func (n *SelectStmt) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*SelectStmt)
	if n.TableHints != nil && len(n.TableHints) != 0 {
		newHints := make([]*TableOptimizerHint, len(n.TableHints))
		for i, hint := range n.TableHints {
			node, ok := hint.Accept(v)
			if !ok {
				return n, false
			}
			newHints[i] = node.(*TableOptimizerHint)
		}
		n.TableHints = newHints
	}
	if n.From != nil {
		node, ok := n.From.Accept(v)
		if !ok {
			return n, false
		}
		n.From = node.(*TableRefsClause)
	}
	if n.Where != nil {
		node, ok := n.Where.Accept(v)
		if !ok {
			return n, false
		}
		n.Where = node.(ExprNode)
	}
	if n.Fields != nil {
		node, ok := n.Fields.Accept(v)
		if !ok {
			return n, false
		}
		n.Fields = node.(*FieldList)
	}
	if n.GroupBy != nil {
		node, ok := n.GroupBy.Accept(v)
		if !ok {
			return n, false
		}
		n.GroupBy = node.(*GroupByClause)
	}
	if n.Having != nil {
		node, ok := n.Having.Accept(v)
		if !ok {
			return n, false
		}
		n.Having = node.(*HavingClause)
	}
	for i, spec := range n.WindowSpecs {
		node, ok := spec.Accept(v)
		if !ok {
			return n, false
		}
		n.WindowSpecs[i] = *node.(*WindowSpec)
	}
	if n.OrderBy != nil {
		node, ok := n.OrderBy.Accept(v)
		if !ok {
			return n, false
		}
		n.OrderBy = node.(*OrderByClause)
	}
	if n.Limit != nil {
		node, ok := n.Limit.Accept(v)
		if !ok {
			return n, false
		}
		n.Limit = node.(*Limit)
	}
	return v.Leave(n)
}
Accept implements Node Accept interface.
package ast
import (
	"github.com/pingcap/parser/auth"
	"github.com/pingcap/parser/model"
	"github.com/pingcap/parser/mysql"
)
var (
	_ DMLNode = &DeleteStmt{}
	_ DMLNode = &InsertStmt{}
	_ DMLNode = &UnionStmt{}
	_ DMLNode = &UpdateStmt{}
	_ DMLNode = &SelectStmt{}
	_ DMLNode = &ShowStmt{}
	_ DMLNode = &LoadDataStmt{}
	_ Node = &Assignment{}
	_ Node = &ByItem{}
	_ Node = &FieldList{}
	_ Node = &GroupByClause{}
	_ Node = &HavingClause{}
	_ Node = &Join{}
	_ Node = &Limit{}
	_ Node = &OnCondition{}
	_ Node = &OrderByClause{}
	_ Node = &SelectField{}
	_ Node = &TableName{}
	_ Node = &TableRefsClause{}
	_ Node = &TableSource{}
	_ Node = &UnionSelectList{}
	_ Node = &WildCardField{}
	_ Node = &WindowSpec{}
	_ Node = &PartitionByClause{}
	_ Node = &FrameClause{}
	_ Node = &FrameBound{}
)
type JoinType int
const (
	CrossJoin JoinType = iota + 1
	LeftJoin
	RightJoin
)
type Join struct {
	node
	resultSetNode
	Left ResultSetNode
	Right ResultSetNode
	Tp JoinType
	On *OnCondition
	Using []*ColumnName
	NaturalJoin bool
	StraightJoin bool
}
func (n *Join) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*Join)
	node, ok := n.Left.Accept(v)
	if !ok {
		return n, false
	}
	n.Left = node.(ResultSetNode)
	if n.Right != nil {
		node, ok = n.Right.Accept(v)
		if !ok {
			return n, false
		}
		n.Right = node.(ResultSetNode)
	}
	if n.On != nil {
		node, ok = n.On.Accept(v)
		if !ok {
			return n, false
		}
		n.On = node.(*OnCondition)
	}
	return v.Leave(n)
}
type TableName struct {
	node
	resultSetNode
	Schema model.CIStr
	Name   model.CIStr
	DBInfo    *model.DBInfo
	TableInfo *model.TableInfo
	IndexHints []*IndexHint
}
type IndexHintType int
const (
	HintUse    IndexHintType = 1
	HintIgnore IndexHintType = 2
	HintForce  IndexHintType = 3
)
type IndexHintScope int
const (
	HintForScan    IndexHintScope = 1
	HintForJoin    IndexHintScope = 2
	HintForOrderBy IndexHintScope = 3
	HintForGroupBy IndexHintScope = 4
)
type IndexHint struct {
	IndexNames []model.CIStr
	HintType   IndexHintType
	HintScope  IndexHintScope
}
func (n *TableName) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*TableName)
	return v.Leave(n)
}
type DeleteTableList struct {
	node
	Tables []*TableName
}
func (n *DeleteTableList) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*DeleteTableList)
	if n != nil {
		for i, t := range n.Tables {
			node, ok := t.Accept(v)
			if !ok {
				return n, false
			}
			n.Tables[i] = node.(*TableName)
		}
	}
	return v.Leave(n)
}
type OnCondition struct {
	node
	Expr ExprNode
}
func (n *OnCondition) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*OnCondition)
	node, ok := n.Expr.Accept(v)
	if !ok {
		return n, false
	}
	n.Expr = node.(ExprNode)
	return v.Leave(n)
}
type TableSource struct {
	node
	Source ResultSetNode
	AsName model.CIStr
}
func (n *TableSource) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*TableSource)
	node, ok := n.Source.Accept(v)
	if !ok {
		return n, false
	}
	n.Source = node.(ResultSetNode)
	return v.Leave(n)
}
type SelectLockType int
const (
	SelectLockNone SelectLockType = iota
	SelectLockForUpdate
	SelectLockInShareMode
)
func (slt SelectLockType) String() string {
	switch slt {
	case SelectLockNone:
		return "none"
	case SelectLockForUpdate:
		return "for update"
	case SelectLockInShareMode:
		return "in share mode"
	}
	return "unsupported select lock type"
}
type WildCardField struct {
	node
	Table  model.CIStr
	Schema model.CIStr
}
func (n *WildCardField) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*WildCardField)
	return v.Leave(n)
}
type SelectField struct {
	node
	Offset int
	WildCard *WildCardField
	Expr ExprNode
	AsName model.CIStr
	Auxiliary bool
}
func (n *SelectField) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*SelectField)
	if n.Expr != nil {
		node, ok := n.Expr.Accept(v)
		if !ok {
			return n, false
		}
		n.Expr = node.(ExprNode)
	}
	return v.Leave(n)
}
type FieldList struct {
	node
	Fields []*SelectField
}
func (n *FieldList) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*FieldList)
	for i, val := range n.Fields {
		node, ok := val.Accept(v)
		if !ok {
			return n, false
		}
		n.Fields[i] = node.(*SelectField)
	}
	return v.Leave(n)
}
type TableRefsClause struct {
	node
	TableRefs *Join
}
func (n *TableRefsClause) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*TableRefsClause)
	node, ok := n.TableRefs.Accept(v)
	if !ok {
		return n, false
	}
	n.TableRefs = node.(*Join)
	return v.Leave(n)
}
type ByItem struct {
	node
	Expr ExprNode
	Desc bool
}
func (n *ByItem) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*ByItem)
	node, ok := n.Expr.Accept(v)
	if !ok {
		return n, false
	}
	n.Expr = node.(ExprNode)
	return v.Leave(n)
}
type GroupByClause struct {
	node
	Items []*ByItem
}
func (n *GroupByClause) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*GroupByClause)
	for i, val := range n.Items {
		node, ok := val.Accept(v)
		if !ok {
			return n, false
		}
		n.Items[i] = node.(*ByItem)
	}
	return v.Leave(n)
}
type HavingClause struct {
	node
	Expr ExprNode
}
func (n *HavingClause) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*HavingClause)
	node, ok := n.Expr.Accept(v)
	if !ok {
		return n, false
	}
	n.Expr = node.(ExprNode)
	return v.Leave(n)
}
type OrderByClause struct {
	node
	Items    []*ByItem
	ForUnion bool
}
func (n *OrderByClause) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*OrderByClause)
	for i, val := range n.Items {
		node, ok := val.Accept(v)
		if !ok {
			return n, false
		}
		n.Items[i] = node.(*ByItem)
	}
	return v.Leave(n)
}
type SelectStmt struct {
	dmlNode
	resultSetNode
	*SelectStmtOpts
	Distinct bool
	From *TableRefsClause
	Where ExprNode
	Fields *FieldList
	GroupBy *GroupByClause
	Having *HavingClause
	WindowSpecs []WindowSpec
	OrderBy *OrderByClause
	Limit *Limit
	LockTp SelectLockType
	TableHints []*TableOptimizerHint
	IsAfterUnionDistinct bool
	IsInBraces bool
}