@SuppressWarnings("unchecked")
final Input<Boolean> condition = (Input<Boolean>) ctx.topLevelInputs().get(0);
@SuppressWarnings("unchecked")
final List<LuceneCollectorExpression> expressions = ctx.docLevelExpressions();
final CollectorContext collectorContext = new CollectorContext();
collectorContext.searchContext(searchContext);
collectorContext.visitor(new LuceneDocCollector.CollectorFieldsVisitor(expressions.size()));
for (LuceneCollectorExpression expression : expressions) {
expression.startCollect(collectorContext);
}