讓我們假設:Ruby on Rails的SQL優化
網絡has_many
頻道 網絡has_many
暱稱
通道has_many
消息 通道belongs_to
網絡
暱稱has_many
消息 暱稱belongs_to
網絡
附加LY:
頻道has_many
暱稱,:through => :messages
暱稱has_many
通道,:through => :messages
我這裏有這個方法記錄消息。非常簡單,它會初始化它並將其鏈接到所需的相關模型。
def log_msg(userinfo, target, message, type = nil, time = nil)
# methods not shown yet obvious
return unless chan = find_channel(target)
return unless nick = find_nickname(userinfo)
msg = Message.new(:message => message)
msg.created_at = time unless time.nil?
if !type.nil? && msg.respond_to?(type)
msg.send("#{type}=", true)
end
msg.channel = chan
msg.nickname = nick
msg.save
end
以下是上述代碼生成的所有查詢。
Channel Load (0.0ms) SELECT * FROM "channels" WHERE ("channels"."name" = '#main_chat') AND ("channels".network_id = 1) LIMIT 1←[0m
Nickname Load (0.0ms) SELECT * FROM "nicknames" WHERE ("nicknames"."nickname" = 'bob_saget') LIMIT 1
Channel Load (0.0ms) SELECT "channels".id FROM "channels" WHERE ("channels"."name" = '#main_chat' AND "channels".network_id = 1 AND "channels".id <> 1) LIMIT 1
Network Load (0.0ms) SELECT * FROM "networks" WHERE ("networks"."id" = 1)
Message Create (0.0ms) INSERT INTO "messages" ("message", "is_action", "channel_id", "is_part", "updated_at", "is_nick", "is_mode", "is_topic", "is_ban", "nickname_id", "is_init", "is_quit", "is_join", "is_kick", "created_at") VALUES(NULL, NULL, 1, NULL, '2009-09-01 20:21:47', NULL, NULL, NULL, NULL, 1, 't', NULL, NULL, NULL, '2009-09-01 20:21:47')
正如你可以看到它查詢頻道表兩次。我只是好奇爲什麼會發生這種情況。當我第一次找到頻道時,它正在做「SELECT *」。似乎沒有必要再次查詢它的ID,因爲它已經是已知的。同樣,它爲什麼還要查詢網絡表。這似乎也不需要,因爲創建新消息記錄時不需要任何網絡相關。