基于Ruby中postgresql的SELECT查询，获得嵌套良好的分组散列

Question

我有一个来自Postgresql的SELECT查询，它返回的结果如下所示：

 brand | model| firmware | direction | mbps 
-------+------+----------+-----------+------
 Cisco | 7602 | 7.2      | up        | 283
 Cisco | 7602 | 7.3      | up        | 192
 Cisco | 7602 | 7.2      | down      | 200  
 Cisco | 7602 | 7.3      | down      | 107 
 Cisco | 7602 | 7.2      | bi        | 249  
 Cisco | 7602 | 7.3      | bi        | 151  

我希望在一个很好的嵌套散列中得到结果，该哈希将对品牌、模型、固件进行分组，然后显示每个方向的mbps值。我想展示嵌套散列的示例，但现在有点不知所措，甚至不知道如何正确地构造它。

当前，我在运行该查询时得到的哈希如下所示：

{"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.2", "direction"=>"up", "mbps"=>"283"}
{"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.3", "direction"=>"up", "mbps"=>"192"}
{"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.2", "direction"=>"down", "mbps"=>"200"}
{"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.3", "direction"=>"down", "mbps"=>"107"}
{"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.2", "direction"=>"bi", "mbps"=>"249"}
{"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.3", "direction"=>"bi", "mbps"=>"151"}

我希望我的问题有意义。

Answer 1

你可以像这样建立分组

rows = [{"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.2", "direction"=>"up", "mbps"=>"283"},
        {"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.3", "direction"=>"up", "mbps"=>"192"},
        {"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.2", "direction"=>"down", "mbps"=>"200"},
        {"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.3", "direction"=>"down", "mbps"=>"107"},
        {"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.2", "direction"=>"bi", "mbps"=>"249"},
        {"brand"=>"Cisco", "model"=>"7602", "firmware"=>"7.3", "direction"=>"bi", "mbps"=>"151"}]
data = {}
rows.each do |row|
  data[row['brand']] ||= {}
  data[row['brand']][row['model']] ||= {}
  data[row['brand']][row['model']][row['firmware']] ||= {} 
  data[row['brand']][row['model']][row['firmware']][row['direction']] = row['mbps']
end

puts data

产出：

{"Cisco"=>{"7602"=>{"7.2"=>{"up"=>"283", "down"=>"200", "bi"=>"249"}, "7.3"=>{"up"=>"192", "down"=>"107", "bi"=>"151"}}}}