endPrefix key
 // no errors are expected during normal operation
 func (b dbReader) NewIter(startPrefix, endPrefix []byte, ops storage.IteratorOption) (storage.Iterator, error) {
+	if bytes.Compare(startPrefix, endPrefix) > 0 {
+		return nil, fmt.Errorf("startPrefix key must be less than or equal to endPrefix key")
+	}
+
 	return newBadgerIterator(b.db, startPrefix, endPrefix, ops), nil
 }
 

storage/operation/pebbleimpl/reader.go

@@ -1,7 +1,9 @@
 package pebbleimpl
 
 import (
+	"bytes"
 	"errors"
+	"fmt"
 	"io"
 
 	"github.com/cockroachdb/pebble"
@@ -50,7 +52,14 @@ func (b dbReader) Get(key []byte) ([]byte, io.Closer, error) {
 //   - have a prefix equal to startPrefix OR
 //   - have a prefix equal to the endPrefix OR
 //   - have a prefix that is lexicographically between startPrefix and endPrefix
+//
+// it returns error if the startPrefix key is greater than the endPrefix key
+// no errors are expected during normal operation
 func (b dbReader) NewIter(startPrefix, endPrefix []byte, ops storage.IteratorOption) (storage.Iterator, error) {
+	if bytes.Compare(startPrefix, endPrefix) > 0 {
+		return nil, fmt.Errorf("startPrefix key must be less than or equal to endPrefix key")
+	}
+
 	return newPebbleIterator(b.db, startPrefix, endPrefix, ops)
 }