Hang using XmlModify with some documents

[CristiAn Fuenzalida]

Hi!,

I want to modify the content of a document, but the application hangs depending the content of the document i set.

For this content the modify() works great:
<?xml version='1.0' encoding='UTF-8' ?>
<root>
  <nombre>valor</nombre>
  <nombre2 att='attval'>valor2</nombre2>
</root>

But for this one, the application hangs
<?xml version='1.0' encoding='UTF-8' ?>
<root>
        <nombre>valor<Test>Test2</Test><Test>Test2</Test></nombre>
        <nombre2 att="attval">valor2</nombre2>
</root>

The code i'm using to modify the content is the following:

   $xquery = "/root/nombre";
    my $env = new DbEnv(0);
    $env->set_cachesize(0, 81024, 1);
    $env->open('/home/user/mydbxml/',
                Db::DB_INIT_MPOOL|Db::DB_CREATE|Db::DB_INIT_LOCK|Db::DB_INIT_LOG|Db::DB_INIT_TXN);
    my $theMgr = new XmlManager($env);
    my $container = $theMgr->openContainer('cont.dbxml', DbXml::DBXML_TRANSACTIONAL);
    my $queryContext = $theMgr->createQueryContext();
    my $updateContext = $theMgr->createUpdateContext();
    my $modify = $theMgr->createModify();

    eval {
        my $document = $container->getDocument($docname);
        my $value = new XmlValue($document);
        my $queryExpression = $theMgr->prepare($xquery, $queryContext);
          $modify->addAppendStep($queryExpression, XmlModify::Element, 'Test', 'Test2');
          $modify->execute($value, $queryContext, $updateContext);  # THE CODE HANGS HERE
    };

    if (my $e = catch std::exception) {
      print $e->what();
    }

I think isn't  a problem caused by the use of transaction, because it works with the first XML i posted.
¿ Any ideas ?

Thanks in advanced,

CristiAn.

[George Feinberg-3]

CristiAn,

> Hi!,
>
> I want to modify the content of a document, but the application  
> hangs depending the content of the document i set.
>
> For this content the modify() works great:
> <?xml version='1.0' encoding='UTF-8' ?>
> <root>
>   <nombre>valor</nombre>
>   <nombre2 att='attval'>valor2</nombre2>
> </root>
>
> But for this one, the application hangs
> <?xml version='1.0' encoding='UTF-8' ?>
> <root>
>         <nombre>valor<Test>Test2</Test><Test>Test2</Test></nombre>
>         <nombre2 att="attval">valor2</nombre2>
> </root>
>
> The code i'm using to modify the content is the following:
>
>    $xquery = "/root/nombre";
>     my $env = new DbEnv(0);
>     $env->set_cachesize(0, 81024, 1);
>     $env->open('/home/user/mydbxml/',
>                 Db::DB_INIT_MPOOL|Db::DB_CREATE|Db::DB_INIT_LOCK|
> Db::DB_INIT_LOG|Db::DB_INIT_TXN);
>     my $theMgr = new XmlManager($env);
>     my $container = $theMgr->openContainer('cont.dbxml',  
> DbXml::DBXML_TRANSACTIONAL);
>     my $queryContext = $theMgr->createQueryContext();
>     my $updateContext = $theMgr->createUpdateContext();
>     my $modify = $theMgr->createModify();
>
>     eval {
>         my $document = $container->getDocument($docname);
>         my $value = new XmlValue($document);
>         my $queryExpression = $theMgr->prepare($xquery,  
> $queryContext);
>           $modify->addAppendStep($queryExpression,  
> XmlModify::Element, 'Test', 'Test2');
>           $modify->execute($value, $queryContext, $updateContext);  
> # THE CODE HANGS HERE
>     };
>
>     if (my $e = catch std::exception) {
>       print $e->what();
>     }
>
> I think isn't  a problem caused by the use of transaction, because  
> it works with the first XML i posted.
> ¿ Any ideas ?

Most hangs are, in fact, due to transactions and/or locks.
In this case, the probable issue is that you've acquire read locks
in a non-transacted getDocument(), and those locks may conflict
with locks acquired during the XmlModify::execute(), which, in a
transactional container, will *automatically* create a transaction,
and use it for the modification.

The solution is to create and use a transaction for both the
XmlContainer::getDocument() and XmlModify::execute() calls.


Regards,

George



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