PlanStage::StageState AndHashStage::work(WorkingSetID* out) {
++_commonStats.works;
if (isEOF()) { return PlanStage::IS_EOF; }
// An AND is either reading the first child into the hash table, probing against the hash
// table with subsequent children, or returning results.
// We read the first child into our hash table.
if (_shouldScanChildren && (0 == _currentChild)) {
return readFirstChild(out);
}
// Probing into our hash table with other children.
if (_shouldScanChildren) {
return hashOtherChildren(out);
}
// Returning results.
verify(!_shouldScanChildren);
// Keep the thing we're returning so we can remove it from our internal map later.
DataMap::iterator returnedIt = _resultIterator;
++_resultIterator;
WorkingSetID idToReturn = returnedIt->second;
_dataMap.erase(returnedIt);
WorkingSetMember* member = _ws->get(idToReturn);
// We should check for matching at the end so the matcher can use information in the
// indices of all our children.
if (Filter::passes(member, _filter)) {
*out = idToReturn;
++_commonStats.advanced;
return PlanStage::ADVANCED;
}
else {
_ws->free(idToReturn);
// Skip over the non-matching thing we currently point at.
++_commonStats.needTime;
return PlanStage::NEED_TIME;
}
}
PlanStage::StageState AndHashStage::work(WorkingSetID* out) {
++_commonStats.works;
if (isEOF()) { return PlanStage::IS_EOF; }
// An AND is either reading the first child into the hash table, probing against the hash
// table with subsequent children, or checking the last child's results to see if they're
// in the hash table.
// We read the first child into our hash table.
if (_hashingChildren) {
if (0 == _currentChild) {
return readFirstChild(out);
}
else if (_currentChild < _children.size() - 1) {
return hashOtherChildren(out);
}
else {
_hashingChildren = false;
// We don't hash our last child. Instead, we probe the table created from the
// previous children, returning results in the order of the last child.
// Fall through to below.
}
}
// Returning results. We read from the last child and return the results that are in our
// hash map.
// We should be EOF if we're not hashing results and the dataMap is empty.
verify(!_dataMap.empty());
// We probe _dataMap with the last child.
verify(_currentChild == _children.size() - 1);
// Work the last child.
StageState childStatus = _children[_children.size() - 1]->work(out);
if (PlanStage::ADVANCED != childStatus) {
return childStatus;
}
// We know that we've ADVANCED. See if the WSM is in our table.
WorkingSetMember* member = _ws->get(*out);
// Maybe the child had an invalidation. We intersect DiskLoc(s) so we can't do anything
// with this WSM.
if (!member->hasLoc()) {
_ws->flagForReview(*out);
return PlanStage::NEED_TIME;
}
DataMap::iterator it = _dataMap.find(member->loc);
if (_dataMap.end() == it) {
// Child's output wasn't in every previous child. Throw it out.
_ws->free(*out);
++_commonStats.needTime;
return PlanStage::NEED_TIME;
}
else {
// Child's output was in every previous child. Merge any key data in
// the child's output and free the child's just-outputted WSM.
WorkingSetID hashID = it->second;
_dataMap.erase(it);
WorkingSetMember* olderMember = _ws->get(hashID);
AndCommon::mergeFrom(olderMember, *member);
_ws->free(*out);
// We should check for matching at the end so the matcher can use information in the
// indices of all our children.
if (Filter::passes(olderMember, _filter)) {
*out = hashID;
++_commonStats.advanced;
return PlanStage::ADVANCED;
}
else {
_ws->free(hashID);
++_commonStats.needTime;
return PlanStage::NEED_TIME;
}
}
}
PlanStage::StageState AndHashStage::work(WorkingSetID* out) {
++_commonStats.works;
if (isEOF()) { return PlanStage::IS_EOF; }
// Fast-path for one of our children being EOF immediately. We work each child a few times.
// If it hits EOF, the AND cannot output anything. If it produces a result, we stash that
// result in _lookAheadResults.
if (_lookAheadResults.empty()) {
// INVALID_ID means that the child didn't produce a valid result.
_lookAheadResults.resize(_children.size(), WorkingSet::INVALID_ID);
// Work each child some number of times until it's either EOF or produces
// a result. If it's EOF this whole stage will be EOF. If it produces a
// result we cache it for later.
for (size_t i = 0; i < _children.size(); ++i) {
PlanStage* child = _children[i];
for (size_t j = 0; j < kLookAheadWorks; ++j) {
StageState childStatus = child->work(&_lookAheadResults[i]);
if (PlanStage::IS_EOF == childStatus || PlanStage::DEAD == childStatus ||
PlanStage::FAILURE == childStatus) {
// A child went right to EOF. Bail out.
_hashingChildren = false;
_dataMap.clear();
return PlanStage::IS_EOF;
}
else if (PlanStage::ADVANCED == childStatus) {
// We have a result cached in _lookAheadResults[i]. Stop looking at this
// child.
break;
}
// We ignore NEED_TIME. TODO: What do we want to do if the child provides
// NEED_FETCH?
}
}
// We did a bunch of work above, return NEED_TIME to be fair.
return PlanStage::NEED_TIME;
}
// An AND is either reading the first child into the hash table, probing against the hash
// table with subsequent children, or checking the last child's results to see if they're
// in the hash table.
// We read the first child into our hash table.
if (_hashingChildren) {
if (0 == _currentChild) {
return readFirstChild(out);
}
else if (_currentChild < _children.size() - 1) {
return hashOtherChildren(out);
}
else {
_hashingChildren = false;
// We don't hash our last child. Instead, we probe the table created from the
// previous children, returning results in the order of the last child.
// Fall through to below.
}
}
// Returning results. We read from the last child and return the results that are in our
// hash map.
// We should be EOF if we're not hashing results and the dataMap is empty.
verify(!_dataMap.empty());
// We probe _dataMap with the last child.
verify(_currentChild == _children.size() - 1);
// Get the next result for the (_children.size() - 1)-th child.
StageState childStatus = workChild(_children.size() - 1, out);
if (PlanStage::ADVANCED != childStatus) {
return childStatus;
}
// We know that we've ADVANCED. See if the WSM is in our table.
WorkingSetMember* member = _ws->get(*out);
// Maybe the child had an invalidation. We intersect DiskLoc(s) so we can't do anything
// with this WSM.
if (!member->hasLoc()) {
_ws->flagForReview(*out);
return PlanStage::NEED_TIME;
}
DataMap::iterator it = _dataMap.find(member->loc);
if (_dataMap.end() == it) {
// Child's output wasn't in every previous child. Throw it out.
_ws->free(*out);
++_commonStats.needTime;
return PlanStage::NEED_TIME;
}
else {
// Child's output was in every previous child. Merge any key data in
// the child's output and free the child's just-outputted WSM.
WorkingSetID hashID = it->second;
_dataMap.erase(it);
WorkingSetMember* olderMember = _ws->get(hashID);
AndCommon::mergeFrom(olderMember, *member);
_ws->free(*out);
// We should check for matching at the end so the matcher can use information in the
// indices of all our children.
if (Filter::passes(olderMember, _filter)) {
*out = hashID;
++_commonStats.advanced;
return PlanStage::ADVANCED;
}
else {
_ws->free(hashID);
++_commonStats.needTime;
return PlanStage::NEED_TIME;
}
}
}