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use hash rather than sorted vector for _usedValues in selectReplicas #12258

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use hash rather than sorted vector for _usedValues in selectReplicas #12258

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dd846d7
use hash rather than manually sorted vector for _usedValues in select…
Jul 17, 2025
777a046
Optimize for _count=3
Jul 24, 2025
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28 changes: 20 additions & 8 deletions fdbrpc/ReplicationPolicy.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -177,8 +177,6 @@ bool PolicyAcross::validate(std::vector<LocalityEntry> const& solutionSet,
// Choose new servers from "least utilized" alsoServers and append the new servers to results
// fromserverse are the servers that have already been chosen and
// that should be excluded from being selected as replicas.
// FIXME: Simplify this function, such as removing unnecessary printf
// fromServers are the servers that must have;
// alsoServers are the servers you can choose.
bool PolicyAcross::selectReplicas(Reference<LocalitySet>& fromServers,
std::vector<LocalityEntry> const& alsoServers,
Expand All @@ -190,16 +188,17 @@ bool PolicyAcross::selectReplicas(Reference<LocalitySet>& fromServers,
int resultsInit = results.size();

// Clear the member variables
AttribValue firstUsedValue, secondUsedValue;
_usedValues.clear();
_newResults.clear();
_addedResults.resize(_arena, 0);

for (auto& alsoServer : alsoServers) {
auto value = fromServers->getValueViaGroupKey(alsoServer, groupIndexKey);
if (value.present()) {
auto lowerBound = std::lower_bound(_usedValues.begin(), _usedValues.end(), value.get());
if ((lowerBound == _usedValues.end()) || (*lowerBound != value.get())) {
//_selected is a set of processes that have the same indexKey and indexValue (value)
if ((firstUsedValue != value.get() && secondUsedValue != value.get()) &&
((lowerBound == _usedValues.end()) || (*lowerBound != value.get()))) {
// _selected is a set of processes that have the same indexKey and indexValue (value)
_selected = fromServers->restrict(indexKey, value.get());
if (_selected->size()) {
// Pass only the also array item which are valid for the value
Expand All @@ -213,7 +212,13 @@ bool PolicyAcross::selectReplicas(Reference<LocalitySet>& fromServers,
}
if (count >= _count)
break;
_usedValues.insert(lowerBound, value.get());
if (firstUsedValue._id == -1) {
firstUsedValue = AttribValue(value.get());
} else if (secondUsedValue._id == -1) {
secondUsedValue = AttribValue(value.get());
} else {
_usedValues.insert(lowerBound, value.get());
}
}
}
}
Expand Down Expand Up @@ -259,14 +264,21 @@ bool PolicyAcross::selectReplicas(Reference<LocalitySet>& fromServers,
auto value = fromServers->getValueViaGroupKey(entry, groupIndexKey);
if (value.present()) {
auto lowerBound = std::lower_bound(_usedValues.begin(), _usedValues.end(), value.get());
if ((lowerBound == _usedValues.end()) || (*lowerBound != value.get())) {
if ((firstUsedValue != value.get() && secondUsedValue != value.get()) &&
((lowerBound == _usedValues.end()) || (*lowerBound != value.get()))) {
_selected = fromServers->restrict(indexKey, value.get());
if (_selected->size()) {
if (_policy->selectReplicas(_selected, emptyEntryArray, results)) {
count++;
if (count >= _count)
break;
_usedValues.insert(lowerBound, value.get());
if (firstUsedValue._id == -1) {
firstUsedValue = AttribValue(value.get());
} else if (secondUsedValue._id == -1) {
secondUsedValue = AttribValue(value.get());
} else {
_usedValues.insert(lowerBound, value.get());
}
}
}
}
Expand Down
7 changes: 7 additions & 0 deletions fdbrpc/include/fdbrpc/ReplicationTypes.h
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,13 @@ struct AttribValue {
bool operator<=(AttribValue const& source) const { return !(*this > source); }
bool operator>=(AttribValue const& source) const { return !(*this < source); }
};
namespace std {
template <>
struct hash<AttribValue> {
std::size_t operator()(const AttribValue& v) const noexcept { return static_cast<std::size_t>(v._id); }
// return std::hash<int>{}(v._id);
};
} // namespace std
struct LocalityEntry {
int _id;
explicit LocalityEntry() : _id(-1) {}
Expand Down