@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;
}
}
private void createIteration() throws QueryEvaluationException {
if (currentLength == 0L) {
ZeroLengthPath zlp = new ZeroLengthPath(scope, startVar, endVar, contextVar);
currentIter = this.evaluationStrategyImpl.evaluate(zlp, bindings);
currentLength++;
} else if (currentLength == 1) {
TupleExpr pathExprClone = pathExpression.clone();
if (startVarFixed && endVarFixed) {
Var replacement =
createAnonVar(JOINVAR_PREFIX + currentLength + "-" + pathExpression.hashCode());
VarReplacer replacer = new VarReplacer(endVar, replacement, 0, false);
pathExprClone.visit(replacer);
}
currentIter = this.evaluationStrategyImpl.evaluate(pathExprClone, bindings);
currentLength++;
} else {
currentVp = valueQueue.poll();
if (currentVp != null) {
TupleExpr pathExprClone = pathExpression.clone();
if (startVarFixed && endVarFixed) {
Var startReplacement =
createAnonVar(JOINVAR_PREFIX + currentLength + "-" + pathExpression.hashCode());
Var endReplacement = createAnonVar("END_" + JOINVAR_PREFIX + pathExpression.hashCode());
startReplacement.setAnonymous(false);
endReplacement.setAnonymous(false);
Value v = currentVp.getEndValue();
startReplacement.setValue(v);
VarReplacer replacer = new VarReplacer(startVar, startReplacement, 0, false);
pathExprClone.visit(replacer);
replacer = new VarReplacer(endVar, endReplacement, 0, false);
pathExprClone.visit(replacer);
} else {
Var toBeReplaced;
Value v;
if (!endVarFixed) {
toBeReplaced = startVar;
v = currentVp.getEndValue();
} else {
toBeReplaced = endVar;
v = currentVp.getStartValue();
}
Var replacement =
createAnonVar(JOINVAR_PREFIX + currentLength + "-" + pathExpression.hashCode());
replacement.setValue(v);
VarReplacer replacer = new VarReplacer(toBeReplaced, replacement, 0, false);
pathExprClone.visit(replacer);
}
currentIter = this.evaluationStrategyImpl.evaluate(pathExprClone, bindings);
} else {
currentIter = new EmptyIteration<BindingSet, QueryEvaluationException>();
}
currentLength++;
}
}