public Iterator<PartitionLocator> locatorScan(
final AbstractScaleOutFederation<?> fed, final IPredicate<?> predicate) {
final long timestamp = getReadTimestamp();
// Note: assumes that we are NOT using a view of two relations.
final IRelation<?> relation =
(IRelation<?>) fed.getResourceLocator().locate(predicate.getOnlyRelationName(), timestamp);
/*
* Find the best access path for the predicate for that relation.
*
* Note: All we really want is the [fromKey] and [toKey] for that
* predicate and index. This MUST NOT layer on expanders since the
* layering also hides the [fromKey] and [toKey].
*/
@SuppressWarnings("unchecked")
final AccessPath<?> accessPath = (AccessPath<?>) relation.getAccessPath((IPredicate) predicate);
// Note: assumes scale-out (EDS or JDS).
final IClientIndex ndx = (IClientIndex) accessPath.getIndex();
/*
* Note: could also be formed from relationName + "." +
* keyOrder.getIndexName(), which is cheaper unless the index metadata
* is cached.
*/
final String name = ndx.getIndexMetadata().getName();
return fed.locatorScan(
name, timestamp, accessPath.getFromKey(), accessPath.getToKey(), false /* reverse */);
}
/**
* The head relation is what we write on for mutation operations and is also responsible for
* minting new elements from computed {@link ISolution}s. This method depends solely on the name
* of the head relation and the timestamp of interest for the view.
*/
public IRelation getHeadRelationView(final IPredicate pred) {
if (pred.getRelationCount() != 1) throw new IllegalArgumentException();
final String relationName = pred.getOnlyRelationName();
final long timestamp =
(getAction().isMutation() ? getWriteTimestamp() : getReadTimestamp(/*relationName*/ ));
return (IRelation<?>) resourceLocator.locate(relationName, timestamp);
}
@SuppressWarnings("unchecked")
public IRelation getTailRelationView(final IPredicate pred) {
final int nsources = pred.getRelationCount();
if (nsources == 1) {
return (IRelation) resourceLocator.locate(pred.getOnlyRelationName(), getReadTimestamp());
} else if (nsources == 2) {
final IRelation<?> relation0 =
(IRelation) resourceLocator.locate(pred.getRelationName(0), readTimestamp);
final IRelation<?> relation1 =
(IRelation) resourceLocator.locate(pred.getRelationName(1), readTimestamp);
return new RelationFusedView(relation0, relation1).init();
} else {
throw new UnsupportedOperationException();
}
}
