ast: change the order of visiting select stmt

ast/dml.go

@@ -764,6 +764,8 @@ type SelectStmt struct {
 	IsAfterUnionDistinct bool
 	// 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
 }
 
 // Restore implements Node interface.
@@ -906,6 +908,14 @@ func (n *SelectStmt) Accept(v Visitor) (Node, bool) {
 		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 {
@@ -922,14 +932,6 @@ func (n *SelectStmt) Accept(v Visitor) (Node, bool) {
 		n.Where = node.(ExprNode)
 	}
 
-	if n.Fields != nil {
-		node, ok := n.Fields.Accept(v)
-		if !ok {
-			return n, false
-		}
-		n.Fields = node.(*FieldList)
-	}
-
 	if n.GroupBy != nil {
 		node, ok := n.GroupBy.Accept(v)
 		if !ok {

parser.y

@@ -5738,6 +5738,7 @@ SelectStmtBasic:
 			SelectStmtOpts: $2.(*ast.SelectStmtOpts),
 			Distinct:      $2.(*ast.SelectStmtOpts).Distinct,
 			Fields:        $3.(*ast.FieldList),
+			QueryBlockOffset: parser.queryBlockOffset(),
 		}
 		if st.SelectStmtOpts.TableHints != nil {
 			st.TableHints = st.SelectStmtOpts.TableHints
@@ -8102,6 +8103,7 @@ StatementList:
 				s.SetText(lexer.stmtText())
 			}
 			parser.result = append(parser.result, s)
+			parser.blockOffset = 0
 		}
 	}
 |	StatementList ';' Statement
@@ -8112,6 +8114,7 @@ StatementList:
 				s.SetText(lexer.stmtText())
 			}
 			parser.result = append(parser.result, s)
+			parser.blockOffset = 0
 		}
 	}
 

parser_test.go

@@ -4290,3 +4290,43 @@ func (checker *nodeTextCleaner) Enter(in ast.Node) (out ast.Node, skipChildren b
 func (checker *nodeTextCleaner) Leave(in ast.Node) (out ast.Node, ok bool) {
 	return in, true
 }
+
+type queryBlockOffsetChecker struct {
+	curOffset int
+	mismatch  bool
+}
+
+func (checker *queryBlockOffsetChecker) Enter(in ast.Node) (ast.Node, bool) {
+	sel, ok := in.(*ast.SelectStmt)
+	if !ok {
+		return in, false
+	}
+	checker.curOffset++
+	if sel.QueryBlockOffset != checker.curOffset {
+		checker.mismatch = true
+	}
+	return in, false
+}
+
+func (checker *queryBlockOffsetChecker) Leave(in ast.Node) (out ast.Node, ok bool) {
+	return in, true
+}
+
+func (s *testParserSuite) SelectStmtOffset(c *C) {
+	parser := parser.New()
+	sqls := []string{
+		"select * from t; select * from t",
+		"select a, (select count(*) from t t1 where t1.b > t.a) from t where b > (select b from t t2 where t2.b = t.a limit 1)",
+		"select count(*) from t t1 where t1.a < (select count(*) from t t2 where t1.a > t2.a)",
+	}
+	checker := &queryBlockOffsetChecker{}
+	for _, sql := range sqls {
+		stmts, _, err := parser.Parse(sql, "", "")
+		c.Assert(err, IsNil)
+		for _, stmt := range stmts {
+			checker.curOffset = 0
+			stmt.Accept(checker)
+			c.Assert(checker.mismatch, IsFalse)
+		}
+	}
+}

yy_parser.go

@@ -91,11 +91,12 @@ func TrimComment(txt string) string {
 
 // Parser represents a parser instance. Some temporary objects are stored in it to reduce object allocation during Parse function.
 type Parser struct {
-	charset   string
-	collation string
-	result    []ast.StmtNode
-	src       string
-	lexer     Scanner
+	charset     string
+	collation   string
+	result      []ast.StmtNode
+	src         string
+	lexer       Scanner
+	blockOffset int
 
 	// the following fields are used by yyParse to reduce allocation.
 	cache  []yySymType
@@ -134,6 +135,7 @@ func (parser *Parser) Parse(sql, charset, collation string) (stmt []ast.StmtNode
 	parser.collation = collation
 	parser.src = sql
 	parser.result = parser.result[:0]
+	parser.blockOffset = 0
 
 	var l yyLexer
 	parser.lexer.reset(sql)
@@ -217,6 +219,11 @@ func (parser *Parser) endOffset(v *yySymType) int {
 	return offset
 }
 
+func (parser *Parser) queryBlockOffset() int {
+	parser.blockOffset++
+	return parser.blockOffset
+}
+
 func toInt(l yyLexer, lval *yySymType, str string) int {
 	n, err := strconv.ParseUint(str, 10, 64)
 	if err != nil {