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https://issues.apache.org/jira/browse/JENA-624?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15033715#comment-15033715
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Andy Seaborne commented on JENA-624:
------------------------------------
Re: multiple invocations of {{end}}:
The code I shown is how I think it could be and I'd like you to confirm or deny
that. Currently it is:
{noformat}
@Override
public void end() {
quadsIndex().end();
defaultGraph().end();
isInTransaction(false);
transactionType(null);
getLock().leaveCriticalSection();
}
{noformat}
so all the transaction manipulation is done before {{leaveCriticalSection}}.
The first {{end}} call by thread1 releases the lock, letting in thread 2
{{begin}}.
The second {{end}} call by thread 1 manipulates {{quadsIndex}}/{{defaultGraph}}
outside the thread2 transaction.
The proposed fix is the {{if (!isInTransaction()) return;}} to make {{end()}}
idempotent at the end of a transaction until the thread starts a new one.
Aside: there only needs to be {{isInTransaction}} in {{DatasetGraphInMemory}}
because it wraps {{Hextable}}/{{TriTable}}.
> Develop a new in-memory RDF Dataset implementation
> --------------------------------------------------
>
> Key: JENA-624
> URL: https://issues.apache.org/jira/browse/JENA-624
> Project: Apache Jena
> Issue Type: Improvement
> Reporter: Andy Seaborne
> Assignee: A. Soroka
> Labels: java, linked_data, rdf
>
> The current (Jan 2014) Jena in-memory dataset uses a general purpose
> container that works for any storage technology for graphs together with
> in-memory graphs.
> This project would develop a new implementation design specifically for RDF
> datasets (triples and quads) and efficient SPARQL execution, for example,
> using multi-core parallel operations and/or multi-version concurrent
> datastructures to maximise true parallel operation.
> This is a system project suitable for someone interested in datatbase
> implementation, datastructure design and implementation, operating systems or
> distributed systems.
> Note that TDB can operate in-memory using a simulated disk with
> copy-in/copy-out semantics for disk-level operations. It is for faithful
> testing TDB infrastructure and is not designed performance, general in-memory
> use or use at scale. While lesson may be learnt from that system, TDB
> in-memory is not the answer here.
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