tidb util 源码
tidb util 代码
文件路径：/parser/ast/util.go
// 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 ast
import "math"
// UnspecifiedSize is unspecified size.
const (
UnspecifiedSize = math.MaxUint64
)
// IsReadOnly checks whether the input ast is readOnly.
func IsReadOnly(node Node) bool {
switch st := node.(type) {
case *SelectStmt:
if st.LockInfo != nil {
switch st.LockInfo.LockType {
case SelectLockForUpdate, SelectLockForUpdateNoWait, SelectLockForUpdateWaitN:
return false
}
}
checker := readOnlyChecker{
readOnly: true,
}
node.Accept(&checker)
return checker.readOnly
case *ExplainStmt:
return !st.Analyze || IsReadOnly(st.Stmt)
case *DoStmt, *ShowStmt:
return true
case *SetOprStmt:
for _, sel := range node.(*SetOprStmt).SelectList.Selects {
if !IsReadOnly(sel) {
return false
}
}
return true
case *SetOprSelectList:
for _, sel := range node.(*SetOprSelectList).Selects {
if !IsReadOnly(sel) {
return false
}
}
return true
case *AdminStmt:
switch node.(*AdminStmt).Tp {
case AdminShowTelemetry, AdminShowDDL, AdminShowDDLJobs, AdminShowSlow,
AdminCaptureBindings, AdminShowNextRowID, AdminShowDDLJobQueries,
AdminShowDDLJobQueriesWithRange:
return true
default:
return false
}
default:
return false
}
}
// readOnlyChecker checks whether a query's ast is readonly, if it satisfied
// 1. selectstmt;
// 2. need not to set var;
// it is readonly statement.
type readOnlyChecker struct {
readOnly bool
}
// Enter implements Visitor interface.
func (checker *readOnlyChecker) Enter(in Node) (out Node, skipChildren bool) {
if node, ok := in.(*VariableExpr); ok {
// like func rewriteVariable(), this stands for SetVar.
if !node.IsSystem && node.Value != nil {
checker.readOnly = false
return in, true
}
}
return in, false
}
// Leave implements Visitor interface.
func (checker *readOnlyChecker) Leave(in Node) (out Node, ok bool) {
return in, checker.readOnly
}
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