//*****************************************************************************
// 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;
}
