//*****************************************************************************
// Add a table to the Self-Join analysis.
// This method, together with doneAddingTables(), implement a state machine
// with the following states:
// ST_START: The start state. No open segments.
// ST_SINGLE: Got the first table of a new segment, don't know segment type yet.
// ST_UNIQUE: Last two tables were different.
// ST_SELFJOIN: Last two tables were the same.
// ST_END: We are done.
// The full state machine diagram is in the MVQR IS document.
//*****************************************************************************
void SelfJoinHandler::addTable(JoinGraphTablePtr table)
{
const NAString& newTable = table->getName();
// This is the current table index.
UInt32 currentIndex = table->getTempNumber();
if (currentIndex == -1)
{
// This subgraph generation was not yet started,
// This must be the initial self-join check.
currentIndex = table->getOrdinalNumber();
}
// Is this table the same as the last one?
// Skip the string comparison if the table is unique in the full join graph.
NABoolean isDifferent = !table->isSelfJoinTable() || newTable != *lastTable_;
// Which state in the state machine are we in?
switch (state_)
{
case ST_START:
segmentStart_ = currentIndex;
state_ = ST_SINGLE;
break;
case ST_SINGLE:
if (isDifferent)
state_ = ST_UNIQUE;
else
state_ = ST_SELFJOIN;
break;
case ST_SELFJOIN:
if (isDifferent)
{
// We have an open selfjoin segment and got a different table.
// The selfjoin segment ends with the previous table, and the next
// segment (which can be either type) starts with this table.
addSegment(SelfJoinSegment::SELF_JOIN_SEGMENT);
segmentStart_ = currentIndex;
state_ = ST_SINGLE;
}
else
{
// do nothing.
}
break;
case ST_UNIQUE:
if (isDifferent)
{
// do nothing.
}
else
{
// OK, we have an open unique segment, and the new table is the same
// as the last one. So actually, the open unique segment ended with the
// table before the prevous one, and the new self-join segment started
// with the previous table.
segmentEnd_--;
addSegment(SelfJoinSegment::UNIQUE_TABLE_SEGMENT);
segmentStart_ = currentIndex-1;
state_ = ST_SELFJOIN;
}
break;
case ST_END:
assertLogAndThrow(CAT_MVMEMO_JOINGRAPH, LL_MVQR_FAIL,
FALSE, QRLogicException,
"Adding a table to SelfJoinHandler in ST_END state.");
break;
}
lastTable_ = &table->getName();
segmentEnd_ = currentIndex;
}
QRJbbSubsetPtr MVCandidatesForJBBSubset::generateDescriptor(CollHeap* heap)
{
// No candidates - no work.
if (candidateList_.entries() == 0)
return NULL;
// Construct the new QRJbbSubset object.
QRJbbSubsetPtr resultDesc = new(heap) QRJbbSubset(ADD_MEMCHECK_ARGS(heap));
resultDesc->setGroupBy(hasGroupBy_);
if (hasGroupBy_)
{
// Add a reference to the query NodeID of the GroupBy node.
const NAString& groupbyID =
getJbbCandidates()->getQueryJbb()->getGroupBy()->getID();
resultDesc->setRef(groupbyID);
}
// For each table included in the subgraph
QRJoinSubGraphPtr subGraph = querySubGraphMap_->getSubGraph();
for(subGraph->reset(); subGraph->hasNext(); subGraph->advance())
{
JoinGraphTablePtr table = subGraph->getCurrent();
// Add it to the JBBSubset descriptor.
QRTablePtr tableDesc = new(heap) QRTable(heap);
tableDesc->setTableName(table->getName());
tableDesc->setRef(table->getID());
resultDesc->addTable(tableDesc);
}
// If candidates are disqualified during the loop itself,
// Don't remove them from the list.
isLoopingOnCandidates_ = TRUE;
// Now add the MVCandidates.
CollIndex maxEntries = candidateList_.entries();
for (CollIndex i=0; i<maxEntries; i++)
{
MVCandidatePtr candidate = candidateList_[i];
if (candidate == NULL)
{
// The candidate was disqualified.
continue;
}
QRCandidatePtr candidateXml;
try
{
candidateXml = candidate->generateDescriptor();
}
catch (...)
{
candidate->logMVWasDisqualified("an exception was thrown.");
candidate->disqualify(); // Propagate the Info element to the result descriptor.
candidateXml = NULL;
}
if (candidateXml == NULL)
{
// The candidate was disqualified when generating the descriptor.
continue;
}
resultDesc->addCandidate(candidateXml);
}
if (resultDesc->getCandidateList()->entries() == 0)
{
// None of the candidates survived the result descriptor generation.
deletePtr(resultDesc);
return NULL;
}
return resultDesc;
} // MVCandidatesForJBBSubset::generateDescriptor()
