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update.go
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// Copyright 2017 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 statistics
import (
"fmt"
"math"
"sync"
"time"
"github.com/juju/errors"
"github.com/pingcap/tidb/infoschema"
"github.com/pingcap/tidb/metrics"
"github.com/pingcap/tidb/model"
"github.com/pingcap/tidb/mysql"
"github.com/pingcap/tidb/sessionctx/variable"
"github.com/pingcap/tidb/store/tikv/oracle"
"github.com/pingcap/tidb/util/sqlexec"
log "github.com/sirupsen/logrus"
"golang.org/x/net/context"
)
type tableDeltaMap map[int64]variable.TableDelta
func (m tableDeltaMap) update(id int64, delta int64, count int64, colSize *map[int64]int64) {
item := m[id]
item.Delta += delta
item.Count += count
if item.ColSize == nil {
item.ColSize = make(map[int64]int64)
}
if colSize != nil {
for key, val := range *colSize {
item.ColSize[key] += val
}
}
m[id] = item
}
func (h *Handle) merge(s *SessionStatsCollector) {
s.Lock()
defer s.Unlock()
for id, item := range s.mapper {
h.globalMap.update(id, item.Delta, item.Count, &item.ColSize)
}
h.feedback = mergeQueryFeedback(h.feedback, s.feedback)
s.mapper = make(tableDeltaMap)
s.feedback = s.feedback[:0]
}
// SessionStatsCollector is a list item that holds the delta mapper. If you want to write or read mapper, you must lock it.
type SessionStatsCollector struct {
sync.Mutex
mapper tableDeltaMap
feedback []*QueryFeedback
prev *SessionStatsCollector
next *SessionStatsCollector
// deleted is set to true when a session is closed. Every time we sweep the list, we will remove the useless collector.
deleted bool
}
// Delete only sets the deleted flag true, it will be deleted from list when DumpStatsDeltaToKV is called.
func (s *SessionStatsCollector) Delete() {
s.Lock()
defer s.Unlock()
s.deleted = true
}
// Update will updates the delta and count for one table id.
func (s *SessionStatsCollector) Update(id int64, delta int64, count int64, colSize *map[int64]int64) {
s.Lock()
defer s.Unlock()
s.mapper.update(id, delta, count, colSize)
}
func mergeQueryFeedback(lq []*QueryFeedback, rq []*QueryFeedback) []*QueryFeedback {
for _, q := range rq {
if len(lq) >= MaxQueryFeedbackCount {
break
}
lq = append(lq, q)
}
return lq
}
// StoreQueryFeedback will merges the feedback into stats collector.
func (s *SessionStatsCollector) StoreQueryFeedback(feedback interface{}) {
q := feedback.(*QueryFeedback)
// TODO: If the error rate is small or actual scan count is small, we do not need to store the feed back.
if !q.valid || q.hist == nil {
return
}
var rate float64
if q.actual == 0 {
if q.expected == 0 {
rate = 0
} else {
rate = 1
}
} else {
rate = math.Abs(float64(q.expected-q.actual) / float64(q.actual))
}
metrics.StatsInaccuracyRate.Observe(rate)
s.Lock()
defer s.Unlock()
if len(s.feedback) >= MaxQueryFeedbackCount {
return
}
s.feedback = append(s.feedback, q)
}
// tryToRemoveFromList will remove this collector from the list if it's deleted flag is set.
func (s *SessionStatsCollector) tryToRemoveFromList() {
s.Lock()
defer s.Unlock()
if !s.deleted {
return
}
next := s.next
prev := s.prev
prev.next = next
if next != nil {
next.prev = prev
}
}
// NewSessionStatsCollector allocates a stats collector for a session.
func (h *Handle) NewSessionStatsCollector() *SessionStatsCollector {
h.listHead.Lock()
defer h.listHead.Unlock()
newCollector := &SessionStatsCollector{
mapper: make(tableDeltaMap),
next: h.listHead.next,
prev: h.listHead,
}
if h.listHead.next != nil {
h.listHead.next.prev = newCollector
}
h.listHead.next = newCollector
return newCollector
}
// DumpStatsDeltaToKV sweeps the whole list and updates the global map. Then we dumps every table that held in map to KV.
func (h *Handle) DumpStatsDeltaToKV() error {
h.listHead.Lock()
for collector := h.listHead.next; collector != nil; collector = collector.next {
collector.tryToRemoveFromList()
h.merge(collector)
}
h.listHead.Unlock()
for id, item := range h.globalMap {
updated, err := h.dumpTableStatCountToKV(id, item)
if err != nil {
return errors.Trace(err)
}
if updated {
h.globalMap.update(id, -item.Delta, -item.Count, nil)
}
if err = h.dumpTableStatColSizeToKV(id, item); err != nil {
return errors.Trace(err)
}
if updated {
delete(h.globalMap, id)
} else {
m := h.globalMap[id]
m.ColSize = nil
h.globalMap[id] = m
}
}
return nil
}
// dumpTableStatDeltaToKV dumps a single delta with some table to KV and updates the version.
func (h *Handle) dumpTableStatCountToKV(id int64, delta variable.TableDelta) (bool, error) {
if delta.Count == 0 {
return true, nil
}
ctx := context.TODO()
_, err := h.ctx.(sqlexec.SQLExecutor).Execute(ctx, "begin")
if err != nil {
return false, errors.Trace(err)
}
var sql string
if delta.Delta < 0 {
sql = fmt.Sprintf("update mysql.stats_meta set version = %d, count = count - %d, modify_count = modify_count + %d where table_id = %d and count >= %d", h.ctx.Txn().StartTS(), -delta.Delta, delta.Count, id, -delta.Delta)
} else {
sql = fmt.Sprintf("update mysql.stats_meta set version = %d, count = count + %d, modify_count = modify_count + %d where table_id = %d", h.ctx.Txn().StartTS(), delta.Delta, delta.Count, id)
}
_, err = h.ctx.(sqlexec.SQLExecutor).Execute(ctx, sql)
if err != nil {
return false, errors.Trace(err)
}
updated := h.ctx.GetSessionVars().StmtCtx.AffectedRows() > 0
_, err = h.ctx.(sqlexec.SQLExecutor).Execute(ctx, "commit")
return updated, errors.Trace(err)
}
func (h *Handle) dumpTableStatColSizeToKV(id int64, delta variable.TableDelta) error {
if len(delta.ColSize) == 0 {
return nil
}
ctx := context.TODO()
_, err := h.ctx.(sqlexec.SQLExecutor).Execute(ctx, "begin")
if err != nil {
return errors.Trace(err)
}
version := h.ctx.Txn().StartTS()
for key, val := range delta.ColSize {
if val == 0 {
continue
}
sql := fmt.Sprintf("update mysql.stats_histograms set version = %d, tot_col_size = tot_col_size + %d where hist_id = %d and table_id = %d and is_index = 0", version, val, key, id)
_, err = h.ctx.(sqlexec.SQLExecutor).Execute(ctx, sql)
if err != nil {
return errors.Trace(err)
}
}
_, err = h.ctx.(sqlexec.SQLExecutor).Execute(ctx, "commit")
return errors.Trace(err)
}
// DumpStatsFeedbackToKV dumps the stats feedback to KV.
func (h *Handle) DumpStatsFeedbackToKV() error {
var err error
var successCount int
for _, fb := range h.feedback {
err = h.dumpFeedbackToKV(fb)
if err != nil {
break
}
successCount++
}
h.feedback = h.feedback[successCount:]
return errors.Trace(err)
}
func (h *Handle) dumpFeedbackToKV(fb *QueryFeedback) error {
vals, err := encodeFeedback(fb)
if err != nil {
log.Debugf("error occurred when encoding feedback, err: ", errors.ErrorStack(err))
return nil
}
var isIndex int64
if fb.hist.tp.Tp == mysql.TypeBlob {
isIndex = 1
} else {
isIndex = 0
}
sql := fmt.Sprintf("insert into mysql.stats_feedback (table_id, hist_id, is_index, feedback) values "+
"(%d, %d, %d, X'%X')", fb.tableID, fb.hist.ID, isIndex, vals)
_, err = h.ctx.(sqlexec.SQLExecutor).Execute(context.TODO(), sql)
if err != nil {
metrics.DumpFeedbackCounter.WithLabelValues(metrics.LblError).Inc()
} else {
metrics.DumpFeedbackCounter.WithLabelValues(metrics.LblOK).Inc()
}
return errors.Trace(err)
}
// HandleUpdateStats update the stats using feedback.
func (h *Handle) HandleUpdateStats(is infoschema.InfoSchema) error {
sql := "select table_id, hist_id, is_index, feedback from mysql.stats_feedback order by table_id, hist_id, is_index"
rows, _, err := h.ctx.(sqlexec.RestrictedSQLExecutor).ExecRestrictedSQL(h.ctx, sql)
if len(rows) == 0 || err != nil {
return errors.Trace(err)
}
tableID, histID, isIndex := int64(-1), int64(-1), int64(-1)
q := &QueryFeedback{}
var (
cms *CMSketch
hist *Histogram
)
for _, row := range rows {
// merge into previous feedback
if row.GetInt64(0) == tableID && row.GetInt64(1) == histID && row.GetInt64(2) == isIndex {
err = decodeFeedback(row.GetBytes(3), q, cms)
if err != nil {
log.Debugf("decode feedback failed, err: %v", errors.ErrorStack(err))
}
continue
}
// dump the stats into kv
if hist != nil {
err = h.dumpStatsUpdateToKV(tableID, int(isIndex), q, hist, cms)
if err != nil {
return errors.Trace(err)
}
}
// initialize new feedback
tableID, histID, isIndex = row.GetInt64(0), row.GetInt64(1), row.GetInt64(2)
table, ok := is.TableByID(tableID)
if !ok {
hist, cms = nil, nil
continue
}
tbl := h.GetTableStats(table.Meta())
if isIndex == 1 {
idx, ok := tbl.Indices[histID]
if !ok {
hist, cms = nil, nil
continue
}
hist = &idx.Histogram
cms = idx.CMSketch.copy()
} else {
col, ok := tbl.Columns[histID]
if !ok {
hist, cms = nil, nil
continue
}
hist = &col.Histogram
cms = nil
}
err = decodeFeedback(row.GetBytes(3), q, cms)
if err != nil {
log.Debugf("decode feedback failed, err: %v", errors.ErrorStack(err))
}
}
// dump the last feedback into kv
err = h.dumpStatsUpdateToKV(tableID, int(isIndex), q, hist, cms)
return errors.Trace(err)
}
func (h *Handle) dumpStatsUpdateToKV(tableID int64, isIndex int, q *QueryFeedback, hist *Histogram, cms *CMSketch) (err error) {
defer func() {
if err != nil {
metrics.UpdateStatsCounter.WithLabelValues(metrics.LblError).Inc()
} else {
metrics.UpdateStatsCounter.WithLabelValues(metrics.LblOK).Inc()
}
}()
hist = UpdateHistogram(hist, q)
err = SaveStatsToStorage(h.ctx, tableID, -1, isIndex, hist, cms)
if err != nil {
return errors.Trace(err)
}
h.ctx.GetSessionVars().BatchDelete = true
sql := fmt.Sprintf("delete from mysql.stats_feedback where table_id = %d and hist_id = %d and is_index = %d", tableID, hist.ID, isIndex)
_, err = h.ctx.(sqlexec.SQLExecutor).Execute(context.TODO(), sql)
q.feedback = q.feedback[:0]
return errors.Trace(err)
}
const (
// StatsOwnerKey is the stats owner path that is saved to etcd.
StatsOwnerKey = "/tidb/stats/owner"
// StatsPrompt is the prompt for stats owner manager.
StatsPrompt = "stats"
)
// AutoAnalyzeMinCnt means if the count of table is less than this value, we needn't do auto analyze.
var AutoAnalyzeMinCnt int64 = 1000
func needAnalyzeTable(tbl *Table, limit time.Duration) bool {
if tbl.ModifyCount == 0 || tbl.Count < AutoAnalyzeMinCnt {
return false
}
t := time.Unix(0, oracle.ExtractPhysical(tbl.Version)*int64(time.Millisecond))
if time.Since(t) < limit {
return false
}
for _, col := range tbl.Columns {
if col.Count > 0 {
return false
}
}
for _, idx := range tbl.Indices {
if idx.Len() > 0 {
return false
}
}
return true
}
// HandleAutoAnalyze analyzes the newly created table or index.
func (h *Handle) HandleAutoAnalyze(is infoschema.InfoSchema) error {
dbs := is.AllSchemaNames()
for _, db := range dbs {
tbls := is.SchemaTables(model.NewCIStr(db))
for _, tbl := range tbls {
tblInfo := tbl.Meta()
statsTbl := h.GetTableStats(tblInfo)
if statsTbl.Pseudo || statsTbl.Count == 0 {
continue
}
tblName := "`" + db + "`.`" + tblInfo.Name.O + "`"
if needAnalyzeTable(statsTbl, 20*h.Lease) {
sql := fmt.Sprintf("analyze table %s", tblName)
log.Infof("[stats] auto analyze table %s now", tblName)
return errors.Trace(h.execAutoAnalyze(sql))
}
for _, idx := range tblInfo.Indices {
if idx.State != model.StatePublic {
continue
}
if _, ok := statsTbl.Indices[idx.ID]; !ok {
sql := fmt.Sprintf("analyze table %s index `%s`", tblName, idx.Name.O)
log.Infof("[stats] auto analyze index `%s` for table %s now", idx.Name.O, tblName)
return errors.Trace(h.execAutoAnalyze(sql))
}
}
}
}
return nil
}
func (h *Handle) execAutoAnalyze(sql string) error {
startTime := time.Now()
_, _, err := h.ctx.(sqlexec.RestrictedSQLExecutor).ExecRestrictedSQL(h.ctx, sql)
metrics.AutoAnalyzeHistogram.Observe(time.Since(startTime).Seconds())
if err != nil {
metrics.AutoAnalyzeCounter.WithLabelValues("failed").Inc()
} else {
metrics.AutoAnalyzeCounter.WithLabelValues("succ").Inc()
}
return errors.Trace(err)
}