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https://issues.apache.org/jira/browse/JENA-1521?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16437775#comment-16437775
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Greg Albiston commented on JENA-1521:
-------------------------------------

Hi Andy,

I understand what your saying about not using it again and the create/destroy 
pattern. However, should there not be some way to reverse a closure without an 
application restarting? There is no obvious method on the Dataset. What if a 
dataset is passed into a third party library which closes it?

Also, how are resources associated with opening the dataset released? For 
example, open the dataset, do some work, go away for a long time, come back and 
reopen. There might only be a small overhead but a developer may wish to they 
are being well behaved and ensuring an in-memory caching is flushed.

>From what you've mentioned the semantics of Datasets are close and can NEVER 
>be accessed again but QueryIterators are MUST close after use to avoid wasting 
>resources.

It just seems strange,

Greg

> 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
>            Priority: Major
>
> 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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