/
ast.go
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/
ast.go
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// Copyright 2020 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 parser
import (
"strings"
"github.com/pingcap/tidb/parser/ast"
"github.com/pingcap/tidb/parser/format"
"github.com/pingcap/tidb/util/logutil"
"go.uber.org/zap"
)
// GetDefaultDB checks if all tables in the AST have explicit DBName. If not, return specified DBName.
func GetDefaultDB(sel ast.StmtNode, dbName string) string {
implicitDB := &implicitDatabase{}
sel.Accept(implicitDB)
if implicitDB.hasImplicit {
return dbName
}
return ""
}
type implicitDatabase struct {
hasImplicit bool
}
func (i *implicitDatabase) Enter(in ast.Node) (out ast.Node, skipChildren bool) {
switch x := in.(type) {
case *ast.TableName:
if x.Schema.L == "" {
i.hasImplicit = true
}
return in, true
default:
return in, i.hasImplicit
}
}
func (*implicitDatabase) Leave(in ast.Node) (out ast.Node, ok bool) {
return in, true
}
func findTablePos(s, t string) int {
l := 0
for i := range s {
if s[i] == ' ' || s[i] == ',' {
if len(t) == i-l && strings.Compare(s[l:i], t) == 0 {
return l
}
l = i + 1
}
}
if len(t) == len(s)-l && strings.Compare(s[l:], t) == 0 {
return l
}
return -1
}
// SimpleCases captures simple SQL statements and uses string replacement instead of `restore` to improve performance.
// See https://github.com/pingcap/tidb/issues/22398.
func SimpleCases(node ast.StmtNode, defaultDB, origin string) (s string, ok bool) {
if len(origin) == 0 {
return "", false
}
insert, ok := node.(*ast.InsertStmt)
if !ok {
return "", false
}
if insert.Select != nil || insert.Setlist != nil || insert.OnDuplicate != nil || (insert.TableHints != nil && len(insert.TableHints) != 0) {
return "", false
}
join := insert.Table.TableRefs
if join.Tp != 0 || join.Right != nil {
return "", false
}
ts, ok := join.Left.(*ast.TableSource)
if !ok {
return "", false
}
tn, ok := ts.Source.(*ast.TableName)
if !ok {
return "", false
}
parenPos := strings.Index(origin, "(")
if parenPos == -1 {
return "", false
}
if strings.Contains(origin[:parenPos], ".") {
return origin, true
}
lower := strings.ToLower(origin[:parenPos])
pos := findTablePos(lower, tn.Name.L)
if pos == -1 {
return "", false
}
var builder strings.Builder
builder.WriteString(origin[:pos])
if tn.Schema.String() != "" {
builder.WriteString(tn.Schema.String())
} else {
builder.WriteString(defaultDB)
}
builder.WriteString(".")
builder.WriteString(origin[pos:])
return builder.String(), true
}
// RestoreWithDefaultDB returns restore strings for StmtNode with defaultDB
// This function is customized for SQL bind usage.
func RestoreWithDefaultDB(node ast.StmtNode, defaultDB, origin string) string {
if s, ok := SimpleCases(node, defaultDB, origin); ok {
return s
}
var sb strings.Builder
// Three flags for restore with default DB:
// 1. RestoreStringSingleQuotes specifies to use single quotes to surround the string;
// 2. RestoreSpacesAroundBinaryOperation specifies to add space around binary operation;
// 3. RestoreStringWithoutCharset specifies to not print charset before string;
// 4. RestoreNameBackQuotes specifies to use back quotes to surround the name;
ctx := format.NewRestoreCtx(format.RestoreStringSingleQuotes|format.RestoreSpacesAroundBinaryOperation|format.RestoreStringWithoutCharset|format.RestoreNameBackQuotes, &sb)
ctx.DefaultDB = defaultDB
if err := node.Restore(ctx); err != nil {
logutil.BgLogger().Debug("[sql-bind] restore SQL failed", zap.Error(err))
return ""
}
return sb.String()
}