parser: create index support LOCK syntax (#5851) (#5853)

Author: winkyao

parser/parser.y

@@ -937,6 +937,10 @@ AlterTableSpec:
 		}
 	}
 
+LockClauseOpt:
+	{}
+| 	LockClause {}
+
 LockClause:
 	"LOCK" eq "NONE"
 	{
@@ -1448,7 +1452,7 @@ NumLiteral:
 
 
 CreateIndexStmt:
-	"CREATE" CreateIndexStmtUnique "INDEX" Identifier IndexTypeOpt "ON" TableName '(' IndexColNameList ')' IndexOptionList
+	"CREATE" CreateIndexStmtUnique "INDEX" Identifier IndexTypeOpt "ON" TableName '(' IndexColNameList ')' IndexOptionList LockClauseOpt
 	{
 		var indexOption *ast.IndexOption
 		if $11 != nil {

parser/parser_test.go

@@ -1474,6 +1474,7 @@ func (s *testParserSuite) TestDDL(c *C) {
 		{"CREATE INDEX idx ON t (a) USING HASH", true},
 		{"CREATE INDEX idx ON t (a) COMMENT 'foo'", true},
 		{"CREATE INDEX idx ON t (a) USING HASH COMMENT 'foo'", true},
+		{"CREATE INDEX idx ON t (a) LOCK=NONE", true},
 		{"CREATE INDEX idx USING BTREE ON t (a) USING HASH COMMENT 'foo'", true},
 		{"CREATE INDEX idx USING BTREE ON t (a)", true},