fix conflict, i cannot resolve it by rewrite yacc syntax, so i using lexer to eliminate ambiguity

Author: sjjian

lexer.go

@@ -82,7 +82,7 @@ func AddTokenBetween(left []byte, right []byte, matchEnd bool, action lexmachine
 	})
 }
 
-func AddIdentToken(rs string, action lexmachine.Action) {
+func genKeywordIdent(rs string) []byte {
 	l := strings.ToLower(rs)
 	u := strings.ToUpper(rs)
 	var regex bytes.Buffer
@@ -96,7 +96,26 @@ func AddIdentToken(rs string, action lexmachine.Action) {
 			regex.WriteString("]")
 		}
 	}
-	lexer.Add(regex.Bytes(), action)
+	return regex.Bytes()
+}
+
+func genGroupKeywordIdent(rss ...string) []byte {
+	var regex bytes.Buffer
+	for i, rs := range rss {
+		regex.Write(genKeywordIdent(rs))
+		if i < len(rss)-1 {
+			regex.Write([]byte("( |\t|\n|\r)+"))
+		}
+	}
+	return regex.Bytes()
+}
+
+func AddIdentToken(rs string, action lexmachine.Action) {
+	lexer.Add(genKeywordIdent(rs), action)
+}
+
+func AddIdentGroupToken(action lexmachine.Action, rss ...string) {
+	lexer.Add(genGroupKeywordIdent(rss...), action)
 }
 
 var stdTokenMap = map[string]int{
@@ -346,6 +365,12 @@ var unReservedKeyword = map[string]int{
 func init() {
 	lexer = lexmachine.NewLexer()
 
+	AddIdentGroupToken(token(_not_deferrable), "not", "deferrable")
+	AddIdentGroupToken(token(_no_inmemory), "no", "inmemory")
+	AddIdentGroupToken(token(_no_duplicate), "no", "duplicate")
+	AddIdentGroupToken(token(_row_level_locking), "row", "level", "locking")
+	AddIdentGroupToken(token(_drop_index), "drop", "index")
+
 	for keyword, tokenId := range stdTokenMap {
 		AddIdentToken(keyword, token(tokenId))
 	}

lexer_test.go

@@ -0,0 +1,57 @@
+package parser
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGenKeywordIdent(t *testing.T) {
+	testCases := map[string][]byte{
+		"a":    []byte("[Aa]"),
+		"B":    []byte("[Bb]"),
+		"case": []byte("[Cc][Aa][Ss][Ee]"),
+		"CASE": []byte("[Cc][Aa][Ss][Ee]"),
+		"CaSe": []byte("[Cc][Aa][Ss][Ee]"),
+		"a_b":  []byte("[Aa]_[Bb]"),
+		"":     nil,
+	}
+	for input, expect := range testCases {
+		actual := genKeywordIdent(input)
+		assert.Equal(t, string(expect), string(actual))
+	}
+}
+
+type genGroupKeywordCase struct {
+	expect []byte
+	input  []string
+}
+
+func TestGenGroupKeywordIdent(t *testing.T) {
+	testCases := []genGroupKeywordCase{
+		{
+			input:  []string{},
+			expect: nil,
+		},
+		{
+			input:  []string{"a"},
+			expect: []byte("[Aa]"),
+		},
+		{
+			input:  []string{"B"},
+			expect: []byte("[Bb]"),
+		},
+		{
+			input:  []string{"a", "B"},
+			expect: []byte("[Aa]( |\t|\n|\r)+[Bb]"),
+		},
+		{
+			input:  []string{"a", "B", "CasE"},
+			expect: []byte("[Aa]( |\t|\n|\r)+[Bb]( |\t|\n|\r)+[Cc][Aa][Ss][Ee]"),
+		},
+	}
+	for _, c := range testCases {
+		actual := genGroupKeywordIdent(c.input...)
+		assert.Equal(t, string(c.expect), string(actual))
+	}
+}