96 lines
2.3 KiB
Go
96 lines
2.3 KiB
Go
// Copyright 2018 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ast
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import "math"
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// UnspecifiedSize is unspecified size.
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const (
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UnspecifiedSize = math.MaxUint64
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)
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// IsReadOnly checks whether the input ast is readOnly.
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func IsReadOnly(node Node) bool {
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switch st := node.(type) {
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case *SelectStmt:
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if st.LockInfo != nil {
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switch st.LockInfo.LockType {
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case SelectLockForUpdate, SelectLockForUpdateNoWait, SelectLockForUpdateWaitN:
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return false
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}
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}
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checker := readOnlyChecker{
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readOnly: true,
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}
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node.Accept(&checker)
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return checker.readOnly
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case *ExplainStmt:
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return !st.Analyze || IsReadOnly(st.Stmt)
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case *DoStmt, *ShowStmt:
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return true
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case *SetOprStmt:
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for _, sel := range node.(*SetOprStmt).SelectList.Selects {
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if !IsReadOnly(sel) {
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return false
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}
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}
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return true
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case *SetOprSelectList:
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for _, sel := range node.(*SetOprSelectList).Selects {
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if !IsReadOnly(sel) {
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return false
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}
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}
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return true
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case *AdminStmt:
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switch node.(*AdminStmt).Tp {
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case AdminShowDDL, AdminShowDDLJobs, AdminShowSlow,
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AdminCaptureBindings, AdminShowNextRowID, AdminShowDDLJobQueries,
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AdminShowDDLJobQueriesWithRange:
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return true
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default:
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return false
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}
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default:
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return false
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}
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}
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// readOnlyChecker checks whether a query's ast is readonly, if it satisfied
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// 1. selectstmt;
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// 2. need not to set var;
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// it is readonly statement.
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type readOnlyChecker struct {
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readOnly bool
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}
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// Enter implements Visitor interface.
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func (checker *readOnlyChecker) Enter(in Node) (out Node, skipChildren bool) {
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if node, ok := in.(*VariableExpr); ok {
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// like func rewriteVariable(), this stands for SetVar.
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if !node.IsSystem && node.Value != nil {
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checker.readOnly = false
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return in, true
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}
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}
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return in, false
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}
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// Leave implements Visitor interface.
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func (checker *readOnlyChecker) Leave(in Node) (out Node, ok bool) {
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return in, checker.readOnly
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}
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