forgejo/vendor/github.com/pingcap/tidb/kv/union_iter.go

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// 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package kv
import "github.com/ngaut/log"
// UnionIter is the iterator on an UnionStore.
type UnionIter struct {
dirtyIt Iterator
snapshotIt Iterator
dirtyValid bool
snapshotValid bool
curIsDirty bool
isValid bool
}
func newUnionIter(dirtyIt Iterator, snapshotIt Iterator) *UnionIter {
it := &UnionIter{
dirtyIt: dirtyIt,
snapshotIt: snapshotIt,
dirtyValid: dirtyIt.Valid(),
snapshotValid: snapshotIt.Valid(),
}
it.updateCur()
return it
}
// Go next and update valid status.
func (iter *UnionIter) dirtyNext() {
iter.dirtyIt.Next()
iter.dirtyValid = iter.dirtyIt.Valid()
}
// Go next and update valid status.
func (iter *UnionIter) snapshotNext() {
iter.snapshotIt.Next()
iter.snapshotValid = iter.snapshotIt.Valid()
}
func (iter *UnionIter) updateCur() {
iter.isValid = true
for {
if !iter.dirtyValid && !iter.snapshotValid {
iter.isValid = false
return
}
if !iter.dirtyValid {
iter.curIsDirty = false
return
}
if !iter.snapshotValid {
iter.curIsDirty = true
// if delete it
if len(iter.dirtyIt.Value()) == 0 {
iter.dirtyNext()
continue
}
break
}
// both valid
if iter.snapshotValid && iter.dirtyValid {
snapshotKey := iter.snapshotIt.Key()
dirtyKey := iter.dirtyIt.Key()
cmp := dirtyKey.Cmp(snapshotKey)
// if equal, means both have value
if cmp == 0 {
if len(iter.dirtyIt.Value()) == 0 {
// snapshot has a record, but txn says we have deleted it
// just go next
iter.dirtyNext()
iter.snapshotNext()
continue
}
// both go next
iter.snapshotNext()
iter.curIsDirty = true
break
} else if cmp > 0 {
// record from snapshot comes first
iter.curIsDirty = false
break
} else {
// record from dirty comes first
if len(iter.dirtyIt.Value()) == 0 {
log.Warnf("[kv] delete a record not exists? k = %q", iter.dirtyIt.Key())
// jump over this deletion
iter.dirtyNext()
continue
}
iter.curIsDirty = true
break
}
}
}
}
// Next implements the Iterator Next interface.
func (iter *UnionIter) Next() error {
if !iter.curIsDirty {
iter.snapshotNext()
} else {
iter.dirtyNext()
}
iter.updateCur()
return nil
}
// Value implements the Iterator Value interface.
// Multi columns
func (iter *UnionIter) Value() []byte {
if !iter.curIsDirty {
return iter.snapshotIt.Value()
}
return iter.dirtyIt.Value()
}
// Key implements the Iterator Key interface.
func (iter *UnionIter) Key() Key {
if !iter.curIsDirty {
return iter.snapshotIt.Key()
}
return iter.dirtyIt.Key()
}
// Valid implements the Iterator Valid interface.
func (iter *UnionIter) Valid() bool {
return iter.isValid
}
// Close implements the Iterator Close interface.
func (iter *UnionIter) Close() {
if iter.snapshotIt != nil {
iter.snapshotIt.Close()
iter.snapshotIt = nil
}
if iter.dirtyIt != nil {
iter.dirtyIt.Close()
iter.dirtyIt = nil
}
}