tidb index 源码
tidb index 代码
文件路径：/table/tables/index.go
// Copyright 2016 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.
package tables
import (
"context"
"sync"
"github.com/opentracing/opentracing-go"
"github.com/pingcap/tidb/kv"
"github.com/pingcap/tidb/parser/model"
"github.com/pingcap/tidb/parser/mysql"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/sessionctx/stmtctx"
"github.com/pingcap/tidb/table"
"github.com/pingcap/tidb/tablecodec"
"github.com/pingcap/tidb/types"
"github.com/pingcap/tidb/util/rowcodec"
)
// index is the data structure for index data in the KV store.
type index struct {
idxInfo *model.IndexInfo
tblInfo *model.TableInfo
prefix kv.Key
phyTblID int64
// initNeedRestoreData is used to initialize `needRestoredData` in `index.Create()`.
// This routine cannot be done in `NewIndex()` because `needRestoreData` relies on `NewCollationEnabled()` and
// the collation global variable is initialized *after* `NewIndex()`.
initNeedRestoreData sync.Once
needRestoredData bool
}
// NeedRestoredData checks whether the index columns needs restored data.
func NeedRestoredData(idxCols []*model.IndexColumn, colInfos []*model.ColumnInfo) bool {
for _, idxCol := range idxCols {
col := colInfos[idxCol.Offset]
if types.NeedRestoredData(&col.FieldType) {
return true
}
}
return false
}
// NewIndex builds a new Index object.
func NewIndex(physicalID int64, tblInfo *model.TableInfo, indexInfo *model.IndexInfo) table.Index {
// The prefix can't encode from tblInfo.ID, because table partition may change the id to partition id.
var prefix kv.Key
if indexInfo.Global {
// In glabal index of partition table, prefix start with tblInfo.ID.
prefix = tablecodec.EncodeTableIndexPrefix(tblInfo.ID, indexInfo.ID)
} else {
// Otherwise, start with physicalID.
prefix = tablecodec.EncodeTableIndexPrefix(physicalID, indexInfo.ID)
}
index := &index{
idxInfo: indexInfo,
tblInfo: tblInfo,
prefix: prefix,
phyTblID: physicalID,
}
return index
}
// Meta returns index info.
func (c *index) Meta() *model.IndexInfo {
return c.idxInfo
}
// GenIndexKey generates storage key for index values. Returned distinct indicates whether the
// indexed values should be distinct in storage (i.e. whether handle is encoded in the key).
func (c *index) GenIndexKey(sc *stmtctx.StatementContext, indexedValues []types.Datum, h kv.Handle, buf []byte) (key []byte, distinct bool, err error) {
idxTblID := c.phyTblID
if c.idxInfo.Global {
idxTblID = c.tblInfo.ID
}
return tablecodec.GenIndexKey(sc, c.tblInfo, c.idxInfo, idxTblID, indexedValues, h, buf)
}
// GenIndexValue generates the index value.
func (c *index) GenIndexValue(sc *stmtctx.StatementContext, distinct bool, indexedValues []types.Datum, h kv.Handle, restoredData []types.Datum) ([]byte, error) {
c.initNeedRestoreData.Do(func() {
c.needRestoredData = NeedRestoredData(c.idxInfo.Columns, c.tblInfo.Columns)
})
return tablecodec.GenIndexValuePortal(sc, c.tblInfo, c.idxInfo, c.needRestoredData, distinct, false, indexedValues, h, c.phyTblID, restoredData)
}
// Create creates a new entry in the kvIndex data.
// If the index is unique and there is an existing entry with the same key,
// Create will return the existing entry's handle as the first return value, ErrKeyExists as the second return value.
func (c *index) Create(sctx sessionctx.Context, txn kv.Transaction, indexedValues []types.Datum, h kv.Handle, handleRestoreData []types.Datum, opts ...table.CreateIdxOptFunc) (kv.Handle, error) {
if c.Meta().Unique {
txn.CacheTableInfo(c.phyTblID, c.tblInfo)
}
var opt table.CreateIdxOpt
for _, fn := range opts {
fn(&opt)
}
vars := sctx.GetSessionVars()
writeBufs := vars.GetWriteStmtBufs()
skipCheck := vars.StmtCtx.BatchCheck
key, distinct, err := c.GenIndexKey(vars.StmtCtx, indexedValues, h, writeBufs.IndexKeyBuf)
if err != nil {
return nil, err
}
var (
tempKey []byte
keyVer byte
keyIsRewritten bool
)
if !opt.FromBackFill {
key, tempKey, keyVer = genTempIdxKeyByState(c.idxInfo, key)
if keyVer == TempIndexKeyTypeBackfill {
key, tempKey = tempKey, nil
keyIsRewritten = true
}
}
ctx := opt.Ctx
if opt.Untouched {
txn, err1 := sctx.Txn(true)
if err1 != nil {
return nil, err1
}
// If the index kv was untouched(unchanged), and the key/value already exists in mem-buffer,
// should not overwrite the key with un-commit flag.
// So if the key exists, just do nothing and return.
v, err := txn.GetMemBuffer().Get(ctx, key)
if err == nil {
if len(v) != 0 {
return nil, nil
}
// The key is marked as deleted in the memory buffer, as the existence check is done lazily
// for optimistic transactions by default. The "untouched" key could still exist in the store,
// it's needed to commit this key to do the existence check so unset the untouched flag.
if !txn.IsPessimistic() {
keyFlags, err := txn.GetMemBuffer().GetFlags(key)
if err != nil {
return nil, err
}
if keyFlags.HasPresumeKeyNotExists() {
opt.Untouched = false
}
}
}
}
// save the key buffer to reuse.
writeBufs.IndexKeyBuf = key
c.initNeedRestoreData.Do(func() {
c.needRestoredData = NeedRestoredData(c.idxInfo.Columns, c.tblInfo.Columns)
})
idxVal, err := tablecodec.GenIndexValuePortal(sctx.GetSessionVars().StmtCtx, c.tblInfo, c.idxInfo, c.needRestoredData, distinct, opt.Untouched, indexedValues, h, c.phyTblID, handleRestoreData)
if err != nil {
return nil, err
}
opt.IgnoreAssertion = opt.IgnoreAssertion || c.idxInfo.State != model.StatePublic
if !distinct || skipCheck || opt.Untouched {
if keyIsRewritten {
idxVal = append(idxVal, keyVer)
}
err = txn.GetMemBuffer().Set(key, idxVal)
if err != nil {
return nil, err
}
if len(tempKey) > 0 {
idxVal = append(idxVal, keyVer)
err = txn.GetMemBuffer().Set(tempKey, idxVal)
if err != nil {
return nil, err
}
}
if !opt.IgnoreAssertion && (!opt.Untouched) {
if sctx.GetSessionVars().LazyCheckKeyNotExists() && !txn.IsPessimistic() {
err = txn.SetAssertion(key, kv.SetAssertUnknown)
} else {
err = txn.SetAssertion(key, kv.SetAssertNotExist)
}
}
return nil, err
}
if ctx != nil {
if span := opentracing.SpanFromContext(ctx); span != nil && span.Tracer() != nil {
span1 := span.Tracer().StartSpan("index.Create", opentracing.ChildOf(span.Context()))
defer span1.Finish()
ctx = opentracing.ContextWithSpan(ctx, span1)
}
} else {
ctx = context.TODO()
}
var value []byte
if c.tblInfo.TempTableType != model.TempTableNone {
// Always check key for temporary table because it does not write to TiKV
value, err = txn.Get(ctx, key)
} else if sctx.GetSessionVars().LazyCheckKeyNotExists() {
value, err = txn.GetMemBuffer().Get(ctx, key)
} else {
value, err = txn.Get(ctx, key)
}
if err != nil && !kv.IsErrNotFound(err) {
return nil, err
}
if err != nil || len(value) == 0 {
lazyCheck := sctx.GetSessionVars().LazyCheckKeyNotExists() && err != nil
if keyIsRewritten {
idxVal = append(idxVal, keyVer)
}
if lazyCheck {
flags := []kv.FlagsOp{kv.SetPresumeKeyNotExists}
if !vars.ConstraintCheckInPlacePessimistic && vars.TxnCtx.IsPessimistic && vars.InTxn() {
flags = append(flags, kv.SetNeedConstraintCheckInPrewrite)
}
err = txn.GetMemBuffer().SetWithFlags(key, idxVal, flags...)
} else {
err = txn.GetMemBuffer().Set(key, idxVal)
}
if err != nil {
return nil, err
}
if len(tempKey) > 0 {
idxVal = append(idxVal, keyVer)
if lazyCheck {
err = txn.GetMemBuffer().SetWithFlags(tempKey, idxVal, kv.SetPresumeKeyNotExists)
} else {
err = txn.GetMemBuffer().Set(tempKey, idxVal)
}
if err != nil {
return nil, err
}
}
if opt.IgnoreAssertion {
return nil, nil
}
if lazyCheck && !txn.IsPessimistic() {
err = txn.SetAssertion(key, kv.SetAssertUnknown)
} else {
err = txn.SetAssertion(key, kv.SetAssertNotExist)
}
return nil, err
}
handle, err := tablecodec.DecodeHandleInUniqueIndexValue(value, c.tblInfo.IsCommonHandle)
if err != nil {
return nil, err
}
return handle, kv.ErrKeyExists
}
var (
// DeleteMarker is a marker that the key is deleted.
DeleteMarker = []byte("delete")
// DeleteMarkerUnique is a marker that the unique index key is deleted.
DeleteMarkerUnique = []byte("deleteu")
)
// Delete removes the entry for handle h and indexedValues from KV index.
func (c *index) Delete(sc *stmtctx.StatementContext, txn kv.Transaction, indexedValues []types.Datum, h kv.Handle) error {
key, distinct, err := c.GenIndexKey(sc, indexedValues, h, nil)
if err != nil {
return err
}
key, tempKey, tempKeyVer := genTempIdxKeyByState(c.idxInfo, key)
if distinct {
if len(key) > 0 {
err = txn.GetMemBuffer().DeleteWithFlags(key, kv.SetNeedLocked)
if err != nil {
return err
}
}
if len(tempKey) > 0 {
val := make([]byte, 0, len(DeleteMarkerUnique)+1)
val = append(val, DeleteMarkerUnique...)
val = append(val, tempKeyVer)
err = txn.GetMemBuffer().Set(tempKey, val)
if err != nil {
return err
}
}
} else {
if len(key) > 0 {
err = txn.GetMemBuffer().Delete(key)
if err != nil {
return err
}
}
if len(tempKey) > 0 {
val := make([]byte, 0, len(DeleteMarker)+1)
val = append(val, DeleteMarker...)
val = append(val, tempKeyVer)
err = txn.GetMemBuffer().Set(tempKey, val)
if err != nil {
return err
}
}
}
if c.idxInfo.State == model.StatePublic {
// If the index is in public state, delete this index means it must exists.
err = txn.SetAssertion(key, kv.SetAssertExist)
}
return err
}
const (
// TempIndexKeyTypeNone means the key is not a temporary index key.
TempIndexKeyTypeNone byte = 0
// TempIndexKeyTypeBackfill indicates this value is written in the backfill stage.
TempIndexKeyTypeBackfill byte = 'b'
// TempIndexKeyTypeMerge indicates this value is written in the merge stage.
TempIndexKeyTypeMerge byte = 'm'
)
// genTempIdxKeyByState is used to get the key version and the temporary key.
// The tempKeyVer means the temp index key/value version.
func genTempIdxKeyByState(indexInfo *model.IndexInfo, indexKey kv.Key) (key, tempKey kv.Key, tempKeyVer byte) {
if indexInfo.State != model.StatePublic {
switch indexInfo.BackfillState {
case model.BackfillStateInapplicable:
return indexKey, nil, TempIndexKeyTypeNone
case model.BackfillStateRunning:
// Write to the temporary index.
tablecodec.IndexKey2TempIndexKey(indexInfo.ID, indexKey)
return nil, indexKey, TempIndexKeyTypeBackfill
case model.BackfillStateReadyToMerge, model.BackfillStateMerging:
// Double write
tmp := make([]byte, len(indexKey))
copy(tmp, indexKey)
tablecodec.IndexKey2TempIndexKey(indexInfo.ID, tmp)
return indexKey, tmp, TempIndexKeyTypeMerge
}
}
return indexKey, nil, TempIndexKeyTypeNone
}
func (c *index) Exist(sc *stmtctx.StatementContext, txn kv.Transaction, indexedValues []types.Datum, h kv.Handle) (bool, kv.Handle, error) {
key, distinct, err := c.GenIndexKey(sc, indexedValues, h, nil)
if err != nil {
return false, nil, err
}
value, err := txn.Get(context.TODO(), key)
if kv.IsErrNotFound(err) {
return false, nil, nil
}
if err != nil {
return false, nil, err
}
// For distinct index, the value of key is handle.
if distinct {
var handle kv.Handle
handle, err := tablecodec.DecodeHandleInUniqueIndexValue(value, c.tblInfo.IsCommonHandle)
if err != nil {
return false, nil, err
}
if !handle.Equal(h) {
return true, handle, kv.ErrKeyExists
}
return true, handle, nil
}
return true, h, nil
}
func (c *index) FetchValues(r []types.Datum, vals []types.Datum) ([]types.Datum, error) {
needLength := len(c.idxInfo.Columns)
if vals == nil || cap(vals) < needLength {
vals = make([]types.Datum, needLength)
}
vals = vals[:needLength]
for i, ic := range c.idxInfo.Columns {
if ic.Offset < 0 || ic.Offset >= len(r) {
return nil, table.ErrIndexOutBound.GenWithStackByArgs(ic.Name, ic.Offset, r)
}
vals[i] = r[ic.Offset]
}
return vals, nil
}
// FindChangingCol finds the changing column in idxInfo.
func FindChangingCol(cols []*table.Column, idxInfo *model.IndexInfo) *table.Column {
for _, ic := range idxInfo.Columns {
if col := cols[ic.Offset]; col.ChangeStateInfo != nil {
return col
}
}
return nil
}
// IsIndexWritable check whether the index is writable.
func IsIndexWritable(idx table.Index) bool {
s := idx.Meta().State
if s != model.StateDeleteOnly && s != model.StateDeleteReorganization {
return true
}
return false
}
// BuildRowcodecColInfoForIndexColumns builds []rowcodec.ColInfo for the given index.
// The result can be used for decoding index key-values.
func BuildRowcodecColInfoForIndexColumns(idxInfo *model.IndexInfo, tblInfo *model.TableInfo) []rowcodec.ColInfo {
colInfo := make([]rowcodec.ColInfo, 0, len(idxInfo.Columns))
for _, idxCol := range idxInfo.Columns {
col := tblInfo.Columns[idxCol.Offset]
colInfo = append(colInfo, rowcodec.ColInfo{
ID: col.ID,
IsPKHandle: tblInfo.PKIsHandle && mysql.HasPriKeyFlag(col.GetFlag()),
Ft: rowcodec.FieldTypeFromModelColumn(col),
})
}
return colInfo
}
// BuildFieldTypesForIndexColumns builds the index columns field types.
func BuildFieldTypesForIndexColumns(idxInfo *model.IndexInfo, tblInfo *model.TableInfo) []*types.FieldType {
tps := make([]*types.FieldType, 0, len(idxInfo.Columns))
for _, idxCol := range idxInfo.Columns {
col := tblInfo.Columns[idxCol.Offset]
tps = append(tps, rowcodec.FieldTypeFromModelColumn(col))
}
return tps
}
// TryAppendCommonHandleRowcodecColInfos tries to append common handle columns to `colInfo`.
func TryAppendCommonHandleRowcodecColInfos(colInfo []rowcodec.ColInfo, tblInfo *model.TableInfo) []rowcodec.ColInfo {
if !tblInfo.IsCommonHandle || tblInfo.CommonHandleVersion == 0 {
return colInfo
}
if pkIdx := FindPrimaryIndex(tblInfo); pkIdx != nil {
for _, idxCol := range pkIdx.Columns {
col := tblInfo.Columns[idxCol.Offset]
colInfo = append(colInfo, rowcodec.ColInfo{
ID: col.ID,
Ft: rowcodec.FieldTypeFromModelColumn(col),
})
}
}
return colInfo
}
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