From 483eb2f56657e8e7f419ab1a4fab8dce9ade8609 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sat, 27 Apr 2024 20:24:20 +0200
Subject: Adding upstream version 14.2.21.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 src/rocksdb/examples/transaction_example.cc | 144 ++++++++++++++++++++++++++++
 1 file changed, 144 insertions(+)
 create mode 100644 src/rocksdb/examples/transaction_example.cc

(limited to 'src/rocksdb/examples/transaction_example.cc')

diff --git a/src/rocksdb/examples/transaction_example.cc b/src/rocksdb/examples/transaction_example.cc
new file mode 100644
index 00000000..7274cf7e
--- /dev/null
+++ b/src/rocksdb/examples/transaction_example.cc
@@ -0,0 +1,144 @@
+// 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/transaction.h"
+#include "rocksdb/utilities/transaction_db.h"
+
+using namespace rocksdb;
+
+std::string kDBPath = "/tmp/rocksdb_transaction_example";
+
+int main() {
+  // open DB
+  Options options;
+  TransactionDBOptions txn_db_options;
+  options.create_if_missing = true;
+  TransactionDB* txn_db;
+
+  Status s = TransactionDB::Open(options, txn_db_options, kDBPath, &txn_db);
+  assert(s.ok());
+
+  WriteOptions write_options;
+  ReadOptions read_options;
+  TransactionOptions txn_options;
+  std::string value;
+
+  ////////////////////////////////////////////////////////
+  //
+  // Simple Transaction 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", "def");
+  assert(s.ok());
+
+  // Read a key OUTSIDE this transaction. Does not affect txn.
+  s = txn_db->Get(read_options, "abc", &value);
+
+  // 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 = txn_db->Put(write_options, "xyz", "zzz");
+
+  // Commit transaction
+  s = txn->Commit();
+  assert(s.ok());
+  delete txn;
+
+  ////////////////////////////////////////////////////////
+  //
+  // "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 = txn_db->Put(write_options, "abc", "xyz");
+  assert(s.ok());
+
+  // Attempt to read a key using the snapshot.  This will fail since
+  // the previous write outside this txn conflicts with this read.
+  read_options.snapshot = snapshot;
+  s = txn->GetForUpdate(read_options, "abc", &value);
+  assert(s.IsBusy());
+
+  txn->Rollback();
+
+  delete txn;
+  // Clear snapshot from read options since it is no longer valid
+  read_options.snapshot = nullptr;
+  snapshot = nullptr;
+
+  ////////////////////////////////////////////////////////
+  //
+  // "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 = txn_db->GetSnapshot();
+  s = txn->Get(read_options, "x", &value);
+  txn->Put("x", "x");
+
+  // Do a write outside of the transaction to key "y"
+  s = txn_db->Put(write_options, "y", "y");
+
+  // Set a new snapshot in the transaction
+  txn->SetSnapshot();
+  txn->SetSavePoint();
+  read_options.snapshot = txn_db->GetSnapshot();
+
+  // Do some reads and writes to key "y"
+  // Since the snapshot was advanced, the write done outside of the
+  // transaction does not conflict.
+  s = txn->GetForUpdate(read_options, "y", &value);
+  txn->Put("y", "y");
+
+  // Decide we want to revert the last write from this transaction.
+  txn->RollbackToSavePoint();
+
+  // Commit.
+  s = txn->Commit();
+  assert(s.ok());
+  delete txn;
+  // Clear snapshot from read options since it is no longer valid
+  read_options.snapshot = nullptr;
+
+  // Cleanup
+  delete txn_db;
+  DestroyDB(kDBPath, options);
+  return 0;
+}
+
+#endif  // ROCKSDB_LITE
-- 
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