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expressions.go 21.77 KB
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// 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 (
"fmt"
"io"
"regexp"
"strconv"
"strings"
"github.com/pingcap/tidb/model"
"github.com/pingcap/tidb/mysql"
"github.com/pingcap/tidb/parser/opcode"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/types"
)
var (
_ ExprNode = &BetweenExpr{}
_ ExprNode = &BinaryOperationExpr{}
_ ExprNode = &CaseExpr{}
_ ExprNode = &ColumnNameExpr{}
_ ExprNode = &CompareSubqueryExpr{}
_ ExprNode = &DefaultExpr{}
_ ExprNode = &ExistsSubqueryExpr{}
_ ExprNode = &IsNullExpr{}
_ ExprNode = &IsTruthExpr{}
_ ExprNode = &ParamMarkerExpr{}
_ ExprNode = &ParenthesesExpr{}
_ ExprNode = &PatternInExpr{}
_ ExprNode = &PatternLikeExpr{}
_ ExprNode = &PatternRegexpExpr{}
_ ExprNode = &PositionExpr{}
_ ExprNode = &RowExpr{}
_ ExprNode = &SubqueryExpr{}
_ ExprNode = &UnaryOperationExpr{}
_ ExprNode = &ValueExpr{}
_ ExprNode = &ValuesExpr{}
_ ExprNode = &VariableExpr{}
_ Node = &ColumnName{}
_ Node = &WhenClause{}
)
// ValueExpr is the simple value expression.
type ValueExpr struct {
exprNode
projectionOffset int
}
// Format the ExprNode into a Writer.
func (n *ValueExpr) Format(w io.Writer) {
var s string
switch n.Kind() {
case types.KindNull:
s = "NULL"
case types.KindInt64:
if n.Type.Flag&mysql.IsBooleanFlag != 0 {
if n.GetInt64() > 0 {
s = "TRUE"
} else {
s = "FALSE"
}
} else {
s = strconv.FormatInt(n.GetInt64(), 10)
}
case types.KindUint64:
s = strconv.FormatUint(n.GetUint64(), 10)
case types.KindFloat32:
s = strconv.FormatFloat(n.GetFloat64(), 'e', -1, 32)
case types.KindFloat64:
s = strconv.FormatFloat(n.GetFloat64(), 'e', -1, 64)
case types.KindString, types.KindBytes:
s = strconv.Quote(n.GetString())
case types.KindMysqlDecimal:
s = n.GetMysqlDecimal().String()
case types.KindBinaryLiteral:
if n.Type.Flag&mysql.UnsignedFlag != 0 {
s = fmt.Sprintf("x'%x'", n.GetBytes())
} else {
s = n.GetBinaryLiteral().ToBitLiteralString(true)
}
default:
panic("Can't format to string")
}
fmt.Fprint(w, s)
}
// NewValueExpr creates a ValueExpr with value, and sets default field type.
func NewValueExpr(value interface{}) *ValueExpr {
if ve, ok := value.(*ValueExpr); ok {
return ve
}
ve := &ValueExpr{}
ve.SetValue(value)
types.DefaultTypeForValue(value, &ve.Type)
ve.projectionOffset = -1
return ve
}
// SetProjectionOffset sets ValueExpr.projectionOffset for logical plan builder.
func (n *ValueExpr) SetProjectionOffset(offset int) {
n.projectionOffset = offset
}
// GetProjectionOffset returns ValueExpr.projectionOffset.
func (n *ValueExpr) GetProjectionOffset() int {
return n.projectionOffset
}
// Accept implements Node interface.
func (n *ValueExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*ValueExpr)
return v.Leave(n)
}
// BetweenExpr is for "between and" or "not between and" expression.
type BetweenExpr struct {
exprNode
// Expr is the expression to be checked.
Expr ExprNode
// Left is the expression for minimal value in the range.
Left ExprNode
// Right is the expression for maximum value in the range.
Right ExprNode
// Not is true, the expression is "not between and".
Not bool
}
// Format the ExprNode into a Writer.
func (n *BetweenExpr) Format(w io.Writer) {
n.Expr.Format(w)
fmt.Fprint(w, " BETWEEN ")
n.Left.Format(w)
fmt.Fprint(w, " AND ")
n.Right.Format(w)
}
// Accept implements Node interface.
func (n *BetweenExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*BetweenExpr)
node, ok := n.Expr.Accept(v)
if !ok {
return n, false
}
n.Expr = node.(ExprNode)
node, ok = n.Left.Accept(v)
if !ok {
return n, false
}
n.Left = node.(ExprNode)
node, ok = n.Right.Accept(v)
if !ok {
return n, false
}
n.Right = node.(ExprNode)
return v.Leave(n)
}
// BinaryOperationExpr is for binary operation like `1 + 1`, `1 - 1`, etc.
type BinaryOperationExpr struct {
exprNode
// Op is the operator code for BinaryOperation.
Op opcode.Op
// L is the left expression in BinaryOperation.
L ExprNode
// R is the right expression in BinaryOperation.
R ExprNode
}
// Format the ExprNode into a Writer.
func (n *BinaryOperationExpr) Format(w io.Writer) {
n.L.Format(w)
fmt.Fprint(w, " ")
n.Op.Format(w)
fmt.Fprint(w, " ")
n.R.Format(w)
}
// Accept implements Node interface.
func (n *BinaryOperationExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*BinaryOperationExpr)
node, ok := n.L.Accept(v)
if !ok {
return n, false
}
n.L = node.(ExprNode)
node, ok = n.R.Accept(v)
if !ok {
return n, false
}
n.R = node.(ExprNode)
return v.Leave(n)
}
// WhenClause is the when clause in Case expression for "when condition then result".
type WhenClause struct {
node
// Expr is the condition expression in WhenClause.
Expr ExprNode
// Result is the result expression in WhenClause.
Result ExprNode
}
// Accept implements Node Accept interface.
func (n *WhenClause) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*WhenClause)
node, ok := n.Expr.Accept(v)
if !ok {
return n, false
}
n.Expr = node.(ExprNode)
node, ok = n.Result.Accept(v)
if !ok {
return n, false
}
n.Result = node.(ExprNode)
return v.Leave(n)
}
// CaseExpr is the case expression.
type CaseExpr struct {
exprNode
// Value is the compare value expression.
Value ExprNode
// WhenClauses is the condition check expression.
WhenClauses []*WhenClause
// ElseClause is the else result expression.
ElseClause ExprNode
}
// Format the ExprNode into a Writer.
func (n *CaseExpr) Format(w io.Writer) {
fmt.Fprint(w, "CASE ")
n.Value.Format(w)
fmt.Fprint(w, " ")
for _, clause := range n.WhenClauses {
fmt.Fprint(w, "WHEN ")
clause.Expr.Format(w)
fmt.Fprint(w, " THEN ")
clause.Result.Format(w)
}
if n.ElseClause != nil {
fmt.Fprint(w, " ELSE ")
n.ElseClause.Format(w)
}
fmt.Fprint(w, " END")
}
// Accept implements Node Accept interface.
func (n *CaseExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*CaseExpr)
if n.Value != nil {
node, ok := n.Value.Accept(v)
if !ok {
return n, false
}
n.Value = node.(ExprNode)
}
for i, val := range n.WhenClauses {
node, ok := val.Accept(v)
if !ok {
return n, false
}
n.WhenClauses[i] = node.(*WhenClause)
}
if n.ElseClause != nil {
node, ok := n.ElseClause.Accept(v)
if !ok {
return n, false
}
n.ElseClause = node.(ExprNode)
}
return v.Leave(n)
}
// SubqueryExec represents a subquery executor interface.
// This interface is implemented in executor and used in plan/evaluator.
// It will execute the subselect and get the result.
type SubqueryExec interface {
// EvalRows executes the subquery and returns the multi rows with rowCount.
// rowCount < 0 means no limit.
// If the ColumnCount is 1, we will return a column result like {1, 2, 3},
// otherwise, we will return a table result like {{1, 1}, {2, 2}}.
EvalRows(ctx sessionctx.Context, rowCount int) ([]types.Datum, error)
// ColumnCount returns column count for the sub query.
ColumnCount() (int, error)
}
// SubqueryExpr represents a subquery.
type SubqueryExpr struct {
exprNode
// Query is the query SelectNode.
Query ResultSetNode
SubqueryExec SubqueryExec
Evaluated bool
Correlated bool
MultiRows bool
Exists bool
}
// Format the ExprNode into a Writer.
func (n *SubqueryExpr) Format(w io.Writer) {
panic("Not implemented")
}
// Accept implements Node Accept interface.
func (n *SubqueryExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*SubqueryExpr)
if n.SubqueryExec != nil {
return v.Leave(n)
}
node, ok := n.Query.Accept(v)
if !ok {
return n, false
}
n.Query = node.(ResultSetNode)
return v.Leave(n)
}
// CompareSubqueryExpr is the expression for "expr cmp (select ...)".
// See https://dev.mysql.com/doc/refman/5.7/en/comparisons-using-subqueries.html
// See https://dev.mysql.com/doc/refman/5.7/en/any-in-some-subqueries.html
// See https://dev.mysql.com/doc/refman/5.7/en/all-subqueries.html
type CompareSubqueryExpr struct {
exprNode
// L is the left expression
L ExprNode
// Op is the comparison opcode.
Op opcode.Op
// R is the subquery for right expression, may be rewritten to other type of expression.
R ExprNode
// All is true, we should compare all records in subquery.
All bool
}
// Format the ExprNode into a Writer.
func (n *CompareSubqueryExpr) Format(w io.Writer) {
panic("Not implemented")
}
// Accept implements Node Accept interface.
func (n *CompareSubqueryExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*CompareSubqueryExpr)
node, ok := n.L.Accept(v)
if !ok {
return n, false
}
n.L = node.(ExprNode)
node, ok = n.R.Accept(v)
if !ok {
return n, false
}
n.R = node.(ExprNode)
return v.Leave(n)
}
// ColumnName represents column name.
type ColumnName struct {
node
Schema model.CIStr
Table model.CIStr
Name model.CIStr
}
// Accept implements Node Accept interface.
func (n *ColumnName) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*ColumnName)
return v.Leave(n)
}
// String implements Stringer interface.
func (n *ColumnName) String() string {
result := n.Name.L
if n.Table.L != "" {
result = n.Table.L + "." + result
}
if n.Schema.L != "" {
result = n.Schema.L + "." + result
}
return result
}
// OrigColName returns the full original column name.
func (n *ColumnName) OrigColName() (ret string) {
ret = n.Name.O
if n.Table.O == "" {
return
}
ret = n.Table.O + "." + ret
if n.Schema.O == "" {
return
}
ret = n.Schema.O + "." + ret
return
}
// ColumnNameExpr represents a column name expression.
type ColumnNameExpr struct {
exprNode
// Name is the referenced column name.
Name *ColumnName
// Refer is the result field the column name refers to.
// The value of Refer.Expr is used as the value of the expression.
Refer *ResultField
}
// Format the ExprNode into a Writer.
func (n *ColumnNameExpr) Format(w io.Writer) {
name := strings.Replace(n.Name.String(), ".", "`.`", -1)
fmt.Fprintf(w, "`%s`", name)
}
// Accept implements Node Accept interface.
func (n *ColumnNameExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*ColumnNameExpr)
node, ok := n.Name.Accept(v)
if !ok {
return n, false
}
n.Name = node.(*ColumnName)
return v.Leave(n)
}
// DefaultExpr is the default expression using default value for a column.
type DefaultExpr struct {
exprNode
// Name is the column name.
Name *ColumnName
}
// Format the ExprNode into a Writer.
func (n *DefaultExpr) Format(w io.Writer) {
panic("Not implemented")
}
// Accept implements Node Accept interface.
func (n *DefaultExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*DefaultExpr)
if n.Name != nil {
node, ok := n.Name.Accept(v)
if !ok {
return n, false
}
n.Name = node.(*ColumnName)
}
return v.Leave(n)
}
// ExistsSubqueryExpr is the expression for "exists (select ...)".
// See https://dev.mysql.com/doc/refman/5.7/en/exists-and-not-exists-subqueries.html
type ExistsSubqueryExpr struct {
exprNode
// Sel is the subquery, may be rewritten to other type of expression.
Sel ExprNode
}
// Format the ExprNode into a Writer.
func (n *ExistsSubqueryExpr) Format(w io.Writer) {
panic("Not implemented")
}
// Accept implements Node Accept interface.
func (n *ExistsSubqueryExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*ExistsSubqueryExpr)
node, ok := n.Sel.Accept(v)
if !ok {
return n, false
}
n.Sel = node.(ExprNode)
return v.Leave(n)
}
// PatternInExpr is the expression for in operator, like "expr in (1, 2, 3)" or "expr in (select c from t)".
type PatternInExpr struct {
exprNode
// Expr is the value expression to be compared.
Expr ExprNode
// List is the list expression in compare list.
List []ExprNode
// Not is true, the expression is "not in".
Not bool
// Sel is the subquery, may be rewritten to other type of expression.
Sel ExprNode
}
// Format the ExprNode into a Writer.
func (n *PatternInExpr) Format(w io.Writer) {
n.Expr.Format(w)
fmt.Fprint(w, " IN (")
for i, expr := range n.List {
expr.Format(w)
if i != len(n.List)-1 {
fmt.Fprint(w, ",")
}
}
fmt.Fprint(w, ")")
}
// Accept implements Node Accept interface.
func (n *PatternInExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*PatternInExpr)
node, ok := n.Expr.Accept(v)
if !ok {
return n, false
}
n.Expr = node.(ExprNode)
for i, val := range n.List {
node, ok = val.Accept(v)
if !ok {
return n, false
}
n.List[i] = node.(ExprNode)
}
if n.Sel != nil {
node, ok = n.Sel.Accept(v)
if !ok {
return n, false
}
n.Sel = node.(ExprNode)
}
return v.Leave(n)
}
// IsNullExpr is the expression for null check.
type IsNullExpr struct {
exprNode
// Expr is the expression to be checked.
Expr ExprNode
// Not is true, the expression is "is not null".
Not bool
}
// Format the ExprNode into a Writer.
func (n *IsNullExpr) Format(w io.Writer) {
n.Expr.Format(w)
if n.Not {
fmt.Fprint(w, " IS NOT NULL")
return
}
fmt.Fprint(w, " IS NULL")
}
// Accept implements Node Accept interface.
func (n *IsNullExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*IsNullExpr)
node, ok := n.Expr.Accept(v)
if !ok {
return n, false
}
n.Expr = node.(ExprNode)
return v.Leave(n)
}
// IsTruthExpr is the expression for true/false check.
type IsTruthExpr struct {
exprNode
// Expr is the expression to be checked.
Expr ExprNode
// Not is true, the expression is "is not true/false".
Not bool
// True indicates checking true or false.
True int64
}
// Format the ExprNode into a Writer.
func (n *IsTruthExpr) Format(w io.Writer) {
n.Expr.Format(w)
if n.Not {
fmt.Fprint(w, " IS NOT")
} else {
fmt.Fprint(w, " IS")
}
if n.True > 0 {
fmt.Fprint(w, " TRUE")
} else {
fmt.Fprint(w, " FALSE")
}
}
// Accept implements Node Accept interface.
func (n *IsTruthExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*IsTruthExpr)
node, ok := n.Expr.Accept(v)
if !ok {
return n, false
}
n.Expr = node.(ExprNode)
return v.Leave(n)
}
// PatternLikeExpr is the expression for like operator, e.g, expr like "%123%"
type PatternLikeExpr struct {
exprNode
// Expr is the expression to be checked.
Expr ExprNode
// Pattern is the like expression.
Pattern ExprNode
// Not is true, the expression is "not like".
Not bool
Escape byte
PatChars []byte
PatTypes []byte
}
// Format the ExprNode into a Writer.
func (n *PatternLikeExpr) Format(w io.Writer) {
n.Expr.Format(w)
fmt.Fprint(w, " LIKE ")
n.Pattern.Format(w)
if n.Escape != '\\' {
fmt.Fprint(w, " ESCAPE ")
fmt.Fprintf(w, "'%c'", n.Escape)
}
}
// Accept implements Node Accept interface.
func (n *PatternLikeExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*PatternLikeExpr)
if n.Expr != nil {
node, ok := n.Expr.Accept(v)
if !ok {
return n, false
}
n.Expr = node.(ExprNode)
}
if n.Pattern != nil {
node, ok := n.Pattern.Accept(v)
if !ok {
return n, false
}
n.Pattern = node.(ExprNode)
}
return v.Leave(n)
}
// ParamMarkerExpr expression holds a place for another expression.
// Used in parsing prepare statement.
type ParamMarkerExpr struct {
exprNode
Offset int
Order int
}
// Format the ExprNode into a Writer.
func (n *ParamMarkerExpr) Format(w io.Writer) {
panic("Not implemented")
}
// Accept implements Node Accept interface.
func (n *ParamMarkerExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*ParamMarkerExpr)
return v.Leave(n)
}
// ParenthesesExpr is the parentheses expression.
type ParenthesesExpr struct {
exprNode
// Expr is the expression in parentheses.
Expr ExprNode
}
// Format the ExprNode into a Writer.
func (n *ParenthesesExpr) Format(w io.Writer) {
fmt.Fprint(w, "(")
n.Expr.Format(w)
fmt.Fprint(w, ")")
}
// Accept implements Node Accept interface.
func (n *ParenthesesExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*ParenthesesExpr)
if n.Expr != nil {
node, ok := n.Expr.Accept(v)
if !ok {
return n, false
}
n.Expr = node.(ExprNode)
}
return v.Leave(n)
}
// PositionExpr is the expression for order by and group by position.
// MySQL use position expression started from 1, it looks a little confused inner.
// maybe later we will use 0 at first.
type PositionExpr struct {
exprNode
// N is the position, started from 1 now.
N int
// Refer is the result field the position refers to.
Refer *ResultField
}
// Format the ExprNode into a Writer.
func (n *PositionExpr) Format(w io.Writer) {
panic("Not implemented")
}
// Accept implements Node Accept interface.
func (n *PositionExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*PositionExpr)
return v.Leave(n)
}
// PatternRegexpExpr is the pattern expression for pattern match.
type PatternRegexpExpr struct {
exprNode
// Expr is the expression to be checked.
Expr ExprNode
// Pattern is the expression for pattern.
Pattern ExprNode
// Not is true, the expression is "not rlike",
Not bool
// Re is the compiled regexp.
Re *regexp.Regexp
// Sexpr is the string for Expr expression.
Sexpr *string
}
// Format the ExprNode into a Writer.
func (n *PatternRegexpExpr) Format(w io.Writer) {
n.Expr.Format(w)
if n.Not {
fmt.Fprint(w, " NOT REGEXP ")
} else {
fmt.Fprint(w, " REGEXP ")
}
n.Pattern.Format(w)
}
// Accept implements Node Accept interface.
func (n *PatternRegexpExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*PatternRegexpExpr)
node, ok := n.Expr.Accept(v)
if !ok {
return n, false
}
n.Expr = node.(ExprNode)
node, ok = n.Pattern.Accept(v)
if !ok {
return n, false
}
n.Pattern = node.(ExprNode)
return v.Leave(n)
}
// RowExpr is the expression for row constructor.
// See https://dev.mysql.com/doc/refman/5.7/en/row-subqueries.html
type RowExpr struct {
exprNode
Values []ExprNode
}
// Format the ExprNode into a Writer.
func (n *RowExpr) Format(w io.Writer) {
panic("Not implemented")
}
// Accept implements Node Accept interface.
func (n *RowExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*RowExpr)
for i, val := range n.Values {
node, ok := val.Accept(v)
if !ok {
return n, false
}
n.Values[i] = node.(ExprNode)
}
return v.Leave(n)
}
// UnaryOperationExpr is the expression for unary operator.
type UnaryOperationExpr struct {
exprNode
// Op is the operator opcode.
Op opcode.Op
// V is the unary expression.
V ExprNode
}
// Format the ExprNode into a Writer.
func (n *UnaryOperationExpr) Format(w io.Writer) {
n.Op.Format(w)
n.V.Format(w)
}
// Accept implements Node Accept interface.
func (n *UnaryOperationExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*UnaryOperationExpr)
node, ok := n.V.Accept(v)
if !ok {
return n, false
}
n.V = node.(ExprNode)
return v.Leave(n)
}
// ValuesExpr is the expression used in INSERT VALUES.
type ValuesExpr struct {
exprNode
// Column is column name.
Column *ColumnNameExpr
}
// Format the ExprNode into a Writer.
func (n *ValuesExpr) Format(w io.Writer) {
panic("Not implemented")
}
// Accept implements Node Accept interface.
func (n *ValuesExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*ValuesExpr)
node, ok := n.Column.Accept(v)
if !ok {
return n, false
}
n.Column = node.(*ColumnNameExpr)
return v.Leave(n)
}
// VariableExpr is the expression for variable.
type VariableExpr struct {
exprNode
// Name is the variable name.
Name string
// IsGlobal indicates whether this variable is global.
IsGlobal bool
// IsSystem indicates whether this variable is a system variable in current session.
IsSystem bool
// Value is the variable value.
Value ExprNode
}
// Format the ExprNode into a Writer.
func (n *VariableExpr) Format(w io.Writer) {
panic("Not implemented")
}
// Accept implements Node Accept interface.
func (n *VariableExpr) Accept(v Visitor) (Node, bool) {
newNode, skipChildren := v.Enter(n)
if skipChildren {
return v.Leave(newNode)
}
n = newNode.(*VariableExpr)
if n.Value == nil {
return v.Leave(n)
}
node, ok := n.Value.Accept(v)
if !ok {
return n, false
}
n.Value = node.(ExprNode)
return v.Leave(n)
}
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