数据聚合与可视化实战指南
1. 聚合测试驱动
聚合功能通过实例学习效果最佳，下面以汽车交易数据为例进行详细说明。
1.1 数据准备
首先，批量索引一些汽车交易数据，包含汽车型号、制造商、销售价格、销售时间等信息。具体操作如下：
POST /cars/transactions/_bulk { "index": {}} { "price" : 10000, "color" : "red", "make" : "honda", "sold" : "2014-10-28" } { "index": {}} { "price" : 20000, "color" : "red", "make" : "honda", "sold" : "2014-11-05" } { "index": {}} { "price" : 30000, "color" : "green", "make" : "ford", "sold" : "2014-05-18" } { "index": {}} { "price" : 15000, "color" : "blue", "make" : "toyota", "sold" : "2014-07-02" } { "index": {}} { "price" : 12000, "color" : "green", "make" : "toyota", "sold" : "2014-08-19" } { "index": {}} { "price" : 20000, "color" : "red", "make" : "honda", "sold" : "2014-11-05" } { "index": {}} { "price"