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set.go
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set.go
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// 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package executor
import (
"fmt"
"strings"
"time"
log "github.com/Sirupsen/logrus"
"github.com/juju/errors"
"github.com/pingcap/tidb/ast"
"github.com/pingcap/tidb/context"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/kv"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/sessionctx/variable"
"github.com/pingcap/tidb/sessionctx/varsutil"
"github.com/pingcap/tidb/terror"
"github.com/pingcap/tidb/util/charset"
"github.com/pingcap/tidb/util/sqlexec"
"github.com/pingcap/tidb/util/types"
)
// SetExecutor executes set statement.
type SetExecutor struct {
baseExecutor
vars []*expression.VarAssignment
done bool
}
// Next implements the Executor Next interface.
func (e *SetExecutor) Next() (Row, error) {
if e.done {
return nil, nil
}
err := e.executeSet()
if err != nil {
return nil, errors.Trace(err)
}
e.done = true
return nil, nil
}
func (e *SetExecutor) executeSet() error {
sessionVars := e.ctx.GetSessionVars()
for _, v := range e.vars {
// Variable is case insensitive, we use lower case.
if v.Name == ast.SetNames {
// This is set charset stmt.
cs := v.Expr.(*expression.Constant).Value.GetString()
var co string
if v.ExtendValue != nil {
co = v.ExtendValue.Value.GetString()
}
err := e.setCharset(cs, co)
if err != nil {
return errors.Trace(err)
}
continue
}
name := strings.ToLower(v.Name)
if !v.IsSystem {
// Set user variable.
value, err := v.Expr.Eval(nil)
if err != nil {
return errors.Trace(err)
}
if value.IsNull() {
delete(sessionVars.Users, name)
} else {
svalue, err1 := value.ToString()
if err1 != nil {
return errors.Trace(err1)
}
sessionVars.Users[name] = fmt.Sprintf("%v", svalue)
}
continue
}
// Set system variable
sysVar := variable.GetSysVar(name)
if sysVar == nil {
return variable.UnknownSystemVar.GenByArgs(name)
}
if sysVar.Scope == variable.ScopeNone {
return errors.Errorf("Variable '%s' is a read only variable", name)
}
if v.IsGlobal {
// Set global scope system variable.
if sysVar.Scope&variable.ScopeGlobal == 0 {
return errors.Errorf("Variable '%s' is a SESSION variable and can't be used with SET GLOBAL", name)
}
value, err := e.getVarValue(v, sysVar)
if err != nil {
return errors.Trace(err)
}
if value.IsNull() {
value.SetString("")
}
svalue, err := value.ToString()
if err != nil {
return errors.Trace(err)
}
err = sessionVars.GlobalVarsAccessor.SetGlobalSysVar(name, svalue)
if err != nil {
return errors.Trace(err)
}
} else {
// Set session scope system variable.
if sysVar.Scope&variable.ScopeSession == 0 {
return errors.Errorf("Variable '%s' is a GLOBAL variable and should be set with SET GLOBAL", name)
}
value, err := e.getVarValue(v, nil)
if err != nil {
return errors.Trace(err)
}
oldSnapshotTS := sessionVars.SnapshotTS
err = varsutil.SetSessionSystemVar(sessionVars, name, value)
if err != nil {
return errors.Trace(err)
}
newSnapshotIsSet := sessionVars.SnapshotTS > 0 && sessionVars.SnapshotTS != oldSnapshotTS
if newSnapshotIsSet {
err = validateSnapshot(e.ctx, sessionVars.SnapshotTS)
if err != nil {
sessionVars.SnapshotTS = oldSnapshotTS
return errors.Trace(err)
}
}
err = e.loadSnapshotInfoSchemaIfNeeded(name)
if err != nil {
sessionVars.SnapshotTS = oldSnapshotTS
return errors.Trace(err)
}
var valStr string
if value.IsNull() {
valStr = "NULL"
} else {
var err error
valStr, err = value.ToString()
terror.Log(errors.Trace(err))
}
log.Infof("[%d] set system variable %s = %s", sessionVars.ConnectionID, name, valStr)
}
if name == variable.TxnIsolation {
if sessionVars.Systems[variable.TxnIsolation] == ast.ReadCommitted {
e.ctx.Txn().SetOption(kv.IsolationLevel, kv.RC)
}
}
}
return nil
}
// validateSnapshot checks that the newly set snapshot time is after GC safe point time.
func validateSnapshot(ctx context.Context, snapshotTS uint64) error {
sql := "SELECT variable_value FROM mysql.tidb WHERE variable_name = 'tikv_gc_safe_point'"
rows, _, err := ctx.(sqlexec.RestrictedSQLExecutor).ExecRestrictedSQL(ctx, sql)
if err != nil {
return errors.Trace(err)
}
if len(rows) != 1 {
return errors.New("can not get 'tikv_gc_safe_point'")
}
safePointString := rows[0].Data[0].GetString()
const gcTimeFormat = "20060102-15:04:05 -0700 MST"
safePointTime, err := time.Parse(gcTimeFormat, safePointString)
if err != nil {
return errors.Trace(err)
}
safePointTS := varsutil.GoTimeToTS(safePointTime)
if safePointTS > snapshotTS {
return variable.ErrSnapshotTooOld.GenByArgs(safePointString)
}
return nil
}
func (e *SetExecutor) setCharset(cs, co string) error {
var err error
if len(co) == 0 {
co, err = charset.GetDefaultCollation(cs)
if err != nil {
return errors.Trace(err)
}
}
sessionVars := e.ctx.GetSessionVars()
for _, v := range variable.SetNamesVariables {
sessionVars.Systems[v] = cs
}
sessionVars.Systems[variable.CollationConnection] = co
return nil
}
func (e *SetExecutor) getVarValue(v *expression.VarAssignment, sysVar *variable.SysVar) (value types.Datum, err error) {
if v.IsDefault {
// To set a SESSION variable to the GLOBAL value or a GLOBAL value
// to the compiled-in MySQL default value, use the DEFAULT keyword.
// See http://dev.mysql.com/doc/refman/5.7/en/set-statement.html
if sysVar != nil {
value = types.NewStringDatum(sysVar.Value)
} else {
s, err1 := varsutil.GetGlobalSystemVar(e.ctx.GetSessionVars(), v.Name)
if err1 != nil {
return value, errors.Trace(err1)
}
value = types.NewStringDatum(s)
}
return
}
value, err = v.Expr.Eval(nil)
return value, errors.Trace(err)
}
func (e *SetExecutor) loadSnapshotInfoSchemaIfNeeded(name string) error {
if name != variable.TiDBSnapshot {
return nil
}
vars := e.ctx.GetSessionVars()
if vars.SnapshotTS == 0 {
vars.SnapshotInfoschema = nil
return nil
}
log.Infof("[%d] loadSnapshotInfoSchema, SnapshotTS:%d", vars.ConnectionID, vars.SnapshotTS)
dom := sessionctx.GetDomain(e.ctx)
snapInfo, err := dom.GetSnapshotInfoSchema(vars.SnapshotTS)
if err != nil {
return errors.Trace(err)
}
vars.SnapshotInfoschema = snapInfo
return nil
}