118 lines
3.6 KiB
Go
118 lines
3.6 KiB
Go
// 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"
|
|
"sync/atomic"
|
|
|
|
"github.com/juju/errors"
|
|
"github.com/ngaut/log"
|
|
"github.com/pingcap/tidb/context"
|
|
"github.com/pingcap/tidb/ddl"
|
|
"github.com/pingcap/tidb/infoschema"
|
|
"github.com/pingcap/tidb/model"
|
|
"github.com/pingcap/tidb/util/sqlexec"
|
|
)
|
|
|
|
type statsCache map[int64]*Table
|
|
|
|
// Handle can update stats info periodically.
|
|
type Handle struct {
|
|
ctx context.Context
|
|
lastVersion uint64
|
|
statsCache atomic.Value
|
|
// ddlEventCh is a channel to notify a ddl operation has happened. It is sent only by owner and read by stats handle.
|
|
ddlEventCh chan *ddl.Event
|
|
}
|
|
|
|
// Clear the statsCache, only for test.
|
|
func (h *Handle) Clear() {
|
|
h.statsCache.Store(statsCache{})
|
|
h.lastVersion = 0
|
|
}
|
|
|
|
// NewHandle creates a Handle for update stats.
|
|
func NewHandle(ctx context.Context) *Handle {
|
|
handle := &Handle{
|
|
ctx: ctx,
|
|
ddlEventCh: make(chan *ddl.Event, 100),
|
|
}
|
|
handle.statsCache.Store(statsCache{})
|
|
return handle
|
|
}
|
|
|
|
// Update reads stats meta from store and updates the stats map.
|
|
func (h *Handle) Update(is infoschema.InfoSchema) error {
|
|
sql := fmt.Sprintf("SELECT version, table_id, count from mysql.stats_meta where version > %d order by version", h.lastVersion)
|
|
rows, _, err := h.ctx.(sqlexec.RestrictedSQLExecutor).ExecRestrictedSQL(h.ctx, sql)
|
|
if err != nil {
|
|
return errors.Trace(err)
|
|
}
|
|
tables := make([]*Table, 0, len(rows))
|
|
for _, row := range rows {
|
|
version, tableID, count := row.Data[0].GetUint64(), row.Data[1].GetInt64(), row.Data[2].GetInt64()
|
|
table, ok := is.TableByID(tableID)
|
|
if !ok {
|
|
log.Debugf("Unknown table ID %d in stats meta table, maybe it has been dropped", tableID)
|
|
continue
|
|
}
|
|
tableInfo := table.Meta()
|
|
tbl, err := h.TableStatsFromStorage(h.ctx, tableInfo, count)
|
|
// Error is not nil may mean that there are some ddl changes on this table, we will not update it.
|
|
if err != nil {
|
|
log.Errorf("Error occurred when read table stats for table id %d. The error message is %s.", tableID, err.Error())
|
|
continue
|
|
}
|
|
tables = append(tables, tbl)
|
|
h.lastVersion = version
|
|
}
|
|
h.UpdateTableStats(tables)
|
|
return nil
|
|
}
|
|
|
|
// GetTableStats retrieves the statistics table from cache, and the cache will be updated by a goroutine.
|
|
func (h *Handle) GetTableStats(tblInfo *model.TableInfo) *Table {
|
|
tbl, ok := h.statsCache.Load().(statsCache)[tblInfo.ID]
|
|
if !ok || tbl == nil {
|
|
return PseudoTable(tblInfo)
|
|
}
|
|
// Here we check the TableInfo because there may be some ddl changes in the duration period.
|
|
// Also, we rely on the fact that TableInfo will not be same if and only if there are ddl changes.
|
|
// TODO: Remove this check.
|
|
if tblInfo == tbl.Info {
|
|
return tbl
|
|
}
|
|
return PseudoTable(tblInfo)
|
|
}
|
|
|
|
func (h *Handle) copyFromOldCache() statsCache {
|
|
newCache := statsCache{}
|
|
oldCache := h.statsCache.Load().(statsCache)
|
|
for k, v := range oldCache {
|
|
newCache[k] = v
|
|
}
|
|
return newCache
|
|
}
|
|
|
|
// UpdateTableStats updates the statistics table cache using copy on write.
|
|
func (h *Handle) UpdateTableStats(tables []*Table) {
|
|
newCache := h.copyFromOldCache()
|
|
for _, tbl := range tables {
|
|
id := tbl.Info.ID
|
|
newCache[id] = tbl
|
|
}
|
|
h.statsCache.Store(newCache)
|
|
}
|