tidb prefix_helper 代码
文件路径：/util/prefix_helper.go
/ Copyright 2015 PingCAP, Inc.
/
/ Licensed under the Apache License, Version 2.0 (the "License");
/ you may not use this file except in compliance with the License.
/ You may obtain a copy of the License at
/
/ http://www.apache.org/licenses/LICENSE-2.0
/
/ Unless required by applicable law or agreed to in writing, software
/ distributed under the License is distributed on an "AS IS" BASIS,
/ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/ See the License for the specific language governing permissions and
/ limitations under the License.
/ Copyright 2014 The ql Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSES/QL-LICENSE file.
package util
import (
"bytes"
"github.com/pingcap/errors"
"github.com/pingcap/tidb/kv"
)
/ ScanMetaWithPrefix scans metadata with the prefix.
func ScanMetaWithPrefix(retriever kv.Retriever, prefix kv.Key, filter func(kv.Key, []byte) bool) error {
iter, err := retriever.Iter(prefix, prefix.PrefixNext())
if err != nil {
return errors.Trace(err)
}
defer iter.Close()
for {
if iter.Valid() && iter.Key().HasPrefix(prefix) {
if !filter(iter.Key(), iter.Value()) {
break
}
err = iter.Next()
if err != nil {
return errors.Trace(err)
}
} else {
break
}
}
return nil
}
/ DelKeyWithPrefix deletes keys with prefix.
func DelKeyWithPrefix(rm kv.RetrieverMutator, prefix kv.Key) error {
var keys []kv.Key
iter, err := rm.Iter(prefix, prefix.PrefixNext())
if err != nil {
return errors.Trace(err)
}
defer iter.Close()
for {
if iter.Valid() && iter.Key().HasPrefix(prefix) {
keys = append(keys, iter.Key().Clone())
err = iter.Next()
if err != nil {
return errors.Trace(err)
}
} else {
break
}
}
for _, key := range keys {
err := rm.Delete(key)
if err != nil {
return errors.Trace(err)
}
}
return nil
}
/ RowKeyPrefixFilter returns a function which checks whether currentKey has decoded rowKeyPrefix as prefix.
func RowKeyPrefixFilter(rowKeyPrefix kv.Key) kv.FnKeyCmp {
return func(currentKey kv.Key) bool {
/ Next until key without prefix of this record.
return !bytes.HasPrefix(currentKey, rowKeyPrefix)
}
}