解析postgresql得删除函数语法报错

[huangyao229328404]

dbtype: postgresql
dbversion: 12
druid verion: 1.2.22
error sql: DROP FUNCTION IF EXISTS add_numbers(a integer) 或者 DROP FUNCTION add_numbers()
testcase code:

String sql = "DROP FUNCTION IF EXISTS add_numbers(a integer)";

SQLStatementParser parser = new SQLStatementParser(sql, DbType.postgresql);
SQLStatement sqlStatement = parser.parseStatement();

stacktrace info:

Exception in thread "main" com.alibaba.druid.sql.parser.ParserException: not supported.pos 23, line 1, column 18, token EXISTS
	at com.alibaba.druid.sql.parser.SQLStatementParser.checkEndToken(SQLStatementParser.java:4983)
	at com.alibaba.druid.sql.parser.SQLStatementParser.parseStatement(SQLStatementParser.java:4973)

和

Exception in thread "main" com.alibaba.druid.sql.parser.ParserException: not supported.pos 26, line 1, column 26, token (
	at com.alibaba.druid.sql.parser.SQLStatementParser.checkEndToken(SQLStatementParser.java:4983)
	at com.alibaba.druid.sql.parser.SQLStatementParser.parseStatement(SQLStatementParser.java:4973)