// Copyright 2015 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 (
	"github.com/pingcap/errors"

	"github.com/pingcap/parser/auth"
	"github.com/pingcap/parser/format"
	"github.com/pingcap/parser/model"
	"github.com/pingcap/parser/mysql"
)

var (
	_ DMLNode = &DeleteStmt{}
	_ DMLNode = &InsertStmt{}
	_ DMLNode = &SetOprStmt{}
	_ DMLNode = &UpdateStmt{}
	_ DMLNode = &SelectStmt{}
	_ DMLNode = &CallStmt{}
	_ DMLNode = &ShowStmt{}
	_ DMLNode = &LoadDataStmt{}
	_ DMLNode = &SplitRegionStmt{}

	_ 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 = &SetOprSelectList{}
	_ Node = &WildCardField{}
	_ Node = &WindowSpec{}
	_ Node = &PartitionByClause{}
	_ Node = &FrameClause{}
	_ Node = &FrameBound{}
)

// JoinType is join type, including cross/left/right/full.
type JoinType int

const (
	// CrossJoin is cross join type.
	CrossJoin JoinType = iota + 1
	// LeftJoin is left Join type.
	LeftJoin
	// RightJoin is right Join type.
	RightJoin
)

// Join represents table join.
type Join struct {
	node

	// Left table can be TableSource or JoinNode.
	Left ResultSetNode
	// Right table can be TableSource or JoinNode or nil.
	Right ResultSetNode
	// Tp represents join type.
	Tp JoinType
	// On represents join on condition.
	On *OnCondition
	// Using represents join using clause.
	Using []*ColumnName
	// NaturalJoin represents join is natural join.
	NaturalJoin bool
	// StraightJoin represents a straight join.
	StraightJoin   bool
	ExplicitParens bool
}

// NewCrossJoin builds a cross join without `on` or `using` clause.
// If the right child is a join tree, we need to handle it differently to make the precedence get right.
// Here is the example: t1 join t2 join t3
//                 JOIN ON t2.a = t3.a
//  t1    join    /    \
//              t2      t3
// (left)         (right)
//
// We can not build it directly to:
//         JOIN
//        /    \
//       t1	   JOIN ON t2.a = t3.a
//             /   \
//            t2    t3
// The precedence would be t1 join (t2 join t3 on t2.a=t3.a), not (t1 join t2) join t3 on t2.a=t3.a
// We need to find the left-most child of the right child, and build a cross join of the left-hand side
// of the left child(t1), and the right hand side with the original left-most child of the right child(t2).
//          JOIN t2.a = t3.a
//         /    \
//       JOIN    t3
//       /  \
//      t1  t2
// Besides, if the right handle side join tree's join type is right join and has explicit parentheses, we need to rewrite it to left join.
// So t1 join t2 right join t3 would be rewrite to t1 join t3 left join t2.
// If not, t1 join (t2 right join t3) would be (t1 join t2) right join t3. After rewrite the right join to left join.
// We get (t1 join t3) left join t2, the semantics is correct.
func NewCrossJoin(left, right ResultSetNode) (n *Join) {
	rj, ok := right.(*Join)
	if !ok || rj.Right == nil {
		return &Join{Left: left, Right: right, Tp: CrossJoin}
	}

	var leftMostLeafFatherOfRight = rj
	// Walk down the right hand side.
	for {
		if leftMostLeafFatherOfRight.Tp == RightJoin && leftMostLeafFatherOfRight.ExplicitParens {
			// Rewrite right join to left join.
			tmpChild := leftMostLeafFatherOfRight.Right
			leftMostLeafFatherOfRight.Right = leftMostLeafFatherOfRight.Left
			leftMostLeafFatherOfRight.Left = tmpChild
			leftMostLeafFatherOfRight.Tp = LeftJoin
		}
		leftChild := leftMostLeafFatherOfRight.Left
		if join, ok := leftChild.(*Join); ok && join.Right != nil {
			leftMostLeafFatherOfRight = join
		} else {
			break
		}
	}

	newCrossJoin := &Join{Left: left, Right: leftMostLeafFatherOfRight.Left, Tp: CrossJoin}
	leftMostLeafFatherOfRight.Left = newCrossJoin
	return rj
}

// Restore implements Node interface.
func (n *Join) Restore(ctx *format.RestoreCtx) error {
	useCommaJoin := false
	_, leftIsJoin := n.Left.(*Join)

	if leftIsJoin && n.Left.(*Join).Right == nil {
		if ts, ok := n.Left.(*Join).Left.(*TableSource); ok {
			switch ts.Source.(type) {
			case *SelectStmt, *SetOprStmt:
				useCommaJoin = true
			}
		}
	}

	if leftIsJoin && !useCommaJoin {
		ctx.WritePlain("(")
	}
	if err := n.Left.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore Join.Left")
	}
	if leftIsJoin && !useCommaJoin {
		ctx.WritePlain(")")
	}
	if n.Right == nil {
		return nil
	}
	if n.NaturalJoin {
		ctx.WriteKeyWord(" NATURAL")
	}
	switch n.Tp {
	case LeftJoin:
		ctx.WriteKeyWord(" LEFT")
	case RightJoin:
		ctx.WriteKeyWord(" RIGHT")
	}
	if n.StraightJoin {
		ctx.WriteKeyWord(" STRAIGHT_JOIN ")
	} else {
		if useCommaJoin {
			ctx.WritePlain(", ")
		} else {
			ctx.WriteKeyWord(" JOIN ")
		}
	}
	_, rightIsJoin := n.Right.(*Join)
	if rightIsJoin {
		ctx.WritePlain("(")
	}
	if err := n.Right.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore Join.Right")
	}
	if rightIsJoin {
		ctx.WritePlain(")")
	}

	if n.On != nil {
		ctx.WritePlain(" ")
		if err := n.On.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore Join.On")
		}
	}
	if len(n.Using) != 0 {
		ctx.WriteKeyWord(" USING ")
		ctx.WritePlain("(")
		for i, v := range n.Using {
			if i != 0 {
				ctx.WritePlain(",")
			}
			if err := v.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore Join.Using")
			}
		}
		ctx.WritePlain(")")
	}

	return nil
}

// Accept implements Node Accept interface.
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)
}

// TableName represents a table name.
type TableName struct {
	node

	Schema model.CIStr
	Name   model.CIStr

	DBInfo    *model.DBInfo
	TableInfo *model.TableInfo

	IndexHints     []*IndexHint
	PartitionNames []model.CIStr
	TableSample    *TableSample
}

// Restore implements Node interface.
func (n *TableName) restoreName(ctx *format.RestoreCtx) {
	if n.Schema.String() != "" {
		ctx.WriteName(n.Schema.String())
		ctx.WritePlain(".")
	} else if ctx.DefaultDB != "" {
		ctx.WriteName(ctx.DefaultDB)
		ctx.WritePlain(".")
	}
	ctx.WriteName(n.Name.String())
}

func (n *TableName) restorePartitions(ctx *format.RestoreCtx) {
	if len(n.PartitionNames) > 0 {
		ctx.WriteKeyWord(" PARTITION")
		ctx.WritePlain("(")
		for i, v := range n.PartitionNames {
			if i != 0 {
				ctx.WritePlain(", ")
			}
			ctx.WriteName(v.String())
		}
		ctx.WritePlain(")")
	}
}

func (n *TableName) restoreIndexHints(ctx *format.RestoreCtx) error {
	for _, value := range n.IndexHints {
		ctx.WritePlain(" ")
		if err := value.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while splicing IndexHints")
		}
	}
	return nil
}

func (n *TableName) Restore(ctx *format.RestoreCtx) error {
	n.restoreName(ctx)
	n.restorePartitions(ctx)
	if err := n.restoreIndexHints(ctx); err != nil {
		return err
	}
	if n.TableSample != nil {
		ctx.WritePlain(" ")
		if err := n.TableSample.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while splicing TableName.TableSample")
		}
	}
	return nil
}

// IndexHintType is the type for index hint use, ignore or force.
type IndexHintType int

// IndexHintUseType values.
const (
	HintUse IndexHintType = iota + 1
	HintIgnore
	HintForce
)

// IndexHintScope is the type for index hint for join, order by or group by.
type IndexHintScope int

// Index hint scopes.
const (
	HintForScan IndexHintScope = iota + 1
	HintForJoin
	HintForOrderBy
	HintForGroupBy
)

// IndexHint represents a hint for optimizer to use/ignore/force for join/order by/group by.
type IndexHint struct {
	IndexNames []model.CIStr
	HintType   IndexHintType
	HintScope  IndexHintScope
}

// IndexHint Restore (The const field uses switch to facilitate understanding)
func (n *IndexHint) Restore(ctx *format.RestoreCtx) error {
	indexHintType := ""
	switch n.HintType {
	case HintUse:
		indexHintType = "USE INDEX"
	case HintIgnore:
		indexHintType = "IGNORE INDEX"
	case HintForce:
		indexHintType = "FORCE INDEX"
	default: // Prevent accidents
		return errors.New("IndexHintType has an error while matching")
	}

	indexHintScope := ""
	switch n.HintScope {
	case HintForScan:
		indexHintScope = ""
	case HintForJoin:
		indexHintScope = " FOR JOIN"
	case HintForOrderBy:
		indexHintScope = " FOR ORDER BY"
	case HintForGroupBy:
		indexHintScope = " FOR GROUP BY"
	default: // Prevent accidents
		return errors.New("IndexHintScope has an error while matching")
	}
	ctx.WriteKeyWord(indexHintType)
	ctx.WriteKeyWord(indexHintScope)
	ctx.WritePlain(" (")
	for i, value := range n.IndexNames {
		if i > 0 {
			ctx.WritePlain(", ")
		}
		ctx.WriteName(value.O)
	}
	ctx.WritePlain(")")

	return nil
}

// Accept implements Node Accept interface.
func (n *TableName) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*TableName)
	if n.TableSample != nil {
		newTs, ok := n.TableSample.Accept(v)
		if !ok {
			return n, false
		}
		n.TableSample = newTs.(*TableSample)
	}
	return v.Leave(n)
}

// DeleteTableList is the tablelist used in delete statement multi-table mode.
type DeleteTableList struct {
	node
	Tables []*TableName
}

// Restore implements Node interface.
func (n *DeleteTableList) Restore(ctx *format.RestoreCtx) error {
	for i, t := range n.Tables {
		if i != 0 {
			ctx.WritePlain(",")
		}
		if err := t.Restore(ctx); err != nil {
			return errors.Annotatef(err, "An error occurred while restore DeleteTableList.Tables[%v]", i)
		}
	}
	return nil
}

// Accept implements Node Accept interface.
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)
}

// OnCondition represents JOIN on condition.
type OnCondition struct {
	node

	Expr ExprNode
}

// Restore implements Node interface.
func (n *OnCondition) Restore(ctx *format.RestoreCtx) error {
	ctx.WriteKeyWord("ON ")
	if err := n.Expr.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore OnCondition.Expr")
	}
	return nil
}

// Accept implements Node Accept interface.
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)
}

// TableSource represents table source with a name.
type TableSource struct {
	node

	// Source is the source of the data, can be a TableName,
	// a SelectStmt, a SetOprStmt, or a JoinNode.
	Source ResultSetNode

	// AsName is the alias name of the table source.
	AsName model.CIStr
}

// Restore implements Node interface.
func (n *TableSource) Restore(ctx *format.RestoreCtx) error {
	needParen := false
	switch n.Source.(type) {
	case *SelectStmt, *SetOprStmt:
		needParen = true
	}

	if tn, tnCase := n.Source.(*TableName); tnCase {
		if needParen {
			ctx.WritePlain("(")
		}

		tn.restoreName(ctx)
		tn.restorePartitions(ctx)

		if asName := n.AsName.String(); asName != "" {
			ctx.WriteKeyWord(" AS ")
			ctx.WriteName(asName)
		}
		if err := tn.restoreIndexHints(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore TableSource.Source.(*TableName).IndexHints")
		}
		if tn.TableSample != nil {
			ctx.WritePlain(" ")
			if err := tn.TableSample.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while splicing TableName.TableSample")
			}
		}

		if needParen {
			ctx.WritePlain(")")
		}
	} else {
		if needParen {
			ctx.WritePlain("(")
		}
		if err := n.Source.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore TableSource.Source")
		}
		if needParen {
			ctx.WritePlain(")")
		}
		if asName := n.AsName.String(); asName != "" {
			ctx.WriteKeyWord(" AS ")
			ctx.WriteName(asName)
		}
	}

	return nil
}

// Accept implements Node Accept interface.
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)
}

// SelectLockType is the lock type for SelectStmt.
type SelectLockType int

// Select lock types.
const (
	SelectLockNone SelectLockType = iota
	SelectLockForUpdate
	SelectLockForShare
	SelectLockForUpdateNoWait
	SelectLockForUpdateWaitN
	SelectLockForShareNoWait
	SelectLockForUpdateSkipLocked
	SelectLockForShareSkipLocked
)

type SelectLockInfo struct {
	LockType SelectLockType
	WaitSec  uint64
}

// String implements fmt.Stringer.
func (n SelectLockType) String() string {
	switch n {
	case SelectLockNone:
		return "none"
	case SelectLockForUpdate:
		return "for update"
	case SelectLockForShare:
		return "for share"
	case SelectLockForUpdateNoWait:
		return "for update nowait"
	case SelectLockForUpdateWaitN:
		return "for update wait"
	case SelectLockForShareNoWait:
		return "for share nowait"
	case SelectLockForUpdateSkipLocked:
		return "for update skip locked"
	case SelectLockForShareSkipLocked:
		return "for share skip locked"
	}
	return "unsupported select lock type"
}

// WildCardField is a special type of select field content.
type WildCardField struct {
	node

	Table  model.CIStr
	Schema model.CIStr
}

// Restore implements Node interface.
func (n *WildCardField) Restore(ctx *format.RestoreCtx) error {
	if schema := n.Schema.String(); schema != "" {
		ctx.WriteName(schema)
		ctx.WritePlain(".")
	}
	if table := n.Table.String(); table != "" {
		ctx.WriteName(table)
		ctx.WritePlain(".")
	}
	ctx.WritePlain("*")
	return nil
}

// Accept implements Node Accept interface.
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)
}

// SelectField represents fields in select statement.
// There are two type of select field: wildcard
// and expression with optional alias name.
type SelectField struct {
	node

	// Offset is used to get original text.
	Offset int
	// WildCard is not nil, Expr will be nil.
	WildCard *WildCardField
	// Expr is not nil, WildCard will be nil.
	Expr ExprNode
	// AsName is alias name for Expr.
	AsName model.CIStr
	// Auxiliary stands for if this field is auxiliary.
	// When we add a Field into SelectField list which is used for having/orderby clause but the field is not in select clause,
	// we should set its Auxiliary to true. Then the TrimExec will trim the field.
	Auxiliary bool
}

// Restore implements Node interface.
func (n *SelectField) Restore(ctx *format.RestoreCtx) error {
	if n.WildCard != nil {
		if err := n.WildCard.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore SelectField.WildCard")
		}
	}
	if n.Expr != nil {
		if err := n.Expr.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore SelectField.Expr")
		}
	}
	if asName := n.AsName.String(); asName != "" {
		ctx.WriteKeyWord(" AS ")
		ctx.WriteName(asName)
	}
	return nil
}

// Accept implements Node Accept interface.
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)
}

// FieldList represents field list in select statement.
type FieldList struct {
	node

	Fields []*SelectField
}

// Restore implements Node interface.
func (n *FieldList) Restore(ctx *format.RestoreCtx) error {
	for i, v := range n.Fields {
		if i != 0 {
			ctx.WritePlain(", ")
		}
		if err := v.Restore(ctx); err != nil {
			return errors.Annotatef(err, "An error occurred while restore FieldList.Fields[%d]", i)
		}
	}
	return nil
}

// Accept implements Node Accept interface.
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)
}

// TableRefsClause represents table references clause in dml statement.
type TableRefsClause struct {
	node

	TableRefs *Join
}

// Restore implements Node interface.
func (n *TableRefsClause) Restore(ctx *format.RestoreCtx) error {
	if err := n.TableRefs.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore TableRefsClause.TableRefs")
	}
	return nil
}

// Accept implements Node Accept interface.
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)
}

// ByItem represents an item in order by or group by.
type ByItem struct {
	node

	Expr      ExprNode
	Desc      bool
	NullOrder bool
}

// Restore implements Node interface.
func (n *ByItem) Restore(ctx *format.RestoreCtx) error {
	if err := n.Expr.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore ByItem.Expr")
	}
	if n.Desc {
		ctx.WriteKeyWord(" DESC")
	}
	return nil
}

// Accept implements Node Accept interface.
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)
}

// GroupByClause represents group by clause.
type GroupByClause struct {
	node
	Items []*ByItem
}

// Restore implements Node interface.
func (n *GroupByClause) Restore(ctx *format.RestoreCtx) error {
	ctx.WriteKeyWord("GROUP BY ")
	for i, v := range n.Items {
		if i != 0 {
			ctx.WritePlain(",")
		}
		if err := v.Restore(ctx); err != nil {
			return errors.Annotatef(err, "An error occurred while restore GroupByClause.Items[%d]", i)
		}
	}
	return nil
}

// Accept implements Node Accept interface.
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)
}

// HavingClause represents having clause.
type HavingClause struct {
	node
	Expr ExprNode
}

// Restore implements Node interface.
func (n *HavingClause) Restore(ctx *format.RestoreCtx) error {
	ctx.WriteKeyWord("HAVING ")
	if err := n.Expr.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore HavingClause.Expr")
	}
	return nil
}

// Accept implements Node Accept interface.
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)
}

// OrderByClause represents order by clause.
type OrderByClause struct {
	node
	Items    []*ByItem
	ForUnion bool
}

// Restore implements Node interface.
func (n *OrderByClause) Restore(ctx *format.RestoreCtx) error {
	ctx.WriteKeyWord("ORDER BY ")
	for i, item := range n.Items {
		if i != 0 {
			ctx.WritePlain(",")
		}
		if err := item.Restore(ctx); err != nil {
			return errors.Annotatef(err, "An error occurred while restore OrderByClause.Items[%d]", i)
		}
	}
	return nil
}

// Accept implements Node Accept interface.
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 SampleMethodType int8

const (
	SampleMethodTypeNone SampleMethodType = iota
	SampleMethodTypeSystem
	SampleMethodTypeBernoulli
	SampleMethodTypeTiDBRegion
)

type SampleClauseUnitType int8

const (
	SampleClauseUnitTypeDefault SampleClauseUnitType = iota
	SampleClauseUnitTypeRow
	SampleClauseUnitTypePercent
)

type TableSample struct {
	node
	SampleMethod     SampleMethodType
	Expr             ExprNode
	SampleClauseUnit SampleClauseUnitType
	RepeatableSeed   ExprNode
}

func (s *TableSample) Restore(ctx *format.RestoreCtx) error {
	ctx.WriteKeyWord("TABLESAMPLE ")
	switch s.SampleMethod {
	case SampleMethodTypeBernoulli:
		ctx.WriteKeyWord("BERNOULLI ")
	case SampleMethodTypeSystem:
		ctx.WriteKeyWord("SYSTEM ")
	case SampleMethodTypeTiDBRegion:
		ctx.WriteKeyWord("REGION ")
	}
	ctx.WritePlain("(")
	if s.Expr != nil {
		if err := s.Expr.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore TableSample.Expr")
		}
	}
	switch s.SampleClauseUnit {
	case SampleClauseUnitTypeDefault:
	case SampleClauseUnitTypePercent:
		ctx.WriteKeyWord(" PERCENT")
	case SampleClauseUnitTypeRow:
		ctx.WriteKeyWord(" ROWS")

	}
	ctx.WritePlain(")")
	if s.RepeatableSeed != nil {
		ctx.WriteKeyWord(" REPEATABLE")
		ctx.WritePlain("(")
		if err := s.RepeatableSeed.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore TableSample.Expr")
		}
		ctx.WritePlain(")")
	}
	return nil
}

func (s *TableSample) Accept(v Visitor) (node Node, ok bool) {
	newNode, skipChildren := v.Enter(s)
	if skipChildren {
		return v.Leave(newNode)
	}
	s = newNode.(*TableSample)
	if s.Expr != nil {
		node, ok = s.Expr.Accept(v)
		if !ok {
			return s, false
		}
		s.Expr = node.(ExprNode)
	}
	if s.RepeatableSeed != nil {
		node, ok = s.RepeatableSeed.Accept(v)
		if !ok {
			return s, false
		}
		s.RepeatableSeed = node.(ExprNode)
	}
	return v.Leave(s)
}

type SelectStmtKind uint8

const (
	SelectStmtKindSelect SelectStmtKind = iota
	SelectStmtKindTable
	SelectStmtKindValues
)

func (s *SelectStmtKind) String() string {
	switch *s {
	case SelectStmtKindSelect:
		return "SELECT"
	case SelectStmtKindTable:
		return "TABLE"
	case SelectStmtKindValues:
		return "VALUES"
	}
	return ""
}

type CommonTableExpression struct {
	node

	Name        model.CIStr
	Query       *SubqueryExpr
	ColNameList []model.CIStr
}

type WithClause struct {
	node

	IsRecursive bool
	CTEs        []*CommonTableExpression
}

// SelectStmt represents the select query node.
// See https://dev.mysql.com/doc/refman/5.7/en/select.html
type SelectStmt struct {
	dmlNode

	// SelectStmtOpts wraps around select hints and switches.
	*SelectStmtOpts
	// Distinct represents whether the select has distinct option.
	Distinct bool
	// From is the from clause of the query.
	From *TableRefsClause
	// Where is the where clause in select statement.
	Where ExprNode
	// Fields is the select expression list.
	Fields *FieldList
	// GroupBy is the group by expression list.
	GroupBy *GroupByClause
	// Having is the having condition.
	Having *HavingClause
	// WindowSpecs is the window specification list.
	WindowSpecs []WindowSpec
	// OrderBy is the ordering expression list.
	OrderBy *OrderByClause
	// Limit is the limit clause.
	Limit *Limit
	// LockInfo is the lock type
	LockInfo *SelectLockInfo
	// TableHints represents the table level Optimizer Hint for join type
	TableHints []*TableOptimizerHint
	// IsInBraces indicates whether it's a stmt in brace.
	IsInBraces bool
	// QueryBlockOffset indicates the order of this SelectStmt if counted from left to right in the sql text.
	QueryBlockOffset int
	// SelectIntoOpt is the select-into option.
	SelectIntoOpt *SelectIntoOption
	// AfterSetOperator indicates the SelectStmt after which type of set operator
	AfterSetOperator *SetOprType
	// Kind refer to three kind of statement: SelectStmt, TableStmt and ValuesStmt
	Kind SelectStmtKind
	// Lists is filled only when Kind == SelectStmtKindValues
	Lists []*RowExpr
	With  *WithClause
}

func (n *WithClause) Restore(ctx *format.RestoreCtx) error {
	ctx.WriteKeyWord("WITH ")
	if n.IsRecursive {
		ctx.WriteKeyWord("RECURSIVE ")
	}
	for i, cte := range n.CTEs {
		if i != 0 {
			ctx.WritePlain(", ")
		}
		ctx.WriteName(cte.Name.String())
		if len(cte.ColNameList) > 0 {
			ctx.WritePlain(" (")
			for j, name := range cte.ColNameList {
				if j != 0 {
					ctx.WritePlain(", ")
				}
				ctx.WriteName(name.String())
			}
			ctx.WritePlain(")")
		}
		ctx.WriteKeyWord(" AS ")
		err := cte.Query.Restore(ctx)
		if err != nil {
			return err
		}
	}
	ctx.WritePlain(" ")
	return nil
}

func (n *WithClause) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}

	for _, cte := range n.CTEs {
		node, ok := cte.Query.Accept(v)
		if !ok {
			return n, false
		}
		cte.Query = node.(*SubqueryExpr)
	}
	return v.Leave(n)
}

// Restore implements Node interface.
func (n *SelectStmt) Restore(ctx *format.RestoreCtx) error {
	if n.IsInBraces {
		ctx.WritePlain("(")
		defer func() {
			ctx.WritePlain(")")
		}()
	}
	if n.With != nil {
		err := n.With.Restore(ctx)
		if err != nil {
			return err
		}
	}

	ctx.WriteKeyWord(n.Kind.String())
	ctx.WritePlain(" ")
	switch n.Kind {
	case SelectStmtKindSelect:
		if n.SelectStmtOpts.Priority > 0 {
			ctx.WriteKeyWord(mysql.Priority2Str[n.SelectStmtOpts.Priority])
			ctx.WritePlain(" ")
		}

		if n.SelectStmtOpts.SQLSmallResult {
			ctx.WriteKeyWord("SQL_SMALL_RESULT ")
		}

		if n.SelectStmtOpts.SQLBigResult {
			ctx.WriteKeyWord("SQL_BIG_RESULT ")
		}

		if n.SelectStmtOpts.SQLBufferResult {
			ctx.WriteKeyWord("SQL_BUFFER_RESULT ")
		}

		if !n.SelectStmtOpts.SQLCache {
			ctx.WriteKeyWord("SQL_NO_CACHE ")
		}

		if n.SelectStmtOpts.CalcFoundRows {
			ctx.WriteKeyWord("SQL_CALC_FOUND_ROWS ")
		}

		if n.TableHints != nil && len(n.TableHints) != 0 {
			ctx.WritePlain("/*+ ")
			for i, tableHint := range n.TableHints {
				if i != 0 {
					ctx.WritePlain(" ")
				}
				if err := tableHint.Restore(ctx); err != nil {
					return errors.Annotatef(err, "An error occurred while restore SelectStmt.TableHints[%d]", i)
				}
			}
			ctx.WritePlain("*/ ")
		}

		if n.Distinct {
			ctx.WriteKeyWord("DISTINCT ")
		} else if n.SelectStmtOpts.ExplicitAll {
			ctx.WriteKeyWord("ALL ")
		}
		if n.SelectStmtOpts.StraightJoin {
			ctx.WriteKeyWord("STRAIGHT_JOIN ")
		}
		if n.Fields != nil {
			for i, field := range n.Fields.Fields {
				if i != 0 {
					ctx.WritePlain(",")
				}
				if err := field.Restore(ctx); err != nil {
					return errors.Annotatef(err, "An error occurred while restore SelectStmt.Fields[%d]", i)
				}
			}
		}

		if n.From != nil {
			ctx.WriteKeyWord(" FROM ")
			if err := n.From.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore SelectStmt.From")
			}
		}

		if n.From == nil && n.Where != nil {
			ctx.WriteKeyWord(" FROM DUAL")
		}

		if n.Where != nil {
			ctx.WriteKeyWord(" WHERE ")
			if err := n.Where.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore SelectStmt.Where")
			}
		}

		if n.GroupBy != nil {
			ctx.WritePlain(" ")
			if err := n.GroupBy.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore SelectStmt.GroupBy")
			}
		}

		if n.Having != nil {
			ctx.WritePlain(" ")
			if err := n.Having.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore SelectStmt.Having")
			}
		}

		if n.WindowSpecs != nil {
			ctx.WriteKeyWord(" WINDOW ")
			for i, windowsSpec := range n.WindowSpecs {
				if i != 0 {
					ctx.WritePlain(",")
				}
				if err := windowsSpec.Restore(ctx); err != nil {
					return errors.Annotatef(err, "An error occurred while restore SelectStmt.WindowSpec[%d]", i)
				}
			}
		}
	case SelectStmtKindTable:
		if err := n.From.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore SelectStmt.From")
		}
	case SelectStmtKindValues:
		for i, v := range n.Lists {
			if err := v.Restore(ctx); err != nil {
				return errors.Annotatef(err, "An error occurred while restore SelectStmt.Lists[%d]", i)
			}
			if i != len(n.Lists)-1 {
				ctx.WritePlain(", ")
			}
		}
	}

	if n.OrderBy != nil {
		ctx.WritePlain(" ")
		if err := n.OrderBy.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore SelectStmt.OrderBy")
		}
	}

	if n.Limit != nil {
		ctx.WritePlain(" ")
		if err := n.Limit.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore SelectStmt.Limit")
		}
	}

	if n.LockInfo != nil {
		ctx.WritePlain(" ")
		switch n.LockInfo.LockType {
		case SelectLockNone:
		case SelectLockForUpdateWaitN:
			ctx.WriteKeyWord(n.LockInfo.LockType.String())
			ctx.WritePlainf(" %d", n.LockInfo.WaitSec)
		default:
			ctx.WriteKeyWord(n.LockInfo.LockType.String())
		}
	}

	if n.SelectIntoOpt != nil {
		ctx.WritePlain(" ")
		if err := n.SelectIntoOpt.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore SelectStmt.SelectIntoOpt")
		}
	}
	return nil
}

// Accept implements Node Accept interface.
func (n *SelectStmt) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}

	n = newNode.(*SelectStmt)

	if n.With != nil {
		node, ok := n.With.Accept(v)
		if !ok {
			return n, false
		}
		n.With = node.(*WithClause)
	}

	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.Fields != nil {
		node, ok := n.Fields.Accept(v)
		if !ok {
			return n, false
		}
		n.Fields = node.(*FieldList)
	}

	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.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, list := range n.Lists {
		node, ok := list.Accept(v)
		if !ok {
			return n, false
		}
		n.Lists[i] = node.(*RowExpr)
	}

	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)
}

// SetOprSelectList represents the SelectStmt/TableStmt/ValuesStmt list in a union statement.
type SetOprSelectList struct {
	node

	AfterSetOperator *SetOprType
	Selects          []Node
}

// Restore implements Node interface.
func (n *SetOprSelectList) Restore(ctx *format.RestoreCtx) error {
	for i, stmt := range n.Selects {
		switch selectStmt := stmt.(type) {
		case *SelectStmt:
			if i != 0 {
				ctx.WriteKeyWord(" " + selectStmt.AfterSetOperator.String() + " ")
			}
			if err := selectStmt.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore SetOprSelectList.SelectStmt")
			}
		case *SetOprSelectList:
			if i != 0 {
				ctx.WriteKeyWord(" " + selectStmt.AfterSetOperator.String() + " ")
			}
			ctx.WritePlain("(")
			err := selectStmt.Restore(ctx)
			if err != nil {
				return err
			}
			ctx.WritePlain(")")
		}
	}
	return nil
}

// Accept implements Node Accept interface.
func (n *SetOprSelectList) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*SetOprSelectList)
	for i, sel := range n.Selects {
		node, ok := sel.Accept(v)
		if !ok {
			return n, false
		}
		n.Selects[i] = node
	}
	return v.Leave(n)
}

type SetOprType uint8

const (
	Union SetOprType = iota
	UnionAll
	Except
	ExceptAll
	Intersect
	IntersectAll
)

func (s *SetOprType) String() string {
	switch *s {
	case Union:
		return "UNION"
	case UnionAll:
		return "UNION ALL"
	case Except:
		return "EXCEPT"
	case ExceptAll:
		return "EXCEPT ALL"
	case Intersect:
		return "INTERSECT"
	case IntersectAll:
		return "INTERSECT ALL"
	}
	return ""
}

// SetOprStmt represents "union/except/intersect statement"
// See https://dev.mysql.com/doc/refman/5.7/en/union.html
// See https://mariadb.com/kb/en/intersect/
// See https://mariadb.com/kb/en/except/
type SetOprStmt struct {
	dmlNode

	SelectList *SetOprSelectList
	OrderBy    *OrderByClause
	Limit      *Limit
	With       *WithClause
}

// Restore implements Node interface.
func (n *SetOprStmt) Restore(ctx *format.RestoreCtx) error {
	if n.With != nil {
		if err := n.With.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore UnionStmt.With")
		}
	}

	if err := n.SelectList.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore SetOprStmt.SelectList")
	}

	if n.OrderBy != nil {
		ctx.WritePlain(" ")
		if err := n.OrderBy.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore SetOprStmt.OrderBy")
		}
	}

	if n.Limit != nil {
		ctx.WritePlain(" ")
		if err := n.Limit.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore SetOprStmt.Limit")
		}
	}
	return nil
}

// Accept implements Node Accept interface.
func (n *SetOprStmt) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	if n.With != nil {
		node, ok := n.With.Accept(v)
		if !ok {
			return n, false
		}
		n.With = node.(*WithClause)
	}
	if n.SelectList != nil {
		node, ok := n.SelectList.Accept(v)
		if !ok {
			return n, false
		}
		n.SelectList = node.(*SetOprSelectList)
	}
	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)
}

// Assignment is the expression for assignment, like a = 1.
type Assignment struct {
	node
	// Column is the column name to be assigned.
	Column *ColumnName
	// Expr is the expression assigning to ColName.
	Expr ExprNode
}

// Restore implements Node interface.
func (n *Assignment) Restore(ctx *format.RestoreCtx) error {
	if err := n.Column.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore Assignment.Column")
	}
	ctx.WritePlain("=")
	if err := n.Expr.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore Assignment.Expr")
	}
	return nil
}

// Accept implements Node Accept interface.
func (n *Assignment) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*Assignment)
	node, ok := n.Column.Accept(v)
	if !ok {
		return n, false
	}
	n.Column = node.(*ColumnName)
	node, ok = n.Expr.Accept(v)
	if !ok {
		return n, false
	}
	n.Expr = node.(ExprNode)
	return v.Leave(n)
}

type ColumnNameOrUserVar struct {
	node
	ColumnName *ColumnName
	UserVar    *VariableExpr
}

func (n *ColumnNameOrUserVar) Restore(ctx *format.RestoreCtx) error {
	if n.ColumnName != nil {
		if err := n.ColumnName.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore ColumnNameOrUserVar.ColumnName")
		}
	}
	if n.UserVar != nil {
		if err := n.UserVar.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore ColumnNameOrUserVar.UserVar")
		}
	}
	return nil
}

func (n *ColumnNameOrUserVar) Accept(v Visitor) (node Node, ok bool) {
	newNode, skipChild := v.Enter(n)
	if skipChild {
		return v.Leave(newNode)
	}
	n = newNode.(*ColumnNameOrUserVar)
	if n.ColumnName != nil {
		node, ok = n.ColumnName.Accept(v)
		if !ok {
			return node, false
		}
		n.ColumnName = node.(*ColumnName)
	}
	if n.UserVar != nil {
		node, ok = n.UserVar.Accept(v)
		if !ok {
			return node, false
		}
		n.UserVar = node.(*VariableExpr)
	}
	return v.Leave(n)
}

// LoadDataStmt is a statement to load data from a specified file, then insert this rows into an existing table.
// See https://dev.mysql.com/doc/refman/5.7/en/load-data.html
type LoadDataStmt struct {
	dmlNode

	IsLocal           bool
	Path              string
	OnDuplicate       OnDuplicateKeyHandlingType
	Table             *TableName
	Columns           []*ColumnName
	FieldsInfo        *FieldsClause
	LinesInfo         *LinesClause
	IgnoreLines       uint64
	ColumnAssignments []*Assignment

	ColumnsAndUserVars []*ColumnNameOrUserVar
}

// Restore implements Node interface.
func (n *LoadDataStmt) Restore(ctx *format.RestoreCtx) error {
	ctx.WriteKeyWord("LOAD DATA ")
	if n.IsLocal {
		ctx.WriteKeyWord("LOCAL ")
	}
	ctx.WriteKeyWord("INFILE ")
	ctx.WriteString(n.Path)
	if n.OnDuplicate == OnDuplicateKeyHandlingReplace {
		ctx.WriteKeyWord(" REPLACE")
	} else if n.OnDuplicate == OnDuplicateKeyHandlingIgnore {
		ctx.WriteKeyWord(" IGNORE")
	}
	ctx.WriteKeyWord(" INTO TABLE ")
	if err := n.Table.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore LoadDataStmt.Table")
	}
	n.FieldsInfo.Restore(ctx)
	n.LinesInfo.Restore(ctx)
	if n.IgnoreLines != 0 {
		ctx.WriteKeyWord(" IGNORE ")
		ctx.WritePlainf("%d", n.IgnoreLines)
		ctx.WriteKeyWord(" LINES")
	}
	if len(n.ColumnsAndUserVars) != 0 {
		ctx.WritePlain(" (")
		for i, c := range n.ColumnsAndUserVars {
			if i != 0 {
				ctx.WritePlain(",")
			}
			if err := c.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore LoadDataStmt.ColumnsAndUserVars")
			}
		}
		ctx.WritePlain(")")
	}

	if n.ColumnAssignments != nil {
		ctx.WriteKeyWord(" SET")
		for i, assign := range n.ColumnAssignments {
			if i != 0 {
				ctx.WritePlain(",")
			}
			ctx.WritePlain(" ")
			if err := assign.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore LoadDataStmt.ColumnAssignments")
			}
		}
	}
	return nil
}

// Accept implements Node Accept interface.
func (n *LoadDataStmt) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*LoadDataStmt)
	if n.Table != nil {
		node, ok := n.Table.Accept(v)
		if !ok {
			return n, false
		}
		n.Table = node.(*TableName)
	}
	for i, val := range n.Columns {
		node, ok := val.Accept(v)
		if !ok {
			return n, false
		}
		n.Columns[i] = node.(*ColumnName)
	}

	for i, assignment := range n.ColumnAssignments {
		node, ok := assignment.Accept(v)
		if !ok {
			return n, false
		}
		n.ColumnAssignments[i] = node.(*Assignment)
	}
	for i, cuVars := range n.ColumnsAndUserVars {
		node, ok := cuVars.Accept(v)
		if !ok {
			return n, false
		}
		n.ColumnsAndUserVars[i] = node.(*ColumnNameOrUserVar)
	}
	return v.Leave(n)
}

const (
	Terminated = iota
	Enclosed
	Escaped
)

type FieldItem struct {
	Type        int
	Value       string
	OptEnclosed bool
}

// FieldsClause represents fields references clause in load data statement.
type FieldsClause struct {
	Terminated  string
	Enclosed    byte
	Escaped     byte
	OptEnclosed bool
}

// Restore for FieldsClause
func (n *FieldsClause) Restore(ctx *format.RestoreCtx) error {
	if n.Terminated != "\t" || n.Escaped != '\\' {
		ctx.WriteKeyWord(" FIELDS")
		if n.Terminated != "\t" {
			ctx.WriteKeyWord(" TERMINATED BY ")
			ctx.WriteString(n.Terminated)
		}
		if n.Enclosed != 0 {
			if n.OptEnclosed {
				ctx.WriteKeyWord(" OPTIONALLY")
			}
			ctx.WriteKeyWord(" ENCLOSED BY ")
			ctx.WriteString(string(n.Enclosed))
		}
		if n.Escaped != '\\' {
			ctx.WriteKeyWord(" ESCAPED BY ")
			if n.Escaped == 0 {
				ctx.WritePlain("''")
			} else {
				ctx.WriteString(string(n.Escaped))
			}
		}
	}
	return nil
}

// LinesClause represents lines references clause in load data statement.
type LinesClause struct {
	Starting   string
	Terminated string
}

// Restore for LinesClause
func (n *LinesClause) Restore(ctx *format.RestoreCtx) error {
	if n.Starting != "" || n.Terminated != "\n" {
		ctx.WriteKeyWord(" LINES")
		if n.Starting != "" {
			ctx.WriteKeyWord(" STARTING BY ")
			ctx.WriteString(n.Starting)
		}
		if n.Terminated != "\n" {
			ctx.WriteKeyWord(" TERMINATED BY ")
			ctx.WriteString(n.Terminated)
		}
	}
	return nil
}

// CallStmt represents a call procedure query node.
// See https://dev.mysql.com/doc/refman/5.7/en/call.html
type CallStmt struct {
	dmlNode

	Procedure *FuncCallExpr
}

// Restore implements Node interface.
func (n *CallStmt) Restore(ctx *format.RestoreCtx) error {
	ctx.WriteKeyWord("CALL ")

	if err := n.Procedure.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore CallStmt.Procedure")
	}

	return nil
}

// Accept implements Node Accept interface.
func (n *CallStmt) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}

	n = newNode.(*CallStmt)

	if n.Procedure != nil {
		node, ok := n.Procedure.Accept(v)
		if !ok {
			return n, false
		}

		n.Procedure = node.(*FuncCallExpr)
	}

	return v.Leave(n)
}

// InsertStmt is a statement to insert new rows into an existing table.
// See https://dev.mysql.com/doc/refman/5.7/en/insert.html
type InsertStmt struct {
	dmlNode

	IsReplace   bool
	IgnoreErr   bool
	Table       *TableRefsClause
	Columns     []*ColumnName
	Lists       [][]ExprNode
	Setlist     []*Assignment
	Priority    mysql.PriorityEnum
	OnDuplicate []*Assignment
	Select      ResultSetNode
	// TableHints represents the table level Optimizer Hint for join type.
	TableHints     []*TableOptimizerHint
	PartitionNames []model.CIStr
}

// Restore implements Node interface.
func (n *InsertStmt) Restore(ctx *format.RestoreCtx) error {
	if n.IsReplace {
		ctx.WriteKeyWord("REPLACE ")
	} else {
		ctx.WriteKeyWord("INSERT ")
	}

	if n.TableHints != nil && len(n.TableHints) != 0 {
		ctx.WritePlain("/*+ ")
		for i, tableHint := range n.TableHints {
			if i != 0 {
				ctx.WritePlain(" ")
			}
			if err := tableHint.Restore(ctx); err != nil {
				return errors.Annotatef(err, "An error occurred while restore InsertStmt.TableHints[%d]", i)
			}
		}
		ctx.WritePlain("*/ ")
	}

	if err := n.Priority.Restore(ctx); err != nil {
		return errors.Trace(err)
	}
	if n.Priority != mysql.NoPriority {
		ctx.WritePlain(" ")
	}
	if n.IgnoreErr {
		ctx.WriteKeyWord("IGNORE ")
	}
	ctx.WriteKeyWord("INTO ")
	if err := n.Table.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore InsertStmt.Table")
	}
	if len(n.PartitionNames) != 0 {
		ctx.WriteKeyWord(" PARTITION")
		ctx.WritePlain("(")
		for i := 0; i < len(n.PartitionNames); i++ {
			if i != 0 {
				ctx.WritePlain(", ")
			}
			ctx.WriteName(n.PartitionNames[i].String())
		}
		ctx.WritePlain(")")
	}
	if n.Columns != nil {
		ctx.WritePlain(" (")
		for i, v := range n.Columns {
			if i != 0 {
				ctx.WritePlain(",")
			}
			if err := v.Restore(ctx); err != nil {
				return errors.Annotatef(err, "An error occurred while restore InsertStmt.Columns[%d]", i)
			}
		}
		ctx.WritePlain(")")
	}
	if n.Lists != nil {
		ctx.WriteKeyWord(" VALUES ")
		for i, row := range n.Lists {
			if i != 0 {
				ctx.WritePlain(",")
			}
			ctx.WritePlain("(")
			for j, v := range row {
				if j != 0 {
					ctx.WritePlain(",")
				}
				if err := v.Restore(ctx); err != nil {
					return errors.Annotatef(err, "An error occurred while restore InsertStmt.Lists[%d][%d]", i, j)
				}
			}
			ctx.WritePlain(")")
		}
	}
	if n.Select != nil {
		ctx.WritePlain(" ")
		switch v := n.Select.(type) {
		case *SelectStmt, *SetOprStmt:
			if err := v.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore InsertStmt.Select")
			}
		default:
			return errors.Errorf("Incorrect type for InsertStmt.Select: %T", v)
		}
	}
	if n.Setlist != nil {
		ctx.WriteKeyWord(" SET ")
		for i, v := range n.Setlist {
			if i != 0 {
				ctx.WritePlain(",")
			}
			if err := v.Restore(ctx); err != nil {
				return errors.Annotatef(err, "An error occurred while restore InsertStmt.Setlist[%d]", i)
			}
		}
	}
	if n.OnDuplicate != nil {
		ctx.WriteKeyWord(" ON DUPLICATE KEY UPDATE ")
		for i, v := range n.OnDuplicate {
			if i != 0 {
				ctx.WritePlain(",")
			}
			if err := v.Restore(ctx); err != nil {
				return errors.Annotatef(err, "An error occurred while restore InsertStmt.OnDuplicate[%d]", i)
			}
		}
	}

	return nil
}

// Accept implements Node Accept interface.
func (n *InsertStmt) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}

	n = newNode.(*InsertStmt)
	if n.Select != nil {
		node, ok := n.Select.Accept(v)
		if !ok {
			return n, false
		}
		n.Select = node.(ResultSetNode)
	}

	node, ok := n.Table.Accept(v)
	if !ok {
		return n, false
	}
	n.Table = node.(*TableRefsClause)

	for i, val := range n.Columns {
		node, ok := val.Accept(v)
		if !ok {
			return n, false
		}
		n.Columns[i] = node.(*ColumnName)
	}
	for i, list := range n.Lists {
		for j, val := range list {
			node, ok := val.Accept(v)
			if !ok {
				return n, false
			}
			n.Lists[i][j] = node.(ExprNode)
		}
	}
	for i, val := range n.Setlist {
		node, ok := val.Accept(v)
		if !ok {
			return n, false
		}
		n.Setlist[i] = node.(*Assignment)
	}
	for i, val := range n.OnDuplicate {
		node, ok := val.Accept(v)
		if !ok {
			return n, false
		}
		n.OnDuplicate[i] = node.(*Assignment)
	}
	return v.Leave(n)
}

// DeleteStmt is a statement to delete rows from table.
// See https://dev.mysql.com/doc/refman/5.7/en/delete.html
type DeleteStmt struct {
	dmlNode

	// TableRefs is used in both single table and multiple table delete statement.
	TableRefs *TableRefsClause
	// Tables is only used in multiple table delete statement.
	Tables       *DeleteTableList
	Where        ExprNode
	Order        *OrderByClause
	Limit        *Limit
	Priority     mysql.PriorityEnum
	IgnoreErr    bool
	Quick        bool
	IsMultiTable bool
	BeforeFrom   bool
	// TableHints represents the table level Optimizer Hint for join type.
	TableHints []*TableOptimizerHint
	With       *WithClause
}

// Restore implements Node interface.
func (n *DeleteStmt) Restore(ctx *format.RestoreCtx) error {
	if n.With != nil {
		err := n.With.Restore(ctx)
		if err != nil {
			return err
		}
	}

	ctx.WriteKeyWord("DELETE ")

	if n.TableHints != nil && len(n.TableHints) != 0 {
		ctx.WritePlain("/*+ ")
		for i, tableHint := range n.TableHints {
			if i != 0 {
				ctx.WritePlain(" ")
			}
			if err := tableHint.Restore(ctx); err != nil {
				return errors.Annotatef(err, "An error occurred while restore UpdateStmt.TableHints[%d]", i)
			}
		}
		ctx.WritePlain("*/ ")
	}

	if err := n.Priority.Restore(ctx); err != nil {
		return errors.Trace(err)
	}
	if n.Priority != mysql.NoPriority {
		ctx.WritePlain(" ")
	}
	if n.Quick {
		ctx.WriteKeyWord("QUICK ")
	}
	if n.IgnoreErr {
		ctx.WriteKeyWord("IGNORE ")
	}

	if n.IsMultiTable { // Multiple-Table Syntax
		if n.BeforeFrom {
			if err := n.Tables.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore DeleteStmt.Tables")
			}

			ctx.WriteKeyWord(" FROM ")
			if err := n.TableRefs.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore DeleteStmt.TableRefs")
			}
		} else {
			ctx.WriteKeyWord("FROM ")
			if err := n.Tables.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore DeleteStmt.Tables")
			}

			ctx.WriteKeyWord(" USING ")
			if err := n.TableRefs.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore DeleteStmt.TableRefs")
			}
		}
	} else { // Single-Table Syntax
		ctx.WriteKeyWord("FROM ")

		if err := n.TableRefs.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore DeleteStmt.TableRefs")
		}
	}

	if n.Where != nil {
		ctx.WriteKeyWord(" WHERE ")
		if err := n.Where.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore DeleteStmt.Where")
		}
	}

	if n.Order != nil {
		ctx.WritePlain(" ")
		if err := n.Order.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore DeleteStmt.Order")
		}
	}

	if n.Limit != nil {
		ctx.WritePlain(" ")
		if err := n.Limit.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore DeleteStmt.Limit")
		}
	}

	return nil
}

// Accept implements Node Accept interface.
func (n *DeleteStmt) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}

	n = newNode.(*DeleteStmt)
	if n.With != nil {
		node, ok := n.With.Accept(v)
		if !ok {
			return n, false
		}
		n.With = node.(*WithClause)
	}
	node, ok := n.TableRefs.Accept(v)
	if !ok {
		return n, false
	}
	n.TableRefs = node.(*TableRefsClause)

	if n.Tables != nil {
		node, ok = n.Tables.Accept(v)
		if !ok {
			return n, false
		}
		n.Tables = node.(*DeleteTableList)
	}

	if n.Where != nil {
		node, ok = n.Where.Accept(v)
		if !ok {
			return n, false
		}
		n.Where = node.(ExprNode)
	}
	if n.Order != nil {
		node, ok = n.Order.Accept(v)
		if !ok {
			return n, false
		}
		n.Order = 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)
}

// UpdateStmt is a statement to update columns of existing rows in tables with new values.
// See https://dev.mysql.com/doc/refman/5.7/en/update.html
type UpdateStmt struct {
	dmlNode

	TableRefs     *TableRefsClause
	List          []*Assignment
	Where         ExprNode
	Order         *OrderByClause
	Limit         *Limit
	Priority      mysql.PriorityEnum
	IgnoreErr     bool
	MultipleTable bool
	TableHints    []*TableOptimizerHint
	With          *WithClause
}

// Restore implements Node interface.
func (n *UpdateStmt) Restore(ctx *format.RestoreCtx) error {
	if n.With != nil {
		err := n.With.Restore(ctx)
		if err != nil {
			return err
		}
	}

	ctx.WriteKeyWord("UPDATE ")

	if n.TableHints != nil && len(n.TableHints) != 0 {
		ctx.WritePlain("/*+ ")
		for i, tableHint := range n.TableHints {
			if i != 0 {
				ctx.WritePlain(" ")
			}
			if err := tableHint.Restore(ctx); err != nil {
				return errors.Annotatef(err, "An error occurred while restore UpdateStmt.TableHints[%d]", i)
			}
		}
		ctx.WritePlain("*/ ")
	}

	if err := n.Priority.Restore(ctx); err != nil {
		return errors.Trace(err)
	}
	if n.Priority != mysql.NoPriority {
		ctx.WritePlain(" ")
	}
	if n.IgnoreErr {
		ctx.WriteKeyWord("IGNORE ")
	}

	if err := n.TableRefs.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occur while restore UpdateStmt.TableRefs")
	}

	ctx.WriteKeyWord(" SET ")
	for i, assignment := range n.List {
		if i != 0 {
			ctx.WritePlain(", ")
		}

		if err := assignment.Column.Restore(ctx); err != nil {
			return errors.Annotatef(err, "An error occur while restore UpdateStmt.List[%d].Column", i)
		}

		ctx.WritePlain("=")

		if err := assignment.Expr.Restore(ctx); err != nil {
			return errors.Annotatef(err, "An error occur while restore UpdateStmt.List[%d].Expr", i)
		}
	}

	if n.Where != nil {
		ctx.WriteKeyWord(" WHERE ")
		if err := n.Where.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occur while restore UpdateStmt.Where")
		}
	}

	if n.Order != nil {
		ctx.WritePlain(" ")
		if err := n.Order.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occur while restore UpdateStmt.Order")
		}
	}

	if n.Limit != nil {
		ctx.WritePlain(" ")
		if err := n.Limit.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occur while restore UpdateStmt.Limit")
		}
	}

	return nil
}

// Accept implements Node Accept interface.
func (n *UpdateStmt) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*UpdateStmt)
	if n.With != nil {
		node, ok := n.With.Accept(v)
		if !ok {
			return n, false
		}
		n.With = node.(*WithClause)
	}
	node, ok := n.TableRefs.Accept(v)
	if !ok {
		return n, false
	}
	n.TableRefs = node.(*TableRefsClause)
	for i, val := range n.List {
		node, ok = val.Accept(v)
		if !ok {
			return n, false
		}
		n.List[i] = node.(*Assignment)
	}
	if n.Where != nil {
		node, ok = n.Where.Accept(v)
		if !ok {
			return n, false
		}
		n.Where = node.(ExprNode)
	}
	if n.Order != nil {
		node, ok = n.Order.Accept(v)
		if !ok {
			return n, false
		}
		n.Order = 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)
}

// Limit is the limit clause.
type Limit struct {
	node

	Count  ExprNode
	Offset ExprNode
}

// Restore implements Node interface.
func (n *Limit) Restore(ctx *format.RestoreCtx) error {
	ctx.WriteKeyWord("LIMIT ")
	if n.Offset != nil {
		if err := n.Offset.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore Limit.Offset")
		}
		ctx.WritePlain(",")
	}
	if err := n.Count.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore Limit.Count")
	}
	return nil
}

// Accept implements Node Accept interface.
func (n *Limit) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	if n.Count != nil {
		node, ok := n.Count.Accept(v)
		if !ok {
			return n, false
		}
		n.Count = node.(ExprNode)
	}
	if n.Offset != nil {
		node, ok := n.Offset.Accept(v)
		if !ok {
			return n, false
		}
		n.Offset = node.(ExprNode)
	}

	n = newNode.(*Limit)
	return v.Leave(n)
}

// ShowStmtType is the type for SHOW statement.
type ShowStmtType int

// Show statement types.
const (
	ShowNone = iota
	ShowEngines
	ShowDatabases
	ShowTables
	ShowTableStatus
	ShowColumns
	ShowWarnings
	ShowCharset
	ShowVariables
	ShowStatus
	ShowCollation
	ShowCreateTable
	ShowCreateView
	ShowCreateUser
	ShowCreateSequence
	ShowGrants
	ShowTriggers
	ShowProcedureStatus
	ShowIndex
	ShowProcessList
	ShowCreateDatabase
	ShowConfig
	ShowEvents
	ShowStatsExtended
	ShowStatsMeta
	ShowStatsHistograms
	ShowStatsTopN
	ShowStatsBuckets
	ShowStatsHealthy
	ShowPlugins
	ShowProfile
	ShowProfiles
	ShowMasterStatus
	ShowPrivileges
	ShowErrors
	ShowBindings
	ShowPumpStatus
	ShowDrainerStatus
	ShowOpenTables
	ShowAnalyzeStatus
	ShowRegions
	ShowBuiltins
	ShowTableNextRowId
	ShowBackups
	ShowRestores
	ShowImports
	ShowCreateImport
)

const (
	ProfileTypeInvalid = iota
	ProfileTypeCPU
	ProfileTypeMemory
	ProfileTypeBlockIo
	ProfileTypeContextSwitch
	ProfileTypePageFaults
	ProfileTypeIpc
	ProfileTypeSwaps
	ProfileTypeSource
	ProfileTypeAll
)

// ShowStmt is a statement to provide information about databases, tables, columns and so on.
// See https://dev.mysql.com/doc/refman/5.7/en/show.html
type ShowStmt struct {
	dmlNode

	Tp          ShowStmtType // Databases/Tables/Columns/....
	DBName      string
	Table       *TableName  // Used for showing columns.
	Column      *ColumnName // Used for `desc table column`.
	IndexName   model.CIStr
	Flag        int // Some flag parsed from sql, such as FULL.
	Full        bool
	User        *auth.UserIdentity   // Used for show grants/create user.
	Roles       []*auth.RoleIdentity // Used for show grants .. using
	IfNotExists bool                 // Used for `show create database if not exists`
	Extended    bool                 // Used for `show extended columns from ...`

	// GlobalScope is used by `show variables` and `show bindings`
	GlobalScope bool
	Pattern     *PatternLikeExpr
	Where       ExprNode

	ShowProfileTypes []int  // Used for `SHOW PROFILE` syntax
	ShowProfileArgs  *int64 // Used for `SHOW PROFILE` syntax
	ShowProfileLimit *Limit // Used for `SHOW PROFILE` syntax
}

// Restore implements Node interface.
func (n *ShowStmt) Restore(ctx *format.RestoreCtx) error {
	restoreOptFull := func() {
		if n.Full {
			ctx.WriteKeyWord("FULL ")
		}
	}
	restoreShowDatabaseNameOpt := func() {
		if n.DBName != "" {
			// FROM OR IN
			ctx.WriteKeyWord(" IN ")
			ctx.WriteName(n.DBName)
		}
	}
	restoreGlobalScope := func() {
		if n.GlobalScope {
			ctx.WriteKeyWord("GLOBAL ")
		} else {
			ctx.WriteKeyWord("SESSION ")
		}
	}
	restoreShowLikeOrWhereOpt := func() error {
		if n.Pattern != nil && n.Pattern.Pattern != nil {
			ctx.WriteKeyWord(" LIKE ")
			if err := n.Pattern.Pattern.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore ShowStmt.Pattern")
			}
		} else if n.Where != nil {
			ctx.WriteKeyWord(" WHERE ")
			if err := n.Where.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore ShowStmt.Where")
			}
		}
		return nil
	}

	ctx.WriteKeyWord("SHOW ")
	switch n.Tp {
	case ShowCreateTable:
		ctx.WriteKeyWord("CREATE TABLE ")
		if err := n.Table.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore ShowStmt.Table")
		}
	case ShowCreateView:
		ctx.WriteKeyWord("CREATE VIEW ")
		if err := n.Table.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore ShowStmt.VIEW")
		}
	case ShowCreateDatabase:
		ctx.WriteKeyWord("CREATE DATABASE ")
		if n.IfNotExists {
			ctx.WriteKeyWord("IF NOT EXISTS ")
		}
		ctx.WriteName(n.DBName)
	case ShowCreateSequence:
		ctx.WriteKeyWord("CREATE SEQUENCE ")
		if err := n.Table.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore ShowStmt.SEQUENCE")
		}
	case ShowCreateUser:
		ctx.WriteKeyWord("CREATE USER ")
		if err := n.User.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore ShowStmt.User")
		}
	case ShowGrants:
		ctx.WriteKeyWord("GRANTS")
		if n.User != nil {
			ctx.WriteKeyWord(" FOR ")
			if err := n.User.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore ShowStmt.User")
			}
		}
		if n.Roles != nil {
			ctx.WriteKeyWord(" USING ")
			for i, r := range n.Roles {
				if err := r.Restore(ctx); err != nil {
					return errors.Annotate(err, "An error occurred while restore ShowStmt.User")
				}
				if i != len(n.Roles)-1 {
					ctx.WritePlain(", ")
				}
			}
		}
	case ShowMasterStatus:
		ctx.WriteKeyWord("MASTER STATUS")
	case ShowProcessList:
		restoreOptFull()
		ctx.WriteKeyWord("PROCESSLIST")
	case ShowStatsExtended:
		ctx.WriteKeyWord("STATS_EXTENDED")
		if err := restoreShowLikeOrWhereOpt(); err != nil {
			return err
		}
	case ShowStatsMeta:
		ctx.WriteKeyWord("STATS_META")
		if err := restoreShowLikeOrWhereOpt(); err != nil {
			return err
		}
	case ShowStatsHistograms:
		ctx.WriteKeyWord("STATS_HISTOGRAMS")
		if err := restoreShowLikeOrWhereOpt(); err != nil {
			return err
		}
	case ShowStatsTopN:
		ctx.WriteKeyWord("STATS_TOPN")
		if err := restoreShowLikeOrWhereOpt(); err != nil {
			return err
		}
	case ShowStatsBuckets:
		ctx.WriteKeyWord("STATS_BUCKETS")
		if err := restoreShowLikeOrWhereOpt(); err != nil {
			return err
		}
	case ShowStatsHealthy:
		ctx.WriteKeyWord("STATS_HEALTHY")
		if err := restoreShowLikeOrWhereOpt(); err != nil {
			return err
		}
	case ShowProfiles:
		ctx.WriteKeyWord("PROFILES")
	case ShowProfile:
		ctx.WriteKeyWord("PROFILE")
		if len(n.ShowProfileTypes) > 0 {
			for i, tp := range n.ShowProfileTypes {
				if i != 0 {
					ctx.WritePlain(",")
				}
				ctx.WritePlain(" ")
				switch tp {
				case ProfileTypeCPU:
					ctx.WriteKeyWord("CPU")
				case ProfileTypeMemory:
					ctx.WriteKeyWord("MEMORY")
				case ProfileTypeBlockIo:
					ctx.WriteKeyWord("BLOCK IO")
				case ProfileTypeContextSwitch:
					ctx.WriteKeyWord("CONTEXT SWITCHES")
				case ProfileTypeIpc:
					ctx.WriteKeyWord("IPC")
				case ProfileTypePageFaults:
					ctx.WriteKeyWord("PAGE FAULTS")
				case ProfileTypeSource:
					ctx.WriteKeyWord("SOURCE")
				case ProfileTypeSwaps:
					ctx.WriteKeyWord("SWAPS")
				case ProfileTypeAll:
					ctx.WriteKeyWord("ALL")
				}
			}
		}
		if n.ShowProfileArgs != nil {
			ctx.WriteKeyWord(" FOR QUERY ")
			ctx.WritePlainf("%d", *n.ShowProfileArgs)
		}
		if n.ShowProfileLimit != nil {
			ctx.WritePlain(" ")
			if err := n.ShowProfileLimit.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore ShowStmt.WritePlain")
			}
		}

	case ShowPrivileges:
		ctx.WriteKeyWord("PRIVILEGES")
	case ShowBuiltins:
		ctx.WriteKeyWord("BUILTINS")
	case ShowCreateImport:
		ctx.WriteKeyWord("CREATE IMPORT ")
		ctx.WriteName(n.DBName)
	// ShowTargetFilterable
	default:
		switch n.Tp {
		case ShowEngines:
			ctx.WriteKeyWord("ENGINES")
		case ShowConfig:
			ctx.WriteKeyWord("CONFIG")
		case ShowDatabases:
			ctx.WriteKeyWord("DATABASES")
		case ShowCharset:
			ctx.WriteKeyWord("CHARSET")
		case ShowTables:
			restoreOptFull()
			ctx.WriteKeyWord("TABLES")
			restoreShowDatabaseNameOpt()
		case ShowOpenTables:
			ctx.WriteKeyWord("OPEN TABLES")
			restoreShowDatabaseNameOpt()
		case ShowTableStatus:
			ctx.WriteKeyWord("TABLE STATUS")
			restoreShowDatabaseNameOpt()
		case ShowIndex:
			// here can be INDEX INDEXES KEYS
			// FROM or IN
			ctx.WriteKeyWord("INDEX IN ")
			if err := n.Table.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while resotre ShowStmt.Table")
			} // TODO: remember to check this case
		case ShowColumns: // equivalent to SHOW FIELDS
			if n.Extended {
				ctx.WriteKeyWord("EXTENDED ")
			}
			restoreOptFull()
			ctx.WriteKeyWord("COLUMNS")
			if n.Table != nil {
				// FROM or IN
				ctx.WriteKeyWord(" IN ")
				if err := n.Table.Restore(ctx); err != nil {
					return errors.Annotate(err, "An error occurred while resotre ShowStmt.Table")
				}
			}
			restoreShowDatabaseNameOpt()
		case ShowWarnings:
			ctx.WriteKeyWord("WARNINGS")
		case ShowErrors:
			ctx.WriteKeyWord("ERRORS")
		case ShowVariables:
			restoreGlobalScope()
			ctx.WriteKeyWord("VARIABLES")
		case ShowStatus:
			restoreGlobalScope()
			ctx.WriteKeyWord("STATUS")
		case ShowCollation:
			ctx.WriteKeyWord("COLLATION")
		case ShowTriggers:
			ctx.WriteKeyWord("TRIGGERS")
			restoreShowDatabaseNameOpt()
		case ShowProcedureStatus:
			ctx.WriteKeyWord("PROCEDURE STATUS")
		case ShowEvents:
			ctx.WriteKeyWord("EVENTS")
			restoreShowDatabaseNameOpt()
		case ShowPlugins:
			ctx.WriteKeyWord("PLUGINS")
		case ShowBindings:
			if n.GlobalScope {
				ctx.WriteKeyWord("GLOBAL ")
			} else {
				ctx.WriteKeyWord("SESSION ")
			}
			ctx.WriteKeyWord("BINDINGS")
		case ShowPumpStatus:
			ctx.WriteKeyWord("PUMP STATUS")
		case ShowDrainerStatus:
			ctx.WriteKeyWord("DRAINER STATUS")
		case ShowAnalyzeStatus:
			ctx.WriteKeyWord("ANALYZE STATUS")
		case ShowRegions:
			ctx.WriteKeyWord("TABLE ")
			if err := n.Table.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore SplitIndexRegionStmt.Table")
			}
			if len(n.IndexName.L) > 0 {
				ctx.WriteKeyWord(" INDEX ")
				ctx.WriteName(n.IndexName.String())
			}
			ctx.WriteKeyWord(" REGIONS")
			if err := restoreShowLikeOrWhereOpt(); err != nil {
				return err
			}
			return nil
		case ShowTableNextRowId:
			ctx.WriteKeyWord("TABLE ")
			if err := n.Table.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore SplitIndexRegionStmt.Table")
			}
			ctx.WriteKeyWord(" NEXT_ROW_ID")
			return nil
		case ShowBackups:
			ctx.WriteKeyWord("BACKUPS")
		case ShowRestores:
			ctx.WriteKeyWord("RESTORES")
		case ShowImports:
			ctx.WriteKeyWord("IMPORTS")
		default:
			return errors.New("Unknown ShowStmt type")
		}
		restoreShowLikeOrWhereOpt()
	}
	return nil
}

// Accept implements Node Accept interface.
func (n *ShowStmt) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*ShowStmt)
	if n.Table != nil {
		node, ok := n.Table.Accept(v)
		if !ok {
			return n, false
		}
		n.Table = node.(*TableName)
	}
	if n.Column != nil {
		node, ok := n.Column.Accept(v)
		if !ok {
			return n, false
		}
		n.Column = node.(*ColumnName)
	}
	if n.Pattern != nil {
		node, ok := n.Pattern.Accept(v)
		if !ok {
			return n, false
		}
		n.Pattern = node.(*PatternLikeExpr)
	}

	if n.Where != nil {
		node, ok := n.Where.Accept(v)
		if !ok {
			return n, false
		}
		n.Where = node.(ExprNode)
	}
	return v.Leave(n)
}

// WindowSpec is the specification of a window.
type WindowSpec struct {
	node

	Name model.CIStr
	// Ref is the reference window of this specification. For example, in `w2 as (w1 order by a)`,
	// the definition of `w2` references `w1`.
	Ref model.CIStr

	PartitionBy *PartitionByClause
	OrderBy     *OrderByClause
	Frame       *FrameClause

	// OnlyAlias will set to true of the first following case.
	// To make compatible with MySQL, we need to distinguish `select func over w` from `select func over (w)`.
	OnlyAlias bool
}

// Restore implements Node interface.
func (n *WindowSpec) Restore(ctx *format.RestoreCtx) error {
	if name := n.Name.String(); name != "" {
		ctx.WriteName(name)
		if n.OnlyAlias {
			return nil
		}
		ctx.WriteKeyWord(" AS ")
	}
	ctx.WritePlain("(")
	sep := ""
	if refName := n.Ref.String(); refName != "" {
		ctx.WriteName(refName)
		sep = " "
	}
	if n.PartitionBy != nil {
		ctx.WritePlain(sep)
		if err := n.PartitionBy.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore WindowSpec.PartitionBy")
		}
		sep = " "
	}
	if n.OrderBy != nil {
		ctx.WritePlain(sep)
		if err := n.OrderBy.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore WindowSpec.OrderBy")
		}
		sep = " "
	}
	if n.Frame != nil {
		ctx.WritePlain(sep)
		if err := n.Frame.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore WindowSpec.Frame")
		}
	}
	ctx.WritePlain(")")

	return nil
}

// Accept implements Node Accept interface.
func (n *WindowSpec) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*WindowSpec)
	if n.PartitionBy != nil {
		node, ok := n.PartitionBy.Accept(v)
		if !ok {
			return n, false
		}
		n.PartitionBy = node.(*PartitionByClause)
	}
	if n.OrderBy != nil {
		node, ok := n.OrderBy.Accept(v)
		if !ok {
			return n, false
		}
		n.OrderBy = node.(*OrderByClause)
	}
	if n.Frame != nil {
		node, ok := n.Frame.Accept(v)
		if !ok {
			return n, false
		}
		n.Frame = node.(*FrameClause)
	}
	return v.Leave(n)
}

type SelectIntoType int

const (
	SelectIntoOutfile SelectIntoType = iota + 1
	SelectIntoDumpfile
	SelectIntoVars
)

type SelectIntoOption struct {
	node

	Tp         SelectIntoType
	FileName   string
	FieldsInfo *FieldsClause
	LinesInfo  *LinesClause
}

// Restore implements Node interface.
func (n *SelectIntoOption) Restore(ctx *format.RestoreCtx) error {
	if n.Tp != SelectIntoOutfile {
		// only support SELECT/TABLE/VALUES ... INTO OUTFILE statement now
		return errors.New("Unsupported SelectionInto type")
	}

	ctx.WriteKeyWord("INTO OUTFILE ")
	ctx.WriteString(n.FileName)
	if n.FieldsInfo != nil {
		if err := n.FieldsInfo.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore SelectInto.FieldsInfo")
		}
	}
	if n.LinesInfo != nil {
		if err := n.LinesInfo.Restore(ctx); err != nil {
			return errors.Annotate(err, "An error occurred while restore SelectInto.LinesInfo")
		}
	}
	return nil
}

// Accept implements Node Accept interface.
func (n *SelectIntoOption) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	return v.Leave(n)
}

// PartitionByClause represents partition by clause.
type PartitionByClause struct {
	node

	Items []*ByItem
}

// Restore implements Node interface.
func (n *PartitionByClause) Restore(ctx *format.RestoreCtx) error {
	ctx.WriteKeyWord("PARTITION BY ")
	for i, v := range n.Items {
		if i != 0 {
			ctx.WritePlain(", ")
		}
		if err := v.Restore(ctx); err != nil {
			return errors.Annotatef(err, "An error occurred while restore PartitionByClause.Items[%d]", i)
		}
	}
	return nil
}

// Accept implements Node Accept interface.
func (n *PartitionByClause) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*PartitionByClause)
	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)
}

// FrameType is the type of window function frame.
type FrameType int

// Window function frame types.
// MySQL only supports `ROWS` and `RANGES`.
const (
	Rows = iota
	Ranges
	Groups
)

// FrameClause represents frame clause.
type FrameClause struct {
	node

	Type   FrameType
	Extent FrameExtent
}

// Restore implements Node interface.
func (n *FrameClause) Restore(ctx *format.RestoreCtx) error {
	switch n.Type {
	case Rows:
		ctx.WriteKeyWord("ROWS")
	case Ranges:
		ctx.WriteKeyWord("RANGE")
	default:
		return errors.New("Unsupported window function frame type")
	}
	ctx.WriteKeyWord(" BETWEEN ")
	if err := n.Extent.Start.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore FrameClause.Extent.Start")
	}
	ctx.WriteKeyWord(" AND ")
	if err := n.Extent.End.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore FrameClause.Extent.End")
	}

	return nil
}

// Accept implements Node Accept interface.
func (n *FrameClause) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*FrameClause)
	node, ok := n.Extent.Start.Accept(v)
	if !ok {
		return n, false
	}
	n.Extent.Start = *node.(*FrameBound)
	node, ok = n.Extent.End.Accept(v)
	if !ok {
		return n, false
	}
	n.Extent.End = *node.(*FrameBound)
	return v.Leave(n)
}

// FrameExtent represents frame extent.
type FrameExtent struct {
	Start FrameBound
	End   FrameBound
}

// FrameType is the type of window function frame bound.
type BoundType int

// Frame bound types.
const (
	Following = iota
	Preceding
	CurrentRow
)

// FrameBound represents frame bound.
type FrameBound struct {
	node

	Type      BoundType
	UnBounded bool
	Expr      ExprNode
	// `Unit` is used to indicate the units in which the `Expr` should be interpreted.
	// For example: '2:30' MINUTE_SECOND.
	Unit TimeUnitType
}

// Restore implements Node interface.
func (n *FrameBound) Restore(ctx *format.RestoreCtx) error {
	if n.UnBounded {
		ctx.WriteKeyWord("UNBOUNDED")
	}
	switch n.Type {
	case CurrentRow:
		ctx.WriteKeyWord("CURRENT ROW")
	case Preceding, Following:
		if n.Unit != TimeUnitInvalid {
			ctx.WriteKeyWord("INTERVAL ")
		}
		if n.Expr != nil {
			if err := n.Expr.Restore(ctx); err != nil {
				return errors.Annotate(err, "An error occurred while restore FrameBound.Expr")
			}
		}
		if n.Unit != TimeUnitInvalid {
			ctx.WritePlain(" ")
			ctx.WriteKeyWord(n.Unit.String())
		}
		if n.Type == Preceding {
			ctx.WriteKeyWord(" PRECEDING")
		} else {
			ctx.WriteKeyWord(" FOLLOWING")
		}
	}
	return nil
}

// Accept implements Node Accept interface.
func (n *FrameBound) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}
	n = newNode.(*FrameBound)
	if n.Expr != nil {
		node, ok := n.Expr.Accept(v)
		if !ok {
			return n, false
		}
		n.Expr = node.(ExprNode)
	}
	return v.Leave(n)
}

type SplitRegionStmt struct {
	dmlNode

	Table          *TableName
	IndexName      model.CIStr
	PartitionNames []model.CIStr

	SplitSyntaxOpt *SplitSyntaxOption

	SplitOpt *SplitOption
}

type SplitOption struct {
	Lower      []ExprNode
	Upper      []ExprNode
	Num        int64
	ValueLists [][]ExprNode
}

type SplitSyntaxOption struct {
	HasRegionFor bool
	HasPartition bool
}

func (n *SplitRegionStmt) Restore(ctx *format.RestoreCtx) error {
	ctx.WriteKeyWord("SPLIT ")
	if n.SplitSyntaxOpt != nil {
		if n.SplitSyntaxOpt.HasRegionFor {
			ctx.WriteKeyWord("REGION FOR ")
		}
		if n.SplitSyntaxOpt.HasPartition {
			ctx.WriteKeyWord("PARTITION ")

		}
	}
	ctx.WriteKeyWord("TABLE ")

	if err := n.Table.Restore(ctx); err != nil {
		return errors.Annotate(err, "An error occurred while restore SplitIndexRegionStmt.Table")
	}
	if len(n.PartitionNames) > 0 {
		ctx.WriteKeyWord(" PARTITION")
		ctx.WritePlain("(")
		for i, v := range n.PartitionNames {
			if i != 0 {
				ctx.WritePlain(", ")
			}
			ctx.WriteName(v.String())
		}
		ctx.WritePlain(")")
	}

	if len(n.IndexName.L) > 0 {
		ctx.WriteKeyWord(" INDEX ")
		ctx.WriteName(n.IndexName.String())
	}
	ctx.WritePlain(" ")
	err := n.SplitOpt.Restore(ctx)
	return err
}

func (n *SplitRegionStmt) Accept(v Visitor) (Node, bool) {
	newNode, skipChildren := v.Enter(n)
	if skipChildren {
		return v.Leave(newNode)
	}

	n = newNode.(*SplitRegionStmt)
	node, ok := n.Table.Accept(v)
	if !ok {
		return n, false
	}
	n.Table = node.(*TableName)
	for i, val := range n.SplitOpt.Lower {
		node, ok := val.Accept(v)
		if !ok {
			return n, false
		}
		n.SplitOpt.Lower[i] = node.(ExprNode)
	}
	for i, val := range n.SplitOpt.Upper {
		node, ok := val.Accept(v)
		if !ok {
			return n, false
		}
		n.SplitOpt.Upper[i] = node.(ExprNode)
	}

	for i, list := range n.SplitOpt.ValueLists {
		for j, val := range list {
			node, ok := val.Accept(v)
			if !ok {
				return n, false
			}
			n.SplitOpt.ValueLists[i][j] = node.(ExprNode)
		}
	}
	return v.Leave(n)
}

func (n *SplitOption) Restore(ctx *format.RestoreCtx) error {
	if len(n.ValueLists) == 0 {
		ctx.WriteKeyWord("BETWEEN ")
		ctx.WritePlain("(")
		for j, v := range n.Lower {
			if j != 0 {
				ctx.WritePlain(",")
			}
			if err := v.Restore(ctx); err != nil {
				return errors.Annotatef(err, "An error occurred while restore SplitOption Lower")
			}
		}
		ctx.WritePlain(")")

		ctx.WriteKeyWord(" AND ")
		ctx.WritePlain("(")
		for j, v := range n.Upper {
			if j != 0 {
				ctx.WritePlain(",")
			}
			if err := v.Restore(ctx); err != nil {
				return errors.Annotatef(err, "An error occurred while restore SplitOption Upper")
			}
		}
		ctx.WritePlain(")")
		ctx.WriteKeyWord(" REGIONS")
		ctx.WritePlainf(" %d", n.Num)
		return nil
	}
	ctx.WriteKeyWord("BY ")
	for i, row := range n.ValueLists {
		if i != 0 {
			ctx.WritePlain(",")
		}
		ctx.WritePlain("(")
		for j, v := range row {
			if j != 0 {
				ctx.WritePlain(",")
			}
			if err := v.Restore(ctx); err != nil {
				return errors.Annotatef(err, "An error occurred while restore SplitOption.ValueLists[%d][%d]", i, j)
			}
		}
		ctx.WritePlain(")")
	}
	return nil
}

type FulltextSearchModifier int

const (
	FulltextSearchModifierNaturalLanguageMode = 0
	FulltextSearchModifierBooleanMode         = 1
	FulltextSearchModifierModeMask            = 0xF
	FulltextSearchModifierWithQueryExpansion  = 1 << 4
)

func (m FulltextSearchModifier) IsBooleanMode() bool {
	return m&FulltextSearchModifierModeMask == FulltextSearchModifierBooleanMode
}

func (m FulltextSearchModifier) IsNaturalLanguageMode() bool {
	return m&FulltextSearchModifierModeMask == FulltextSearchModifierNaturalLanguageMode
}

func (m FulltextSearchModifier) WithQueryExpansion() bool {
	return m&FulltextSearchModifierWithQueryExpansion == FulltextSearchModifierWithQueryExpansion
}

type TimestampBound struct {
	Mode      TimestampBoundMode
	Timestamp ExprNode
}

type TimestampBoundMode int

const (
	TimestampBoundStrong TimestampBoundMode = iota
	TimestampBoundMaxStaleness
	TimestampBoundExactStaleness
	TimestampBoundReadTimestamp
	TimestampBoundMinReadTimestamp
)