bool Step::predicatesAreContextListInsensitive() const
{
for (size_t i = 0; i < m_predicates.size(); ++i) {
Predicate* predicate = m_predicates[i].get();
if (predicate->isContextPositionSensitive() || predicate->isContextSizeSensitive())
return false;
}
for (size_t i = 0; i < m_nodeTest.mergedPredicates().size(); ++i) {
Predicate* predicate = m_nodeTest.mergedPredicates()[i].get();
if (predicate->isContextPositionSensitive() || predicate->isContextSizeSensitive())
return false;
}
return true;
}
void Step::optimize()
{
// Evaluate predicates as part of node test if possible to avoid building unnecessary NodeSets.
// E.g., there is no need to build a set of all "foo" nodes to evaluate "foo[@bar]", we can check the predicate while enumerating.
// This optimization can be applied to predicates that are not context node list sensitive, or to first predicate that is only context position sensitive, e.g. foo[position() mod 2 = 0].
Vector<Predicate*> remainingPredicates;
for (size_t i = 0; i < m_predicates.size(); ++i) {
Predicate* predicate = m_predicates[i];
if ((!predicate->isContextPositionSensitive() || m_nodeTest.mergedPredicates().isEmpty()) && !predicate->isContextSizeSensitive() && remainingPredicates.isEmpty()) {
m_nodeTest.mergedPredicates().append(predicate);
} else
remainingPredicates.append(predicate);
}
swap(remainingPredicates, m_predicates);
}