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https://issues.apache.org/jira/browse/JENA-1521?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16437941#comment-16437941
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Andy Seaborne commented on JENA-1521:
-------------------------------------
If a library closes a dataset then it had better put that in its contract. If
it were a file, then the file is closed and the file position lost. Anyway, now
TDB1 (when transactional) and TDB2 datasets can be closed. Close was never
thread/transaction safe because of other threads using a dataset.
The overheads of a dataset are not small. There is a lot of caching going on,
both in JVM and in the OS file system cache.
Closing does not flush in-memory - the end of write transaction does that (or
"sync" if TBD, non-transactional).
> TDB2 backed Datasets cannot be re-opened.
> -----------------------------------------
>
> Key: JENA-1521
> URL: https://issues.apache.org/jira/browse/JENA-1521
> Project: Apache Jena
> Issue Type: Bug
> Environment: Apache Jena: 3.7.0
> Java: 1.8_162
> Reporter: Greg Albiston
> Assignee: Andy Seaborne
> Priority: Major
> Fix For: Jena 3.8.0
>
>
> If a Dataset connected to with TDB2Factory.connectDataset() is opened, closed
> and then later re-opened it is reported that the Dataset is closed.
> Opening, closing and re-opening a Dataset with TDBFactory.createDataset()
> causes no issues.
> Example code to reproduce:
> {noformat}
> public void testTDB2OpenClose() {
> System.out.println("TDB2 Open Close");
> try {
> Dataset dataset = TDB2Factory.connectDataset("test_tdb2");
> dataset.begin(ReadWrite.WRITE);
> Model defaultModel = dataset.getDefaultModel();
>
> defaultModel.add(ResourceFactory.createResource("http://example.org/my#SubjA";),
> ResourceFactory.createProperty("http://example.org/my#PropA";),
> ResourceFactory.createResource("http://example.org/my#ObjA";));
> dataset.commit();
> dataset.end();
> dataset.close();
> Dataset dataset2 = TDB2Factory.connectDataset("test_tdb2");
> dataset2.begin(ReadWrite.READ);
> Model readModel = dataset2.getDefaultModel();
> Iterator<Statement> statements = readModel.listStatements();
> while (statements.hasNext())
> { Statement statement = statements.next(); System.out.println(statement); }
> dataset2.end();
> dataset2.close();
> } catch (Exception ex) \{ System.out.println("Exception: " +
> ex.getMessage()); }
> }
> {noformat}
> {noformat}
> public void testTDB1OpenClose() {
>
> System.out.println("TDB1 Open Close");
> try {
> Dataset dataset = TDBFactory.createDataset("test_tdb1");
> dataset.begin(ReadWrite.WRITE);
> Model defaultModel = dataset.getDefaultModel();
>
> defaultModel.add(ResourceFactory.createResource("http://example.org/my#SubjA";),
> ResourceFactory.createProperty("http://example.org/my#PropA";),
> ResourceFactory.createResource("http://example.org/my#ObjA";));
> dataset.commit();
> dataset.end();
> dataset.close();
>
> Dataset dataset2 = TDBFactory.createDataset("test_tdb1");
> dataset2.begin(ReadWrite.READ);
> Model readModel = dataset2.getDefaultModel();
> Iterator<Statement> statements = readModel.listStatements();
> while (statements.hasNext()) \{ Statement statement = statements.next();
> System.out.println(statement); }
> dataset2.end();
> dataset2.close();
> } catch (Exception ex)
> { System.out.println("Exception: " + ex.getMessage()); }
> }
> {noformat}
>
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