Support Cypher transactions

[mavadat]

Migrated From https://bitbucket.org/Readify/neo4jclient/issue/91/support-cypher-transactions

@tathamoddie created an issue 2013-04-24 http://docs.neo4j.org/chunked/milestone/rest-api-transactional.html

Some thoughts: We should throw a NotSupportedException if they try to start a transaction where graphClient.Version < 2.0. We should throw a NotSupportedException if they try to invoke non-Cypher graph calls within a transaction

@mavadat In terms of API design how about the following basic API:

ITransaction IGraphClient.BeginTransaction();
void ITransaction.Commit();
void ITransaction.Rollback();
void KeepAlive(); //optional - to prevent transaction becoming orphan but comes with great responsibility
void ITransaction:IDisposable.Dispose(); //mainly for the "using" keyword

• Default isolation level is used: READ_COMMITTED which supports repeatable read within same transaction
• Default transaction timeout value is used (org.neo4j.server.transaction.timeout : 60 seconds)
• Read/write locks are only applicable to node and relationship CRUD operations. So we'll introduce the following API changes as well:

NodeReference<TNode> IGraphClient.Create<TNode>(
   TNode node,
   IEnumerable<IRelationshipAllowingParticipantNode<TNode>> relationships,
   ITransaction transaction = null);

Node<TNode> IGraphClient.Get<TNode>(NodeReference reference, ITransaction transaction = null);

Task<Node<TNode>> IGraphClient.GetAsync<TNode>(NodeReference reference, ITransaction transaction = null);

void IGraphClient.Update<TNode>(
   NodeReference<TNode> nodeReference,
   TNode replacementData,
   ITransaction transaction = null); //no option to update indexes

void IGraphClient.Delete(NodeReference reference, DeleteMode mode, ITransaction transaction);

RelationshipReference IGraphClient.CreateRelationship<TSourceNode, TRelationship>(
   NodeReference<TSourceNode> sourceNodeReference,
   TRelationship relationship,
   ITransaction transaction = null);

void IGraphClient.DeleteRelationship(RelationshipReference reference, ITransaction transaction = null);

void ICypherFluentQuery.Delete(string identities, ITransaction transaction = null);
void ICypherFluentQuery Relate(string relateText, ITransaction transaction = null);

Notice:

• No gremlin support
• INDEX operations cannot be done within transaction
• There would be some breaking changes like after deleting a node/relationship within transaction we can still read them until transaction commits. This behaviour has potential in breaking existing code.

Thoughts? How can we improve this?

Related discussion impacting transaction support design: https://groups.google.com/forum/#!topic/neo4j/ZPjBW6wARI8

[kumpikov]

Any heads up on how far the transaction implementation has taken? I hope, it is something we can see soon.

[tekiegirl]

I hope that transactions will be supported soon, I don't really want to have to look at another library instead. Many thanks :)

[dgmachado]

Any heads up on how far the transaction implementation has taken? I hope, it is something we can see soon.