Thanks, Michael. I'm using an embedded graph database with the java api.
I think I fixed it with the "synchronized" key word on the method.
On Wed, Jun 15, 2016 at 8:53 PM, 'Michael Hunger' via Neo4j <
neo4j@googlegroups.com> wrote:
> You have to create a lock to make that an exclusive operation.
>
> Best with cypher's MERGE and a unique constraint which take care of
> creating that index lock for you:
>
> create constraint on t:Top assert t.id is unique;
>
> MERGE (t:Top {id:123}) RETURN t;
>
>
> On Wed, Jun 15, 2016 at 12:27 AM, David Starkweather <stark...@gmail.com>
> wrote:
>
>> Hell all,
>>
>> Thanks for all your hard work in delivering such a great product.
>>
>> I have an application built on top of neo4j using the java api for
>> v3.0.1. It requires finding a "top" node first at the beginning of every
>> one of my
>> graph operations. This top node serves as the start of my graph db. I
>> noticed an earlier edition of neo4j used a
>> reference node from which to retrieve the graph. Since that apparently
>> is no longer a feature in newer releases,
>> I chose to label this top node with a "TOP" label, and then simply
>> retrieve this node using findNode method. Now, this method works
>> great so long as the testing is done in a single thread. However, when
>> used in multiple threads, it occasionally gets a
>> MultipleFoundException thrown when invoking this findNode method. I feel
>> quite certain that my code only creates one top
>> node at a time, and whenever it creates a new top node, it deletes the
>> old top node and always does so within a single transaction block.
>> However, if findNodes() is used instead, I find that two nodes can be
>> counted by iterating through the ResourceIterator (with hasNext/getNext).
>> (Although I'm not sure if they are both viable active nodes.)
>>
>> Is this the best technique for maintaining such a single top node? Or is
>> there a more preferred way?
>>
>> Does the ResourceIterator that is returned ever contain outdated entries?
>> (I notice the javadocs for this class is missing.)
>>
>> I would appreciate any ideas you may have on this.
>>
>> Thanks again.
>> David Starkweather
>>
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