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Store more stuff in the evaluation cache

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In particular, we store whether an attribute failed to evaluate (threw
an exception) or was an unsupported type. This is to ensure that a
repeated 'nix flake show' never has to evaluate anything, so it can
execute without fetching the flake.

With this, 'nix flake show nixpkgs/nixos-20.03 --legacy' executes in
0.6s (was 3.4s).
This commit is contained in:
Eelco Dolstra 2020-04-19 23:07:06 +02:00
parent 3738bcb05e
commit 0725ab2fd7
1 changed files with 152 additions and 37 deletions
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189
src/nix/flake.cc
View file

@ -682,9 +682,11 @@ create table if not exists Attributes (
enum AttrType {
Placeholder = 0,
// FIXME: distinguish between full / partial attrsets
Attrs = 1,
FullAttrs = 1,
String = 2,
Missing = 3,
Misc = 4,
Failed = 5,
};
struct AttrDb
@ -693,16 +695,18 @@ struct AttrDb
{
SQLite db;
SQLiteStmt insertAttribute;
SQLiteStmt insertPlaceholder;
SQLiteStmt queryAttribute;
SQLiteStmt queryAttributes;
std::unique_ptr<SQLiteTxn> txn;
};
struct placeholder_t {};
struct missing_t {};
struct misc_t {};
struct failed_t {};
typedef uint64_t AttrId;
typedef std::pair<AttrId, Symbol> AttrKey;
typedef std::variant<std::vector<Symbol>, std::string, placeholder_t> AttrValue;
typedef std::variant<std::vector<Symbol>, std::string, placeholder_t, missing_t, misc_t, failed_t> AttrValue;
std::unique_ptr<Sync<State>> _state;
@ -723,9 +727,6 @@ struct AttrDb
state->insertAttribute.create(state->db,
"insert or replace into Attributes(parent, name, type, value) values (?, ?, ?, ?)");
state->insertPlaceholder.create(state->db,
fmt("insert or ignore into Attributes(parent, name, type) values (?, ?, %d)", Placeholder));
state->queryAttribute.create(state->db,
"select rowid, type, value from Attributes where parent = ? and name = ?");
@ -746,7 +747,7 @@ struct AttrDb
}
}
AttrId setAttr(
AttrId setAttrs(
AttrKey key,
const std::vector<Symbol> & attrs)
{
@ -755,21 +756,23 @@ struct AttrDb
state->insertAttribute.use()
(key.first)
(key.second)
(AttrType::Attrs)
(AttrType::FullAttrs)
(0, false).exec();
AttrId rowId = state->db.getLastInsertedRowId();
assert(rowId);
for (auto & attr : attrs)
state->insertPlaceholder.use()
state->insertAttribute.use()
(rowId)
(attr).exec();
(attr)
(AttrType::Placeholder)
(0, false).exec();
return rowId;
}
AttrId setAttr(
AttrId setString(
AttrKey key,
std::string_view s)
{
@ -784,6 +787,58 @@ struct AttrDb
return state->db.getLastInsertedRowId();
}
AttrId setPlaceholder(AttrKey key)
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(key.second)
(AttrType::Placeholder)
(0, false).exec();
return state->db.getLastInsertedRowId();
}
AttrId setMissing(AttrKey key)
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(key.second)
(AttrType::Missing)
(0, false).exec();
return state->db.getLastInsertedRowId();
}
AttrId setMisc(AttrKey key)
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(key.second)
(AttrType::Misc)
(0, false).exec();
return state->db.getLastInsertedRowId();
}
AttrId setFailed(AttrKey key)
{
auto state(_state->lock());
state->insertAttribute.use()
(key.first)
(key.second)
(AttrType::Failed)
(0, false).exec();
return state->db.getLastInsertedRowId();
}
std::optional<std::pair<AttrId, AttrValue>> getAttr(
AttrKey key,
SymbolTable & symbols)
@ -798,7 +853,7 @@ struct AttrDb
if (type == AttrType::Placeholder)
return {{rowId, placeholder_t()}};
else if (type == AttrType::Attrs) {
else if (type == AttrType::FullAttrs) {
// FIXME: expensive, should separate this out.
std::vector<Symbol> attrs;
auto queryAttributes(state->queryAttributes.use()(rowId));
@ -807,6 +862,12 @@ struct AttrDb
return {{rowId, attrs}};
} else if (type == AttrType::String) {
return {{rowId, queryAttribute.getStr(2)}};
} else if (type == AttrType::Missing) {
return {{rowId, missing_t()}};
} else if (type == AttrType::Misc) {
return {{rowId, misc_t()}};
} else if (type == AttrType::Failed) {
return {{rowId, failed_t()}};
} else
throw Error("unexpected type in evaluation cache");
}
@ -832,7 +893,7 @@ struct AttrRoot : std::enable_shared_from_this<AttrRoot>
Value * getRootValue()
{
if (!value) {
//printError("GET ROOT");
debug("getting root value");
value = allocRootValue(rootLoader());
}
return *value;
@ -918,6 +979,33 @@ struct AttrCursor : std::enable_shared_from_this<AttrCursor>
return concatStringsSep(".", getAttrPath(name));
}
Value & forceValue()
{
debug("evaluating uncached attribute %s", getAttrPathStr());
auto & v = getValue();
try {
root->state.forceValue(v);
} catch (EvalError &) {
debug("setting '%s' to failed", getAttrPathStr());
if (root->db)
cachedValue = {root->db->setFailed(getAttrKey()), AttrDb::failed_t()};
throw;
}
if (root->db && (!cachedValue || std::get_if<AttrDb::placeholder_t>(&cachedValue->second))) {
if (v.type == tString)
cachedValue = {root->db->setString(getAttrKey(), v.string.s), v.string.s};
else if (v.type == tAttrs)
; // FIXME: do something?
else
cachedValue = {root->db->setMisc(getAttrKey()), AttrDb::misc_t()};
}
return v;
}
std::shared_ptr<AttrCursor> maybeGetAttr(Symbol name)
{
if (root->db) {
@ -932,29 +1020,47 @@ struct AttrCursor : std::enable_shared_from_this<AttrCursor>
return nullptr;
} else if (std::get_if<AttrDb::placeholder_t>(&cachedValue->second)) {
auto attr = root->db->getAttr({cachedValue->first, name}, root->state.symbols);
if (attr)
return std::make_shared<AttrCursor>(root, std::make_pair(shared_from_this(), name), nullptr, std::move(attr));
if (attr) {
if (std::get_if<AttrDb::missing_t>(&attr->second))
return nullptr;
else if (std::get_if<AttrDb::failed_t>(&attr->second))
throw EvalError("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
// FIXME: throw error?
return nullptr;
//throw TypeError("'%s' is not an attribute set", getAttrPathStr());
}
}
//printError("GET ATTR %s", getAttrPathStr(name));
auto & v = forceValue();
root->state.forceValue(getValue());
if (getValue().type != tAttrs)
if (v.type != tAttrs)
return nullptr;
//throw TypeError("'%s' is not an attribute set", getAttrPathStr());
auto attr = getValue().attrs->get(name);
auto attr = v.attrs->get(name);
if (!attr)
if (!attr) {
if (root->db) {
assert(cachedValue);
root->db->setMissing({cachedValue->first, name});
}
return nullptr;
}
return std::make_shared<AttrCursor>(root, std::make_pair(shared_from_this(), name), attr->value);
std::optional<std::pair<AttrDb::AttrId, AttrDb::AttrValue>> cachedValue2;
if (root->db) {
assert(cachedValue);
cachedValue2 = {root->db->setPlaceholder({cachedValue->first, name}), AttrDb::placeholder_t()};
}
return std::make_shared<AttrCursor>(
root, std::make_pair(shared_from_this(), name), attr->value, std::move(cachedValue2));
}
std::shared_ptr<AttrCursor> maybeGetAttr(std::string_view name)
@ -982,19 +1088,19 @@ struct AttrCursor : std::enable_shared_from_this<AttrCursor>
cachedValue = root->db->getAttr(getAttrKey(), root->state.symbols);
if (cachedValue && !std::get_if<AttrDb::placeholder_t>(&cachedValue->second)) {
if (auto s = std::get_if<std::string>(&cachedValue->second)) {
//printError("GOT STRING %s", getAttrPathStr());
debug("using cached string attribute '%s'", getAttrPathStr());
return *s;
} else
throw Error("unexpected type mismatch in evaluation cache (string expected)");
throw TypeError("'%s' is not a string", getAttrPathStr());
}
}
//printError("GET STRING %s", getAttrPathStr());
auto s = root->state.forceString(getValue());
if (root->db)
cachedValue = {root->db->setAttr(getAttrKey(), s), s};
auto & v = forceValue();
return s;
if (v.type != tString)
throw TypeError("'%s' is not a string", getAttrPathStr());
return v.string.s;
}
std::vector<Symbol> getAttrs()
@ -1004,23 +1110,27 @@ struct AttrCursor : std::enable_shared_from_this<AttrCursor>
cachedValue = root->db->getAttr(getAttrKey(), root->state.symbols);
if (cachedValue && !std::get_if<AttrDb::placeholder_t>(&cachedValue->second)) {
if (auto attrs = std::get_if<std::vector<Symbol>>(&cachedValue->second)) {
//printError("GOT ATTRS %s", getAttrPathStr());
debug("using cached attrset attribute '%s'", getAttrPathStr());
return *attrs;
} else
throw Error("unexpected type mismatch in evaluation cache (attrs expected)");
throw TypeError("'%s' is not an attribute set", getAttrPathStr());
}
}
//printError("GET ATTRS %s", getAttrPathStr());
auto & v = forceValue();
if (v.type != tAttrs)
throw TypeError("'%s' is not an attribute set", getAttrPathStr());
std::vector<Symbol> attrs;
root->state.forceAttrs(getValue());
for (auto & attr : *getValue().attrs)
attrs.push_back(attr.name);
std::sort(attrs.begin(), attrs.end(), [](const Symbol & a, const Symbol & b) {
return (const string &) a < (const string &) b;
});
if (root->db)
cachedValue = {root->db->setAttr(getAttrKey(), attrs), attrs};
cachedValue = {root->db->setAttrs(getAttrKey(), attrs), attrs};
return attrs;
}
@ -1172,7 +1282,7 @@ struct CmdFlakeShow : FlakeCommand
}
} catch (EvalError & e) {
if (!(attrPath.size() > 0 && attrPath[0] == "legacyPackages"))
logger->stdout("%s: " ANSI_RED "%s" ANSI_NORMAL, headerPrefix, e.what());
throw;
}
};
@ -1181,6 +1291,11 @@ struct CmdFlakeShow : FlakeCommand
auto root = std::make_shared<AttrRoot>(db, *state,
[&]()
{
/* For testing whether the evaluation cache is
complete. */
if (getEnv("NIX_ALLOW_EVAL").value_or("1") == "0")
throw Error("not everything is cached, but evaluation is not allowed");
auto vFlake = state->allocValue();
flake::callFlake(*state, flake, *vFlake);