ast.go

/*
Copyright 2017 Google 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 sqlparser

import (
	"bytes"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"strings"

	"github.com/xwb1989/sqlparser/dependency/querypb"
	"github.com/xwb1989/sqlparser/dependency/sqltypes"
)

// Instructions for creating new types: If a type
// needs to satisfy an interface, declare that function
// along with that interface. This will help users
// identify the list of types to which they can assert
// those interfaces.
// If the member of a type has a string with a predefined
// list of values, declare those values as const following
// the type.
// For interfaces that define dummy functions to consolidate
// a set of types, define the function as iTypeName.
// This will help avoid name collisions.

// Parse parses the SQL in full and returns a Statement, which
// is the AST representation of the query. If a DDL statement
// is partially parsed but still contains a syntax error, the
// error is ignored and the DDL is returned anyway.
func Parse(sql string) (Statement, error) {
	tokenizer := NewStringTokenizer(sql)
	if yyParse(tokenizer) != 0 {
		if tokenizer.partialDDL != nil {
			log.Printf("ignoring error parsing DDL '%s': %v", sql, tokenizer.LastError)
			tokenizer.ParseTree = tokenizer.partialDDL
			return tokenizer.ParseTree, nil
		}
		return nil, tokenizer.LastError
	}
	return tokenizer.ParseTree, nil
}

// ParseStrictDDL is the same as Parse except it errors on
// partially parsed DDL statements.
func ParseStrictDDL(sql string) (Statement, error) {
	tokenizer := NewStringTokenizer(sql)
	if yyParse(tokenizer) != 0 {
		return nil, tokenizer.LastError
	}
	return tokenizer.ParseTree, nil
}

// ParseNext parses a single SQL statement from the tokenizer
// returning a Statement which is the AST representation of the query.
// The tokenizer will always read up to the end of the statement, allowing for
// the next call to ParseNext to parse any subsequent SQL statements. When
// there are no more statements to parse, a error of io.EOF is returned.
func ParseNext(tokenizer *Tokenizer) (Statement, error) {
	if tokenizer.lastChar == ';' {
		tokenizer.next()
		tokenizer.skipBlank()
	}
	if tokenizer.lastChar == eofChar {
		return nil, io.EOF
	}

	tokenizer.reset()
	tokenizer.multi = true
	if yyParse(tokenizer) != 0 {
		if tokenizer.partialDDL != nil {
			tokenizer.ParseTree = tokenizer.partialDDL
			return tokenizer.ParseTree, nil
		}
		return nil, tokenizer.LastError
	}
	return tokenizer.ParseTree, nil
}

// SplitStatement returns the first sql statement up to either a ; or EOF
// and the remainder from the given buffer
func SplitStatement(blob string) (string, string, error) {
	tokenizer := NewStringTokenizer(blob)
	tkn := 0
	for {
		tkn, _ = tokenizer.Scan()
		if tkn == 0 || tkn == ';' || tkn == eofChar {
			break
		}
	}
	if tokenizer.LastError != nil {
		return "", "", tokenizer.LastError
	}
	if tkn == ';' {
		return blob[:tokenizer.Position-2], blob[tokenizer.Position-1:], nil
	}
	return blob, "", nil
}

// SQLNode defines the interface for all nodes
// generated by the parser.
type SQLNode interface {
	Format(buf *TrackedBuffer)
	// WalkSubtree calls visit on all underlying nodes
	// of the subtree, but not the current one. Walking
	// must be interrupted if visit returns an error.
	WalkSubtree(visit Visit) error
}

// Visit defines the signature of a function that
// can be used to visit all nodes of a parse tree.
type Visit func(node SQLNode) (kontinue bool, err error)

// Walk calls visit on every node.
// If visit returns true, the underlying nodes
// are also visited. If it returns an error, walking
// is interrupted, and the error is returned.
func Walk(visit Visit, nodes ...SQLNode) error {
	for _, node := range nodes {
		if node == nil {
			continue
		}
		kontinue, err := visit(node)
		if err != nil {
			return err
		}
		if kontinue {
			err = node.WalkSubtree(visit)
			if err != nil {
				return err
			}
		}
	}
	return nil
}

// String returns a string representation of an SQLNode.
func String(node SQLNode) string {
	if node == nil {
		return "<nil>"
	}

	buf := NewTrackedBuffer(nil)
	buf.Myprintf("%v", node)
	return buf.String()
}

// Append appends the SQLNode to the buffer.
func Append(buf *bytes.Buffer, node SQLNode) {
	tbuf := &TrackedBuffer{
		Buffer: buf,
	}
	node.Format(tbuf)
}

// Statement represents a statement.
type Statement interface {
	iStatement()
	SQLNode
}

func (*Union) iStatement()      {}
func (*Select) iStatement()     {}
func (*Insert) iStatement()     {}
func (*Update) iStatement()     {}
func (*Delete) iStatement()     {}
func (*Set) iStatement()        {}
func (*DDL) iStatement()        {}
func (*Show) iStatement()       {}
func (*Use) iStatement()        {}
func (*OtherRead) iStatement()  {}
func (*OtherAdmin) iStatement() {}

// ParenSelect can actually not be a top level statement,
// but we have to allow it because it's a requirement
// of SelectStatement.
func (*ParenSelect) iStatement() {}

// SelectStatement any SELECT statement.
type SelectStatement interface {
	iSelectStatement()
	iStatement()
	iInsertRows()
	AddOrder(*Order)
	SetLimit(*Limit)
	SQLNode
}

func (*Select) iSelectStatement()      {}
func (*Union) iSelectStatement()       {}
func (*ParenSelect) iSelectStatement() {}

// Select represents a SELECT statement.
type Select struct {
	Cache       string
	Comments    Comments
	Distinct    string
	Hints       string
	SelectExprs SelectExprs
	From        TableExprs
	Where       *Where
	GroupBy     GroupBy
	Having      *Where
	OrderBy     OrderBy
	Limit       *Limit
	Lock        string
}

// Select.Distinct
const (
	DistinctStr      = "distinct "
	StraightJoinHint = "straight_join "
)

// Select.Lock
const (
	ForUpdateStr = " for update"
	ShareModeStr = " lock in share mode"
)

// Select.Cache
const (
	SQLCacheStr   = "sql_cache "
	SQLNoCacheStr = "sql_no_cache "
)

// AddOrder adds an order by element
func (node *Select) AddOrder(order *Order) {
	node.OrderBy = append(node.OrderBy, order)
}

// SetLimit sets the limit clause
func (node *Select) SetLimit(limit *Limit) {
	node.Limit = limit
}

// Format formats the node.
func (node *Select) Format(buf *TrackedBuffer) {
	buf.Myprintf("select %v%s%s%s%v from %v%v%v%v%v%v%s",
		node.Comments, node.Cache, node.Distinct, node.Hints, node.SelectExprs,
		node.From, node.Where,
		node.GroupBy, node.Having, node.OrderBy,
		node.Limit, node.Lock)
}

// WalkSubtree walks the nodes of the subtree.
func (node *Select) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Comments,
		node.SelectExprs,
		node.From,
		node.Where,
		node.GroupBy,
		node.Having,
		node.OrderBy,
		node.Limit,
	)
}

// AddWhere adds the boolean expression to the
// WHERE clause as an AND condition. If the expression
// is an OR clause, it parenthesizes it. Currently,
// the OR operator is the only one that's lower precedence
// than AND.
func (node *Select) AddWhere(expr Expr) {
	if _, ok := expr.(*OrExpr); ok {
		expr = &ParenExpr{Expr: expr}
	}
	if node.Where == nil {
		node.Where = &Where{
			Type: WhereStr,
			Expr: expr,
		}
		return
	}
	node.Where.Expr = &AndExpr{
		Left:  node.Where.Expr,
		Right: expr,
	}
	return
}

// AddHaving adds the boolean expression to the
// HAVING clause as an AND condition. If the expression
// is an OR clause, it parenthesizes it. Currently,
// the OR operator is the only one that's lower precedence
// than AND.
func (node *Select) AddHaving(expr Expr) {
	if _, ok := expr.(*OrExpr); ok {
		expr = &ParenExpr{Expr: expr}
	}
	if node.Having == nil {
		node.Having = &Where{
			Type: HavingStr,
			Expr: expr,
		}
		return
	}
	node.Having.Expr = &AndExpr{
		Left:  node.Having.Expr,
		Right: expr,
	}
	return
}

// ParenSelect is a parenthesized SELECT statement.
type ParenSelect struct {
	Select SelectStatement
}

// AddOrder adds an order by element
func (node *ParenSelect) AddOrder(order *Order) {
	panic("unreachable")
}

// SetLimit sets the limit clause
func (node *ParenSelect) SetLimit(limit *Limit) {
	panic("unreachable")
}

// Format formats the node.
func (node *ParenSelect) Format(buf *TrackedBuffer) {
	buf.Myprintf("(%v)", node.Select)
}

// WalkSubtree walks the nodes of the subtree.
func (node *ParenSelect) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Select,
	)
}

// Union represents a UNION statement.
type Union struct {
	Type        string
	Left, Right SelectStatement
	OrderBy     OrderBy
	Limit       *Limit
	Lock        string
}

// Union.Type
const (
	UnionStr         = "union"
	UnionAllStr      = "union all"
	UnionDistinctStr = "union distinct"
)

// AddOrder adds an order by element
func (node *Union) AddOrder(order *Order) {
	node.OrderBy = append(node.OrderBy, order)
}

// SetLimit sets the limit clause
func (node *Union) SetLimit(limit *Limit) {
	node.Limit = limit
}

// Format formats the node.
func (node *Union) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v %s %v%v%v%s", node.Left, node.Type, node.Right,
		node.OrderBy, node.Limit, node.Lock)
}

// WalkSubtree walks the nodes of the subtree.
func (node *Union) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Left,
		node.Right,
	)
}

// Insert represents an INSERT or REPLACE statement.
// Per the MySQL docs, http://dev.mysql.com/doc/refman/5.7/en/replace.html
// Replace is the counterpart to `INSERT IGNORE`, and works exactly like a
// normal INSERT except if the row exists. In that case it first deletes
// the row and re-inserts with new values. For that reason we keep it as an Insert struct.
// Replaces are currently disallowed in sharded schemas because
// of the implications the deletion part may have on vindexes.
// If you add fields here, consider adding them to calls to validateSubquerySamePlan.
type Insert struct {
	Action   string
	Comments Comments
	Ignore   string
	Table    TableName
	Columns  Columns
	Rows     InsertRows
	OnDup    OnDup
}

// DDL strings.
const (
	InsertStr  = "insert"
	ReplaceStr = "replace"
)

// Format formats the node.
func (node *Insert) Format(buf *TrackedBuffer) {
	buf.Myprintf("%s %v%sinto %v%v %v%v",
		node.Action,
		node.Comments, node.Ignore,
		node.Table, node.Columns, node.Rows, node.OnDup)
}

// WalkSubtree walks the nodes of the subtree.
func (node *Insert) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Comments,
		node.Table,
		node.Columns,
		node.Rows,
		node.OnDup,
	)
}

// InsertRows represents the rows for an INSERT statement.
type InsertRows interface {
	iInsertRows()
	SQLNode
}

func (*Select) iInsertRows()      {}
func (*Union) iInsertRows()       {}
func (Values) iInsertRows()       {}
func (*ParenSelect) iInsertRows() {}

// Update represents an UPDATE statement.
// If you add fields here, consider adding them to calls to validateSubquerySamePlan.
type Update struct {
	Comments   Comments
	TableExprs TableExprs
	Exprs      UpdateExprs
	Where      *Where
	OrderBy    OrderBy
	Limit      *Limit
}

// Format formats the node.
func (node *Update) Format(buf *TrackedBuffer) {
	buf.Myprintf("update %v%v set %v%v%v%v",
		node.Comments, node.TableExprs,
		node.Exprs, node.Where, node.OrderBy, node.Limit)
}

// WalkSubtree walks the nodes of the subtree.
func (node *Update) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Comments,
		node.TableExprs,
		node.Exprs,
		node.Where,
		node.OrderBy,
		node.Limit,
	)
}

// Delete represents a DELETE statement.
// If you add fields here, consider adding them to calls to validateSubquerySamePlan.
type Delete struct {
	Comments   Comments
	Targets    TableNames
	TableExprs TableExprs
	Where      *Where
	OrderBy    OrderBy
	Limit      *Limit
}

// Format formats the node.
func (node *Delete) Format(buf *TrackedBuffer) {
	buf.Myprintf("delete %v", node.Comments)
	if node.Targets != nil {
		buf.Myprintf("%v ", node.Targets)
	}
	buf.Myprintf("from %v%v%v%v", node.TableExprs, node.Where, node.OrderBy, node.Limit)
}

// WalkSubtree walks the nodes of the subtree.
func (node *Delete) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Comments,
		node.Targets,
		node.TableExprs,
		node.Where,
		node.OrderBy,
		node.Limit,
	)
}

// Set represents a SET statement.
type Set struct {
	Comments Comments
	Exprs    UpdateExprs
	Charset  ColIdent
}

// Format formats the node.
func (node *Set) Format(buf *TrackedBuffer) {
	buf.Myprintf("set %v%v", node.Comments, node.Exprs)
}

// WalkSubtree walks the nodes of the subtree.
func (node *Set) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Comments,
		node.Exprs,
	)
}

// DDL represents a CREATE, ALTER, DROP, RENAME or TRUNCATE statement.
// Table is set for AlterStr, DropStr, RenameStr, TruncateStr
// NewName is set for AlterStr, CreateStr, RenameStr.
type DDL struct {
	Action        string
	Table         TableName
	NewName       TableName
	IfExists      bool
	TableSpec     *TableSpec
	PartitionSpec *PartitionSpec
}

// DDL strings.
const (
	CreateStr   = "create"
	AlterStr    = "alter"
	DropStr     = "drop"
	RenameStr   = "rename"
	TruncateStr = "truncate"
)

// Format formats the node.
func (node *DDL) Format(buf *TrackedBuffer) {
	switch node.Action {
	case CreateStr:
		if node.TableSpec == nil {
			buf.Myprintf("%s table %v", node.Action, node.NewName)
		} else {
			buf.Myprintf("%s table %v %v", node.Action, node.NewName, node.TableSpec)
		}
	case DropStr:
		exists := ""
		if node.IfExists {
			exists = " if exists"
		}
		buf.Myprintf("%s table%s %v", node.Action, exists, node.Table)
	case RenameStr:
		buf.Myprintf("%s table %v %v", node.Action, node.Table, node.NewName)
	case AlterStr:
		if node.PartitionSpec != nil {
			buf.Myprintf("%s table %v %v", node.Action, node.Table, node.PartitionSpec)
		} else {
			buf.Myprintf("%s table %v", node.Action, node.Table)
		}
	default:
		buf.Myprintf("%s table %v", node.Action, node.Table)
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node *DDL) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Table,
		node.NewName,
	)
}

// Partition strings
const (
	ReorganizeStr = "reorganize partition"
)

// PartitionSpec describe partition actions (for alter and create)
type PartitionSpec struct {
	Action      string
	Name        ColIdent
	Definitions []*PartitionDefinition
}

// Format formats the node.
func (node *PartitionSpec) Format(buf *TrackedBuffer) {
	switch node.Action {
	case ReorganizeStr:
		buf.Myprintf("%s %v into (", node.Action, node.Name)
		var prefix string
		for _, pd := range node.Definitions {
			buf.Myprintf("%s%v", prefix, pd)
			prefix = ", "
		}
		buf.Myprintf(")")
	default:
		panic("unimplemented")
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node *PartitionSpec) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	if err := Walk(visit, node.Name); err != nil {
		return err
	}
	for _, def := range node.Definitions {
		if err := Walk(visit, def); err != nil {
			return err
		}
	}
	return nil
}

// PartitionDefinition describes a very minimal partition definition
type PartitionDefinition struct {
	Name     ColIdent
	Limit    Expr
	Maxvalue bool
}

// Format formats the node
func (node *PartitionDefinition) Format(buf *TrackedBuffer) {
	if !node.Maxvalue {
		buf.Myprintf("partition %v values less than (%v)", node.Name, node.Limit)
	} else {
		buf.Myprintf("partition %v values less than (maxvalue)", node.Name)
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node *PartitionDefinition) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Name,
		node.Limit,
	)
}

// TableSpec describes the structure of a table from a CREATE TABLE statement
type TableSpec struct {
	Columns []*ColumnDefinition
	Indexes []*IndexDefinition
	Options string
}

// Format formats the node.
func (ts *TableSpec) Format(buf *TrackedBuffer) {
	buf.Myprintf("(\n")
	for i, col := range ts.Columns {
		if i == 0 {
			buf.Myprintf("\t%v", col)
		} else {
			buf.Myprintf(",\n\t%v", col)
		}
	}
	for _, idx := range ts.Indexes {
		buf.Myprintf(",\n\t%v", idx)
	}

	buf.Myprintf("\n)%s", strings.Replace(ts.Options, ", ", ",\n  ", -1))
}

// AddColumn appends the given column to the list in the spec
func (ts *TableSpec) AddColumn(cd *ColumnDefinition) {
	ts.Columns = append(ts.Columns, cd)
}

// AddIndex appends the given index to the list in the spec
func (ts *TableSpec) AddIndex(id *IndexDefinition) {
	ts.Indexes = append(ts.Indexes, id)
}

// WalkSubtree walks the nodes of the subtree.
func (ts *TableSpec) WalkSubtree(visit Visit) error {
	if ts == nil {
		return nil
	}

	for _, n := range ts.Columns {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}

	for _, n := range ts.Indexes {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}

	return nil
}

// ColumnDefinition describes a column in a CREATE TABLE statement
type ColumnDefinition struct {
	Name ColIdent
	Type ColumnType
}

// Format formats the node.
func (col *ColumnDefinition) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v %v", col.Name, &col.Type)
}

// WalkSubtree walks the nodes of the subtree.
func (col *ColumnDefinition) WalkSubtree(visit Visit) error {
	if col == nil {
		return nil
	}
	return Walk(
		visit,
		col.Name,
		&col.Type,
	)
}

// ColumnType represents a sql type in a CREATE TABLE statement
// All optional fields are nil if not specified
type ColumnType struct {
	// The base type string
	Type string

	// Generic field options.
	NotNull       BoolVal
	Autoincrement BoolVal
	Default       *SQLVal
	OnUpdate      *SQLVal
	Comment       *SQLVal

	// Numeric field options
	Length   *SQLVal
	Unsigned BoolVal
	Zerofill BoolVal
	Scale    *SQLVal

	// Text field options
	Charset string
	Collate string

	// Enum values
	EnumValues []string

	// Key specification
	KeyOpt ColumnKeyOption
}

// Format returns a canonical string representation of the type and all relevant options
func (ct *ColumnType) Format(buf *TrackedBuffer) {
	buf.Myprintf("%s", ct.Type)

	if ct.Length != nil && ct.Scale != nil {
		buf.Myprintf("(%v,%v)", ct.Length, ct.Scale)

	} else if ct.Length != nil {
		buf.Myprintf("(%v)", ct.Length)
	}

	if ct.EnumValues != nil {
		buf.Myprintf("(%s)", strings.Join(ct.EnumValues, ", "))
	}

	opts := make([]string, 0, 16)
	if ct.Unsigned {
		opts = append(opts, keywordStrings[UNSIGNED])
	}
	if ct.Zerofill {
		opts = append(opts, keywordStrings[ZEROFILL])
	}
	if ct.Charset != "" {
		opts = append(opts, keywordStrings[CHARACTER], keywordStrings[SET], ct.Charset)
	}
	if ct.Collate != "" {
		opts = append(opts, keywordStrings[COLLATE], ct.Collate)
	}
	if ct.NotNull {
		opts = append(opts, keywordStrings[NOT], keywordStrings[NULL])
	}
	if ct.Default != nil {
		opts = append(opts, keywordStrings[DEFAULT], String(ct.Default))
	}
	if ct.OnUpdate != nil {
		opts = append(opts, keywordStrings[ON], keywordStrings[UPDATE], String(ct.OnUpdate))
	}
	if ct.Autoincrement {
		opts = append(opts, keywordStrings[AUTO_INCREMENT])
	}
	if ct.Comment != nil {
		opts = append(opts, keywordStrings[COMMENT_KEYWORD], String(ct.Comment))
	}
	if ct.KeyOpt == colKeyPrimary {
		opts = append(opts, keywordStrings[PRIMARY], keywordStrings[KEY])
	}
	if ct.KeyOpt == colKeyUnique {
		opts = append(opts, keywordStrings[UNIQUE])
	}
	if ct.KeyOpt == colKeyUniqueKey {
		opts = append(opts, keywordStrings[UNIQUE], keywordStrings[KEY])
	}
	if ct.KeyOpt == colKey {
		opts = append(opts, keywordStrings[KEY])
	}

	if len(opts) != 0 {
		buf.Myprintf(" %s", strings.Join(opts, " "))
	}
}

// DescribeType returns the abbreviated type information as required for
// describe table
func (ct *ColumnType) DescribeType() string {
	buf := NewTrackedBuffer(nil)
	buf.Myprintf("%s", ct.Type)
	if ct.Length != nil && ct.Scale != nil {
		buf.Myprintf("(%v,%v)", ct.Length, ct.Scale)
	} else if ct.Length != nil {
		buf.Myprintf("(%v)", ct.Length)
	}

	opts := make([]string, 0, 16)
	if ct.Unsigned {
		opts = append(opts, keywordStrings[UNSIGNED])
	}
	if ct.Zerofill {
		opts = append(opts, keywordStrings[ZEROFILL])
	}
	if len(opts) != 0 {
		buf.Myprintf(" %s", strings.Join(opts, " "))
	}
	return buf.String()
}

// SQLType returns the sqltypes type code for the given column
func (ct *ColumnType) SQLType() querypb.Type {
	switch ct.Type {
	case keywordStrings[TINYINT]:
		if ct.Unsigned {
			return sqltypes.Uint8
		}
		return sqltypes.Int8
	case keywordStrings[SMALLINT]:
		if ct.Unsigned {
			return sqltypes.Uint16
		}
		return sqltypes.Int16
	case keywordStrings[MEDIUMINT]:
		if ct.Unsigned {
			return sqltypes.Uint24
		}
		return sqltypes.Int24
	case keywordStrings[INT]:
		fallthrough
	case keywordStrings[INTEGER]:
		if ct.Unsigned {
			return sqltypes.Uint32
		}
		return sqltypes.Int32
	case keywordStrings[BIGINT]:
		if ct.Unsigned {
			return sqltypes.Uint64
		}
		return sqltypes.Int64
	case keywordStrings[TEXT]:
		return sqltypes.Text
	case keywordStrings[TINYTEXT]:
		return sqltypes.Text
	case keywordStrings[MEDIUMTEXT]:
		return sqltypes.Text
	case keywordStrings[LONGTEXT]:
		return sqltypes.Text
	case keywordStrings[BLOB]:
		return sqltypes.Blob
	case keywordStrings[TINYBLOB]:
		return sqltypes.Blob
	case keywordStrings[MEDIUMBLOB]:
		return sqltypes.Blob
	case keywordStrings[LONGBLOB]:
		return sqltypes.Blob
	case keywordStrings[CHAR]:
		return sqltypes.Char
	case keywordStrings[VARCHAR]:
		return sqltypes.VarChar
	case keywordStrings[BINARY]:
		return sqltypes.Binary
	case keywordStrings[VARBINARY]:
		return sqltypes.VarBinary
	case keywordStrings[DATE]:
		return sqltypes.Date
	case keywordStrings[TIME]:
		return sqltypes.Time
	case keywordStrings[DATETIME]:
		return sqltypes.Datetime
	case keywordStrings[TIMESTAMP]:
		return sqltypes.Timestamp
	case keywordStrings[YEAR]:
		return sqltypes.Year
	case keywordStrings[FLOAT_TYPE]:
		return sqltypes.Float32
	case keywordStrings[DOUBLE]:
		return sqltypes.Float64
	case keywordStrings[DECIMAL]:
		return sqltypes.Decimal
	case keywordStrings[BIT]:
		return sqltypes.Bit
	case keywordStrings[ENUM]:
		return sqltypes.Enum
	case keywordStrings[JSON]:
		return sqltypes.TypeJSON
	}
	panic("unimplemented type " + ct.Type)
}

// WalkSubtree walks the nodes of the subtree.
func (ct *ColumnType) WalkSubtree(visit Visit) error {
	return nil
}

// IndexDefinition describes an index in a CREATE TABLE statement
type IndexDefinition struct {
	Info    *IndexInfo
	Columns []*IndexColumn
}

// Format formats the node.
func (idx *IndexDefinition) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v (", idx.Info)
	for i, col := range idx.Columns {
		if i != 0 {
			buf.Myprintf(", %v", col.Column)
		} else {
			buf.Myprintf("%v", col.Column)
		}
		if col.Length != nil {
			buf.Myprintf("(%v)", col.Length)
		}
	}
	buf.Myprintf(")")
}

// WalkSubtree walks the nodes of the subtree.
func (idx *IndexDefinition) WalkSubtree(visit Visit) error {
	if idx == nil {
		return nil
	}

	for _, n := range idx.Columns {
		if err := Walk(visit, n.Column); err != nil {
			return err
		}
	}

	return nil
}

// IndexInfo describes the name and type of an index in a CREATE TABLE statement
type IndexInfo struct {
	Type    string
	Name    ColIdent
	Primary bool
	Unique  bool
}

// Format formats the node.
func (ii *IndexInfo) Format(buf *TrackedBuffer) {
	if ii.Primary {
		buf.Myprintf("%s", ii.Type)
	} else {
		buf.Myprintf("%s %v", ii.Type, ii.Name)
	}
}

// WalkSubtree walks the nodes of the subtree.
func (ii *IndexInfo) WalkSubtree(visit Visit) error {
	return Walk(visit, ii.Name)
}

// IndexColumn describes a column in an index definition with optional length
type IndexColumn struct {
	Column ColIdent
	Length *SQLVal
}

// LengthScaleOption is used for types that have an optional length
// and scale
type LengthScaleOption struct {
	Length *SQLVal
	Scale  *SQLVal
}

// ColumnKeyOption indicates whether or not the given column is defined as an
// index element and contains the type of the option
type ColumnKeyOption int

const (
	colKeyNone ColumnKeyOption = iota
	colKeyPrimary
	colKeyUnique
	colKeyUniqueKey
	colKey
)

// Show represents a show statement.
type Show struct {
	Type string
}

// The frollowing constants represent SHOW statements.
const (
	ShowDatabasesStr     = "databases"
	ShowKeyspacesStr     = "vitess_keyspaces"
	ShowShardsStr        = "vitess_shards"
	ShowTablesStr        = "tables"
	ShowVSchemaTablesStr = "vschema_tables"
	ShowUnsupportedStr   = "unsupported"
)

// Format formats the node.
func (node *Show) Format(buf *TrackedBuffer) {
	buf.Myprintf("show %s", node.Type)
}

// WalkSubtree walks the nodes of the subtree.
func (node *Show) WalkSubtree(visit Visit) error {
	return nil
}

// Use represents a use statement.
type Use struct {
	DBName TableIdent
}

// Format formats the node.
func (node *Use) Format(buf *TrackedBuffer) {
	if node.DBName.v != "" {
		buf.Myprintf("use %v", node.DBName)
	} else {
		buf.Myprintf("use")
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node *Use) WalkSubtree(visit Visit) error {
	return Walk(visit, node.DBName)
}

// OtherRead represents a DESCRIBE, or EXPLAIN statement.
// It should be used only as an indicator. It does not contain
// the full AST for the statement.
type OtherRead struct{}

// Format formats the node.
func (node *OtherRead) Format(buf *TrackedBuffer) {
	buf.WriteString("otherread")
}

// WalkSubtree walks the nodes of the subtree.
func (node *OtherRead) WalkSubtree(visit Visit) error {
	return nil
}

// OtherAdmin represents a misc statement that relies on ADMIN privileges,
// such as REPAIR, OPTIMIZE, or TRUNCATE statement.
// It should be used only as an indicator. It does not contain
// the full AST for the statement.
type OtherAdmin struct{}

// Format formats the node.
func (node *OtherAdmin) Format(buf *TrackedBuffer) {
	buf.WriteString("otheradmin")
}

// WalkSubtree walks the nodes of the subtree.
func (node *OtherAdmin) WalkSubtree(visit Visit) error {
	return nil
}

// Comments represents a list of comments.
type Comments [][]byte

// Format formats the node.
func (node Comments) Format(buf *TrackedBuffer) {
	for _, c := range node {
		buf.Myprintf("%s ", c)
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node Comments) WalkSubtree(visit Visit) error {
	return nil
}

// SelectExprs represents SELECT expressions.
type SelectExprs []SelectExpr

// Format formats the node.
func (node SelectExprs) Format(buf *TrackedBuffer) {
	var prefix string
	for _, n := range node {
		buf.Myprintf("%s%v", prefix, n)
		prefix = ", "
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node SelectExprs) WalkSubtree(visit Visit) error {
	for _, n := range node {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}
	return nil
}

// SelectExpr represents a SELECT expression.
type SelectExpr interface {
	iSelectExpr()
	SQLNode
}

func (*StarExpr) iSelectExpr()    {}
func (*AliasedExpr) iSelectExpr() {}
func (Nextval) iSelectExpr()      {}

// StarExpr defines a '*' or 'table.*' expression.
type StarExpr struct {
	TableName TableName
}

// Format formats the node.
func (node *StarExpr) Format(buf *TrackedBuffer) {
	if !node.TableName.IsEmpty() {
		buf.Myprintf("%v.", node.TableName)
	}
	buf.Myprintf("*")
}

// WalkSubtree walks the nodes of the subtree.
func (node *StarExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.TableName,
	)
}

// AliasedExpr defines an aliased SELECT expression.
type AliasedExpr struct {
	Expr Expr
	As   ColIdent
}

// Format formats the node.
func (node *AliasedExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v", node.Expr)
	if !node.As.IsEmpty() {
		buf.Myprintf(" as %v", node.As)
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node *AliasedExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
		node.As,
	)
}

// Nextval defines the NEXT VALUE expression.
type Nextval struct {
	Expr Expr
}

// Format formats the node.
func (node Nextval) Format(buf *TrackedBuffer) {
	buf.Myprintf("next %v values", node.Expr)
}

// WalkSubtree walks the nodes of the subtree.
func (node Nextval) WalkSubtree(visit Visit) error {
	return Walk(visit, node.Expr)
}

// Columns represents an insert column list.
type Columns []ColIdent

// Format formats the node.
func (node Columns) Format(buf *TrackedBuffer) {
	if node == nil {
		return
	}
	prefix := "("
	for _, n := range node {
		buf.Myprintf("%s%v", prefix, n)
		prefix = ", "
	}
	buf.WriteString(")")
}

// WalkSubtree walks the nodes of the subtree.
func (node Columns) WalkSubtree(visit Visit) error {
	for _, n := range node {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}
	return nil
}

// FindColumn finds a column in the column list, returning
// the index if it exists or -1 otherwise
func (node Columns) FindColumn(col ColIdent) int {
	for i, colName := range node {
		if colName.Equal(col) {
			return i
		}
	}
	return -1
}

// TableExprs represents a list of table expressions.
type TableExprs []TableExpr

// Format formats the node.
func (node TableExprs) Format(buf *TrackedBuffer) {
	var prefix string
	for _, n := range node {
		buf.Myprintf("%s%v", prefix, n)
		prefix = ", "
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node TableExprs) WalkSubtree(visit Visit) error {
	for _, n := range node {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}
	return nil
}

// TableExpr represents a table expression.
type TableExpr interface {
	iTableExpr()
	SQLNode
}

func (*AliasedTableExpr) iTableExpr() {}
func (*ParenTableExpr) iTableExpr()   {}
func (*JoinTableExpr) iTableExpr()    {}

// AliasedTableExpr represents a table expression
// coupled with an optional alias or index hint.
// If As is empty, no alias was used.
type AliasedTableExpr struct {
	Expr  SimpleTableExpr
	As    TableIdent
	Hints *IndexHints
}

// Format formats the node.
func (node *AliasedTableExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v", node.Expr)
	if !node.As.IsEmpty() {
		buf.Myprintf(" as %v", node.As)
	}
	if node.Hints != nil {
		// Hint node provides the space padding.
		buf.Myprintf("%v", node.Hints)
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node *AliasedTableExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
		node.As,
		node.Hints,
	)
}

// SimpleTableExpr represents a simple table expression.
type SimpleTableExpr interface {
	iSimpleTableExpr()
	SQLNode
}

func (TableName) iSimpleTableExpr() {}
func (*Subquery) iSimpleTableExpr() {}

// TableNames is a list of TableName.
type TableNames []TableName

// Format formats the node.
func (node TableNames) Format(buf *TrackedBuffer) {
	var prefix string
	for _, n := range node {
		buf.Myprintf("%s%v", prefix, n)
		prefix = ", "
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node TableNames) WalkSubtree(visit Visit) error {
	for _, n := range node {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}
	return nil
}

// TableName represents a table  name.
// Qualifier, if specified, represents a database or keyspace.
// TableName is a value struct whose fields are case sensitive.
// This means two TableName vars can be compared for equality
// and a TableName can also be used as key in a map.
type TableName struct {
	Name, Qualifier TableIdent
}

// Format formats the node.
func (node TableName) Format(buf *TrackedBuffer) {
	if node.IsEmpty() {
		return
	}
	if !node.Qualifier.IsEmpty() {
		buf.Myprintf("%v.", node.Qualifier)
	}
	buf.Myprintf("%v", node.Name)
}

// WalkSubtree walks the nodes of the subtree.
func (node TableName) WalkSubtree(visit Visit) error {
	return Walk(
		visit,
		node.Name,
		node.Qualifier,
	)
}

// IsEmpty returns true if TableName is nil or empty.
func (node TableName) IsEmpty() bool {
	// If Name is empty, Qualifer is also empty.
	return node.Name.IsEmpty()
}

// ToViewName returns a TableName acceptable for use as a VIEW. VIEW names are
// always lowercase, so ToViewName lowercasese the name. Databases are case-sensitive
// so Qualifier is left untouched.
func (node TableName) ToViewName() TableName {
	return TableName{
		Qualifier: node.Qualifier,
		Name:      NewTableIdent(strings.ToLower(node.Name.v)),
	}
}

// ParenTableExpr represents a parenthesized list of TableExpr.
type ParenTableExpr struct {
	Exprs TableExprs
}

// Format formats the node.
func (node *ParenTableExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("(%v)", node.Exprs)
}

// WalkSubtree walks the nodes of the subtree.
func (node *ParenTableExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Exprs,
	)
}

// JoinCondition represents the join conditions (either a ON or USING clause)
// of a JoinTableExpr.
type JoinCondition struct {
	On    Expr
	Using Columns
}

// Format formats the node.
func (node JoinCondition) Format(buf *TrackedBuffer) {
	if node.On != nil {
		buf.Myprintf(" on %v", node.On)
	}
	if node.Using != nil {
		buf.Myprintf(" using %v", node.Using)
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node JoinCondition) WalkSubtree(visit Visit) error {
	return Walk(
		visit,
		node.On,
		node.Using,
	)
}

// JoinTableExpr represents a TableExpr that's a JOIN operation.
type JoinTableExpr struct {
	LeftExpr  TableExpr
	Join      string
	RightExpr TableExpr
	Condition JoinCondition
}

// JoinTableExpr.Join
const (
	JoinStr             = "join"
	StraightJoinStr     = "straight_join"
	LeftJoinStr         = "left join"
	RightJoinStr        = "right join"
	NaturalJoinStr      = "natural join"
	NaturalLeftJoinStr  = "natural left join"
	NaturalRightJoinStr = "natural right join"
)

// Format formats the node.
func (node *JoinTableExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v %s %v%v", node.LeftExpr, node.Join, node.RightExpr, node.Condition)
}

// WalkSubtree walks the nodes of the subtree.
func (node *JoinTableExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.LeftExpr,
		node.RightExpr,
		node.Condition,
	)
}

// IndexHints represents a list of index hints.
type IndexHints struct {
	Type    string
	Indexes []ColIdent
}

// Index hints.
const (
	UseStr    = "use "
	IgnoreStr = "ignore "
	ForceStr  = "force "
)

// Format formats the node.
func (node *IndexHints) Format(buf *TrackedBuffer) {
	buf.Myprintf(" %sindex ", node.Type)
	prefix := "("
	for _, n := range node.Indexes {
		buf.Myprintf("%s%v", prefix, n)
		prefix = ", "
	}
	buf.Myprintf(")")
}

// WalkSubtree walks the nodes of the subtree.
func (node *IndexHints) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	for _, n := range node.Indexes {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}
	return nil
}

// Where represents a WHERE or HAVING clause.
type Where struct {
	Type string
	Expr Expr
}

// Where.Type
const (
	WhereStr  = "where"
	HavingStr = "having"
)

// NewWhere creates a WHERE or HAVING clause out
// of a Expr. If the expression is nil, it returns nil.
func NewWhere(typ string, expr Expr) *Where {
	if expr == nil {
		return nil
	}
	return &Where{Type: typ, Expr: expr}
}

// Format formats the node.
func (node *Where) Format(buf *TrackedBuffer) {
	if node == nil || node.Expr == nil {
		return
	}
	buf.Myprintf(" %s %v", node.Type, node.Expr)
}

// WalkSubtree walks the nodes of the subtree.
func (node *Where) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
	)
}

// Expr represents an expression.
type Expr interface {
	iExpr()
	SQLNode
}

func (*AndExpr) iExpr()          {}
func (*OrExpr) iExpr()           {}
func (*NotExpr) iExpr()          {}
func (*ParenExpr) iExpr()        {}
func (*ComparisonExpr) iExpr()   {}
func (*RangeCond) iExpr()        {}
func (*IsExpr) iExpr()           {}
func (*ExistsExpr) iExpr()       {}
func (*SQLVal) iExpr()           {}
func (*NullVal) iExpr()          {}
func (BoolVal) iExpr()           {}
func (*ColName) iExpr()          {}
func (ValTuple) iExpr()          {}
func (*Subquery) iExpr()         {}
func (ListArg) iExpr()           {}
func (*BinaryExpr) iExpr()       {}
func (*UnaryExpr) iExpr()        {}
func (*IntervalExpr) iExpr()     {}
func (*CollateExpr) iExpr()      {}
func (*FuncExpr) iExpr()         {}
func (*CaseExpr) iExpr()         {}
func (*ValuesFuncExpr) iExpr()   {}
func (*ConvertExpr) iExpr()      {}
func (*ConvertUsingExpr) iExpr() {}
func (*MatchExpr) iExpr()        {}
func (*GroupConcatExpr) iExpr()  {}
func (*Default) iExpr()          {}

// Exprs represents a list of value expressions.
// It's not a valid expression because it's not parenthesized.
type Exprs []Expr

// Format formats the node.
func (node Exprs) Format(buf *TrackedBuffer) {
	var prefix string
	for _, n := range node {
		buf.Myprintf("%s%v", prefix, n)
		prefix = ", "
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node Exprs) WalkSubtree(visit Visit) error {
	for _, n := range node {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}
	return nil
}

// AndExpr represents an AND expression.
type AndExpr struct {
	Left, Right Expr
}

// Format formats the node.
func (node *AndExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v and %v", node.Left, node.Right)
}

// WalkSubtree walks the nodes of the subtree.
func (node *AndExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Left,
		node.Right,
	)
}

// OrExpr represents an OR expression.
type OrExpr struct {
	Left, Right Expr
}

// Format formats the node.
func (node *OrExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v or %v", node.Left, node.Right)
}

// WalkSubtree walks the nodes of the subtree.
func (node *OrExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Left,
		node.Right,
	)
}

// NotExpr represents a NOT expression.
type NotExpr struct {
	Expr Expr
}

// Format formats the node.
func (node *NotExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("not %v", node.Expr)
}

// WalkSubtree walks the nodes of the subtree.
func (node *NotExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
	)
}

// ParenExpr represents a parenthesized boolean expression.
type ParenExpr struct {
	Expr Expr
}

// Format formats the node.
func (node *ParenExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("(%v)", node.Expr)
}

// WalkSubtree walks the nodes of the subtree.
func (node *ParenExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
	)
}

// ComparisonExpr represents a two-value comparison expression.
type ComparisonExpr struct {
	Operator    string
	Left, Right Expr
	Escape      Expr
}

// ComparisonExpr.Operator
const (
	EqualStr             = "="
	LessThanStr          = "<"
	GreaterThanStr       = ">"
	LessEqualStr         = "<="
	GreaterEqualStr      = ">="
	NotEqualStr          = "!="
	NullSafeEqualStr     = "<=>"
	InStr                = "in"
	NotInStr             = "not in"
	LikeStr              = "like"
	NotLikeStr           = "not like"
	RegexpStr            = "regexp"
	NotRegexpStr         = "not regexp"
	JSONExtractOp        = "->"
	JSONUnquoteExtractOp = "->>"
)

// Format formats the node.
func (node *ComparisonExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v %s %v", node.Left, node.Operator, node.Right)
	if node.Escape != nil {
		buf.Myprintf(" escape %v", node.Escape)
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node *ComparisonExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Left,
		node.Right,
		node.Escape,
	)
}

// RangeCond represents a BETWEEN or a NOT BETWEEN expression.
type RangeCond struct {
	Operator string
	Left     Expr
	From, To Expr
}

// RangeCond.Operator
const (
	BetweenStr    = "between"
	NotBetweenStr = "not between"
)

// Format formats the node.
func (node *RangeCond) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v %s %v and %v", node.Left, node.Operator, node.From, node.To)
}

// WalkSubtree walks the nodes of the subtree.
func (node *RangeCond) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Left,
		node.From,
		node.To,
	)
}

// IsExpr represents an IS ... or an IS NOT ... expression.
type IsExpr struct {
	Operator string
	Expr     Expr
}

// IsExpr.Operator
const (
	IsNullStr     = "is null"
	IsNotNullStr  = "is not null"
	IsTrueStr     = "is true"
	IsNotTrueStr  = "is not true"
	IsFalseStr    = "is false"
	IsNotFalseStr = "is not false"
)

// Format formats the node.
func (node *IsExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v %s", node.Expr, node.Operator)
}

// WalkSubtree walks the nodes of the subtree.
func (node *IsExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
	)
}

// ExistsExpr represents an EXISTS expression.
type ExistsExpr struct {
	Subquery *Subquery
}

// Format formats the node.
func (node *ExistsExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("exists %v", node.Subquery)
}

// WalkSubtree walks the nodes of the subtree.
func (node *ExistsExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Subquery,
	)
}

// ExprFromValue converts the given Value into an Expr or returns an error.
func ExprFromValue(value sqltypes.Value) (Expr, error) {
	// The type checks here follow the rules defined in sqltypes/types.go.
	switch {
	case value.Type() == sqltypes.Null:
		return &NullVal{}, nil
	case value.IsIntegral():
		return NewIntVal(value.ToBytes()), nil
	case value.IsFloat() || value.Type() == sqltypes.Decimal:
		return NewFloatVal(value.ToBytes()), nil
	case value.IsQuoted():
		return NewStrVal(value.ToBytes()), nil
	default:
		// We cannot support sqltypes.Expression, or any other invalid type.
		return nil, fmt.Errorf("cannot convert value %v to AST", value)
	}
}

// ValType specifies the type for SQLVal.
type ValType int

// These are the possible Valtype values.
// HexNum represents a 0x... value. It cannot
// be treated as a simple value because it can
// be interpreted differently depending on the
// context.
const (
	StrVal = ValType(iota)
	IntVal
	FloatVal
	HexNum
	HexVal
	ValArg
	BitVal
)

// SQLVal represents a single value.
type SQLVal struct {
	Type ValType
	Val  []byte
}

// NewStrVal builds a new StrVal.
func NewStrVal(in []byte) *SQLVal {
	return &SQLVal{Type: StrVal, Val: in}
}

// NewIntVal builds a new IntVal.
func NewIntVal(in []byte) *SQLVal {
	return &SQLVal{Type: IntVal, Val: in}
}

// NewFloatVal builds a new FloatVal.
func NewFloatVal(in []byte) *SQLVal {
	return &SQLVal{Type: FloatVal, Val: in}
}

// NewHexNum builds a new HexNum.
func NewHexNum(in []byte) *SQLVal {
	return &SQLVal{Type: HexNum, Val: in}
}

// NewHexVal builds a new HexVal.
func NewHexVal(in []byte) *SQLVal {
	return &SQLVal{Type: HexVal, Val: in}
}

// NewBitVal builds a new BitVal containing a bit literal.
func NewBitVal(in []byte) *SQLVal {
	return &SQLVal{Type: BitVal, Val: in}
}

// NewValArg builds a new ValArg.
func NewValArg(in []byte) *SQLVal {
	return &SQLVal{Type: ValArg, Val: in}
}

// Format formats the node.
func (node *SQLVal) Format(buf *TrackedBuffer) {
	switch node.Type {
	case StrVal:
		sqltypes.MakeTrusted(sqltypes.VarBinary, node.Val).EncodeSQL(buf)
	case IntVal, FloatVal, HexNum:
		buf.Myprintf("%s", []byte(node.Val))
	case HexVal:
		buf.Myprintf("X'%s'", []byte(node.Val))
	case BitVal:
		buf.Myprintf("B'%s'", []byte(node.Val))
	case ValArg:
		buf.WriteArg(string(node.Val))
	default:
		panic("unexpected")
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node *SQLVal) WalkSubtree(visit Visit) error {
	return nil
}

// HexDecode decodes the hexval into bytes.
func (node *SQLVal) HexDecode() ([]byte, error) {
	dst := make([]byte, hex.DecodedLen(len([]byte(node.Val))))
	_, err := hex.Decode(dst, []byte(node.Val))
	if err != nil {
		return nil, err
	}
	return dst, err
}

// NullVal represents a NULL value.
type NullVal struct{}

// Format formats the node.
func (node *NullVal) Format(buf *TrackedBuffer) {
	buf.Myprintf("null")
}

// WalkSubtree walks the nodes of the subtree.
func (node *NullVal) WalkSubtree(visit Visit) error {
	return nil
}

// BoolVal is true or false.
type BoolVal bool

// Format formats the node.
func (node BoolVal) Format(buf *TrackedBuffer) {
	if node {
		buf.Myprintf("true")
	} else {
		buf.Myprintf("false")
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node BoolVal) WalkSubtree(visit Visit) error {
	return nil
}

// ColName represents a column name.
type ColName struct {
	// Metadata is not populated by the parser.
	// It's a placeholder for analyzers to store
	// additional data, typically info about which
	// table or column this node references.
	Metadata  interface{}
	Name      ColIdent
	Qualifier TableName
}

// Format formats the node.
func (node *ColName) Format(buf *TrackedBuffer) {
	if !node.Qualifier.IsEmpty() {
		buf.Myprintf("%v.", node.Qualifier)
	}
	buf.Myprintf("%v", node.Name)
}

// WalkSubtree walks the nodes of the subtree.
func (node *ColName) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Name,
		node.Qualifier,
	)
}

// Equal returns true if the column names match.
func (node *ColName) Equal(c *ColName) bool {
	// Failsafe: ColName should not be empty.
	if node == nil || c == nil {
		return false
	}
	return node.Name.Equal(c.Name) && node.Qualifier == c.Qualifier
}

// ColTuple represents a list of column values.
// It can be ValTuple, Subquery, ListArg.
type ColTuple interface {
	iColTuple()
	Expr
}

func (ValTuple) iColTuple()  {}
func (*Subquery) iColTuple() {}
func (ListArg) iColTuple()   {}

// ValTuple represents a tuple of actual values.
type ValTuple Exprs

// Format formats the node.
func (node ValTuple) Format(buf *TrackedBuffer) {
	buf.Myprintf("(%v)", Exprs(node))
}

// WalkSubtree walks the nodes of the subtree.
func (node ValTuple) WalkSubtree(visit Visit) error {
	return Walk(visit, Exprs(node))
}

// Subquery represents a subquery.
type Subquery struct {
	Select SelectStatement
}

// Format formats the node.
func (node *Subquery) Format(buf *TrackedBuffer) {
	buf.Myprintf("(%v)", node.Select)
}

// WalkSubtree walks the nodes of the subtree.
func (node *Subquery) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Select,
	)
}

// ListArg represents a named list argument.
type ListArg []byte

// Format formats the node.
func (node ListArg) Format(buf *TrackedBuffer) {
	buf.WriteArg(string(node))
}

// WalkSubtree walks the nodes of the subtree.
func (node ListArg) WalkSubtree(visit Visit) error {
	return nil
}

// BinaryExpr represents a binary value expression.
type BinaryExpr struct {
	Operator    string
	Left, Right Expr
}

// BinaryExpr.Operator
const (
	BitAndStr     = "&"
	BitOrStr      = "|"
	BitXorStr     = "^"
	PlusStr       = "+"
	MinusStr      = "-"
	MultStr       = "*"
	DivStr        = "/"
	IntDivStr     = "div"
	ModStr        = "%"
	ShiftLeftStr  = "<<"
	ShiftRightStr = ">>"
)

// Format formats the node.
func (node *BinaryExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v %s %v", node.Left, node.Operator, node.Right)
}

// WalkSubtree walks the nodes of the subtree.
func (node *BinaryExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Left,
		node.Right,
	)
}

// UnaryExpr represents a unary value expression.
type UnaryExpr struct {
	Operator string
	Expr     Expr
}

// UnaryExpr.Operator
const (
	UPlusStr   = "+"
	UMinusStr  = "-"
	TildaStr   = "~"
	BangStr    = "!"
	BinaryStr  = "binary "
	UBinaryStr = "_binary "
)

// Format formats the node.
func (node *UnaryExpr) Format(buf *TrackedBuffer) {
	if _, unary := node.Expr.(*UnaryExpr); unary {
		buf.Myprintf("%s %v", node.Operator, node.Expr)
		return
	}
	buf.Myprintf("%s%v", node.Operator, node.Expr)
}

// WalkSubtree walks the nodes of the subtree.
func (node *UnaryExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
	)
}

// IntervalExpr represents a date-time INTERVAL expression.
type IntervalExpr struct {
	Expr Expr
	Unit string
}

// Format formats the node.
func (node *IntervalExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("interval %v %s", node.Expr, node.Unit)
}

// WalkSubtree walks the nodes of the subtree.
func (node *IntervalExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
	)
}

// CollateExpr represents dynamic collate operator.
type CollateExpr struct {
	Expr    Expr
	Charset string
}

// Format formats the node.
func (node *CollateExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v collate %s", node.Expr, node.Charset)
}

// WalkSubtree walks the nodes of the subtree.
func (node *CollateExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
	)
}

// FuncExpr represents a function call.
type FuncExpr struct {
	Qualifier TableIdent
	Name      ColIdent
	Distinct  bool
	Exprs     SelectExprs
}

// Format formats the node.
func (node *FuncExpr) Format(buf *TrackedBuffer) {
	var distinct string
	if node.Distinct {
		distinct = "distinct "
	}
	if !node.Qualifier.IsEmpty() {
		buf.Myprintf("%v.", node.Qualifier)
	}
	// Function names should not be back-quoted even
	// if they match a reserved word. So, print the
	// name as is.
	buf.Myprintf("%s(%s%v)", node.Name.String(), distinct, node.Exprs)
}

// WalkSubtree walks the nodes of the subtree.
func (node *FuncExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Qualifier,
		node.Name,
		node.Exprs,
	)
}

// Aggregates is a map of all aggregate functions.
var Aggregates = map[string]bool{
	"avg":          true,
	"bit_and":      true,
	"bit_or":       true,
	"bit_xor":      true,
	"count":        true,
	"group_concat": true,
	"max":          true,
	"min":          true,
	"std":          true,
	"stddev_pop":   true,
	"stddev_samp":  true,
	"stddev":       true,
	"sum":          true,
	"var_pop":      true,
	"var_samp":     true,
	"variance":     true,
}

// IsAggregate returns true if the function is an aggregate.
func (node *FuncExpr) IsAggregate() bool {
	return Aggregates[node.Name.Lowered()]
}

// GroupConcatExpr represents a call to GROUP_CONCAT
type GroupConcatExpr struct {
	Distinct  string
	Exprs     SelectExprs
	OrderBy   OrderBy
	Separator string
}

// Format formats the node
func (node *GroupConcatExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("group_concat(%s%v%v%s)", node.Distinct, node.Exprs, node.OrderBy, node.Separator)
}

// WalkSubtree walks the nodes of the subtree.
func (node *GroupConcatExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Exprs,
		node.OrderBy,
	)
}

// ValuesFuncExpr represents a function call.
type ValuesFuncExpr struct {
	Name ColIdent
}

// Format formats the node.
func (node *ValuesFuncExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("values(%s)", node.Name.String())
}

// WalkSubtree walks the nodes of the subtree.
func (node *ValuesFuncExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Name,
	)
}

// ConvertExpr represents a call to CONVERT(expr, type)
// or it's equivalent CAST(expr AS type). Both are rewritten to the former.
type ConvertExpr struct {
	Expr Expr
	Type *ConvertType
}

// Format formats the node.
func (node *ConvertExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("convert(%v, %v)", node.Expr, node.Type)
}

// WalkSubtree walks the nodes of the subtree.
func (node *ConvertExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
		node.Type,
	)
}

// ConvertUsingExpr represents a call to CONVERT(expr USING charset).
type ConvertUsingExpr struct {
	Expr Expr
	Type string
}

// Format formats the node.
func (node *ConvertUsingExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("convert(%v using %s)", node.Expr, node.Type)
}

// WalkSubtree walks the nodes of the subtree.
func (node *ConvertUsingExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
	)
}

// ConvertType represents the type in call to CONVERT(expr, type)
type ConvertType struct {
	Type     string
	Length   *SQLVal
	Scale    *SQLVal
	Operator string
	Charset  string
}

// this string is "character set" and this comment is required
const (
	CharacterSetStr = " character set"
)

// Format formats the node.
func (node *ConvertType) Format(buf *TrackedBuffer) {
	buf.Myprintf("%s", node.Type)
	if node.Length != nil {
		buf.Myprintf("(%v", node.Length)
		if node.Scale != nil {
			buf.Myprintf(", %v", node.Scale)
		}
		buf.Myprintf(")")
	}
	if node.Charset != "" {
		buf.Myprintf("%s %s", node.Operator, node.Charset)
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node *ConvertType) WalkSubtree(visit Visit) error {
	return nil
}

// MatchExpr represents a call to the MATCH function
type MatchExpr struct {
	Columns SelectExprs
	Expr    Expr
	Option  string
}

// MatchExpr.Option
const (
	BooleanModeStr                           = " in boolean mode"
	NaturalLanguageModeStr                   = " in natural language mode"
	NaturalLanguageModeWithQueryExpansionStr = " in natural language mode with query expansion"
	QueryExpansionStr                        = " with query expansion"
)

// Format formats the node
func (node *MatchExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("match(%v) against (%v%s)", node.Columns, node.Expr, node.Option)
}

// WalkSubtree walks the nodes of the subtree.
func (node *MatchExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Columns,
		node.Expr,
	)
}

// CaseExpr represents a CASE expression.
type CaseExpr struct {
	Expr  Expr
	Whens []*When
	Else  Expr
}

// Format formats the node.
func (node *CaseExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("case ")
	if node.Expr != nil {
		buf.Myprintf("%v ", node.Expr)
	}
	for _, when := range node.Whens {
		buf.Myprintf("%v ", when)
	}
	if node.Else != nil {
		buf.Myprintf("else %v ", node.Else)
	}
	buf.Myprintf("end")
}

// WalkSubtree walks the nodes of the subtree.
func (node *CaseExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	if err := Walk(visit, node.Expr); err != nil {
		return err
	}
	for _, n := range node.Whens {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}
	return Walk(visit, node.Else)
}

// Default represents a DEFAULT expression.
type Default struct {
	ColName string
}

// Format formats the node.
func (node *Default) Format(buf *TrackedBuffer) {
	buf.Myprintf("default")
	if node.ColName != "" {
		buf.Myprintf("(%s)", node.ColName)
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node *Default) WalkSubtree(visit Visit) error {
	return nil
}

// When represents a WHEN sub-expression.
type When struct {
	Cond Expr
	Val  Expr
}

// Format formats the node.
func (node *When) Format(buf *TrackedBuffer) {
	buf.Myprintf("when %v then %v", node.Cond, node.Val)
}

// WalkSubtree walks the nodes of the subtree.
func (node *When) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Cond,
		node.Val,
	)
}

// GroupBy represents a GROUP BY clause.
type GroupBy []Expr

// Format formats the node.
func (node GroupBy) Format(buf *TrackedBuffer) {
	prefix := " group by "
	for _, n := range node {
		buf.Myprintf("%s%v", prefix, n)
		prefix = ", "
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node GroupBy) WalkSubtree(visit Visit) error {
	for _, n := range node {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}
	return nil
}

// OrderBy represents an ORDER By clause.
type OrderBy []*Order

// Format formats the node.
func (node OrderBy) Format(buf *TrackedBuffer) {
	prefix := " order by "
	for _, n := range node {
		buf.Myprintf("%s%v", prefix, n)
		prefix = ", "
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node OrderBy) WalkSubtree(visit Visit) error {
	for _, n := range node {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}
	return nil
}

// Order represents an ordering expression.
type Order struct {
	Expr      Expr
	Direction string
}

// Order.Direction
const (
	AscScr  = "asc"
	DescScr = "desc"
)

// Format formats the node.
func (node *Order) Format(buf *TrackedBuffer) {
	if node, ok := node.Expr.(*NullVal); ok {
		buf.Myprintf("%v", node)
		return
	}
	buf.Myprintf("%v %s", node.Expr, node.Direction)
}

// WalkSubtree walks the nodes of the subtree.
func (node *Order) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Expr,
	)
}

// Limit represents a LIMIT clause.
type Limit struct {
	Offset, Rowcount Expr
}

// Format formats the node.
func (node *Limit) Format(buf *TrackedBuffer) {
	if node == nil {
		return
	}
	buf.Myprintf(" limit ")
	if node.Offset != nil {
		buf.Myprintf("%v, ", node.Offset)
	}
	buf.Myprintf("%v", node.Rowcount)
}

// WalkSubtree walks the nodes of the subtree.
func (node *Limit) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Offset,
		node.Rowcount,
	)
}

// Values represents a VALUES clause.
type Values []ValTuple

// Format formats the node.
func (node Values) Format(buf *TrackedBuffer) {
	prefix := "values "
	for _, n := range node {
		buf.Myprintf("%s%v", prefix, n)
		prefix = ", "
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node Values) WalkSubtree(visit Visit) error {
	for _, n := range node {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}
	return nil
}

// UpdateExprs represents a list of update expressions.
type UpdateExprs []*UpdateExpr

// Format formats the node.
func (node UpdateExprs) Format(buf *TrackedBuffer) {
	var prefix string
	for _, n := range node {
		buf.Myprintf("%s%v", prefix, n)
		prefix = ", "
	}
}

// WalkSubtree walks the nodes of the subtree.
func (node UpdateExprs) WalkSubtree(visit Visit) error {
	for _, n := range node {
		if err := Walk(visit, n); err != nil {
			return err
		}
	}
	return nil
}

// UpdateExpr represents an update expression.
type UpdateExpr struct {
	Name *ColName
	Expr Expr
}

// Format formats the node.
func (node *UpdateExpr) Format(buf *TrackedBuffer) {
	buf.Myprintf("%v = %v", node.Name, node.Expr)
}

// WalkSubtree walks the nodes of the subtree.
func (node *UpdateExpr) WalkSubtree(visit Visit) error {
	if node == nil {
		return nil
	}
	return Walk(
		visit,
		node.Name,
		node.Expr,
	)
}

// OnDup represents an ON DUPLICATE KEY clause.
type OnDup UpdateExprs

// Format formats the node.
func (node OnDup) Format(buf *TrackedBuffer) {
	if node == nil {
		return
	}
	buf.Myprintf(" on duplicate key update %v", UpdateExprs(node))
}

// WalkSubtree walks the nodes of the subtree.
func (node OnDup) WalkSubtree(visit Visit) error {
	return Walk(visit, UpdateExprs(node))
}

// ColIdent is a case insensitive SQL identifier. It will be escaped with
// backquotes if necessary.
type ColIdent struct {
	// This artifact prevents this struct from being compared
	// with itself. It consumes no space as long as it's not the
	// last field in the struct.
	_            [0]struct{ _ []byte }
	val, lowered string
}

// NewColIdent makes a new ColIdent.
func NewColIdent(str string) ColIdent {
	return ColIdent{
		val: str,
	}
}

// Format formats the node.
func (node ColIdent) Format(buf *TrackedBuffer) {
	formatID(buf, node.val, node.Lowered())
}

// WalkSubtree walks the nodes of the subtree.
func (node ColIdent) WalkSubtree(visit Visit) error {
	return nil
}

// IsEmpty returns true if the name is empty.
func (node ColIdent) IsEmpty() bool {
	return node.val == ""
}

// String returns the unescaped column name. It must
// not be used for SQL generation. Use sqlparser.String
// instead. The Stringer conformance is for usage
// in templates.
func (node ColIdent) String() string {
	return node.val
}

// CompliantName returns a compliant id name
// that can be used for a bind var.
func (node ColIdent) CompliantName() string {
	return compliantName(node.val)
}

// Lowered returns a lower-cased column name.
// This function should generally be used only for optimizing
// comparisons.
func (node ColIdent) Lowered() string {
	if node.val == "" {
		return ""
	}
	if node.lowered == "" {
		node.lowered = strings.ToLower(node.val)
	}
	return node.lowered
}

// Equal performs a case-insensitive compare.
func (node ColIdent) Equal(in ColIdent) bool {
	return node.Lowered() == in.Lowered()
}

// EqualString performs a case-insensitive compare with str.
func (node ColIdent) EqualString(str string) bool {
	return node.Lowered() == strings.ToLower(str)
}

// MarshalJSON marshals into JSON.
func (node ColIdent) MarshalJSON() ([]byte, error) {
	return json.Marshal(node.val)
}

// UnmarshalJSON unmarshals from JSON.
func (node *ColIdent) UnmarshalJSON(b []byte) error {
	var result string
	err := json.Unmarshal(b, &result)
	if err != nil {
		return err
	}
	node.val = result
	return nil
}

// TableIdent is a case sensitive SQL identifier. It will be escaped with
// backquotes if necessary.
type TableIdent struct {
	v string
}

// NewTableIdent creates a new TableIdent.
func NewTableIdent(str string) TableIdent {
	return TableIdent{v: str}
}

// Format formats the node.
func (node TableIdent) Format(buf *TrackedBuffer) {
	formatID(buf, node.v, strings.ToLower(node.v))
}

// WalkSubtree walks the nodes of the subtree.
func (node TableIdent) WalkSubtree(visit Visit) error {
	return nil
}

// IsEmpty returns true if TabIdent is empty.
func (node TableIdent) IsEmpty() bool {
	return node.v == ""
}

// String returns the unescaped table name. It must
// not be used for SQL generation. Use sqlparser.String
// instead. The Stringer conformance is for usage
// in templates.
func (node TableIdent) String() string {
	return node.v
}

// CompliantName returns a compliant id name
// that can be used for a bind var.
func (node TableIdent) CompliantName() string {
	return compliantName(node.v)
}

// MarshalJSON marshals into JSON.
func (node TableIdent) MarshalJSON() ([]byte, error) {
	return json.Marshal(node.v)
}

// UnmarshalJSON unmarshals from JSON.
func (node *TableIdent) UnmarshalJSON(b []byte) error {
	var result string
	err := json.Unmarshal(b, &result)
	if err != nil {
		return err
	}
	node.v = result
	return nil
}

// Backtick produces a backticked literal given an input string.
func Backtick(in string) string {
	var buf bytes.Buffer
	buf.WriteByte('`')
	for _, c := range in {
		buf.WriteRune(c)
		if c == '`' {
			buf.WriteByte('`')
		}
	}
	buf.WriteByte('`')
	return buf.String()
}

func formatID(buf *TrackedBuffer, original, lowered string) {
	for i, c := range original {
		if !isLetter(uint16(c)) {
			if i == 0 || !isDigit(uint16(c)) {
				goto mustEscape
			}
		}
	}
	if _, ok := keywords[lowered]; ok {
		goto mustEscape
	}
	buf.Myprintf("%s", original)
	return

mustEscape:
	buf.WriteByte('`')
	for _, c := range original {
		buf.WriteRune(c)
		if c == '`' {
			buf.WriteByte('`')
		}
	}
	buf.WriteByte('`')
}

func compliantName(in string) string {
	var buf bytes.Buffer
	for i, c := range in {
		if !isLetter(uint16(c)) {
			if i == 0 || !isDigit(uint16(c)) {
				buf.WriteByte('_')
				continue
			}
		}
		buf.WriteRune(c)
	}
	return buf.String()
}