Rails從活動記錄創建視圖

Question

我可以從下面的代碼創建postgresql視圖嗎？是否有必要？因爲現在需要幾秒鐘才能加載，但將來我必須在其上添加日期範圍。如果是的話，有人可以幫我寫下它。

report = self.project_reports 
    results_total = report.where('value < ?', 50).group("key_id").select('key_id') 
    fifty = report.where('value BETWEEN ? AND ?', 41, 50).group("key_id").select('key_id') 
    forty = report.where('value BETWEEN ? AND ?', 31, 40).group("key_id").select('key_id') 
    thirty = report.where('value BETWEEN ? AND ?', 21, 30).group("key_id").select('key_id') 
    twenty = report.where('value BETWEEN ? AND ?', 11, 20).group("key_id").select('key_id') 
    ten = report.where('value BETWEEN ? AND ?', 4, 10).group("key_id").select('key_id') 
    three = report.where('value = ?', 3).group("key_id").select('key_id') 
    two = report.where('value = ?', 2).group("key_id").select('key_id') 
    one = report.where('value = ?', 1).group("key_id").select('key_id') 
    pos = {fif: fifty.count.size, four: forty.count.size, thir: thirty.count.size, twen: twenty.count.size, te: ten.count.size, thr: three.count.size, tw: two.count.size, on: one.count.size, result_t: total} 

Answer 1

這會不會是在SQL意義上的真正的「視圖」（你只能創建通過DDL查詢），但你肯定可以建立一個ActiveRelation（這是你無論如何的意思大概是什麼）。請注意，您正在任意切換'數值'和'位置'，這是故意的嗎？爲了一致起見，我在這裏使用「值」：

group_sql = <<-SQL 
    CASE WHEN value = 1 THEN 'one' 
     WHEN value = 2 THEN 'two' 
     WHEN value = 3 THEN 'three' 
     WHEN value <= 10 THEN 'ten' 
     WHEN value <= 20 THEN 'twenty' 
     WHEN value <= 30 THEN 'thirty' 
     WHEN value <= 40 THEN 'forty' 
     WHEN value <= 50 THEN 'fifty' 
SQL 
report = self.project_reports.where('value < 50').group(group_sql) 
positions = report.count 
positions['total'] = positions.values.sum