Function TidNext

src/backend/executor/nodeTidscan.c:311–397

---------------------------------------------------------------- * TidNext * * Retrieve a tuple from the TidScan node's currentRelation * using the tids in the TidScanState information. * * ---------------------------------------------------------------- */

 * ----------------------------------------------------------------
 */
static TupleTableSlot *
TidNext(TidScanState *node)
{
	EState	   *estate;
	ScanDirection direction;
	Snapshot	snapshot;
	TableScanDesc scan;
	Relation	heapRelation;
	TupleTableSlot *slot;
	ItemPointerData *tidList;
	int			numTids;
	bool		bBackward;

	/*
	 * extract necessary information from tid scan node
	 */
	estate = node->ss.ps.state;
	direction = estate->es_direction;
	snapshot = estate->es_snapshot;
	heapRelation = node->ss.ss_currentRelation;
	slot = node->ss.ss_ScanTupleSlot;

	/*
	 * First time through, compute the list of TIDs to be visited
	 */
	if (node->tss_TidList == NULL)
		TidListEval(node);

	scan = node->ss.ss_currentScanDesc;
	tidList = node->tss_TidList;
	numTids = node->tss_NumTids;

	/*
	 * Initialize or advance scan position, depending on direction.
	 */
	bBackward = ScanDirectionIsBackward(direction);
	if (bBackward)
	{
		if (node->tss_TidPtr < 0)
		{
			/* initialize for backward scan */
			node->tss_TidPtr = numTids - 1;
		}
		else
			node->tss_TidPtr--;
	}
	else
	{
		if (node->tss_TidPtr < 0)
		{
			/* initialize for forward scan */
			node->tss_TidPtr = 0;
		}
		else
			node->tss_TidPtr++;
	}

	while (node->tss_TidPtr >= 0 && node->tss_TidPtr < numTids)