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179 lines
3.9 KiB
Go
179 lines
3.9 KiB
Go
// Copyright 2015 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package localstore
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import (
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"github.com/juju/errors"
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"github.com/pingcap/tidb/kv"
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"github.com/pingcap/tidb/store/localstore/engine"
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"github.com/pingcap/tidb/terror"
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)
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var (
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_ kv.Snapshot = (*dbSnapshot)(nil)
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_ kv.Iterator = (*dbIter)(nil)
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)
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// dbSnapshot implements MvccSnapshot interface.
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type dbSnapshot struct {
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store *dbStore
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version kv.Version // transaction begin version
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}
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func newSnapshot(store *dbStore, ver kv.Version) *dbSnapshot {
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ss := &dbSnapshot{
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store: store,
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version: ver,
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}
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return ss
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}
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// mvccSeek seeks for the first key in db which has a k >= key and a version <=
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// snapshot's version, returns kv.ErrNotExist if such key is not found. If exact
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// is true, only k == key can be returned.
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func (s *dbSnapshot) mvccSeek(key kv.Key, exact bool) (kv.Key, []byte, error) {
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// Key layout:
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// ...
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// Key_verMax -- (1)
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// ...
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// Key_ver+1 -- (2)
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// Key_ver -- (3)
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// Key_ver-1 -- (4)
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// ...
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// Key_0 -- (5)
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// NextKey_verMax -- (6)
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// ...
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// NextKey_ver+1 -- (7)
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// NextKey_ver -- (8)
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// NextKey_ver-1 -- (9)
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// ...
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// NextKey_0 -- (10)
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// ...
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// EOF
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for {
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mvccKey := MvccEncodeVersionKey(key, s.version)
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mvccK, v, err := s.store.Seek([]byte(mvccKey)) // search for [3...EOF)
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if err != nil {
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if terror.ErrorEqual(err, engine.ErrNotFound) { // EOF
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return nil, nil, errors.Trace(kv.ErrNotExist)
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}
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return nil, nil, errors.Trace(err)
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}
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k, ver, err := MvccDecode(mvccK)
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if err != nil {
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return nil, nil, errors.Trace(err)
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}
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// quick test for exact mode
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if exact {
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if key.Cmp(k) != 0 || isTombstone(v) {
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return nil, nil, errors.Trace(kv.ErrNotExist)
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}
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return k, v, nil
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}
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if ver.Ver > s.version.Ver {
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// currently on [6...7]
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key = k // search for [8...EOF) next loop
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continue
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}
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// currently on [3...5] or [8...10]
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if isTombstone(v) {
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key = k.Next() // search for (5...EOF) or (10..EOF) next loop
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continue
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}
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// target found
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return k, v, nil
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}
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}
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func (s *dbSnapshot) Get(key kv.Key) ([]byte, error) {
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_, v, err := s.mvccSeek(key, true)
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if err != nil {
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return nil, errors.Trace(err)
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}
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return v, nil
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}
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func (s *dbSnapshot) BatchGet(keys []kv.Key) (map[string][]byte, error) {
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m := make(map[string][]byte)
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for _, k := range keys {
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v, err := s.Get(k)
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if err != nil && !kv.IsErrNotFound(err) {
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return nil, errors.Trace(err)
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}
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if len(v) > 0 {
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m[string(k)] = v
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}
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}
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return m, nil
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}
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func (s *dbSnapshot) Seek(k kv.Key) (kv.Iterator, error) {
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it, err := newDBIter(s, k)
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return it, errors.Trace(err)
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}
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func (s *dbSnapshot) Release() {
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}
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type dbIter struct {
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s *dbSnapshot
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valid bool
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k kv.Key
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v []byte
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}
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func newDBIter(s *dbSnapshot, startKey kv.Key) (*dbIter, error) {
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k, v, err := s.mvccSeek(startKey, false)
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if err != nil {
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if terror.ErrorEqual(err, kv.ErrNotExist) {
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err = nil
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}
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return &dbIter{valid: false}, errors.Trace(err)
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}
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return &dbIter{
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s: s,
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valid: true,
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k: k,
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v: v,
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}, nil
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}
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func (it *dbIter) Next() error {
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k, v, err := it.s.mvccSeek(it.k.Next(), false)
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if err != nil {
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it.valid = false
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if !terror.ErrorEqual(err, kv.ErrNotExist) {
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return errors.Trace(err)
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}
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}
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it.k, it.v = k, v
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return nil
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}
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func (it *dbIter) Valid() bool {
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return it.valid
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}
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func (it *dbIter) Key() kv.Key {
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return it.k
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}
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func (it *dbIter) Value() []byte {
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return it.v
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}
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func (it *dbIter) Close() {}
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