Java 如何获取spring数据mongodb的趋势？

参考此链接，我们使用的是spring数据mongodb，我们希望计算趋势和总销售额。我们现在有两个查询来获取趋势和总销售额，有没有有效的方法可以做到这一点？请帮忙

样本数据：

 {"2000-01-01", 1000, "$"}
 {"2000-01-01", 1000, "$"}
 {"2000-01-01", 1000, "$"}
 {"2001-02-01", 2000, "$"}
 {"2001-02-01", 2000, "$"}
 {"2001-02-01", 2000, "$"}
 {"2002-03-01", 3000, "$"}
 {"2002-03-01", 3000, "$"}
 {"2002-03-01", 3000, "$"}
 {"2003-04-01", 4000, "$"}  
 {"2003-04-01", 4000, "$"} 
 {"2003-04-01", 4000, "$"}

例如，我们在查询中计算从“2003-01-01”（开始日期）到“2004-01-01”（结束日期）期间的总销售额，结果是：$12000。 我们通过另一个查询“2002-01-01”（开始日期）到“2003-01-01”（上一个查询的开始日期）计算的趋势

及

在spring数据mongodb中，是否可以编写一个高效的查询来计算总销售额和总趋势？ 我们尝试了以下方法：

   ** by concurrently running the two tasks (one of calculation gross sales and other of calculating trends) by threads and it seems forking thread from the java web application can be disastrous

 ** by using map reduce program in spring-data-mongodb, but of NO use, because we were unable to get the query for pre-dated date to run using map reduce.

请帮助我了解使用SpringDataMongoDB同时计算趋势和总销售额的其他更好的选择。 当做 克里斯

  subtract the previous result $12000 - $9000 (current result) = $3000 trends.

   ** by concurrently running the two tasks (one of calculation gross sales and other of calculating trends) by threads and it seems forking thread from the java web application can be disastrous

 ** by using map reduce program in spring-data-mongodb, but of NO use, because we were unable to get the query for pre-dated date to run using map reduce.