読み取りの分離、整合性、最新性

// Example 1: Use a causally consistent session to ensure that the update occurs before the insert.
ClientSession session1 = client.startSession(ClientSessionOptions.builder().causallyConsistent(true).build());
Date currentDate = new Date();
MongoCollection<Document> items = client.getDatabase("test")
        .withReadConcern(ReadConcern.MAJORITY)
        .withWriteConcern(WriteConcern.MAJORITY.withWTimeout(1000, TimeUnit.MILLISECONDS))
        .getCollection("test");
items.updateOne(session1, eq("sku", "111"), set("end", currentDate));
Document document = new Document("sku", "nuts-111")
        .append("name", "Pecans")
        .append("start", currentDate);
items.insertOne(session1, document);

  async with await client.start_session(causal_consistency=True) as s1:
      current_date = datetime.datetime.today()
      items = client.get_database(
          "test",
          read_concern=ReadConcern("majority"),
          write_concern=WriteConcern("majority", wtimeout=1000),
      ).items
      await items.update_one(
          {"sku": "111", "end": None}, {"$set": {"end": current_date}}, session=s1
      )
      await items.insert_one(
          {"sku": "nuts-111", "name": "Pecans", "start": current_date}, session=s1
      )

my $s1 = $conn->start_session({ causalConsistency => 1 });
$items = $conn->get_database(
    "test", {
        read_concern => { level => 'majority' },
        write_concern => { w => 'majority', wtimeout => 10000 },
    }
)->get_collection("items");
$items->update_one(
    {
        sku => 111,
        end  => undef
    },
    {
        '$set' => { end => $current_date}
    },
    {
        session => $s1
    }
);
$items->insert_one(
    {
        sku => "nuts-111",
        name  => "Pecans",
        start => $current_date
    },
    {
        session => $s1
    }
);

$items = $client->selectDatabase(
    'test',
    [
        'readConcern' => new \MongoDB\Driver\ReadConcern(\MongoDB\Driver\ReadConcern::MAJORITY),
        'writeConcern' => new \MongoDB\Driver\WriteConcern(\MongoDB\Driver\WriteConcern::MAJORITY, 1000),
    ],
)->items;
$s1 = $client->startSession(
    ['causalConsistency' => true],
);
$currentDate = new \MongoDB\BSON\UTCDateTime();
$items->updateOne(
    ['sku' => '111', 'end' => ['$exists' => false]],
    ['$set' => ['end' => $currentDate]],
    ['session' => $s1],
);
$items->insertOne(
    ['sku' => '111-nuts', 'name' => 'Pecans', 'start' => $currentDate],
    ['session' => $s1],
);

with client.start_session(causal_consistency=True) as s1:
    current_date = datetime.datetime.today()
    items = client.get_database(
        "test",
        read_concern=ReadConcern("majority"),
        write_concern=WriteConcern("majority", wtimeout=1000),
    ).items
    items.update_one(
        {"sku": "111", "end": None}, {"$set": {"end": current_date}}, session=s1
    )
    items.insert_one(
        {"sku": "nuts-111", "name": "Pecans", "start": current_date}, session=s1
    )

// Example 2: Advance the cluster time and the operation time to that of the other session to ensure that
// this client is causally consistent with the other session and read after the two writes.
ClientSession session2 = client.startSession(ClientSessionOptions.builder().causallyConsistent(true).build());
session2.advanceClusterTime(session1.getClusterTime());
session2.advanceOperationTime(session1.getOperationTime());
items = client.getDatabase("test")
        .withReadPreference(ReadPreference.secondary())
        .withReadConcern(ReadConcern.MAJORITY)
        .withWriteConcern(WriteConcern.MAJORITY.withWTimeout(1000, TimeUnit.MILLISECONDS))
        .getCollection("items");
for (Document item: items.find(session2, eq("end", BsonNull.VALUE))) {
    System.out.println(item);
}

  async with await client.start_session(causal_consistency=True) as s2:
      s2.advance_cluster_time(s1.cluster_time)
      s2.advance_operation_time(s1.operation_time)
      items = client.get_database(
          "test",
          read_preference=ReadPreference.SECONDARY,
          read_concern=ReadConcern("majority"),
          write_concern=WriteConcern("majority", wtimeout=1000),
      ).items
      async for item in items.find({"end": None}, session=s2):
          print(item)

my $s2 = $conn->start_session({ causalConsistency => 1 });
$s2->advance_cluster_time( $s1->cluster_time );
$s2->advance_operation_time( $s1->operation_time );
$items = $conn->get_database(
    "test", {
        read_preference => 'secondary',
        read_concern => { level => 'majority' },
        write_concern => { w => 'majority', wtimeout => 10000 },
    }
)->get_collection("items");
$cursor = $items->find( { end => undef }, { session => $s2 } );
for my $item ( $cursor->all ) {
    say join(" ", %$item);
}

$s2 = $client->startSession(
    ['causalConsistency' => true],
);
$s2->advanceClusterTime($s1->getClusterTime());
$s2->advanceOperationTime($s1->getOperationTime());
$items = $client->selectDatabase(
    'test',
    [
        'readPreference' => new \MongoDB\Driver\ReadPreference(\MongoDB\Driver\ReadPreference::SECONDARY),
        'readConcern' => new \MongoDB\Driver\ReadConcern(\MongoDB\Driver\ReadConcern::MAJORITY),
        'writeConcern' => new \MongoDB\Driver\WriteConcern(\MongoDB\Driver\WriteConcern::MAJORITY, 1000),
    ],
)->items;
$result = $items->find(
    ['end' => ['$exists' => false]],
    ['session' => $s2],
);
foreach ($result as $item) {
    var_dump($item);
}

with client.start_session(causal_consistency=True) as s2:
    s2.advance_cluster_time(s1.cluster_time)
    s2.advance_operation_time(s1.operation_time)
    items = client.get_database(
        "test",
        read_preference=ReadPreference.SECONDARY,
        read_concern=ReadConcern("majority"),
        write_concern=WriteConcern("majority", wtimeout=1000),
    ).items
    for item in items.find({"end": None}, session=s2):
        print(item)