public void PrepareComputeTableStatistics(Context context, TableReference tr, out string connectionString, out string sql)
{
// Assign a database server to the query
// TODO: maybe make this function generic
// TODO: check this part to use appropriate server and database
var sm = GetSchemaManager(false);
var ds = sm.Datasets[tr.DatasetName];
if (ds is GraywulfDataset && !((GraywulfDataset)ds).IsSpecificInstanceRequired)
{
var gds = (GraywulfDataset)ds;
var dd = new DatabaseDefinition(context);
dd.Guid = gds.DatabaseDefinition.Guid;
dd.Load();
// Get a server from the scheduler
var si = new ServerInstance(Context);
si.Guid = Scheduler.GetNextServerInstance(new Guid[] { dd.Guid }, StatDatabaseVersionName, null);
si.Load();
connectionString = si.GetConnectionString().ConnectionString;
SubstituteDatabaseName(tr, si.Guid, StatDatabaseVersionName);
tr.DatabaseObject = null;
}
else
{
// Run it on the specific database
connectionString = ds.ConnectionString;
}
// Generate statistics query
sql = CodeGenerator.GenerateTableStatisticsQuery(tr);
}
public void DeterminePartitionCount(Context context, IScheduler scheduler, out int partitionCount, out Guid assignedServerInstanceGuid)
{
partitionCount = 1;
assignedServerInstanceGuid = Guid.Empty;
// Single server mode will run on one partition by definition,
// Graywulf mode has to look at the registry for available machines
switch (ExecutionMode)
{
case ExecutionMode.SingleServer:
InitializeQueryObject(null);
break;
case ExecutionMode.Graywulf:
InitializeQueryObject(context, scheduler);
// If query is partitioned, statistics must be gathered
if (IsPartitioned)
{
// Assign a server that will run the statistics queries
// Try to find a server that contains all required datasets. This is true right now for
// SkyQuery where all databases are mirrored but will have to be updated later
// Collect all datasets that are required to answer the query
var dss = FindRequiredDatasets();
// Datasets that are mirrored and can be on any server
var reqds = (from ds in dss.Values
where !ds.IsSpecificInstanceRequired
select ds.DatabaseDefinition.Guid).ToArray();
// Datasets that are only available at a specific server instance
var spds = (from ds in dss.Values
where ds.IsSpecificInstanceRequired && !ds.DatabaseInstance.IsEmpty
select ds.DatabaseInstance.Guid).ToArray();
var si = new ServerInstance(context);
si.Guid = scheduler.GetNextServerInstance(reqds, StatDatabaseVersionName, spds);
si.Load();
AssignedServerInstance = si;
assignedServerInstanceGuid = si.Guid;
// *** TODO: find optimal number of partitions
// TODO: replace "2" with a value from settings
partitionCount = 2 * scheduler.GetServerInstances(reqds, SourceDatabaseVersionName, spds).Length;
// Now have to reinitialize to load the assigned server instances
InitializeQueryObject(context, scheduler, true);
}
break;
default:
throw new NotImplementedException();
}
}
protected override void Execute(CodeActivityContext activityContext)
{
QueryPartitionBase queryPartition = QueryPartition.Get(activityContext);
switch (queryPartition.Query.ExecutionMode)
{
case ExecutionMode.SingleServer:
queryPartition.InitializeQueryObject(null, null, true);
break;
case ExecutionMode.Graywulf:
using (var context = ContextManager.Instance.CreateContext(this, activityContext, ConnectionMode.AutoOpen, TransactionMode.AutoCommit))
{
var scheduler = activityContext.GetExtension <IScheduler>();
//queryPartition.DatabaseVersionName = queryPartition.Query.SourceDatabaseVersionName; TODO: delete
queryPartition.InitializeQueryObject(context, scheduler, false);
var dss = queryPartition.FindRequiredDatasets();
// Check if there are any Graywulf datasets referenced in the query
var assignmydb = (dss.Values.FirstOrDefault(ds => !ds.IsSpecificInstanceRequired) == null);
// *** TODO: replace this whole thing to use JOIN graphs
// If no graywulf datasets are used, use the server containing myDB,
// otherwise ask the scheduler for an appropriate server
if (dss.Count == 0 || assignmydb)
{
// use MyDB's server
var ef = new EntityFactory(context);
var federation = queryPartition.FederationReference.Value;
var user = ef.LoadEntity <User>(context.UserGuid);
var di = federation.MyDBDatabaseVersion.GetUserDatabaseInstance(user);
queryPartition.AssignedServerInstance = di.ServerInstance;
}
else
{
// Assign new server instance
var si = new ServerInstance(context);
si.Guid = scheduler.GetNextServerInstance(
dss.Values.Where(x => !x.IsSpecificInstanceRequired).Select(x => x.DatabaseDefinition.Guid).ToArray(),
queryPartition.Query.SourceDatabaseVersionName,
null);
si.Load();
queryPartition.AssignedServerInstance = si;
}
queryPartition.InitializeQueryObject(context, scheduler, true);
EntityGuid.Set(activityContext, queryPartition.AssignedServerInstance.Guid);
}
break;
}
}