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libstore/derivations: speed up DerivationOutput JSON parsing #14871

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libstore/derivations: speed up DerivationOutput JSON parsing #14871

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85 changes: 43 additions & 42 deletions src/libstore/derivations.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1425,12 +1425,8 @@ void adl_serializer<DerivationOutput>::to_json(json & res, const DerivationOutpu
DerivationOutput
adl_serializer<DerivationOutput>::from_json(const json & _json, const ExperimentalFeatureSettings & xpSettings)
{
std::set<std::string_view> keys;
auto & json = getObject(_json);

for (const auto & [key, _] : json)
keys.insert(key);

auto methodAlgo = [&]() -> std::pair<ContentAddressMethod, HashAlgorithm> {
ContentAddressMethod method = ContentAddressMethod::parse(getString(valueAt(json, "method")));
if (method == ContentAddressMethod::Raw::Text)
Expand All @@ -1440,52 +1436,57 @@ adl_serializer<DerivationOutput>::from_json(const json & _json, const Experiment
return {std::move(method), std::move(hashAlgo)};
};

if (keys == (std::set<std::string_view>{"path"})) {
return DerivationOutput::InputAddressed{
.path = valueAt(json, "path"),
};
}
switch (json.size()) {
case 0:
return DerivationOutput::Deferred{};
case 1:
if (auto * path = optionalValueAt(json, "path"))
return DerivationOutput::InputAddressed{
.path = *path,
};
break;
case 2: {
const bool hasMethod = optionalValueAt(json, "method");

else if (keys == (std::set<std::string_view>{"method", "hash"})) {
auto dof = DerivationOutput::CAFixed{
.ca = static_cast<ContentAddress>(_json),
};
if (dof.ca.method == ContentAddressMethod::Raw::Text)
xpSettings.require(Xp::DynamicDerivations, "text-hashed derivation output in JSON");
/* We no longer produce this (denormalized) field (for the
reasons described above), so we don't need to check it. */
if (hasMethod && optionalValueAt(json, "hash")) {
auto dof = DerivationOutput::CAFixed{
.ca = static_cast<ContentAddress>(_json),
};
if (dof.ca.method == ContentAddressMethod::Raw::Text)
xpSettings.require(Xp::DynamicDerivations, "text-hashed derivation output in JSON");
/* We no longer produce this (denormalized) field (for the
reasons described above), so we don't need to check it. */
#if 0
if (dof.path(store, drvName, outputName) != static_cast<StorePath>(valueAt(json, "path")))
throw Error("Path doesn't match derivation output");
if (dof.path(store, drvName, outputName) != static_cast<StorePath>(valueAt(json, "path")))
throw Error("Path doesn't match derivation output");
#endif
return dof;
}
return dof;
}

else if (keys == (std::set<std::string_view>{"method", "hashAlgo"})) {
xpSettings.require(Xp::CaDerivations);
auto [method, hashAlgo] = methodAlgo();
return DerivationOutput::CAFloating{
.method = std::move(method),
.hashAlgo = std::move(hashAlgo),
};
}
if (hasMethod && optionalValueAt(json, "hashAlgo")) {
xpSettings.require(Xp::CaDerivations);
auto [method, hashAlgo] = methodAlgo();
return DerivationOutput::CAFloating{
.method = std::move(method),
.hashAlgo = std::move(hashAlgo),
};
}

else if (keys == (std::set<std::string_view>{})) {
return DerivationOutput::Deferred{};
break;
}

else if (keys == (std::set<std::string_view>{"method", "hashAlgo", "impure"})) {
xpSettings.require(Xp::ImpureDerivations);
auto [method, hashAlgo] = methodAlgo();
return DerivationOutput::Impure{
.method = std::move(method),
.hashAlgo = hashAlgo,
};
case 3:
if (optionalValueAt(json, "method") && optionalValueAt(json, "hashAlgo") && optionalValueAt(json, "impure")) {
xpSettings.require(Xp::ImpureDerivations);
auto [method, hashAlgo] = methodAlgo();
return DerivationOutput::Impure{
.method = std::move(method),
.hashAlgo = hashAlgo,
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@Radvendii Radvendii Jan 1, 2026

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This should presumably also be std::move(hashAlgo). I realise this is unrelated to the main change of this PR

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@xokdvium xokdvium Jan 2, 2026

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That's an enum, so that's pointless.

};
}
break;
}

else {
throw Error("invalid JSON for derivation output");
}
throw Error("invalid JSON for derivation output");
}

void adl_serializer<Derivation>::to_json(json & res, const Derivation & d)
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