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POCypher query to match strong two way relationship and filter by property values in Neo4j
 

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  1. POCypher query to match strong two way relationship and filter by property values in Neo4j
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    <p>I would like to find a subgraph in Neo4j DB with only strong two way relationships.</p> <p>Let's say the relationship is LOVES and attribute is Kisses then I would like to only find a subgraph where both sides have kissed the other more than 2 times.</p> <pre><code>START n=node(*) MATCH n-[r1:LOVES]-&gt;friend&lt;-[r2:LOVES]-n WHERE r1.Kisses &gt; 2 and r2.Kisses &gt; 2 RETURN n, friend, r1, r2 LIMIT 20 </code></pre> <p>the problem is that the query seems to run forever on a 3M node 30M relationship graph, on a 32GB RAM, quad core system with 16GB max heap for neo4j(neo4j calculator suggested 8GB).</p> <p>I suspect, there is an endless loop hiding somewhere.</p> <p>OS: Ubuntu 12.04.1 LTS server</p> <p>Soft: neo4j-community-1.8.1</p> <p>java version "1.7.0_10" (neo4j start says to use JDK6)</p> <p>Java(TM) SE Runtime Environment (build 1.7.0_10-b18)</p> <p>Java HotSpot(TM) 64-Bit Server VM (build 23.6-b04, mixed mode)</p> <p>EDIT: match is incorrect it should be </p> <pre><code>MATCH n-[r1:LOVES]-&gt;friend-[r2:LOVES]-&gt;n </code></pre> <p>UPDATE: After correcting semantics above, I am still unable to get a full result in 5 minutes.</p> <p>LOVES is the only relationship type and about 10-20% or relationships have a corresponding one going the other way. </p> <p>My ultimate goal is to find appropriate Kiss values so that I am left with &lt;100k nodes (and all appropriate LOVES relationships) and can export this subgraph.</p> <p>Here's pseudocode for algorithm for what I am trying to do:</p> <pre><code>let E be edge.list to be processed let myedgelist be empty list for e in E: if e.n1 &gt; e.n2: # so we do not look twice continue if not exist(e[n2][n1]): # this is where lookup can be a problem O(1) for hash, O(logn) for sorted, O(n) for something random) continue if e.kisses &gt; 2 and e[n2][n1].kisses &gt; 2: add e to myedgelist add e[n2][n1] to myedgelist return myedgelist </code></pre> <p>This algorithm should run at most edgecount * log(edgecount), unless there is no effective way to lookup existence of reverse relationship in neo4j, which would seem rather inconceivable.</p>
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    1. COShould'nt your MATCH sentence be like in http://console.neo4j.org/?id=yuv3nx ?
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    2. COYou are completely right!
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    3. CODoes it still run forever?
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