neo4j cypher
一直以来，我一直在使用neo4j的密码查询语言， 迈克尔一直在告诉我在查询中使用参数，但是查询的性能始终可以接受，因此我没有必要。 但是，最近我正在研究一个数据集，并使用类似于以下的代码创建了约500个节点：
require 'open-uri'open("data/people.cyp", 'w') { |f|(1..500).each do |value|f.puts("CREATE (p:Person{name: \"#{value}\"})")end
}这将创建一个如下所示的cypher语句文件：
CREATE (:Person{name: "person1"})
CREATE (:Person{name: "person2"})
CREATE (:Person{name: "person3"})
CREATE (:Person{name: "person4"})
CREATE (:Person{name: "person5"})
...如果我们在neo4j-shell或Web管理员中执行这些语句，则会得到以下输出：
==> +-------------------+
==> | No data returned. |
==> +-------------------+
==> Nodes created: 500
==> Properties set: 500
==> Labels added: 500
==> 27706 ms据我了解，之所以需要这么长时间是因为密码创建然后为每个create语句缓存了一个查询计划，因为它无法知道它们实际上是相同的。 由于我经常删除/重新加载数据，因此我想使反馈循环更快一些，因此终于可以应用Michael的建议了。 参数的工作方式是在占位符查询中添加占位符，然后提供在执行查询时应用于验证那些占位符的值。 在这种情况下，似乎最容易利用neography对正在运行的neo4j服务器执行查询。 如果我们想用参数化名称创建一个人，那么我们将编写以下代码：
require 'neography'params = { :name => "Mark" }Neography::Rest.new.execute_query("CREATE (:Person {name: {name} })", params)如果我们运行查询以找回所有人员，我们可以看到他们已经成功创建：
neo4j-sh (0)$ match p:Person return p;
==> +----------------------+
==> | p |
==> +----------------------+
==> | Node[1]{name:"Mark"} |
==> +----------------------+
==> 1 row
==> 175 ms我想传入一个我最初认为可以做到的名称数组，但是将params哈希中的值更改为一个数组：
require 'neography'params = { :name => [] }
(1..500).each do |value|params[:name] << "person#{value}"
endNeography::Rest.new.execute_query("CREATE (:Person {name: {name} })", params)我进行了一次查询以取回我的500个人，但只有一个人返回：
neo4j-sh (0)$ MATCH p:Person RETURN p
> ;
==> +-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------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==> | p |
==> +-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------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==> | 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","perso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|
==> 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==> 1 row我实际上以这样一种方式使用了参数：只有一个人被创建，并且他们的'name'属性设置为500个名字的数组！ 我调整了代码以传递地图数组，而不是像这样的字符串：
require 'neography'params = { :people => [] }
(1..500).each do |value|params[:people] << { :name => "person#{value}"}
endNeography::Rest.new.execute_query("CREATE (:Person {people})", params)我运行了脚本来填充数据库，然后再次查询它：
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这次我得到了预期的结果，所以唯一要做的就是快速检查将参数化数据输入数据库所花费的时间：
$ time bundle exec ruby people.rb real 0m0.993s
user 0m0.733s
sys 0m0.097s获胜者是……迈克尔，每次跑步大约26秒。
在此版本中，cypher首次遇到CREATE语句时会创建查询计划，但此后它可以将查询计划用于后续调用，从而大大提高了性能。
Alistair指出，查询参数方法在应用程序中使用时非常好，因为您不必担心字符串连接，您只需更改映射中的值即可。
基于这种经验，我现在可以确认上周Max De Marzi的推文：
@ neo4j和Cypher 新手的公共服务公告：请在查询中使用参数http://docs.neo4j.org/chunked/milestone/cypher-parameters.html #MuchFaster
参考： neo4j / cypher：在Mark Needham博客博客上，从我们的JCG合作伙伴 Mark Needham 获得了很多查询参数 。
翻译自: https://www.javacodegeeks.com/2013/08/neo4jcypher-getting-the-hang-of-query-parameters.html
neo4j cypher
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