From 9cf30372a03668971fb80dd99d303e4dab30d0d0 Mon Sep 17 00:00:00 2001
From: Jun-Seok Heo <jun.seok.heo@samsung.com>
Date: Thu, 8 Nov 2018 15:20:00 +0900
Subject: [PATCH] [parser] Revert "parser,ast: fix the TiDB issue #8153 (#20)"
 (#24)

---
 parser/ast/expressions.go |  9 +--------
 parser/parser.go          | 10 ++++++----
 parser/parser.y           | 12 +++++++-----
 3 files changed, 14 insertions(+), 17 deletions(-)

diff --git a/parser/ast/expressions.go b/parser/ast/expressions.go
index c3d38dcf7bcef..e81f878760b8d 100644
--- a/parser/ast/expressions.go
+++ b/parser/ast/expressions.go
@@ -699,7 +699,7 @@ func (n *ParenthesesExpr) Accept(v Visitor) (Node, bool) {
 type PositionExpr struct {
 	exprNode
 	// N is the position, started from 1 now.
-	N ExprNode
+	N int
 	// Refer is the result field the position refers to.
 	Refer *ResultField
 }
@@ -716,13 +716,6 @@ func (n *PositionExpr) Accept(v Visitor) (Node, bool) {
 		return v.Leave(newNode)
 	}
 	n = newNode.(*PositionExpr)
-	if n.N != nil {
-		node, ok := n.N.Accept(v)
-		if !ok {
-			return n, false
-		}
-		n.N = node.(ExprNode)
-	}
 	return v.Leave(n)
 }
 
diff --git a/parser/parser.go b/parser/parser.go
index edbae2a25e0a1..0e57c82e4a53f 100644
--- a/parser/parser.go
+++ b/parser/parser.go
@@ -8408,10 +8408,12 @@ yynewstate:
 	case 607:
 		{
 			expr := yyS[yypt-1].expr
-			if valueExpr, ok := expr.(ast.ValueExpr); ok {
-				expr = &ast.PositionExpr{N: valueExpr}
-			} else if paramExpr, ok := expr.(ast.ParamMarkerExpr); ok {
-				expr = &ast.PositionExpr{N: paramExpr}
+			valueExpr, ok := expr.(ast.ValueExpr)
+			if ok {
+				position, isPosition := valueExpr.GetValue().(int64)
+				if isPosition {
+					expr = &ast.PositionExpr{N: int(position)}
+				}
 			}
 			parser.yyVAL.item = &ast.ByItem{Expr: expr, Desc: yyS[yypt-0].item.(bool)}
 		}
diff --git a/parser/parser.y b/parser/parser.y
index b1be8c27dc6aa..229620ff2c167 100644
--- a/parser/parser.y
+++ b/parser/parser.y
@@ -3188,11 +3188,13 @@ ByItem:
 	Expression Order
 	{
 		expr := $1
-		if valueExpr, ok := expr.(ast.ValueExpr); ok {
-			expr = &ast.PositionExpr{N: valueExpr}
-		} else if paramExpr, ok := expr.(ast.ParamMarkerExpr); ok {
-			expr = &ast.PositionExpr{N: paramExpr}
- 		}
+		valueExpr, ok := expr.(ast.ValueExpr)
+		if ok {
+			position, isPosition := valueExpr.GetValue().(int64)
+			if isPosition {
+				expr = &ast.PositionExpr{N: int(position)}
+			}
+		}
 		$$ = &ast.ByItem{Expr: expr, Desc: $2.(bool)}
 	}