Format function names correctly

go/vt/sqlparser/ast.go

@@ -1544,9 +1544,15 @@ func (node *FuncExpr) Format(buf *TrackedBuffer) {
 		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)
+	// if they match a reserved word, only if they contain illegal characters
+	funcName := node.Name.String()
+
+	if containEscapableChars(funcName) {
+		writeEscapedString(buf, funcName)
+	} else {
+		buf.WriteString(funcName)
+	}
+	buf.Myprintf("(%s%v)", distinct, node.Exprs)
 }
 
 // Format formats the node

go/vt/sqlparser/ast_funcs.go

@@ -631,26 +631,37 @@ func (node *TableIdent) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
-func formatID(buf *TrackedBuffer, original, lowered string) {
+func containEscapableChars(s string) bool {
 	isDbSystemVariable := false
-	if len(original) > 1 && original[:2] == "@@" {
+	if len(s) > 1 && s[:2] == "@@" {
 		isDbSystemVariable = true
 	}
 
-	for i, c := range original {
+	for i, c := range s {
 		if !isLetter(uint16(c)) && (!isDbSystemVariable || !isCarat(uint16(c))) {
 			if i == 0 || !isDigit(uint16(c)) {
-				goto mustEscape
+				return true
 			}
 		}
 	}
-	if _, ok := keywords[lowered]; ok {
-		goto mustEscape
+
+	return false
+}
+
+func isKeyword(s string) bool {
+	_, isKeyword := keywords[s]
+	return isKeyword
+}
+
+func formatID(buf *TrackedBuffer, original, lowered string) {
+	if containEscapableChars(original) || isKeyword(lowered) {
+		writeEscapedString(buf, original)
+	} else {
+		buf.Myprintf("%s", original)
 	}
-	buf.Myprintf("%s", original)
-	return
+}
 
-mustEscape:
+func writeEscapedString(buf *TrackedBuffer, original string) {
 	buf.WriteByte('`')
 	for _, c := range original {
 		buf.WriteRune(c)

go/vt/sqlparser/parse_test.go

@@ -1523,6 +1523,12 @@ var (
 	}, {
 		input:  "select distinctrow a.* from (select (1) from dual union all select 1 from dual) a",
 		output: "select distinct a.* from (select (1) from dual union all select 1 from dual) as a",
+	}, {
+		input: "select `weird function name`() from t",
+	}, {
+		input: "select status() from t", // should not escape function names that are keywords
+	}, {
+		input: "select * from `weird table name`",
 	}}
 )