public PathIteration(
StrictEvaluationStrategy evaluationStrategyImpl,
Scope scope,
Var startVar,
TupleExpr pathExpression,
Var endVar,
Var contextVar,
long minLength,
BindingSet bindings)
throws QueryEvaluationException {
this.evaluationStrategyImpl = evaluationStrategyImpl;
this.scope = scope;
this.startVar = startVar;
this.endVar = endVar;
this.startVarFixed = startVar.hasValue() || bindings.hasBinding(startVar.getName());
this.endVarFixed = endVar.hasValue() || bindings.hasBinding(endVar.getName());
this.pathExpression = pathExpression;
this.contextVar = contextVar;
this.currentLength = minLength;
this.bindings = bindings;
this.reportedValues = makeSet();
this.unreportedValues = makeSet();
this.valueQueue = makeQueue();
createIteration();
}
@Override
protected BindingSet getNextElement() throws QueryEvaluationException {
again:
while (true) {
while (!currentIter.hasNext()) {
Iterations.closeCloseable(currentIter);
createIteration();
// stop condition: if the iter is an EmptyIteration
if (currentIter instanceof EmptyIteration<?, ?>) {
break;
}
}
while (currentIter.hasNext()) {
BindingSet nextElement = currentIter.next();
if (!startVarFixed && !endVarFixed && currentVp != null) {
Value startValue = currentVp.getStartValue();
if (startValue != null) {
nextElement = new QueryBindingSet(nextElement);
((QueryBindingSet) nextElement).addBinding(startVar.getName(), startValue);
}
}
Value v1, v2;
if (startVarFixed && endVarFixed && currentLength > 2) {
v1 = getVarValue(startVar, startVarFixed, nextElement);
v2 = nextElement.getValue("END_" + JOINVAR_PREFIX + pathExpression.hashCode());
} else if (startVarFixed && endVarFixed && currentLength == 2) {
v1 = getVarValue(startVar, startVarFixed, nextElement);
v2 =
nextElement.getValue(
JOINVAR_PREFIX + (currentLength - 1) + "-" + pathExpression.hashCode());
} else {
v1 = getVarValue(startVar, startVarFixed, nextElement);
v2 = getVarValue(endVar, endVarFixed, nextElement);
}
if (!isCyclicPath(v1, v2)) {
ValuePair vp = new ValuePair(v1, v2);
if (reportedValues.contains(vp)) {
// new arbitrary-length path semantics: filter out
// duplicates
if (currentIter.hasNext()) {
continue;
} else {
// if the current iter is exhausted, we need to check
// that no further paths of greater length still exists.
continue again;
}
}
if (startVarFixed && endVarFixed) {
Value endValue = getVarValue(endVar, endVarFixed, nextElement);
if (endValue.equals(v2)) {
add(reportedValues, vp);
if (!v1.equals(v2)) {
addToQueue(valueQueue, vp);
}
if (!nextElement.hasBinding(startVar.getName())) {
((QueryBindingSet) nextElement).addBinding(startVar.getName(), v1);
}
if (!nextElement.hasBinding(endVar.getName())) {
((QueryBindingSet) nextElement).addBinding(endVar.getName(), v2);
}
return nextElement;
} else {
if (add(unreportedValues, vp)) {
if (!v1.equals(v2)) {
addToQueue(valueQueue, vp);
}
}
continue again;
}
} else {
add(reportedValues, vp);
if (!v1.equals(v2)) {
addToQueue(valueQueue, vp);
}
if (!nextElement.hasBinding(startVar.getName())) {
((QueryBindingSet) nextElement).addBinding(startVar.getName(), v1);
}
if (!nextElement.hasBinding(endVar.getName())) {
((QueryBindingSet) nextElement).addBinding(endVar.getName(), v2);
}
return nextElement;
}
} else {
continue again;
}
}
// if we're done, throw away the cached lists of values to avoid
// hogging resources
reportedValues.clear();
unreportedValues.clear();
valueQueue.clear();
return null;
}
}