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Use aliasing shared pointers instead of extra lifetime object #2690

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dee3cc2
Use aliasing shared pointers instead of extra lifetime object
RobinTF Feb 2, 2026
ce2a6b5
Polish code a little bit more
RobinTF Feb 3, 2026
3ed553e
Perform a micro-optimization
RobinTF Feb 3, 2026
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50 changes: 27 additions & 23 deletions src/engine/CartesianProductJoin.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -369,51 +369,55 @@ Result::LazyResult CartesianProductJoin::createLazyConsumer(
std::vector<std::shared_ptr<const Result>> subresults,
std::shared_ptr<const Result> lazyResult) const {
AD_CONTRACT_CHECK(lazyResult);
std::vector<std::reference_wrapper<const IdTable>> idTables;
std::vector<std::shared_ptr<const IdTable>> idTables;
idTables.reserve(subresults.size() + 1);
for (const auto& result : subresults) {
idTables.emplace_back(result->idTable());
for (auto& result : subresults) {
auto* idTable = &result->idTable();
idTables.emplace_back(std::move(result), idTable);
}
// Placeholder, will be replaced with the current `IdTable` from the lazy
// result.
idTables.emplace_back(std::make_shared<IdTable>(IdTable{0, allocator()}));

auto generatedTables = lazyResult->idTables();

auto get = [self = this, staticMergedVocab = std::move(staticMergedVocab),
limit = getLimitOffset().limitOrDefault(),
offset = getLimitOffset()._offset, idTables = std::move(idTables),
subresults = std::move(subresults), lastTableOffset = size_t{0},
producedTableSize = size_t{0},
idTableOpt = std::optional<Result::IdTableVocabPair>{}](
auto& idTableVocabPair) mutable {
lastTableOffset = size_t{0}, producedTableSize = size_t{0},
lazyResult =
std::move(lazyResult)](auto& idTableVocabPair) mutable {
// These things have to be done after handling a single input, so we do them
// at the beginning of each but the last iteration.
if (idTableOpt.has_value()) {
idTables.pop_back();
lastTableOffset += idTableOpt->idTable_.size();
limit -= producedTableSize;
offset += producedTableSize;
producedTableSize = 0;
}

idTableOpt = std::move(idTableVocabPair);
auto& [idTable, localVocab] = idTableOpt.value();
if (idTable.empty()) {
lastTableOffset += idTables.back()->size();
limit -= producedTableSize;
offset += producedTableSize;
producedTableSize = 0;

auto& [idTable, localVocab] = idTableVocabPair;
// We know that the last id table is mutable (we inserted it ourselves), so
// we can replace it without paying the cost of creating and destroying a
// shared pointer.
const_cast<IdTable&>(*idTables.back()) = std::move(idTable);
if (idTables.back()->empty()) {
return Result::IdTableLoopControl::makeContinue();
}

idTables.emplace_back(idTable);
localVocab.mergeWith(staticMergedVocab);

return Result::IdTableLoopControl::yieldAll(
ad_utility::InputRangeTypeErased{
ad_utility::OwningView{self->produceTablesLazily(
std::move(localVocab),
ql::views::transform(idTables,
ad_utility::staticCast<const IdTable&>),
offset, limit, lastTableOffset)} |
ql::views::transform(idTables, ad_utility::dereference), offset,
limit, lastTableOffset)} |
ql::views::transform([&producedTableSize](auto& tableAndVocab) {
producedTableSize += tableAndVocab.idTable_.size();
return std::move(tableAndVocab);
})});
};
return Result::LazyResult(ad_utility::CachingContinuableTransformInputRange(
lazyResult->idTables(), std::move(get)));
std::move(generatedTables), std::move(get)));
}

// _____________________________________________________________________________
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