neo4j cypher

一直以來，我一直在使用neo4j的密碼查詢語言， 邁克爾一直在告訴我在查詢中使用參數，但是查詢的性能始終可以接受，因此我沒有必要。 但是，最近我正在研究一個數據集，并使用類似于以下的代碼創建了約500個節點：

require 'open-uri'open("data/people.cyp", 'w') { |f|(1..500).each do |value|f.puts("CREATE (p:Person{name: \"#{value}\"})")end }

這將創建一個如下所示的cypher語句文件：

CREATE (:Person{name: "person1"}) CREATE (:Person{name: "person2"}) CREATE (:Person{name: "person3"}) CREATE (:Person{name: "person4"}) CREATE (:Person{name: "person5"}) ...

如果我們在neo4j-shell或Web管理員中執行這些語句，則會得到以下輸出：

==> +-------------------+ ==> | No data returned. | ==> +-------------------+ ==> Nodes created: 500 ==> Properties set: 500 ==> Labels added: 500 ==> 27706 ms

據我了解，之所以需要這么長時間是因為密碼創建然后為每個create語句緩存了一個查詢計劃，因為它無法知道它們實際上是相同的。 由于我經常刪除/重新加載數據，因此我想使反饋循環更快一些，因此終于可以應用Michael的建議了。 參數的工作方式是在占位符查詢中添加占位符，然后提供在執行查詢時應用于驗證那些占位符的值。 在這種情況下，似乎最容易利用neography對正在運行的neo4j服務器執行查詢。 如果我們想用參數化名稱創建一個人，那么我們將編寫以下代碼：

require 'neography'params = { :name => "Mark" }Neography::Rest.new.execute_query("CREATE (:Person {name: {name} })", params)

如果我們運行查詢以找回所有人員，我們可以看到他們已經成功創建：

neo4j-sh (0)$ match p:Person return p; ==> +----------------------+ ==> | p | ==> +----------------------+ ==> | Node[1]{name:"Mark"} | ==> +----------------------+ ==> 1 row ==> 175 ms

我想傳入一個我最初認為可以做到的名稱數組，但是將params哈希中的值更改為一個數組：

require 'neography'params = { :name => [] } (1..500).each do |value|params[:name] << "person#{value}" endNeography::Rest.new.execute_query("CREATE (:Person {name: {name} })", params)

我進行了一次查詢以取回我的500個人，但只有一個人返回：

neo4j-sh (0)$ MATCH p:Person RETURN p > ; ==> +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ ==> | p | ==> +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ ==> | Node[1]{name:["person1","person2","person3","person4","person5","person6","person7","person8","person9","person10","person11","person12","person13","person14","person15","person16","person17","person18","person19","person20","person21","person22","person23","person24","person25","person26","person27","person28","person29","person30","person31","person32","person33","person34","person35","person36","person37","person38","person39","person40","person41","person42","person43","person44","person45","person46","person47","person48","person49","person50","person51","person52","person53","person54","person55","person56","person57","person58","person59","person60","person61","person62","person63","person64","person65","person66","person67","person68","person69","person70","person71","person72","person73","person74","person75","person76","person77","person78","person79","person80","person81","person82","person83","person84","person85","person86","person87","person88","person89","person90","person91","person92","person93","person94","person95","person96","person97","person98","person99","person100","person101","person102","person103","person104","person105","person106","person107","person108","person109","person110","person111","person112","person113","person114","person115","person116","person117","person118","person119","person120","person121","person122","person123","person124","person125","person126","person127","person128","person129","person130","person131","person132","person133","person134","person135","person136","person137","person138","person139","person140","person141","person142","person143","person144","person145","person146","person147","person148","person149","person150","person151","person152","person153","person154","person155","person156","person157","person158","person159","person160","person161","person162","person163","person164","person165","person166","person167","person168","person169","person170","person171","person172","person173","person174","person175","person176","person177","person178","person179","person180","person181","person182","person183","person184","person185","person186","person187","person188","person189","person190","person191","person192","person193","person194","person195","person196","person197","person198","person199","person200","person201","person202","person203","person204","person205","person206","person207","person208","person209","person210","person211","person212","person213","person214","person215","person216","person217","person218","person219","person220","person221","person222","person223","person224","person225","person226","person227","person228","person229","person230","person231","person232","person233","person234","person235","person236","person237","person238","person239","person240","person241","person242","person243","person244","person245","person246","person247","person248","person249","person250","person251","person252","person253","person254","person255","person256","person257","person258","person259","person260","person261","person262","person263","person264","person265","person266","person267","person268","person269","person270","person271","person272","person273","person274","person275","person276","person277","person278","person279","person280","person281","person282","person283","person284","person285","person286","person287","person288","person289","person290","person291","person292","person293","person294","person295","person296","person297","person298","person299","person300","person301","person302","person303","person304","person305","person306","person307","person308","person309","person310","person311","person312","person313","person314","person315","person316","person317","person318","person319","person320","person321","person322","person323","person324","person325","person326","person327","person328","person329","person330","person331","person332","person333","person334","person335","person336","person337","person338","person339","person340","person341","person342","person343","person344","person345","person346","person347","person348","person349","person350","person351","person352","person353","person354","person355","person356","person357","person358","person359","person360","person361","person362","person363","person364","person365","person366","person367","person368","person369","person370","person371","person372","person373","person374","person375","person376","person377","person378","person379","person380","person381","person382","person383","person384","person385","person386","person387","person388","person389","person390","person391","person392","person393","person394","person395","person396","person397","person398","person399","person400","person401","person402","person403","person404","person405","person406","person407","person408","person409","person410","person411","person412","person413","person414","person415","person416","person417","person418","person419","person420","person421","person422","person423","person424","person425","person426","person427","person428","person429","person430","person431","person432","person433","person434","person435","person436","person437","person438","person439","person440","person441","person442","person443","person444","person445","person446","person447","person448","person449","person450","person451","person452","person453","person454","person455","person456","person457","person458","person459","person460","person461","person462","person463","person464","person465","person466","person467","person468","person469","person470","person471","person472","person473","person474","person475","person476","person477","person478","person479","person480","person481","person482","person483","person484","person485","person486","person487","person488","person489","person490","person491","person492","person493","person494","person495","person496","person497","person498","person499","person500"]} | ==> +-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ ==> 1 row

我實際上以這樣一種方式使用了參數：只有一個人被創建，并且他們的'name'屬性設置為500個名字的數組！ 我調整了代碼以傳遞地圖數組，而不是像這樣的字符串：

require 'neography'params = { :people => [] } (1..500).each do |value|params[:people] << { :name => "person#{value}"} endNeography::Rest.new.execute_query("CREATE (:Person {people})", params)

我運行了腳本來填充數據庫，然后再次查詢它：

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

這次我得到了預期的結果，所以唯一要做的就是快速檢查將參數化數據輸入數據庫所花費的時間：

$ time bundle exec ruby people.rb real 0m0.993s user 0m0.733s sys 0m0.097s

獲勝者是……邁克爾，每次跑步大約26秒。

在此版本中，cypher首次遇到CREATE語句時會創建查詢計劃，但此后它可以將查詢計劃用于后續調用，從而大大提高了性能。

Alistair指出，查詢參數方法在應用程序中使用時非常好，因為您不必擔心字符串連接，您只需更改映射中的值即可。

基于這種經驗，我現在可以確認上周Max De Marzi的推文：

@ neo4j和Cypher 新手的公共服務公告：請在查詢中使用參數http://docs.neo4j.org/chunked/milestone/cypher-parameters.html #MuchFaster

參考： neo4j / cypher：在Mark Needham博客博客上，從我們的JCG合作伙伴 Mark Needham 獲得了很多查詢參數 。

翻譯自: https://www.javacodegeeks.com/2013/08/neo4jcypher-getting-the-hang-of-query-parameters.html

neo4j cypher

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