lix/src/libexpr/eval-cache.cc
Eelco Dolstra a17ce0a8a9 Fix evaluation cache
98e361ad4c introduced a regression where
previously stored attributes were replaced by placeholders. As a
result, a command like 'nix build nixpkgs#hello' had to be executed at
least twice to get caching.

This code does not seem necessary for suggestions to work.
2022-08-24 21:19:43 +02:00

751 lines
22 KiB
C++

#include "eval-cache.hh"
#include "sqlite.hh"
#include "eval.hh"
#include "eval-inline.hh"
#include "store-api.hh"
namespace nix::eval_cache {
static const char * schema = R"sql(
create table if not exists Attributes (
parent integer not null,
name text,
type integer not null,
value text,
context text,
primary key (parent, name)
);
)sql";
struct AttrDb
{
std::atomic_bool failed{false};
const Store & cfg;
struct State
{
SQLite db;
SQLiteStmt insertAttribute;
SQLiteStmt insertAttributeWithContext;
SQLiteStmt queryAttribute;
SQLiteStmt queryAttributes;
std::unique_ptr<SQLiteTxn> txn;
};
std::unique_ptr<Sync<State>> _state;
SymbolTable & symbols;
AttrDb(
const Store & cfg,
const Hash & fingerprint,
SymbolTable & symbols)
: cfg(cfg)
, _state(std::make_unique<Sync<State>>())
, symbols(symbols)
{
auto state(_state->lock());
Path cacheDir = getCacheDir() + "/nix/eval-cache-v4";
createDirs(cacheDir);
Path dbPath = cacheDir + "/" + fingerprint.to_string(Base16, false) + ".sqlite";
state->db = SQLite(dbPath);
state->db.isCache();
state->db.exec(schema);
state->insertAttribute.create(state->db,
"insert or replace into Attributes(parent, name, type, value) values (?, ?, ?, ?)");
state->insertAttributeWithContext.create(state->db,
"insert or replace into Attributes(parent, name, type, value, context) values (?, ?, ?, ?, ?)");
state->queryAttribute.create(state->db,
"select rowid, type, value, context from Attributes where parent = ? and name = ?");
state->queryAttributes.create(state->db,
"select name from Attributes where parent = ?");
state->txn = std::make_unique<SQLiteTxn>(state->db);
}
~AttrDb()
{
try {
auto state(_state->lock());
if (!failed)
state->txn->commit();
state->txn.reset();
} catch (...) {
ignoreException();
}
}
template<typename F>
AttrId doSQLite(F && fun)
{
if (failed) return 0;
try {
return fun();
} catch (SQLiteError &) {
ignoreException();
failed = true;
return 0;
}
}
AttrId setAttrs(
AttrKey key,
const std::vector<Symbol> & attrs)
{
return doSQLite([&]()
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(symbols[key.second])
(AttrType::FullAttrs)
(0, false).exec();
AttrId rowId = state->db.getLastInsertedRowId();
assert(rowId);
for (auto & attr : attrs)
state->insertAttribute.use()
(rowId)
(symbols[attr])
(AttrType::Placeholder)
(0, false).exec();
return rowId;
});
}
AttrId setString(
AttrKey key,
std::string_view s,
const char * * context = nullptr)
{
return doSQLite([&]()
{
auto state(_state->lock());
if (context) {
std::string ctx;
for (const char * * p = context; *p; ++p) {
if (p != context) ctx.push_back(' ');
ctx.append(*p);
}
state->insertAttributeWithContext.use()
(key.first)
(symbols[key.second])
(AttrType::String)
(s)
(ctx).exec();
} else {
state->insertAttribute.use()
(key.first)
(symbols[key.second])
(AttrType::String)
(s).exec();
}
return state->db.getLastInsertedRowId();
});
}
AttrId setBool(
AttrKey key,
bool b)
{
return doSQLite([&]()
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(symbols[key.second])
(AttrType::Bool)
(b ? 1 : 0).exec();
return state->db.getLastInsertedRowId();
});
}
AttrId setInt(
AttrKey key,
int n)
{
return doSQLite([&]()
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(symbols[key.second])
(AttrType::Int)
(n).exec();
return state->db.getLastInsertedRowId();
});
}
AttrId setListOfStrings(
AttrKey key,
const std::vector<std::string> & l)
{
return doSQLite([&]()
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(symbols[key.second])
(AttrType::ListOfStrings)
(concatStringsSep("\t", l)).exec();
return state->db.getLastInsertedRowId();
});
}
AttrId setPlaceholder(AttrKey key)
{
return doSQLite([&]()
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(symbols[key.second])
(AttrType::Placeholder)
(0, false).exec();
return state->db.getLastInsertedRowId();
});
}
AttrId setMissing(AttrKey key)
{
return doSQLite([&]()
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(symbols[key.second])
(AttrType::Missing)
(0, false).exec();
return state->db.getLastInsertedRowId();
});
}
AttrId setMisc(AttrKey key)
{
return doSQLite([&]()
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(symbols[key.second])
(AttrType::Misc)
(0, false).exec();
return state->db.getLastInsertedRowId();
});
}
AttrId setFailed(AttrKey key)
{
return doSQLite([&]()
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(symbols[key.second])
(AttrType::Failed)
(0, false).exec();
return state->db.getLastInsertedRowId();
});
}
std::optional<std::pair<AttrId, AttrValue>> getAttr(AttrKey key)
{
auto state(_state->lock());
auto queryAttribute(state->queryAttribute.use()(key.first)(symbols[key.second]));
if (!queryAttribute.next()) return {};
auto rowId = (AttrId) queryAttribute.getInt(0);
auto type = (AttrType) queryAttribute.getInt(1);
switch (type) {
case AttrType::Placeholder:
return {{rowId, placeholder_t()}};
case AttrType::FullAttrs: {
// FIXME: expensive, should separate this out.
std::vector<Symbol> attrs;
auto queryAttributes(state->queryAttributes.use()(rowId));
while (queryAttributes.next())
attrs.emplace_back(symbols.create(queryAttributes.getStr(0)));
return {{rowId, attrs}};
}
case AttrType::String: {
NixStringContext context;
if (!queryAttribute.isNull(3))
for (auto & s : tokenizeString<std::vector<std::string>>(queryAttribute.getStr(3), ";"))
context.push_back(decodeContext(cfg, s));
return {{rowId, string_t{queryAttribute.getStr(2), context}}};
}
case AttrType::Bool:
return {{rowId, queryAttribute.getInt(2) != 0}};
case AttrType::Int:
return {{rowId, int_t{queryAttribute.getInt(2)}}};
case AttrType::ListOfStrings:
return {{rowId, tokenizeString<std::vector<std::string>>(queryAttribute.getStr(2), "\t")}};
case AttrType::Missing:
return {{rowId, missing_t()}};
case AttrType::Misc:
return {{rowId, misc_t()}};
case AttrType::Failed:
return {{rowId, failed_t()}};
default:
throw Error("unexpected type in evaluation cache");
}
}
};
static std::shared_ptr<AttrDb> makeAttrDb(
const Store & cfg,
const Hash & fingerprint,
SymbolTable & symbols)
{
try {
return std::make_shared<AttrDb>(cfg, fingerprint, symbols);
} catch (SQLiteError &) {
ignoreException();
return nullptr;
}
}
EvalCache::EvalCache(
std::optional<std::reference_wrapper<const Hash>> useCache,
EvalState & state,
RootLoader rootLoader)
: db(useCache ? makeAttrDb(*state.store, *useCache, state.symbols) : nullptr)
, state(state)
, rootLoader(rootLoader)
{
}
Value * EvalCache::getRootValue()
{
if (!value) {
debug("getting root value");
value = allocRootValue(rootLoader());
}
return *value;
}
ref<AttrCursor> EvalCache::getRoot()
{
return make_ref<AttrCursor>(ref(shared_from_this()), std::nullopt);
}
AttrCursor::AttrCursor(
ref<EvalCache> root,
Parent parent,
Value * value,
std::optional<std::pair<AttrId, AttrValue>> && cachedValue)
: root(root), parent(parent), cachedValue(std::move(cachedValue))
{
if (value)
_value = allocRootValue(value);
}
AttrKey AttrCursor::getKey()
{
if (!parent)
return {0, root->state.sEpsilon};
if (!parent->first->cachedValue) {
parent->first->cachedValue = root->db->getAttr(parent->first->getKey());
assert(parent->first->cachedValue);
}
return {parent->first->cachedValue->first, parent->second};
}
Value & AttrCursor::getValue()
{
if (!_value) {
if (parent) {
auto & vParent = parent->first->getValue();
root->state.forceAttrs(vParent, noPos);
auto attr = vParent.attrs->get(parent->second);
if (!attr)
throw Error("attribute '%s' is unexpectedly missing", getAttrPathStr());
_value = allocRootValue(attr->value);
} else
_value = allocRootValue(root->getRootValue());
}
return **_value;
}
std::vector<Symbol> AttrCursor::getAttrPath() const
{
if (parent) {
auto attrPath = parent->first->getAttrPath();
attrPath.push_back(parent->second);
return attrPath;
} else
return {};
}
std::vector<Symbol> AttrCursor::getAttrPath(Symbol name) const
{
auto attrPath = getAttrPath();
attrPath.push_back(name);
return attrPath;
}
std::string AttrCursor::getAttrPathStr() const
{
return concatStringsSep(".", root->state.symbols.resolve(getAttrPath()));
}
std::string AttrCursor::getAttrPathStr(Symbol name) const
{
return concatStringsSep(".", root->state.symbols.resolve(getAttrPath(name)));
}
Value & AttrCursor::forceValue()
{
debug("evaluating uncached attribute '%s'", getAttrPathStr());
auto & v = getValue();
try {
root->state.forceValue(v, noPos);
} catch (EvalError &) {
debug("setting '%s' to failed", getAttrPathStr());
if (root->db)
cachedValue = {root->db->setFailed(getKey()), failed_t()};
throw;
}
if (root->db && (!cachedValue || std::get_if<placeholder_t>(&cachedValue->second))) {
if (v.type() == nString)
cachedValue = {root->db->setString(getKey(), v.string.s, v.string.context),
string_t{v.string.s, {}}};
else if (v.type() == nPath)
cachedValue = {root->db->setString(getKey(), v.path), string_t{v.path, {}}};
else if (v.type() == nBool)
cachedValue = {root->db->setBool(getKey(), v.boolean), v.boolean};
else if (v.type() == nInt)
cachedValue = {root->db->setInt(getKey(), v.integer), int_t{v.integer}};
else if (v.type() == nAttrs)
; // FIXME: do something?
else
cachedValue = {root->db->setMisc(getKey()), misc_t()};
}
return v;
}
Suggestions AttrCursor::getSuggestionsForAttr(Symbol name)
{
auto attrNames = getAttrs();
std::set<std::string> strAttrNames;
for (auto & name : attrNames)
strAttrNames.insert(root->state.symbols[name]);
return Suggestions::bestMatches(strAttrNames, root->state.symbols[name]);
}
std::shared_ptr<AttrCursor> AttrCursor::maybeGetAttr(Symbol name, bool forceErrors)
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
if (cachedValue) {
if (auto attrs = std::get_if<std::vector<Symbol>>(&cachedValue->second)) {
for (auto & attr : *attrs)
if (attr == name)
return std::make_shared<AttrCursor>(root, std::make_pair(shared_from_this(), attr));
return nullptr;
} else if (std::get_if<placeholder_t>(&cachedValue->second)) {
auto attr = root->db->getAttr({cachedValue->first, name});
if (attr) {
if (std::get_if<missing_t>(&attr->second))
return nullptr;
else if (std::get_if<failed_t>(&attr->second)) {
if (forceErrors)
debug("reevaluating failed cached attribute '%s'", getAttrPathStr(name));
else
throw CachedEvalError("cached failure of attribute '%s'", getAttrPathStr(name));
} else
return std::make_shared<AttrCursor>(root,
std::make_pair(shared_from_this(), name), nullptr, std::move(attr));
}
// Incomplete attrset, so need to fall thru and
// evaluate to see whether 'name' exists
} else
return nullptr;
//throw TypeError("'%s' is not an attribute set", getAttrPathStr());
}
}
auto & v = forceValue();
if (v.type() != nAttrs)
return nullptr;
//throw TypeError("'%s' is not an attribute set", getAttrPathStr());
auto attr = v.attrs->get(name);
if (!attr) {
if (root->db) {
if (!cachedValue)
cachedValue = {root->db->setPlaceholder(getKey()), placeholder_t()};
root->db->setMissing({cachedValue->first, name});
}
return nullptr;
}
std::optional<std::pair<AttrId, AttrValue>> cachedValue2;
if (root->db) {
if (!cachedValue)
cachedValue = {root->db->setPlaceholder(getKey()), placeholder_t()};
cachedValue2 = {root->db->setPlaceholder({cachedValue->first, name}), placeholder_t()};
}
return make_ref<AttrCursor>(
root, std::make_pair(shared_from_this(), name), attr->value, std::move(cachedValue2));
}
std::shared_ptr<AttrCursor> AttrCursor::maybeGetAttr(std::string_view name)
{
return maybeGetAttr(root->state.symbols.create(name));
}
ref<AttrCursor> AttrCursor::getAttr(Symbol name, bool forceErrors)
{
auto p = maybeGetAttr(name, forceErrors);
if (!p)
throw Error("attribute '%s' does not exist", getAttrPathStr(name));
return ref(p);
}
ref<AttrCursor> AttrCursor::getAttr(std::string_view name)
{
return getAttr(root->state.symbols.create(name));
}
OrSuggestions<ref<AttrCursor>> AttrCursor::findAlongAttrPath(const std::vector<Symbol> & attrPath, bool force)
{
auto res = shared_from_this();
for (auto & attr : attrPath) {
auto child = res->maybeGetAttr(attr, force);
if (!child) {
auto suggestions = res->getSuggestionsForAttr(attr);
return OrSuggestions<ref<AttrCursor>>::failed(suggestions);
}
res = child;
}
return ref(res);
}
std::string AttrCursor::getString()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto s = std::get_if<string_t>(&cachedValue->second)) {
debug("using cached string attribute '%s'", getAttrPathStr());
return s->first;
} else
root->state.debugThrowLastTrace(TypeError("'%s' is not a string", getAttrPathStr()));
}
}
auto & v = forceValue();
if (v.type() != nString && v.type() != nPath)
root->state.debugThrowLastTrace(TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type())));
return v.type() == nString ? v.string.s : v.path;
}
string_t AttrCursor::getStringWithContext()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto s = std::get_if<string_t>(&cachedValue->second)) {
bool valid = true;
for (auto & c : s->second) {
if (!root->state.store->isValidPath(c.first)) {
valid = false;
break;
}
}
if (valid) {
debug("using cached string attribute '%s'", getAttrPathStr());
return *s;
}
} else
root->state.debugThrowLastTrace(TypeError("'%s' is not a string", getAttrPathStr()));
}
}
auto & v = forceValue();
if (v.type() == nString)
return {v.string.s, v.getContext(*root->state.store)};
else if (v.type() == nPath)
return {v.path, {}};
else
root->state.debugThrowLastTrace(TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type())));
}
bool AttrCursor::getBool()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto b = std::get_if<bool>(&cachedValue->second)) {
debug("using cached Boolean attribute '%s'", getAttrPathStr());
return *b;
} else
root->state.debugThrowLastTrace(TypeError("'%s' is not a Boolean", getAttrPathStr()));
}
}
auto & v = forceValue();
if (v.type() != nBool)
root->state.debugThrowLastTrace(TypeError("'%s' is not a Boolean", getAttrPathStr()));
return v.boolean;
}
NixInt AttrCursor::getInt()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto i = std::get_if<int_t>(&cachedValue->second)) {
debug("using cached Integer attribute '%s'", getAttrPathStr());
return i->x;
} else
throw TypeError("'%s' is not an Integer", getAttrPathStr());
}
}
auto & v = forceValue();
if (v.type() != nInt)
throw TypeError("'%s' is not an Integer", getAttrPathStr());
return v.integer;
}
std::vector<std::string> AttrCursor::getListOfStrings()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto l = std::get_if<std::vector<std::string>>(&cachedValue->second)) {
debug("using cached list of strings attribute '%s'", getAttrPathStr());
return *l;
} else
throw TypeError("'%s' is not a list of strings", getAttrPathStr());
}
}
debug("evaluating uncached attribute '%s'", getAttrPathStr());
auto & v = getValue();
root->state.forceValue(v, noPos);
if (v.type() != nList)
throw TypeError("'%s' is not a list", getAttrPathStr());
std::vector<std::string> res;
for (auto & elem : v.listItems())
res.push_back(std::string(root->state.forceStringNoCtx(*elem)));
if (root->db)
cachedValue = {root->db->setListOfStrings(getKey(), res), res};
return res;
}
std::vector<Symbol> AttrCursor::getAttrs()
{
if (root->db) {
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto attrs = std::get_if<std::vector<Symbol>>(&cachedValue->second)) {
debug("using cached attrset attribute '%s'", getAttrPathStr());
return *attrs;
} else
root->state.debugThrowLastTrace(TypeError("'%s' is not an attribute set", getAttrPathStr()));
}
}
auto & v = forceValue();
if (v.type() != nAttrs)
root->state.debugThrowLastTrace(TypeError("'%s' is not an attribute set", getAttrPathStr()));
std::vector<Symbol> attrs;
for (auto & attr : *getValue().attrs)
attrs.push_back(attr.name);
std::sort(attrs.begin(), attrs.end(), [&](Symbol a, Symbol b) {
std::string_view sa = root->state.symbols[a], sb = root->state.symbols[b];
return sa < sb;
});
if (root->db)
cachedValue = {root->db->setAttrs(getKey(), attrs), attrs};
return attrs;
}
bool AttrCursor::isDerivation()
{
auto aType = maybeGetAttr("type");
return aType && aType->getString() == "derivation";
}
StorePath AttrCursor::forceDerivation()
{
auto aDrvPath = getAttr(root->state.sDrvPath, true);
auto drvPath = root->state.store->parseStorePath(aDrvPath->getString());
if (!root->state.store->isValidPath(drvPath) && !settings.readOnlyMode) {
/* The eval cache contains 'drvPath', but the actual path has
been garbage-collected. So force it to be regenerated. */
aDrvPath->forceValue();
if (!root->state.store->isValidPath(drvPath))
throw Error("don't know how to recreate store derivation '%s'!",
root->state.store->printStorePath(drvPath));
}
return drvPath;
}
}