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<?php
namespace SMW\SQLStore\QueryEngine\DescriptionInterpreters;
use RuntimeException;
use SMW\Query\Language\ConceptDescription;
use SMW\Query\Language\Conjunction;
use SMW\Query\Language\Description;
use SMW\Query\Language\Disjunction;
use SMW\Query\Parser as QueryParser;
use SMW\SQLStore\QueryEngine\DescriptionInterpreter;
use SMW\SQLStore\QueryEngine\QuerySegment;
use SMW\SQLStore\QueryEngine\QuerySegmentListBuilder;
use SMWSQLStore3;
/**
* @license GNU GPL v2+
* @since 2.2
*
* @author Markus Krötzsch
* @author Jeroen De Dauw
* @author mwjames
*/
class ConceptDescriptionInterpreter implements DescriptionInterpreter {
/**
* @var QuerySegmentListBuilder
*/
private $querySegmentListBuilder;
/**
* @var QueryParser
*/
private $queryParser;
/**
* @since 2.2
*
* @param QuerySegmentListBuilder $querySegmentListBuilder
*/
public function __construct( QuerySegmentListBuilder $querySegmentListBuilder ) {
$this->querySegmentListBuilder = $querySegmentListBuilder;
}
/**
* @since 2.2
*
* @return boolean
*/
public function canInterpretDescription( Description $description ) {
return $description instanceof ConceptDescription;
}
/**
* @since 3.0
*
* @param QueryParser $queryParser
*/
public function setQueryParser( QueryParser $queryParser ) {
$this->queryParser = $queryParser;
}
/**
* @since 2.2
*
* @param Description $description
*
* @return QuerySegment
*/
public function interpretDescription( Description $description ) {
$query = new QuerySegment();
$concept = $description->getConcept();
$conceptId = $this->querySegmentListBuilder->getStore()->getObjectIds()->getSMWPageID(
$concept->getDBkey(),
SMW_NS_CONCEPT,
'',
''
);
$hash = 'concept-' . $conceptId;
$this->querySegmentListBuilder->getCircularReferenceGuard()->mark( $hash );
if ( $this->querySegmentListBuilder->getCircularReferenceGuard()->isCircular( $hash ) ) {
$this->querySegmentListBuilder->addError(
[ 'smw-query-condition-circular', $description->getQueryString() ]
);
return $query;
}
$db = $this->querySegmentListBuilder->getStore()->getConnection( 'mw.db.queryengine' );
$row = $this->getConceptForId( $db, $conceptId );
// No description found, concept does not exist.
if ( $row === false ) {
$this->querySegmentListBuilder->getCircularReferenceGuard()->unmark( 'concept-' . $conceptId );
// keep the above query object, it yields an empty result
// TODO: announce an error here? (maybe not, since the query processor can check for
// non-existing concept pages which is probably the main reason for finding nothing here)
return $query;
};
global $smwgQConceptCaching, $smwgQMaxSize, $smwgQMaxDepth, $smwgQFeatures, $smwgQConceptCacheLifetime;
$may_be_computed = ( $smwgQConceptCaching == CONCEPT_CACHE_NONE ) ||
( ( $smwgQConceptCaching == CONCEPT_CACHE_HARD ) && ( ( ~( ~( $row->concept_features + 0 ) | $smwgQFeatures ) ) == 0 ) &&
( $smwgQMaxSize >= $row->concept_size ) && ( $smwgQMaxDepth >= $row->concept_depth ) );
if ( $row->cache_date &&
( ( $row->cache_date > ( strtotime( "now" ) - $smwgQConceptCacheLifetime * 60 ) ) ||
!$may_be_computed ) ) { // Cached concept, use cache unless it is dead and can be revived.
$query->joinTable = SMWSQLStore3::CONCEPT_CACHE_TABLE;
$query->joinfield = "$query->alias.s_id";
$query->where = "$query->alias.o_id=" . $db->addQuotes( $conceptId );
} elseif ( $row->concept_txt ) { // Parse description and process it recursively.
if ( $may_be_computed ) {
$description = $this->getConceptQueryDescriptionFrom( $row->concept_txt );
$this->findCircularDescription(
$concept,
$description
);
$qid = $this->querySegmentListBuilder->getQuerySegmentFrom( $description );
if ($qid != -1) {
$query = $this->querySegmentListBuilder->findQuerySegment( $qid );
} else { // somehow the concept query is no longer valid; maybe some syntax changed (upgrade) or global settings were modified since storing it
$this->querySegmentListBuilder->addError( 'smw_emptysubquery' ); // not the right message, but this case is very rare; let us not make detailed messages for this
}
} else {
$this->querySegmentListBuilder->addError(
[ 'smw_concept_cache_miss', $concept->getDBkey() ]
);
}
} // else: no cache, no description (this may happen); treat like empty concept
$this->querySegmentListBuilder->getCircularReferenceGuard()->unmark( $hash );
return $query;
}
/**
* We bypass the storage interface here (which is legal as we control it,
* and safe if we are careful with changes ...)
*
* This should be faster, but we must implement the unescaping that concepts
* do on getWikiValue
*/
private function getConceptForId( $db, $id ) {
return $db->selectRow(
'smw_fpt_conc',
[ 'concept_txt', 'concept_features', 'concept_size', 'concept_depth', 'cache_date' ],
[ 's_id' => $id ],
__METHOD__
);
}
/**
* No defaultnamespaces here; If any, these are already in the concept.
* Unescaping is the same as in SMW_DV_Conept's getWikiValue().
*/
private function getConceptQueryDescriptionFrom( $conceptQuery ) {
if ( $this->queryParser === null ) {
throw new RuntimeException( 'Missing a QueryParser instance' );
}
return $this->queryParser->getQueryDescription(
str_replace( [ '<', '>', '&' ], [ '<', '>', '&' ], $conceptQuery )
);
}
private function findCircularDescription( $concept, &$description ) {
if ( $description instanceof ConceptDescription ) {
if ( $description->getConcept()->equals( $concept ) ) {
$this->querySegmentListBuilder->addError(
[ 'smw-query-condition-circular', $description->getQueryString() ]
);
return;
}
}
if ( $description instanceof Conjunction || $description instanceof Disjunction ) {
foreach ( $description->getDescriptions() as $desc ) {
$this->findCircularDescription( $concept, $desc );
}
}
}
}
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