減少創建時的數據庫查詢

Question

目前，我正在研究一個應用程序，該應用程序必須解析大型XML文件並使用其中的數據在數據庫中創建實體。用於創建實體的代碼是一個控制器調用的以下部分：

def create 
    parser = EuroPassVacancy.new params[:vacancy][:file].tempfile.path 
    ids = parser.collect_vacancy_ids 
    ids.each do |vacancy_id| 
     country = Country.find_or_create_by_code(:code => parser.country_code(vacancy_id), :name => parser.country_code(vacancy_id)) 
     company = Company.find_or_create_by_name(:name => parser.employer_name(vacancy_id), :address => parser.employer_address(vacancy_id), 
                :contact => parser.employer_contact(vacancy_id), :phone => parser.employer_phone(vacancy_id), 
                :email => parser.employer_email(vacancy_id), :fax => parser.employer_fax(vacancy_id), 
                :country => country) 
     Vacancy.create(:pes_id => parser.pes_id(vacancy_id), :title => parser.title(vacancy_id), :description => parser.description(vacancy_id), 
        :country => country, :region_code => parser.region_code(vacancy_id), :company_id => company, :isco_code => parser.isco_code(vacancy_id), 
        :nace_code => parser.nace_code(vacancy_id)) 
    end 
    redirect_to :action => :index 
    end 

這是一個相當沉重的循環，但我有理由相信，解析會確定。目前困擾我的是每個創建語句生成的查詢數量。以下是空缺的2 INSERT語句的小副本：

AREL (0.0ms) INSERT INTO `vacancies` (`country_id`, `pes_id`, `title`, `region_code`, `isco_code`, `created_at`, `updated_at`, `description`, `company_id`, `nace_code`) VALUES (9, 50, 'Konstruktér strojní, Strojírenští technici projektanti, konstruktéři', 'RL041', 3118, '2011-05-25 13:19:16', '2011-05-25 13:19:16', 'ÚSO - strojní. Konstrukce nástrojů na tváření a lisování kovů, forem na lisování plastů. Znalost tech. a právních norem, ISO 9001, 14001 souvisejících s výrobním programem v rozsahu potřebném pro vývoj produktu a konstrukci výrobních prostředků - lisování a tváření kovů, plastů, montážních přípravků, PC - konstruk�ní SW - CAD, 3-D (Solid Edge výhodou), OFFICE Outlook, NJ/AJ uživatelská úroveň, ŘP sk. B.', 1, 0) 
    SQL (31.2ms) COMMIT 
    Country Load (0.0ms) SELECT `countries`.* FROM `countries` WHERE `countries`.`code` = 'cy' LIMIT 1 
    SQL (0.0ms) BEGIN 
    AREL (0.0ms) INSERT INTO `countries` (`updated_at`, `name`, `code`, `created_at`) VALUES ('2011-05-25 13:19:18', 'cy', 'cy', '2011-05-25 13:19:18') 
    SQL (63.0ms) COMMIT 
    Company Load (0.0ms) SELECT `companies`.* FROM `companies` WHERE `companies`.`name` = 'ΚΛΕΙΤΟΣ Î「ΕΩΡÎ「ΙΟΥ & ΥΙΟΣ ΛΙΜΙΤΕÎ」' LIMIT 1 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) SELECT 1 FROM `companies` WHERE `companies`.`name` = 'ΚΛΕΙΤΟΣ Î「ΕΩΡÎ「ΙΟΥ & ΥΙΟΣ ΛΙΜΙΤΕÎ」' AND `companies`.`country_id` = 10 AND (`companies`.`name` = BINARY 'ΚΛΕΙΤΟΣ Î「ΕΩΡÎ「ΙΟΥ & ΥΙΟΣ ΛΙΜΙΤΕÎ」') LIMIT 1 
    SQL (0.0ms) ROLLBACK 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) ROLLBACK 
    Country Load (0.0ms) SELECT `countries`.* FROM `countries` WHERE `countries`.`code` = 'cy' LIMIT 1 
    Company Load (0.0ms) SELECT `companies`.* FROM `companies` WHERE `companies`.`name` = 'ΠΑÎ�ΙΚΚΟΣ ΠΙΣΣΟΥΡΙΟΣ ΚΑΙ ΑÎ」ΕΛΦΟΣ ΚΟ ΛΤÎ」' LIMIT 1 
    SQL (0.0ms) BEGIN 
    SQL (15.6ms) SELECT 1 FROM `companies` WHERE `companies`.`name` = 'ΠΑÎ�ΙΚΚΟΣ ΠΙΣΣΟΥΡΙΟΣ ΚΑΙ ΑÎ」ΕΛΦΟΣ ΚΟ ΛΤÎ」' AND `companies`.`country_id` = 10 AND (`companies`.`name` = BINARY 'ΠΑÎ�ΙΚΚΟΣ ΠΙΣΣΟΥΡΙΟΣ ΚΑΙ ΑÎ」ΕΛΦΟΣ ΚΟ ΛΤÎ」') LIMIT 1 
    SQL (0.0ms) ROLLBACK 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) ROLLBACK 
    CACHE (0.0ms) SELECT `countries`.* FROM `countries` WHERE `countries`.`code` = 'cy' LIMIT 1 
    Company Load (0.0ms) SELECT `companies`.* FROM `companies` WHERE `companies`.`name` = 'THE DELHI PALACE INDIAN RESTAURANT LTD' LIMIT 1 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) SELECT 1 FROM `companies` WHERE `companies`.`name` = 'THE DELHI PALACE INDIAN RESTAURANT LTD' AND `companies`.`country_id` = 10 AND (`companies`.`name` = BINARY 'THE DELHI PALACE INDIAN RESTAURANT LTD') LIMIT 1 
    SQL (0.0ms) ROLLBACK 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) ROLLBACK 
    CACHE (0.0ms) SELECT `countries`.* FROM `countries` WHERE `countries`.`code` = 'cy' LIMIT 1 
    Company Load (0.0ms) SELECT `companies`.* FROM `companies` WHERE `companies`.`name` = 'EURES ADVISOR , STELLA PAPADOPOULOU APPIOU' LIMIT 1 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) SELECT 1 FROM `companies` WHERE `companies`.`name` = 'EURES ADVISOR , STELLA PAPADOPOULOU APPIOU' AND `companies`.`country_id` = 10 AND (`companies`.`name` = BINARY 'EURES ADVISOR , STELLA PAPADOPOULOU APPIOU') LIMIT 1 
    AREL (0.0ms) INSERT INTO `companies` (`email`, `phone`, `country_id`, `created_at`, `address`, `contact`, `fax`, `updated_at`, `name`) VALUES ('sappiou@dl.mlsi.gov.cy', '00357 22 403000', 10, '2011-05-25 13:20:13', 'MOUSEIOU STREET 3 1102 , ΛΕΥΚΩΣΙΑ', 'STELLA PAPADOPOULOU APPIOU', '00357 22 873170/1', '2011-05-25 13:20:13', 'EURES ADVISOR , STELLA PAPADOPOULOU APPIOU') 
    SQL (31.2ms) COMMIT 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) ROLLBACK 
    Country Load (0.0ms) SELECT `countries`.* FROM `countries` WHERE `countries`.`code` = 'cy' LIMIT 1 
    Company Load (0.0ms) SELECT `companies`.* FROM `companies` WHERE `companies`.`name` = 'EURES ASSISTANT , NORA LANDA' LIMIT 1 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) SELECT 1 FROM `companies` WHERE `companies`.`name` = 'EURES ASSISTANT , NORA LANDA' AND `companies`.`country_id` = 10 AND (`companies`.`name` = BINARY 'EURES ASSISTANT , NORA LANDA') LIMIT 1 
    AREL (0.0ms) INSERT INTO `companies` (`email`, `phone`, `country_id`, `created_at`, `address`, `contact`, `fax`, `updated_at`, `name`) VALUES ('nlanda@dl.mlsi.gov.cy', '00357 25 827327', 10, '2011-05-25 13:20:29', '67 FRANKLIN ROOSEVELT AV 3011 , ΛΕΜΕΣΟΣ', 'NOT AVAILABLE', '00357 25 306563', '2011-05-25 13:20:29', 'EURES ASSISTANT , NORA LANDA') 
    SQL (31.2ms) COMMIT 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) ROLLBACK 
    Country Load (0.0ms) SELECT `countries`.* FROM `countries` WHERE `countries`.`code` = 'cy' LIMIT 1 
    Company Load (0.0ms) SELECT `companies`.* FROM `companies` WHERE `companies`.`name` = 'ΕΛΕ�Α ΤΖΙΟΒΑ�Η' LIMIT 1 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) SELECT 1 FROM `companies` WHERE `companies`.`name` = 'ΕΛΕ�Α ΤΖΙΟΒΑ�Η' AND `companies`.`country_id` = 10 AND (`companies`.`name` = BINARY 'ΕΛΕ�Α ΤΖΙΟΒΑ�Η') LIMIT 1 
    AREL (0.0ms) INSERT INTO `companies` (`email`, `phone`, `country_id`, `created_at`, `address`, `contact`, `fax`, `updated_at`, `name`) VALUES ('georgiam85@hotmail.com', '0035723833780', 10, '2011-05-25 13:20:45', 'Î」ΑΦÎ�ΗΣ 11-13 5314 AMMOHOSTOS', 'MRS GEORGIA MASIA', '0035723833177', '2011-05-25 13:20:45', 'ΕΛΕÎ�Α ΤΖΙΟΒΑÎ�Η') 
    SQL (31.2ms) COMMIT 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) ROLLBACK 
    Country Load (0.0ms) SELECT `countries`.* FROM `countries` WHERE `countries`.`code` = 'cy' LIMIT 1 
    Company Load (0.0ms) SELECT `companies`.* FROM `companies` WHERE `companies`.`name` = 'EURES ADVISOR , MINAS HADJICONSTANTI' LIMIT 1 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) SELECT 1 FROM `companies` WHERE `companies`.`name` = 'EURES ADVISOR , MINAS HADJICONSTANTI' AND `companies`.`country_id` = 10 AND (`companies`.`name` = BINARY 'EURES ADVISOR , MINAS HADJICONSTANTI') LIMIT 1 
    AREL (0.0ms) INSERT INTO `companies` (`email`, `phone`, `country_id`, `created_at`, `address`, `contact`, `fax`, `updated_at`, `name`) VALUES ('mhadjiconstanti@dl.mlsi.gov.cy', '00357 24 805328', 10, '2011-05-25 13:21:01', 'P.O.BOX 40136 6301 , ΛΑΡ�ΑΚΑ', 'MINAS HADJICONSTANTI', '00357 24 304532', '2011-05-25 13:21:01', 'EURES ADVISOR , MINAS HADJICONSTANTI') 
    SQL (62.4ms) COMMIT 
    SQL (0.0ms) BEGIN 
    SQL (1.0ms) ROLLBACK 
    Country Load (0.0ms) SELECT `countries`.* FROM `countries` WHERE `countries`.`code` = 'it' LIMIT 1 
    Company Load (0.0ms) SELECT `companies`.* FROM `companies` WHERE `companies`.`name` = 'SAILER ANDREAS' LIMIT 1 
    SQL (0.0ms) BEGIN 
    SQL (0.0ms) SELECT 1 FROM `companies` WHERE `companies`.`name` = 'SAILER ANDREAS' AND `companies`.`country_id` = 8 AND (`companies`.`name` = BINARY 'SAILER ANDREAS') LIMIT 1 
    AREL (0.0ms) INSERT INTO `companies` (`email`, `phone`, `country_id`, `created_at`, `address`, `contact`, `fax`, `updated_at`, `name`) VALUES ('info@asailer.it', '+39-0471-932632', 8, '2011-05-25 13:21:18', 'A.Duerer-Str. 20 - Via Duerer 20 39100-Bozen - Bolzano', 'Giulia Morello', '+39-0471-932691', '2011-05-25 13:21:18', 'SAILER ANDREAS') 
    SQL (30.0ms) COMMIT 
    SQL (0.0ms) BEGIN 
    AREL (0.0ms) INSERT INTO `vacancies` (`country_id`, `pes_id`, `title`, `region_code`, `isco_code`, `created_at`, `updated_at`, `description`, `company_id`, `nace_code`) VALUES (8, 64, 'ricerca di ingegnere e architetto per studio di ingegneria', 'R3311', 4190, '2011-05-25 13:21:24', '2011-05-25 13:21:24', 'Studio di ingegneria cerca, anche per subito, un ingegnere e un architetto, per la progettazione architettonica e strutturale, stima e contabilità di opere, il tutto nel settore delle costruzioni civili e delle opere speciali . E\' richiesta ottima conoscenza di autocad, pacchetto office e programmi di strutture e contabilità. Sede di lavoro: Bolzano centro: si chiede gentilmente che venga inviato un curriculum professionale con foto allegata.', 1, 74) 
    SQL (62.4ms) COMMIT 

人們似乎對這些國家&企業走出去的比我想有很多更選擇查詢。我想知道是否可以對代碼進行優化以減少這些查詢。

Answer 1

解決這個問題的最簡單方法是緩存您執行的查找或創建。例如，你一次又一次地選擇了同一個國家，就像你所認定的那樣，這是浪費的。

您可以通過定義一個輔助方法做到這一點：

class Country < ActiveRecord::Base 
    def self.resolve_country(options) 
    @resolved_countries ||= { } 

    @resolved_countries[options[:code]] ||= Country.find_or_create_by_code(options) 
    end 
end 

這將載入您的國家只有一次，如果這種模式應用到其他車型應該顯著加快你的加載。

需要注意的一件事是，您可能需要重置這些緩存以用於測試目的。添加到做到這一點的方法始終是一個好主意，是不是很困難：

def self.reset_cache! 
    @resolved_countries = nil 
end 

這可以把你的模型的單元測試setup方法。