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// Copyright 2018 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 domain
import (
"sync"
"time"
"github.com/pingcap/parser/ast"
"github.com/pingcap/tidb/sessionctx/variable"
"github.com/pingcap/tidb/util/chunk"
"github.com/pingcap/tidb/util/stmtsummary"
)
// GlobalVariableCache caches global variables.
type GlobalVariableCache struct {
sync.RWMutex
lastModify time.Time
rows []chunk.Row
fields []*ast.ResultField
// Unit test may like to disable it.
disable bool
}
const globalVariableCacheExpiry time.Duration = 2 * time.Second
// Update updates the global variable cache.
func (gvc *GlobalVariableCache) Update(rows []chunk.Row, fields []*ast.ResultField) {
gvc.Lock()
gvc.lastModify = time.Now()
gvc.rows = rows
gvc.fields = fields
gvc.Unlock()
checkEnableServerGlobalVar(rows)
}
// Get gets the global variables from cache.
func (gvc *GlobalVariableCache) Get() (succ bool, rows []chunk.Row, fields []*ast.ResultField) {
gvc.RLock()
defer gvc.RUnlock()
if time.Since(gvc.lastModify) < globalVariableCacheExpiry {
succ, rows, fields = !gvc.disable, gvc.rows, gvc.fields
return
}
succ = false
return
}
// Disable disables the global variabe cache, used in test only.
func (gvc *GlobalVariableCache) Disable() {
gvc.Lock()
defer gvc.Unlock()
gvc.disable = true
return
}
// checkEnableServerGlobalVar processes variables that acts in server and global level.
func checkEnableServerGlobalVar(rows []chunk.Row) {
for _, row := range rows {
switch row.GetString(0) {
case variable.TiDBEnableStmtSummary:
sVal := ""
if !row.IsNull(1) {
sVal = row.GetString(1)
}
stmtsummary.StmtSummaryByDigestMap.SetEnabled(sVal, false)
case variable.TiDBCapturePlanBaseline:
sVal := ""
if !row.IsNull(1) {
sVal = row.GetString(1)
}
variable.CapturePlanBaseline.Set(sVal, false)
}
}
}
// GetGlobalVarsCache gets the global variable cache.
func (do *Domain) GetGlobalVarsCache() *GlobalVariableCache {
return &do.gvc
}
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