/**
* The query engine's main method.
*
* @param Dataset $dataset the RDF Dataset
* @param mixed $query the parsed SPARQL query
* @param String $resultform the result form. If set to 'xml' the result will be
* SPARQL Query Results XML Format as described in http://www.w3.org/TR/rdf-sparql-XMLres/ .
* @return Array/String Type of the result depends on $resultform.
*/
public function queryModel($dataset, Query $query, $resultform = false)
{
$this->query = $query;
$this->dataset = $dataset;
if ($this->query->isEmpty) {
$vartable[0]['patternResult'] = null;
return SparqlEngine_ResultConverter::convertFromResult($vartable, $this, $resultform);
}
$graphlist = $this->preselectGraphs();
/// match graph patterns against the RDF Dataset
$patternlist = $this->matchPatterns($graphlist);
// filter results- apply inner filters
$patternlist = $this->filterPatterns($patternlist, false);
// join pattern results
$vartable = $this->joinResults($patternlist);
// filter results- apply outer filters
$vartable = $this->filterPatterns($vartable, true);
if ($vartable[0]['patternResult'] != null) {
// sort vars (ORDER BY, LIMIT, OFFSET)
$vartable = $this->sortVars($vartable[0]['patternResult']);
$qrf = $this->query->getResultForm();
if ($qrf == 'select' || $qrf == 'select distinct') {
$vars = $this->query->getResultVars();
$vartable = $this->selectVars($vartable, $vars);
if ($qrf == 'select distinct') {
$vartable = $this->distinct($vartable);
}
}
} else {
$vartable = null;
}
return SparqlEngine_ResultConverter::convertFromResult($vartable, $this, $resultform);
}
/**
* Parses the SELECT part of a query.
*
* @return void
* @throws SparqlParserException
*/
protected function parseSelect()
{
$this->_fastForward();
$curLow = strtolower(current($this->tokens));
prev($this->tokens);
if ($curLow == 'distinct') {
$this->query->setResultForm('select distinct');
} else {
$this->query->setResultForm('select');
}
$currentVar = null;
$currentFunc = null;
$bWaitForRenaming = false;
while ($curLow != 'from' && $curLow != 'where' && $curLow != "{") {
$this->_fastForward();
$curTok = current($this->tokens);
$curLow = strtolower($curTok);
if ($this->varCheck($curTok) || $curLow == '*') {
if ($bWaitForRenaming) {
$bWaitForRenaming = false;
$currentVar->setAlias($curTok);
if ($currentFunc != null) {
$currentVar->setFunc($currentFunc);
}
$this->query->addResultVar($currentVar);
$currentVar = null;
} else {
if ($currentVar != null) {
$this->query->addResultVar($currentVar);
$currentVar = null;
}
$currentVar = new Query_ResultVariable($curTok);
if ($currentFunc != null) {
$currentVar->setFunc($currentFunc);
}
}
$currentFunc = null;
} else {
if ($curLow == 'as') {
if ($currentVar === null) {
throw new SparqlParserException('AS requires a variable left and right', null, key($this->tokens));
}
$bWaitForRenaming = true;
} else {
if (in_array($curLow, self::$sops)) {
$currentFunc = $curLow;
}
}
}
if (!current($this->tokens)) {
throw new SparqlParserException("Unexpected end of File.", null, key($this->tokens));
}
}
if ($currentVar != null) {
$this->query->addResultVar($currentVar);
}
prev($this->tokens);
if (count($this->query->getResultVars()) == 0) {
throw new SparqlParserException("Variable or '*' expected.", null, key($this->tokens));
}
}
