格式的Postgres row_to_json響應查詢

Question

我有以下Postgres的查詢：

"SELECT \"responses\".\"index\", \"responses\".\"created_at\", 
ROUND(AVG(\"responses\".\"numeric\")) AS numeric 
FROM \"responses\" 
WHERE \"responses\".\"time\" = '#{time}' 
GROUP BY \"responses\".\"index\", \"responses\".\"created_at\"" 

我試圖輸出JSON使用row_to_json的響應。我可以使用：

"select row_to_json(row) 
from (
    SELECT \"responses\".\"index\", \"responses\".\"created_at\", 
    ROUND(AVG(\"responses\".\"numeric\")) AS numeric 
    FROM \"responses\" 
    WHERE \"responses\".\"time\" = '#{time}' 
    GROUP BY \"responses\".\"index\", \"responses\".\"created_at\" 
) row" 

哪位能給我：

{"row_to_json"=>"{\"index\":1,\"created_at\":\"2014-07-12 03:51:00\",\"numeric\":3}"} 

但是我真的不希望嵌套在row_to_json哈希的響應。有沒有一種簡單的方法來去除，所以我剛剛返回：

"{\"index\":1,\"created_at\":\"2014-07-12 03:51:00\",\"numeric\":3}" 

Answer 1

您應該使用array_to_json和array_agg功能。

例如：

SELECT array_to_json(array_agg(row_to_json(row))) FROM ... 

它將返回正確的JSON陣列

參考文獻：

• http://hashrocket.com/blog/posts/faster-json-generation-with-postgresql
• http://reefpoints.dockyard.com/2014/05/27/avoid-rails-when-generating-json-responses-with-postgresql.html