mycat-encrypt-server如何支持模糊查询的

最近在研究数据库加密，看到了mycat-encrypt-server项目，看了一下代码，说是支持加密字段的模糊查询：

private void parserBinaryExpression(Expression expression, Set columns, String tableAlias, String tableName) {
   BinaryExpression binartex = (BinaryExpression) expression;
   Expression leftExpression = binartex.getLeftExpression();
   if (leftExpression instanceof Column) {
      Column column = (Column) leftExpression;
      String columnTable = column.getTable() == null ? null : column.getTable().getName().toLowerCase().replaceAll("`", "");
      String columnName = column.getColumnName().toLowerCase().replaceAll("`", "");
      if (columns.contains(columnName)) {
         if (isNotOwn(tableAlias, tableName, columnTable)) {
            return;
         }
         //如果是需要加密的列，获取右边
         Expression rightExpression = binartex.getRightExpression();
         if ((binartex instanceof EqualsTo || binartex instanceof NotEqualsTo) && rightExpression instanceof StringValue) {
            StringValue value = (StringValue) rightExpression;
            //如果是相等
            if (StringUtils.isNotEmpty(value.getValue())) {
               value.setValue(EncryptHelper.hexWithPre(EncryptHelper.encode(value.getValue().getBytes(StandardCharsets.UTF_8))));
            }
         } else if (binartex instanceof LikeExpression && rightExpression instanceof StringValue) {
            //如果是like
            StringValue stringValue = (StringValue) rightExpression;
            String strVal = stringValue.getValue();
            String start = strVal.startsWith("%") ? "%" : EncryptHelper.PRE_ENCRYPT;
            String end = strVal.endsWith("%") ? "%" : "";
            String value = strVal.replaceAll("^%+|%+$", "");
            if (StringUtils.isNotEmpty(value)) {
               stringValue.setValue(start + EncryptHelper.hex(EncryptHelper.encode(value.getBytes(StandardCharsets.UTF_8))) + end);
            }
         }
      }
   }
}