Пока я использовал язык запросов neo4j, Майкл говорил мне использовать параметры в моих запросах, но производительность запросов всегда была приемлемой, поэтому я не чувствовал в этом необходимости. Однако недавно я поиграл с набором данных и создал ~ 500 узлов, используя код, подобный следующему:
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require 'open-uri'open("data/people.cyp", 'w') { |f| (1..500).each do |value| f.puts("CREATE (p:Person{name: \"#{value}\"})") end} |
Это создает файл операторов шифрования, которые выглядят так:
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CREATE (:Person{name: "person1"})CREATE (:Person{name: "person2"})CREATE (:Person{name: "person3"})CREATE (:Person{name: "person4"})CREATE (:Person{name: "person5"})... |
Если мы выполним эти операторы в neo4j-shell или веб-администраторе, мы получим следующий вывод:
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==> +-------------------+==> | No data returned. |==> +-------------------+==> Nodes created: 500==> Properties set: 500==> Labels added: 500==> 27706 ms |
Насколько я понимаю, причина, по которой это занимает много времени, заключается в том, что cypher создает, а затем кэширует план запроса для каждого оператора create, потому что он не может знать, что они фактически совпадают. Так как я довольно часто удалял / перезагружал данные, я хотел немного ускорить цикл обратной связи, так что пришло время применить совет Майкла. Способ работы параметров заключается в том, что вы добавляете заполнители в свои запросы шифров, а затем предоставляете значения, которые должны соответствовать этим заполнителям при выполнении запроса. В этом случае казалось проще всего использовать neography для выполнения моего запроса на работающем сервере neo4j. Если мы хотим создать одного человека с параметризованным именем, мы напишем следующий код:
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require 'neography'params = { :name => "Mark" }Neography::Rest.new.execute_query("CREATE (:Person {name: {name} })", params) |
Если мы выполним запрос, чтобы вернуть всех людей, мы увидим, что они были успешно созданы:
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neo4j-sh (0)$ match p:Person return p;==> +----------------------+==> | p |==> +----------------------+==> | Node[1]{name:"Mark"} |==> +----------------------+==> 1 row==> 175 ms |
Я хотел передать массив имен, которые я изначально думал, что смогу сделать, но изменив значение в хэше params на массив:
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require 'neography'params = { :name => [] }(1..500).each do |value| params[:name] << "person#{value}"endNeography::Rest.new.execute_query("CREATE (:Person {name: {name} })", params) |
Я выполнил запрос, чтобы вернуть свои 500 человек, но получил только один:
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neo4j-sh (0)$ MATCH p:Person RETURN p> ;==> +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+==> | p |==> +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+==> | 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|==> +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+==> 1 row |
Я на самом деле использовал параметры таким образом, что только один человек был создан, и его свойство name было установлено в массив из 500 имен! Я настроил код для передачи в массив карт вместо строк, например, так:
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require 'neography'params = { :people => [] }(1..500).each do |value| params[:people] << { :name => "person#{value}"}endNeography::Rest.new.execute_query("CREATE (:Person {people})", params) |
Я запустил свой скрипт, чтобы заполнить базу данных, прежде чем запросить ее снова:
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neo4j-sh (0)$ MATCH p:Person RETURN p;==> +-----------------------------+==> | p |==> +-----------------------------+==> | Node[1]{name:"person1"} |==> | Node[2]{name:"person2"} |==> | Node[3]{name:"person3"} |==> | Node[4]{name:"person4"} |==> | Node[5]{name:"person5"} |==> | Node[6]{name:"person6"} |==> | Node[7]{name:"person7"} |==> | Node[8]{name:"person8"} |==> | Node[9]{name:"person9"} |==> | Node[10]{name:"person10"} |==> | Node[11]{name:"person11"} |...==> +-----------------------------+==> 500 rows==> 1081 ms |
На этот раз я получил ожидаемый результат, поэтому единственное, что нужно было сделать, это быстро проверить, сколько времени потребовалось для ввода параметризованных данных в базу данных:
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$ time bundle exec ruby people.rb real 0m0.993suser 0m0.733ssys 0m0.097s |
И победителем становится … Майкл, примерно на 26 секунд за пробег.
В этой версии cypher создает план запроса при первом обращении к оператору CREATE, но после этого он может использовать план запроса для последующих вызовов, что приводит к значительному повышению производительности.
Алистер отметил, что подход с использованием параметров запроса весьма удобен при использовании в приложениях, поскольку вам не нужно беспокоиться о конкатенации строк, вместо этого вы можете просто изменить значения в картах.
Основываясь на этом опыте, теперь я могу подтвердить твит Макс Де Марци с прошлой недели:
Объявление о государственной службе для новичков в @ neo4j и Cypher: пожалуйста, используйте параметры в своих запросах http://docs.neo4j.org/chunked/milestone/cypher-parameters.html #MuchFaster
Ссылка: neo4j / cypher : ознакомление с параметрами запроса от нашего партнера по JCG Марка Нидхэма в блоге Марка Нидхэма .