cypher - How can I optimise a Neo4j MERGE query on a node with many relationships? -


i have graph node has many outgoing relationships. time takes add new outgoing relationships degrades add more relationships. degradation appears due time taken check relationship doesn't exist (i'm using merge add relationships).

the destination nodes of relationships have few relationships themselves. there way can force neo4j check existence of relationship destination node instead of source node?

here's test script reproduce problem. creates 1 node id 0 followed 1000 nodes connected node 0 has relationship. nodes added execution time increases linearly.

create constraint on (n:node) assert n.id unique  unwind range(1,1000) merge (from:node { id: 0 }) merge (to:node { id: i}) merge (from)-[:has]->to

added 1001 labels, created 1001 nodes, set 1001 properties, created 1000 relationships, statement executed in 3496 ms.

unwind range(1001,2000) merge (from:node { id: 0 }) merge (to:node { id: i}) merge (from)-[:has]->to

added 1000 labels, created 1000 nodes, set 1000 properties, created 1000 relationships, statement executed in 7030 ms.

unwind range(2001,3000) merge (from:node { id: 0 }) merge (to:node { id: i}) merge (from)-[:has]->to

added 1000 labels, created 1000 nodes, set 1000 properties, created 1000 relationships, statement executed in 10489 ms.

unwind range(3001,4000) merge (from:node { id: 0 }) merge (to:node { id: i}) merge (from)-[:has]->to

added 1000 labels, created 1000 nodes, set 1000 properties, created 1000 relationships, statement executed in 14390 ms.

if create used instead of merge performance better. can't use create though because want ensure relationships unique.

unwind range(4001,5000) merge (from:node { id: 0 }) merge (to:node { id: i}) create (from)-[:has]->to

added 1000 labels, created 1000 nodes, set 1000 properties, created 1000 relationships, statement executed in 413 ms.

note: tested neo4j v2.2.2

this because cypher not clever enough yet use degree of nodes when executing merge. in cost optimizer used reads cleverer updates old rule optimizer used.

after playing around bit unsuccessfully * changing order of & * using create unique instead of merge * trying use path-expressions use get-degree in cost

i remembered shortestpath takes degree's account , goes left right

so tried combine create, , worked well, here example 100.000 nodes.

neo4j-sh (?)$ create constraint on (n:node) assert n.id unique; +-------------------+ | no data returned. | +-------------------+ constraints added: 1 1054 ms neo4j-sh (?)$  neo4j-sh (?)$ unwind range(0,100000) create (to:node { id: i}); +-------------------+ | no data returned. | +-------------------+ nodes created: 100001 properties set: 100001 labels added: 100001 2375 ms neo4j-sh (?)$  neo4j-sh (?)$  neo4j-sh (?)$ match (from:node { id: 0 }) > unwind range(1,100000) > match (to:node { id: i}) > shortestpath((to)<-[:has]-(from)) null > create (from)-[:has]->(to); +-------------------+ | no data returned. | +-------------------+ relationships created: 100000 2897 ms neo4j-sh (?)$  neo4j-sh (?)$  neo4j-sh (?)$ match (from:node { id: 0 }) > unwind range(1,100000) > match (to:node { id: i}) > shortestpath((to)<-[:has]-(from)) null > create (from)-[:has]->(to); +--------------------------------------------+ | no data returned, , nothing changed. | +--------------------------------------------+ 2360 ms

Comments

Post a Comment

Popular posts from this blog

How to connect android app to App engine -

i'm trying connect app in android server i've opened on appengine. my server's name : dddd-daniel-2345 , website server : http://dddd-daniel-2345.appspot.com/ this how connect android app server in app engine: app.yaml: application: dddd-daniel-2345 version: 1 runtime: python27 api_version: 1 threadsafe: yes handlers: - url: .* script: main.app libraries: - name: webapp2 version: "2.5.2" main.py: #!/usr/bin/env python # # copyright 2007 google inc. google.appengine.api import users import webapp2 class userhandler(webapp2.requesthandler): def get(self): user = users.get_current_user() if user: greeting = ('%s,%s,%s' % (user.email(),user.user_id(),user.nickname())) else: greeting = ('not logged in') self.response.out.write(greeting) app = webapp2.wsgiapplication([('/', userhandler),], debug=true) my applications code : add manifast main....
Read more

gcc - MinGW's ld cannot perform PE operations on non PE output file -

i know there other similar questions out there, stackoverflow or not. i've researched lot this, , still didn't find single solution. i'm doing operative system side project. i've been doing in assembly, wanna join c code. test, made assembly code file (called test.asm): [bits 32] global _a section .text _a: jmp $ then made c file (called main.c): extern void a(void); int main(void) { a(); } to link, used file (called make.bat): "c:\mingw\bin\gcc.exe" -ffreestanding -c -o c.o main.c nasm -f coff -o asm.o test.asm "c:\mingw\bin\ld.exe" -ttext 0x100000 --oformat binary -o out.bin c.o asm.o pause i've been researching ages, , i'm still struggling find answer. hope won't flagged duplicate. acknowledge existence of similar questions, have different answers, , none work me. question: what doing wrong? old mingw versions had problem "ld" not able create non-pe files @ all. maybe current versions...
Read more

php - display validation error message next to the textbox in codeigniter -

Image
i'm newbie codeigniter.i want display error message next text box.my view file create.php contains following code. <?php echo validation_errors(); //validation echo form_open('news/create'); //create form ?> <div class="boxes"> <div class="common"> <div class="lables"> <label for="name">name</label> </div> <div class="text_boxes"> <input type="text" name="uname" /><div id="infomessage"><?php echo $message;?></br> </div> </div>` and below controller model: public function create() { $this->load->helper('form'); $this->load->library('form_validation'); $data['title'] = 'insert items'; $this->form_validation->set_rules('uname','required|min_length[6]|m...
Read more