diff --git a/examples/optimistic_transaction_example.cc b/examples/optimistic_transaction_example.cc index 94444e162..fda50d6ab 100644 --- a/examples/optimistic_transaction_example.cc +++ b/examples/optimistic_transaction_example.cc @@ -46,21 +46,34 @@ int main() { assert(s.IsNotFound()); // Write a key in this transaction - txn->Put("abc", "def"); + s = txn->Put("abc", "xyz"); + assert(s.ok()); // Read a key OUTSIDE this transaction. Does not affect txn. s = db->Get(read_options, "abc", &value); + assert(s.IsNotFound()); // Write a key OUTSIDE of this transaction. // Does not affect txn since this is an unrelated key. If we wrote key 'abc' // here, the transaction would fail to commit. s = db->Put(write_options, "xyz", "zzz"); + assert(s.ok()); + s = db->Put(write_options, "abc", "def"); + assert(s.ok()); // Commit transaction s = txn->Commit(); - assert(s.ok()); + assert(s.IsBusy()); delete txn; + s = db->Get(read_options, "xyz", &value); + assert(s.ok()); + assert(value == "zzz"); + + s = db->Get(read_options, "abc", &value); + assert(s.ok()); + assert(value == "def"); + //////////////////////////////////////////////////////// // // "Repeatable Read" (Snapshot Isolation) Example @@ -75,11 +88,13 @@ int main() { const Snapshot* snapshot = txn->GetSnapshot(); // Write a key OUTSIDE of transaction - db->Put(write_options, "abc", "xyz"); + s = db->Put(write_options, "abc", "xyz"); + assert(s.ok()); // Read a key using the snapshot read_options.snapshot = snapshot; s = txn->GetForUpdate(read_options, "abc", &value); + assert(s.ok()); assert(value == "def"); // Attempt to commit transaction @@ -94,6 +109,10 @@ int main() { read_options.snapshot = nullptr; snapshot = nullptr; + s = db->Get(read_options, "abc", &value); + assert(s.ok()); + assert(value == "xyz"); + //////////////////////////////////////////////////////// // // "Read Committed" (Monotonic Atomic Views) Example @@ -112,10 +131,18 @@ int main() { // Do some reads and writes to key "x" read_options.snapshot = db->GetSnapshot(); s = txn->Get(read_options, "x", &value); - txn->Put("x", "x"); + assert(s.IsNotFound()); + s = txn->Put("x", "x"); + assert(s.ok()); + + // The transaction hasn't committed, so the write is not visible + // outside of txn. + s = db->Get(read_options, "x", &value); + assert(s.IsNotFound()); // Do a write outside of the transaction to key "y" - s = db->Put(write_options, "y", "y"); + s = db->Put(write_options, "y", "z"); + assert(s.ok()); // Set a new snapshot in the transaction txn->SetSnapshot(); @@ -123,6 +150,8 @@ int main() { // Do some reads and writes to key "y" s = txn->GetForUpdate(read_options, "y", &value); + assert(s.ok()); + assert(value == "z"); txn->Put("y", "y"); // Commit. Since the snapshot was advanced, the write done outside of the @@ -133,6 +162,15 @@ int main() { // Clear snapshot from read options since it is no longer valid read_options.snapshot = nullptr; + // txn is committed, read the latest values. + s = db->Get(read_options, "x", &value); + assert(s.ok()); + assert(value == "x"); + + s = db->Get(read_options, "y", &value); + assert(s.ok()); + assert(value == "y"); + // Cleanup delete txn_db; DestroyDB(kDBPath, options);