internal async Task <long> CommitToPersistence(StringBuilder dmlCollector, long?position)
{
if (position.HasValue == false)
{
throw new ArgumentException("Commit's must have a position", nameof(position));
}
using (var readDb = SqlExecution.OpenWriteConnection(_commitConnectionstring))
{
//Consider a write-lock around _dmlCollector, is it necessary?
//Consider pre-pending a "BEGIN TRANSACTION" and have a all-or-nothing write
dmlCollector.PrependLine("SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED; BEGIN TRANSACTION;");
dmlCollector.AppendLine(
$"UPDATE Inf_ReadSubscriptions SET ReadPosition = {position.Value} WHERE SchemaName = '{_projection.SchemaIdentifier.Name}';");
dmlCollector.AppendLine("COMMIT TRANSACTION;");
var dml = new SqlCommand(dmlCollector.ToString(), readDb);
var effect = await dml.ExecuteNonQueryAsync();
if (effect == 0)
{
throw new InvalidOperationException(
"Something went wrong while updating the state of a readservice. SQL:\r\n" + dmlCollector);
}
//todo: Error handling?
return(position.Value);
}
}
internal IEnumerable <SqlProjectionSubscription> WakeReadProjections(ISqlProjection[] projections)
{
// Subscriptions are scoped as: 1 instance per 'SchemaName' per database (connectionstring becomes the partition-key)
using (var connection = SqlExecution.OpenWriteConnection(_connectionString))
{
var existingSubscriptions = connection.Query(
"SELECT SchemaName, SchemaRevision, ReadPosition FROM Inf_ReadSubscriptions")
.Select(x => new
{
SchemaName = (string)x.SchemaName,
SchemaRevision = (string)x.SchemaRevision,
ReadPosition = (long?)x.ReadPosition
}).ToDictionary(x => x.SchemaName);
foreach (var projection in projections)
{
if (existingSubscriptions.TryGetValue(projection.SchemaIdentifier.Name, out var state) &&
projection.SchemaIdentifier.Revision.Equals(state.SchemaRevision))
{
yield return(WakeReadProjection(projection, new SubscriptionState
{
AlreadyExists = true,
ReadPosition = state.ReadPosition
}, connection));
}
else
{
//if not already existing (or existing in another revision), (re)register it
yield return(WakeReadProjection(projection, new SubscriptionState
{
AlreadyExists = false,
ReadPosition = null
}, connection));
}
}
}
}
private static void PrepareSubscriptionSchema(string sqlConnectionString)
{
using (SqlConnection connection = SqlExecution.OpenWriteConnection(sqlConnectionString))
SqlExecution.Run(_subscriberSchemaSetup, connection);
}