parser extenstions:

- allow " for strings
- allow ` for identifiers
- allow @ for identifiers

go/vt/sqlparser/ast.go

@@ -213,8 +213,14 @@ func (self *Node) Format(buf *TrackedBuffer) {
 		if self.Len() != 0 {
 			Fprintf(buf, " on duplicate key update %v", self.At(0))
 		}
-	case NUMBER, NULL, ID, SELECT_STAR, NO_DISTINCT, COMMENT, FOR_UPDATE, NOT_FOR_UPDATE, TABLE:
+	case NUMBER, NULL, SELECT_STAR, NO_DISTINCT, COMMENT, FOR_UPDATE, NOT_FOR_UPDATE, TABLE:
 		Fprintf(buf, "%s", self.Value)
+	case ID:
+		if _, ok := keywords[string(self.Value)]; ok {
+			Fprintf(buf, "`%s`", self.Value)
+		} else {
+			Fprintf(buf, "%s", self.Value)
+		}
 	case VALUE_ARG:
 		buf.bind_locations = append(buf.bind_locations, BindLocation{buf.Len(), len(self.Value)})
 		Fprintf(buf, "%s", self.Value)

go/vt/sqlparser/test/parse_pass.sql

@@ -1,6 +1,9 @@
 select 1 from t
 select -1 from t where b = -2
 select /* simplest */ 1 from t
+select /* back-quote */ 1 from `t`#select /* back-quote */ 1 from t
+select /* back-quote keyword */ 1 from `from`#select /* back-quote keyword */ 1 from `from`
+select /* @ */ @@a from b
 select 1 /* drop this comment */ from t#select 1 from t
 select /* union */ 1 from t union select 1 from t
 select /* union all */ 1 from t union all select 1 from t
@@ -77,7 +80,10 @@ select /* function with distinct */ count(distinct a) from t
 select /* a */ a from t
 select /* a.b */ a.b from t
 select /* string */ 'a' from t
+select /* double quoted string */ "a" from t#select /* double quoted string */ 'a' from t
 select /* quote quote in string */ 'a''a' from t#select /* quote quote in string */ 'a\'a' from t
+select /* double quote quote in string */ "a""a" from t#select /* double quote quote in string */ 'a\"a' from t
+select /* quote in double quoted string */ "a'a" from t#select /* quote in double quoted string */ 'a\'a' from t
 select /* backslash quote in string */ 'a\'a' from t
 select /* literal backslash in string */ 'a\\na' from t
 select /* all escapes */ '\0\'\"\b\n\r\t\Z\\' from t

go/vt/sqlparser/token.go

@@ -247,8 +247,12 @@ func (self *Tokenizer) Scan() (parseNode *Node) {
 			} else {
 				return NewSimpleParseNode(LEX_ERROR, "Unexpected character '!'")
 			}
-		case '\'':
-			return self.scanString()
+		case '\'', '"':
+			return self.scanString(ch)
+		case '`':
+			tok := self.scanString(ch)
+			tok.Type = ID
+			return tok
 		default:
 			return NewSimpleParseNode(LEX_ERROR, fmt.Sprintf("Unexpected character '%c'", ch))
 		}
@@ -353,13 +357,13 @@ exit:
 	return NewParseNode(NUMBER, buffer.Bytes())
 }
 
-func (self *Tokenizer) scanString() *Node {
+func (self *Tokenizer) scanString(delim uint16) *Node {
 	buffer := bytes.NewBuffer(make([]byte, 0, 8))
 	for {
 		ch := self.lastChar
 		self.Next()
-		if ch == '\'' {
-			if self.lastChar == '\'' {
+		if ch == delim {
+			if self.lastChar == delim {
 				self.Next()
 			} else {
 				break
@@ -436,7 +440,7 @@ func (self *Tokenizer) Next() {
 }
 
 func isLetter(ch uint16) bool {
-	return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_'
+	return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch == '_' || ch == '@'
 }
 
 func digitVal(ch uint16) int {