From e6918187568dbd01842d8d1d2c808ce16a894239 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 21 Apr 2024 13:54:28 +0200 Subject: Adding upstream version 18.2.2. Signed-off-by: Daniel Baumann --- .../examples/optimistic_transaction_example.cc | 192 +++++++++++++++++++++ 1 file changed, 192 insertions(+) create mode 100644 src/rocksdb/examples/optimistic_transaction_example.cc (limited to 'src/rocksdb/examples/optimistic_transaction_example.cc') diff --git a/src/rocksdb/examples/optimistic_transaction_example.cc b/src/rocksdb/examples/optimistic_transaction_example.cc new file mode 100644 index 000000000..fb0514a69 --- /dev/null +++ b/src/rocksdb/examples/optimistic_transaction_example.cc @@ -0,0 +1,192 @@ +// Copyright (c) 2011-present, Facebook, Inc. All rights reserved. +// This source code is licensed under both the GPLv2 (found in the +// COPYING file in the root directory) and Apache 2.0 License +// (found in the LICENSE.Apache file in the root directory). + +#ifndef ROCKSDB_LITE + +#include "rocksdb/db.h" +#include "rocksdb/options.h" +#include "rocksdb/slice.h" +#include "rocksdb/utilities/optimistic_transaction_db.h" +#include "rocksdb/utilities/transaction.h" + +using ROCKSDB_NAMESPACE::DB; +using ROCKSDB_NAMESPACE::OptimisticTransactionDB; +using ROCKSDB_NAMESPACE::OptimisticTransactionOptions; +using ROCKSDB_NAMESPACE::Options; +using ROCKSDB_NAMESPACE::ReadOptions; +using ROCKSDB_NAMESPACE::Snapshot; +using ROCKSDB_NAMESPACE::Status; +using ROCKSDB_NAMESPACE::Transaction; +using ROCKSDB_NAMESPACE::WriteOptions; + +#if defined(OS_WIN) +std::string kDBPath = "C:\\Windows\\TEMP\\rocksdb_transaction_example"; +#else +std::string kDBPath = "/tmp/rocksdb_transaction_example"; +#endif + +int main() { + // open DB + Options options; + options.create_if_missing = true; + DB* db; + OptimisticTransactionDB* txn_db; + + Status s = OptimisticTransactionDB::Open(options, kDBPath, &txn_db); + assert(s.ok()); + db = txn_db->GetBaseDB(); + + WriteOptions write_options; + ReadOptions read_options; + OptimisticTransactionOptions txn_options; + std::string value; + + //////////////////////////////////////////////////////// + // + // Simple OptimisticTransaction Example ("Read Committed") + // + //////////////////////////////////////////////////////// + + // Start a transaction + Transaction* txn = txn_db->BeginTransaction(write_options); + assert(txn); + + // Read a key in this transaction + s = txn->Get(read_options, "abc", &value); + assert(s.IsNotFound()); + + // Write a key in this transaction + 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.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 + // -- Using a single Snapshot + // + //////////////////////////////////////////////////////// + + // Set a snapshot at start of transaction by setting set_snapshot=true + txn_options.set_snapshot = true; + txn = txn_db->BeginTransaction(write_options, txn_options); + + const Snapshot* snapshot = txn->GetSnapshot(); + + // Write a key OUTSIDE of transaction + 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 + s = txn->Commit(); + + // Transaction could not commit since the write outside of the txn conflicted + // with the read! + assert(s.IsBusy()); + + delete txn; + // Clear snapshot from read options since it is no longer valid + 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 + // --Using multiple Snapshots + // + //////////////////////////////////////////////////////// + + // In this example, we set the snapshot multiple times. This is probably + // only necessary if you have very strict isolation requirements to + // implement. + + // Set a snapshot at start of transaction + txn_options.set_snapshot = true; + txn = txn_db->BeginTransaction(write_options, txn_options); + + // Do some reads and writes to key "x" + read_options.snapshot = db->GetSnapshot(); + s = txn->Get(read_options, "x", &value); + 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", "z"); + assert(s.ok()); + + // Set a new snapshot in the transaction + txn->SetSnapshot(); + read_options.snapshot = db->GetSnapshot(); + + // 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 + // transaction does not prevent this transaction from Committing. + s = txn->Commit(); + assert(s.ok()); + delete txn; + // 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); + return 0; +} + +#endif // ROCKSDB_LITE -- cgit v1.2.3