public virtual DataTable GetChunk(IDataLoadEventListener listener, GracefulCancellationToken cancellationToken)
{
// we are in the Global Commands case, let's return an empty DataTable (not null)
// so we can trigger the destination to extract the globals docs and sql
if (GlobalsRequest != null)
{
GlobalsRequest.ElevateState(ExtractCommandState.WaitingForSQLServer);
if (firstGlobalChunk)
{
//unless we are checking, start auditing
StartAuditGlobals();
firstGlobalChunk = false;
return(new DataTable(ExtractionDirectory.GLOBALS_DATA_NAME));
}
return(null);
}
if (Request == null)
{
throw new Exception("Component has not been initialized before being asked to GetChunk(s)");
}
Request.ElevateState(ExtractCommandState.WaitingForSQLServer);
if (_cancel)
{
throw new Exception("User cancelled data extraction");
}
if (_hostedSource == null)
{
StartAudit(Request.QueryBuilder.SQL);
if (Request.DatasetBundle.DataSet.DisableExtraction)
{
throw new Exception("Cannot extract " + Request.DatasetBundle.DataSet + " because DisableExtraction is set to true");
}
_hostedSource = new DbDataCommandDataFlowSource(GetCommandSQL(listener),
"ExecuteDatasetExtraction " + Request.DatasetBundle.DataSet,
Request.GetDistinctLiveDatabaseServer().Builder,
ExecutionTimeout);
// If we are running in batches then always allow empty extractions
_hostedSource.AllowEmptyResultSets = AllowEmptyExtractions || Request.IsBatchResume;
_hostedSource.BatchSize = BatchSize;
}
DataTable chunk = null;
try
{
chunk = _hostedSource.GetChunk(listener, cancellationToken);
chunk = _peeker.AddPeekedRowsIfAny(chunk);
//if we are trying to distinct the records in memory based on release id
if (DistinctStrategy == DistinctStrategy.OrderByAndDistinctInMemory)
{
var releaseIdentifierColumn = Request.ReleaseIdentifierSubstitutions.First().GetRuntimeName();
if (chunk != null)
{
//last release id in the current chunk
var lastReleaseId = chunk.Rows[chunk.Rows.Count - 1][releaseIdentifierColumn];
_peeker.AddWhile(_hostedSource, r => Equals(r[releaseIdentifierColumn], lastReleaseId), chunk);
chunk = MakeDistinct(chunk, listener, cancellationToken);
}
}
}
catch (AggregateException a)
{
if (a.GetExceptionIfExists <TaskCanceledException>() != null)
{
_cancel = true;
}
throw;
}
catch (Exception e)
{
listener.OnNotify(this, new NotifyEventArgs(ProgressEventType.Error, "Read from source failed", e));
}
if (cancellationToken.IsCancellationRequested)
{
throw new Exception("Data read cancelled because our cancellationToken was set, aborting data reading");
}
//if the first chunk is null
if (firstChunk && chunk == null && !AllowEmptyExtractions)
{
throw new Exception("There is no data to load, query returned no rows, query was:" + Environment.NewLine +
(_hostedSource.Sql ?? Request.QueryBuilder.SQL));
}
//not the first chunk anymore
firstChunk = false;
//data exhausted
if (chunk == null)
{
listener.OnNotify(this, new NotifyEventArgs(ProgressEventType.Information, "Data exhausted after reading " + _rowsRead + " rows of data (" + UniqueReleaseIdentifiersEncountered.Count + " unique release identifiers seen)"));
if (Request != null)
{
Request.CumulativeExtractionResults.DistinctReleaseIdentifiersEncountered = Request.IsBatchResume ? -1 : UniqueReleaseIdentifiersEncountered.Count;
}
return(null);
}
_rowsRead += chunk.Rows.Count;
//chunk will have datatypes for all the things in the buffer so we can populate our dictionary of facts about what columns/catalogue items have spontaneously changed name/type etc
if (ExtractTimeTransformationsObserved == null)
{
GenerateExtractionTransformObservations(chunk);
}
//see if the SqlDataReader has a column with the same name as the ReleaseIdentifierSQL (if so then we can use it to count the number of distinct subjects written out to the csv)
bool includesReleaseIdentifier = _extractionIdentifiersidx.Count > 0;
//first line - lets see what columns we wrote out
//looks at the buffer and computes any transforms performed on the column
_timeSpentValidating.Start();
//build up the validation report (Missing/Wrong/Etc) - this has no mechanical effect on the extracted data just some metadata that goes into a flat file
if (ExtractionTimeValidator != null && Request.IncludeValidation)
{
try
{
chunk.Columns.Add(ValidationColumnName);
ExtractionTimeValidator.Validate(chunk, ValidationColumnName);
_rowsValidated += chunk.Rows.Count;
listener.OnProgress(this, new ProgressEventArgs("Validation", new ProgressMeasurement(_rowsValidated, ProgressType.Records), _timeSpentValidating.Elapsed));
}
catch (Exception ex)
{
listener.OnNotify(this, new NotifyEventArgs(ProgressEventType.Error, "Could not validate data chunk", ex));
ValidationFailureException = ex;
ExtractionTimeValidator = null;
}
}
_timeSpentValidating.Stop();
_timeSpentBuckettingDates.Start();
if (ExtractionTimeTimeCoverageAggregator != null)
{
_rowsBucketted += chunk.Rows.Count;
foreach (DataRow row in chunk.Rows)
{
ExtractionTimeTimeCoverageAggregator.ProcessRow(row);
}
listener.OnProgress(this, new ProgressEventArgs("Bucketting Dates", new ProgressMeasurement(_rowsBucketted, ProgressType.Records), _timeSpentCalculatingDISTINCT.Elapsed));
}
_timeSpentBuckettingDates.Stop();
_timeSpentCalculatingDISTINCT.Start();
//record unique release identifiers found
if (includesReleaseIdentifier)
{
foreach (string idx in _extractionIdentifiersidx)
{
foreach (DataRow r in chunk.Rows)
{
if (r[idx] == DBNull.Value)
{
if (_extractionIdentifiersidx.Count == 1)
{
throw new Exception("Null release identifier found in extract of dataset " + Request.DatasetBundle.DataSet);
}
else
{
continue; //there are multiple extraction identifiers thats fine if one or two are null
}
}
if (!UniqueReleaseIdentifiersEncountered.Contains(r[idx]))
{
UniqueReleaseIdentifiersEncountered.Add(r[idx]);
}
}
listener.OnProgress(this, new ProgressEventArgs("Calculating Distinct Release Identifiers", new ProgressMeasurement(UniqueReleaseIdentifiersEncountered.Count, ProgressType.Records), _timeSpentCalculatingDISTINCT.Elapsed));
}
}
_timeSpentCalculatingDISTINCT.Stop();
return(chunk);
}
public void RetrieveChunks()
{
var source = new DbDataCommandDataFlowSource("Select top 3 * from master.sys.tables", "Query Sys tables", DiscoveredServerICanCreateRandomDatabasesAndTablesOn.Builder, 30);
Assert.AreEqual(3, source.GetChunk(new ThrowImmediatelyDataLoadEventListener(), new GracefulCancellationToken()).Rows.Count);
}