QueryEngine

The QueryEngine handles the transformation of the ask query language into a SQL construct and is also responsible to return query results from the SQL back-end with the help of the following components:

• The QuerySegmentListBuilder transforms ask descriptions into individual QuerySegment's (aka QuerySegmentList)
• The DescriptionInterpreter interface describes classes that are responsible to interpret a specific Description object and turn it into an abstract SQL construct (a QuerySegment)
• The QuerySegmentListProcessor flattens and transforms a list of QuerySegment's into a non-recursive tree of SQL statements (including resolving of property/category hierarchies)
• The ConceptQueryResolver encapsulates query processing of a concept description in connection with the ConceptCache class

Overview

### Examples

$classDescription = new ClassDescription(
    new DIWikiPage( 'Foo', NS_CATEGORY )
);

$namespaceDescription = new NamespaceDescription(
    NS_MAIN
);

$someProperty = new SomeProperty(
    new DIProperty( 'Foo' ),
    new ThingDescription()
);

$description = new Conjunction( [
    $namespaceDescription,
    $classDescription,
    $someProperty
] );

$query = new Query( $description );
$query->setLimit( 10 );

$sqlStorefactory = new SQLStoreFactory(
  new SQLStore()
);

$queryEngine = $sqlStorefactory->newMasterQueryEngine();
$queryResult = $queryEngine->getQueryResult( $query );