/
statscache.go
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/
statscache.go
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// Copyright 2022 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 handle
import (
"github.com/wuhuizuo/tidb6/config"
"github.com/wuhuizuo/tidb6/sessionctx/variable"
"github.com/wuhuizuo/tidb6/statistics"
)
// statsCacheInner is the interface to manage the statsCache, it can be implemented by map, lru cache or other structures.
type statsCacheInner interface {
GetByQuery(int64) (*statistics.Table, bool)
Get(int64) (*statistics.Table, bool)
PutByQuery(int64, *statistics.Table)
Put(int64, *statistics.Table)
Del(int64)
Cost() int64
Keys() []int64
Values() []*statistics.Table
Map() map[int64]*statistics.Table
Len() int
FreshMemUsage()
Copy() statsCacheInner
SetCapacity(int64)
EnableQuota() bool
// Front returns the front element's owner tableID, only used for test
Front() int64
}
func newStatsCache() statsCache {
enableQuota := config.GetGlobalConfig().Performance.EnableStatsCacheMemQuota
if enableQuota {
capacity := variable.StatsCacheMemQuota.Load()
return statsCache{
statsCacheInner: newStatsLruCache(capacity),
}
}
return statsCache{
statsCacheInner: &mapCache{
tables: make(map[int64]cacheItem),
memUsage: 0,
},
}
}
// statsCache caches the tables in memory for Handle.
type statsCache struct {
// version is the latest version of cache. It is bumped when new records of `mysql.stats_meta` are loaded into cache.
version uint64
// minorVersion is to differentiate the cache when the version is unchanged while the cache contents are
// modified indeed. This can happen when we load extra column histograms into cache, or when we modify the cache with
// statistics feedbacks, etc. We cannot bump the version then because no new changes of `mysql.stats_meta` are loaded,
// while the override of statsCache is in a copy-on-write way, to make sure the statsCache is unchanged by others during the
// the interval of 'copy' and 'write', every 'write' should bump / check this minorVersion if the version keeps
// unchanged.
// This bump / check logic is encapsulated in `statsCache.update` and `updateStatsCache`, callers don't need to care
// about this minorVersion actually.
minorVersion uint64
statsCacheInner
}
func (sc statsCache) len() int {
return sc.statsCacheInner.Len()
}
func (sc statsCache) copy() statsCache {
newCache := statsCache{
version: sc.version,
minorVersion: sc.minorVersion,
}
newCache.statsCacheInner = sc.statsCacheInner.Copy()
return newCache
}
// update updates the statistics table cache using copy on write.
func (sc statsCache) update(tables []*statistics.Table, deletedIDs []int64, newVersion uint64, opts ...TableStatsOpt) statsCache {
option := &tableStatsOption{}
for _, opt := range opts {
opt(option)
}
newCache := sc.copy()
if newVersion == newCache.version {
newCache.minorVersion += uint64(1)
} else {
newCache.version = newVersion
newCache.minorVersion = uint64(0)
}
for _, tbl := range tables {
id := tbl.PhysicalID
if option.byQuery {
newCache.PutByQuery(id, tbl)
} else {
newCache.Put(id, tbl)
}
}
for _, id := range deletedIDs {
newCache.Del(id)
}
return newCache
}
type cacheItem struct {
key int64
value *statistics.Table
cost int64
}
func (c cacheItem) copy() cacheItem {
return cacheItem{
key: c.key,
value: c.value,
cost: c.cost,
}
}
type mapCache struct {
tables map[int64]cacheItem
memUsage int64
}
// GetByQuery implements statsCacheInner
func (m *mapCache) GetByQuery(k int64) (*statistics.Table, bool) {
return m.Get(k)
}
// Get implements statsCacheInner
func (m *mapCache) Get(k int64) (*statistics.Table, bool) {
v, ok := m.tables[k]
return v.value, ok
}
// PutByQuery implements statsCacheInner
func (m *mapCache) PutByQuery(k int64, v *statistics.Table) {
m.Put(k, v)
}
// Put implements statsCacheInner
func (m *mapCache) Put(k int64, v *statistics.Table) {
item, ok := m.tables[k]
if ok {
oldCost := item.cost
newCost := v.MemoryUsage().TotalMemUsage
item.value = v
item.cost = newCost
m.tables[k] = item
m.memUsage += newCost - oldCost
return
}
cost := v.MemoryUsage().TotalMemUsage
item = cacheItem{
key: k,
value: v,
cost: cost,
}
m.tables[k] = item
m.memUsage += cost
}
// Del implements statsCacheInner
func (m *mapCache) Del(k int64) {
item, ok := m.tables[k]
if !ok {
return
}
delete(m.tables, k)
m.memUsage -= item.cost
}
// Cost implements statsCacheInner
func (m *mapCache) Cost() int64 {
return m.memUsage
}
// Keys implements statsCacheInner
func (m *mapCache) Keys() []int64 {
ks := make([]int64, 0, len(m.tables))
for k := range m.tables {
ks = append(ks, k)
}
return ks
}
// Values implements statsCacheInner
func (m *mapCache) Values() []*statistics.Table {
vs := make([]*statistics.Table, 0, len(m.tables))
for _, v := range m.tables {
vs = append(vs, v.value)
}
return vs
}
// Map implements statsCacheInner
func (m *mapCache) Map() map[int64]*statistics.Table {
t := make(map[int64]*statistics.Table, len(m.tables))
for k, v := range m.tables {
t[k] = v.value
}
return t
}
// Len implements statsCacheInner
func (m *mapCache) Len() int {
return len(m.tables)
}
// FreshMemUsage implements statsCacheInner
func (m *mapCache) FreshMemUsage() {
for _, v := range m.tables {
oldCost := v.cost
newCost := v.value.MemoryUsage().TotalMemUsage
m.memUsage += newCost - oldCost
}
}
// Copy implements statsCacheInner
func (m *mapCache) Copy() statsCacheInner {
newM := &mapCache{
tables: make(map[int64]cacheItem, len(m.tables)),
memUsage: m.memUsage,
}
for k, v := range m.tables {
newM.tables[k] = v.copy()
}
return newM
}
// SetCapacity implements statsCacheInner
func (m *mapCache) SetCapacity(int64) {}
// EnableQuota implements statsCacheInner
func (m *mapCache) EnableQuota() bool {
return false
}
// Front implements statsCacheInner
func (m *mapCache) Front() int64 {
return 0
}