/// <summary>
/// Gets the list of temperature stored for a provided weather station and day.
/// </summary>
public RowSet GetTemperatureRecords(string weatherStationId, DateTime day)
{
var selectCql = "SELECT * FROM temperature_by_day WHERE weatherstation_id = ? AND date = ?";
//Create a statement
var selectStatement = new SimpleStatement(selectCql);
//Add the parameters
selectStatement.Bind(weatherStationId, DateTime.Now.ToString("yyyyMMdd"));
//Execute the select statement
return Session.Execute(selectStatement);
}
/// <summary>
/// Add a temperature information for a given weather station
/// </summary>
public void AddTemperature(string weatherStationId, decimal value)
{
var insertCql = @"
INSERT INTO temperature_by_day
(weatherstation_id, date, event_time, temperature)
VALUES
(?, ?, ?, ?)";
//Create an insert statement
var insertStatement = new SimpleStatement(insertCql);
//Bind the parameters to the statement
insertStatement.Bind(weatherStationId, DateTime.Now.ToString("yyyyMMdd"), DateTime.Now, value);
//You can set other options of the statement execution, for example the consistency level.
insertStatement.SetConsistencyLevel(ConsistencyLevel.Quorum);
//Execute the insert
Session.Execute(insertStatement);
}
/// <summary>
/// Add a temperature information for a given weather station asynchronously
/// </summary>
public Task AddTemperatureAsync(string weatherStationId, decimal value)
{
//It is basically the same code as the AddTemperature
//Except it returns a Task that already started but didn't finished
//The row would not be in Cassandra yet when this method finishes executing.
var insertCql = @"
INSERT INTO temperature_by_day
(weatherstation_id, date, event_time, temperature)
VALUES
(?, ?, ?, ?)";
//Create an insert statement
var insertStatement = new SimpleStatement(insertCql);
//Bind the parameters to the statement
insertStatement.Bind(weatherStationId, DateTime.Now.ToString("yyyyMMdd"), DateTime.Now, value);
//You can set other options of the statement execution, for example the consistency level.
insertStatement.SetConsistencyLevel(ConsistencyLevel.Quorum);
//Execute the insert
return Session.ExecuteAsync(insertStatement);
}
/// <summary>
/// Gets multiple user profiles by their Ids.
/// </summary>
public async Task<IEnumerable<UserProfile>> GetUserProfiles(ISet<Guid> userIds)
{
if (userIds == null || userIds.Count == 0) return Enumerable.Empty<UserProfile>();
// Since we're essentially doing a multi-get here, limit the number userIds (i.e. partition keys) to 20 in an attempt
// to enforce some performance sanity. Anything larger and we might want to consider a different data model that doesn't
// involve doing a multi-get
if (userIds.Count > 20) throw new ArgumentOutOfRangeException("userIds", "Cannot do multi-get on more than 20 user id keys.");
// As an example, we'll do the multi-get at the CQL level using an IN() clause (i.e. let Cassandra handle it). For an example of
// doing it at the driver level, see the VideoReadModel.GetVideoPreviews method
// Build a parameterized CQL statement with an IN clause
var parameterList = string.Join(", ", Enumerable.Repeat("?", userIds.Count));
var statement =
new SimpleStatement(string.Format("SELECT userid, firstname, lastname, email FROM users WHERE userid IN ({0})", parameterList));
statement.Bind(userIds.Cast<object>().ToArray());
// Execute and map to UserProfile object
RowSet resultRows = await _session.ExecuteAsync(statement).ConfigureAwait(false);
return resultRows.Select(MapRowToUserProfile).ToList();
}
