Simple queries

Question

Hiya,
I'm trying to run simple queries against my database but get the following error:
Error: Could not fetch DOM element for doc id: 9167 in ..../mydbxml/lib/i386-linux-thread-multi/Sleepycat/DbXml.pm, line 497
Some simplified test code that still generates this error is:
     $fullQuery = 'collection("/local/scratch/ar283/anthology/dbxml/anthology.dbxml")//PAPER';
     $txn = $mgr->createTransaction();
     $context = $mgr->createQueryContext();
     $expression = $mgr->prepare($txn,$fullQuery,$context);
     $results = $expression->execute($txn,$context);
     my $value;
     while( $results->next($value) ) {
print "$value\n";
print $results->size() . " objects returned for expression '" . "$fullQuery'\n" ;
     $txn->commit();
I've also tried variations on the $results = $expression->execute($txn,$context); line, e.g.
     $results = $mgr->query($txn,$fullQuery,$context);
     $results = $mgr->query($txn,$fullQuery);
But the same error occurs. Can anyone tell me what I'm doing wrong?
Thanks,
Anna

Answer 1

Have you removed
any environment files by accident.Not that I'm aware of. What files? From within my code? How could I be doing this?
Once you are in this situation, it won't be fixed
other than by recreating the data.Okay, thanks.
How far do you get in your application before you hit
this problem? I.e. what is
working?Well, in the case of the the test query at the end of the building script, I successfully create the database as follows:
my $theContainer = "/local/scratch/ar283/anthology/dbxml/anthology.dbxml";
my $env = new DbEnv(0);
$env->set_cachesize(0, 64 * 1024, 1);
$env->open("/local/scratch/ar283/anthology/dbxml/",
Db::DB_INIT_MPOOL|Db::DB_CREATE|Db::DB_INIT_LOCK|Db::DB_INIT_LOG|Db::DB_INIT_TXN|Db::DB_RECOVER, 0);
my $mgr = new XmlManager($env);
my $txn = $mgr->createTransaction();
if ($mgr->existsContainer($theContainer)){
$mgr->removeContainer($txn,$theContainer);
$txn->commit();
$txn = $mgr->createTransaction();
my $container = $mgr->openContainer($txn, $theContainer, Db::DB_CREATE);
$txn->commit();
Then I populate it in a for loop of transactions like:
my $xmlDoc = $mgr->createDocument();
$xmlDoc->setContent( $recordString );
$xmlDoc->setName( $theName );
$container->putDocument($txn, $xmlDoc);
$txn->commit();
That all seems to work fine. When I tag on the following code for querying the container, I get the error message:
$fullQuery = 'collection("/local/scratch/ar283/anthology/dbxml/anthology.dbxml")//PAPER';
$txn = $mgr->createTransaction();
$context = $mgr->createQueryContext();
$expression = $mgr->prepare($txn,$fullQuery,$context);
if ($debug){
     print "$0: full query is $fullQuery, expression is $expression\n";
$results = $mgr->query($txn,$fullQuery);
$txn->commit();
I get my debug output of "full query is collection("/local/scratch/ar283/anthology/dbxml
/anthology.dbxml")//PAPER, expression is XmlQueryExpression=ARRAY(0x87a7770)" then the next line causes the error.