There may be a time where many user sessions attempt to update the same property on the same node. Unlikely, but possible. This may be a 'sequence' node, where you're keeping track of an increasing identifier, a sort of autoincrement. How can you be, almost, certain that your CYPHER statement will not be blocked by another session updating the node property at that exact time? Assume the sequence node: CREATE (s:Sequences {counterToIncrement: 0}) Then call the following CYPHER MATCH (s:Sequences) CALL apoc.atomic.add(s,'counterToIncrement',1,10) YIELD newValue as seq RETURN seq This will attempt to add 1 to the sequence property 'counterToIncrement' , and will attempt up to 10 times if the property is locked, and finally the new value of 'counterToIncrement' is yielded and returned. From a post : https://community.neo4j.com/t5/neo4j-graph-platform/integer-sequence-generator-in-neo4j-apoc/td-p/19403
Controlling the service System services are controlled with the systemctl command. It accepts a number of commands and follows the format: systemctl {start|stop|restart} neo4j you may find that you need to prefix the systemctl command with sudo like: sudo systemctl stop neo4j looking at the output of the status command we get : sudo systemctl status neo4j ● neo4j.service - Neo4j Graph Database Loaded: loaded (/etc/systemd/system/neo4j.service; enabled; vendor preset: enabled) Active: active (running) since Thu 2020-07-23 09:53:29 UTC; 1h 33min ago Main PID: 958 (pre-neo4j.sh) Tasks: 64 Memory: 14.3G CPU: 22min 1.740s CGroup: /system.slice/neo4j.service ├─ 958 /bin/bash /etc/neo4j/pre-neo4j.sh ├─ 996 /bin/sh /etc/neo4j/reset-password-aws.sh ├─ 997 /usr/bin/java -cp /va...
MERGE is a powerful and misunderstood component of the CYPHER toolbox. Assume you have two :Person nodes each with a name property ('Adam' and 'Bob'). You might assume that you could MERGE as follows to create a [:KNOWS] relationship: MERGE (a:Person {name:'Adam'})-[r:KNOWS]->(b:Person {name:'Bob'}); and you'd be correct, it works perfectly Always remember MERGE is based on matching the entire pattern in the statement. Say you now want to set the age of Adam to 21 in the same statement. You might think it's as simple as MERGE (a:Person {name:'Adam',age:21})-[r:KNOWS]->(b:Person {name:'Bob'}); will create 2 new Person nodes and a [:KNOWS] relationship. If there is a unique constraint on :Person (name) there will be errors thrown and no new nodes or relationships. Why, the initial part of the MERGE 'looks' for a pattern match on the :Person node of name:'Adam' and age:21, it doesn't create a property. No m...
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