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Lazily initialize _cf_KV sqlite table.
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This way, if a Durable Object never actually uses the KV storage interface -- only uses SQL -- we'll never create the table and can skip preparing statements for it.

This will also make it easier for the edge runtime to clean up actors that never had data.
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@kentonv
kentonv committed Aug 17, 2024
1 parent 5438f7d commit 32bdb4b
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Showing 3 changed files with 121 additions and 85 deletions.
1 change: 1 addition & 0 deletions src/workerd/api/sql-test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -264,6 +264,7 @@ async function test(state) {
() => sql.exec('CREATE TABLE _cf_invalid (name TEXT)'),
/not authorized/
)
storage.put("blah", 123); // force creation of _cf_KV table
assert.throws(
() => sql.exec('SELECT * FROM _cf_KV'),
/access to _cf_KV.key is prohibited/
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46 changes: 33 additions & 13 deletions src/workerd/util/sqlite-kv.c++
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Original file line number Diff line number Diff line change
Expand Up @@ -6,30 +6,50 @@

namespace workerd {

SqliteKv::SqliteKv(SqliteDatabase& db, bool): db(db) {}

SqliteDatabase& SqliteKv::ensureInitialized(SqliteDatabase& db) {
db.run(R"(
CREATE TABLE IF NOT EXISTS _cf_KV (
key TEXT PRIMARY KEY,
value BLOB
) WITHOUT ROWID;
)");
SqliteKv::SqliteKv(SqliteDatabase& db) {
if (db.run("SELECT name FROM sqlite_master WHERE type='table' AND name='_cf_KV'").isDone()) {
// The _cf_KV table doesn't exist. Defer initialization.
state = Uninitialized { db };
} else {
// The KV table was initialized in the past. We can go ahead and prepare our statements.
// (We don't call ensureInitialized() here because the `CREATE TABLE IF NOT EXISTS` query it
// executes would be redundant.)
state = Initialized(db);
}
}

return db;
SqliteKv::Initialized& SqliteKv::ensureInitialized() {
KJ_SWITCH_ONEOF(state) {
KJ_CASE_ONEOF(uninitialized, Uninitialized) {
auto& db = uninitialized.db;

db.run(R"(
CREATE TABLE IF NOT EXISTS _cf_KV (
key TEXT PRIMARY KEY,
value BLOB
) WITHOUT ROWID;
)");

return state.init<Initialized>(db);
}
KJ_CASE_ONEOF(initialized, Initialized) {
return initialized;
}
}
KJ_UNREACHABLE;
}

void SqliteKv::put(KeyPtr key, ValuePtr value) {
stmtPut.run(key, value);
ensureInitialized().stmtPut.run(key, value);
}

bool SqliteKv::delete_(KeyPtr key) {
auto query = stmtDelete.run(key);
auto query = ensureInitialized().stmtDelete.run(key);
return query.changeCount() > 0;
}

uint SqliteKv::deleteAll() {
auto query = stmtDeleteAll.run();
auto query = ensureInitialized().stmtDeleteAll.run();
return query.changeCount();
}

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159 changes: 87 additions & 72 deletions src/workerd/util/sqlite-kv.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ namespace workerd {
// obnoxious amount of string allocation.)
class SqliteKv {
public:
explicit SqliteKv(SqliteDatabase& db): SqliteKv(ensureInitialized(db), true) {}
explicit SqliteKv(SqliteDatabase& db);

typedef kj::StringPtr KeyPtr;
typedef kj::ArrayPtr<const kj::byte> ValuePtr;
Expand Down Expand Up @@ -54,68 +54,79 @@ class SqliteKv {
// byte blobs or strings containing NUL bytes.

private:
SqliteDatabase& db;

SqliteDatabase::Statement stmtGet = db.prepare(R"(
SELECT value FROM _cf_KV WHERE key = ?
)");
SqliteDatabase::Statement stmtPut = db.prepare(R"(
INSERT INTO _cf_KV VALUES(?, ?)
ON CONFLICT DO UPDATE SET value = excluded.value;
)");
SqliteDatabase::Statement stmtDelete = db.prepare(R"(
DELETE FROM _cf_KV WHERE key = ?
)");
SqliteDatabase::Statement stmtList = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ?
ORDER BY key
)");
SqliteDatabase::Statement stmtListEnd = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ? AND key < ?
ORDER BY key
)");
SqliteDatabase::Statement stmtListLimit = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ?
ORDER BY key
LIMIT ?
)");
SqliteDatabase::Statement stmtListEndLimit = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ? AND key < ?
ORDER BY key
LIMIT ?
)");
SqliteDatabase::Statement stmtListReverse = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ?
ORDER BY key DESC
)");
SqliteDatabase::Statement stmtListEndReverse = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ? AND key < ?
ORDER BY key DESC
)");
SqliteDatabase::Statement stmtListLimitReverse = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ?
ORDER BY key DESC
LIMIT ?
)");
SqliteDatabase::Statement stmtListEndLimitReverse = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ? AND key < ?
ORDER BY key DESC
LIMIT ?
)");
SqliteDatabase::Statement stmtDeleteAll = db.prepare(R"(
DELETE FROM _cf_KV
)");

SqliteDatabase& ensureInitialized(SqliteDatabase& db);
// Make sure the KV table is created, then return the same object.
struct Uninitialized {
SqliteDatabase& db;
};

struct Initialized {
SqliteDatabase& db;

SqliteDatabase::Statement stmtGet = db.prepare(R"(
SELECT value FROM _cf_KV WHERE key = ?
)");
SqliteDatabase::Statement stmtPut = db.prepare(R"(
INSERT INTO _cf_KV VALUES(?, ?)
ON CONFLICT DO UPDATE SET value = excluded.value;
)");
SqliteDatabase::Statement stmtDelete = db.prepare(R"(
DELETE FROM _cf_KV WHERE key = ?
)");
SqliteDatabase::Statement stmtList = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ?
ORDER BY key
)");
SqliteDatabase::Statement stmtListEnd = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ? AND key < ?
ORDER BY key
)");
SqliteDatabase::Statement stmtListLimit = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ?
ORDER BY key
LIMIT ?
)");
SqliteDatabase::Statement stmtListEndLimit = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ? AND key < ?
ORDER BY key
LIMIT ?
)");
SqliteDatabase::Statement stmtListReverse = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ?
ORDER BY key DESC
)");
SqliteDatabase::Statement stmtListEndReverse = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ? AND key < ?
ORDER BY key DESC
)");
SqliteDatabase::Statement stmtListLimitReverse = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ?
ORDER BY key DESC
LIMIT ?
)");
SqliteDatabase::Statement stmtListEndLimitReverse = db.prepare(R"(
SELECT * FROM _cf_KV
WHERE key >= ? AND key < ?
ORDER BY key DESC
LIMIT ?
)");
SqliteDatabase::Statement stmtDeleteAll = db.prepare(R"(
DELETE FROM _cf_KV
)");

Initialized(SqliteDatabase& db): db(db) {}
};

kj::OneOf<Uninitialized, Initialized> state;

Initialized& ensureInitialized();
// Make sure the KV table is created and prepared statements are ready. Not called until the
// first write.

SqliteKv(SqliteDatabase& db, bool);
};
Expand All @@ -129,7 +140,9 @@ class SqliteKv {

template <typename Func>
bool SqliteKv::get(KeyPtr key, Func&& callback) {
auto query = stmtGet.run(key);
auto& stmts = KJ_UNWRAP_OR(state.tryGet<Initialized>(), return false);

auto query = stmts.stmtGet.run(key);

if (query.isDone()) {
return false;
Expand All @@ -142,6 +155,8 @@ bool SqliteKv::get(KeyPtr key, Func&& callback) {
template <typename Func>
uint SqliteKv::list(KeyPtr begin, kj::Maybe<KeyPtr> end, kj::Maybe<uint> limit, Order order,
Func&& callback) {
auto& stmts = KJ_UNWRAP_OR(state.tryGet<Initialized>(), return 0);

auto iterate = [&](SqliteDatabase::Query&& query) {
size_t count = 0;
while (!query.isDone()) {
Expand All @@ -155,29 +170,29 @@ uint SqliteKv::list(KeyPtr begin, kj::Maybe<KeyPtr> end, kj::Maybe<uint> limit,
if (order == Order::FORWARD) {
KJ_IF_SOME(e, end) {
KJ_IF_SOME(l, limit) {
return iterate(stmtListEndLimit.run(begin, e, (int64_t)l));
return iterate(stmts.stmtListEndLimit.run(begin, e, (int64_t)l));
} else {
return iterate(stmtListEnd.run(begin, e));
return iterate(stmts.stmtListEnd.run(begin, e));
}
} else {
KJ_IF_SOME(l, limit) {
return iterate(stmtListLimit.run(begin, (int64_t)l));
return iterate(stmts.stmtListLimit.run(begin, (int64_t)l));
} else {
return iterate(stmtList.run(begin));
return iterate(stmts.stmtList.run(begin));
}
}
} else {
KJ_IF_SOME(e, end) {
KJ_IF_SOME(l, limit) {
return iterate(stmtListEndLimitReverse.run(begin, e, (int64_t)l));
return iterate(stmts.stmtListEndLimitReverse.run(begin, e, (int64_t)l));
} else {
return iterate(stmtListEndReverse.run(begin, e));
return iterate(stmts.stmtListEndReverse.run(begin, e));
}
} else {
KJ_IF_SOME(l, limit) {
return iterate(stmtListLimitReverse.run(begin, (int64_t)l));
return iterate(stmts.stmtListLimitReverse.run(begin, (int64_t)l));
} else {
return iterate(stmtListReverse.run(begin));
return iterate(stmts.stmtListReverse.run(begin));
}
}
}
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