Sulu\Component\Content\Query\ContentQueryBuilder::buildSelectorForExcerpt PHP Method

    private function buildSelectorForExcerpt($locale, &$additionalFields)
    {
        $excerptStructure = $this->structureManager->getStructure('excerpt');
        $extension = $this->extensionManager->getExtension('', 'excerpt');
        foreach ($excerptStructure->getProperties(true) as $property) {
            $additionalFields[$locale][] = ['extension' => $extension, 'target' => 'excerpt', 'property' => $property->getName(), 'name' => $property->getName()];
        }
    }