Clickhouse-jdbc源码阅读笔记

ClickHouse

clickhouse-jdbc 0.1.36

1. executeQuery和execute的区别
   execute其实还是调用的是executeQuery方法，只是返回的是isSelect(sql)，因此在执行INSERT方法时返回false

   @Override
   public boolean execute(String sql) throws SQLException {
       // currentResult is stored here. InputString and currentResult will be closed on this.close()
       executeQuery(sql);
       return isSelect(sql);
   }
   private static boolean isSelect(String sql) {
       String upper = sql.toUpperCase().trim();
       return upper.startsWith("SELECT") || upper.startsWith("WITH") || upper.startsWith("SHOW") ||
           upper.startsWith("DESC") || upper.startsWith("EXISTS");
   }

2. clickhousifySql
   在执行最终的SQL之前，会将用户传入的SQL clickhouse化，也是只针对SELECT、SHOW等方法

   static String clickhousifySql(String sql) {
       return addFormatIfAbsent(sql, "TabSeparatedWithNamesAndTypes");
   }
   private static String addFormatIfAbsent(String sql, String format) {
       sql = sql.trim();
       String woSemicolon = Patterns.SEMICOLON.matcher(sql).replaceAll("").trim();
       if (isSelect(sql)
           && !woSemicolon.endsWith(" TabSeparatedWithNamesAndTypes")
           && !woSemicolon.endsWith(" TabSeparated")
           && !woSemicolon.endsWith(" JSONCompact")) {
           if (sql.endsWith(";")) {
               sql = sql.substring(0, sql.length() - 1);
           }
           sql += " FORMAT " + format + ';';
       }
       return sql;
   }