Function TidRangeEval

src/backend/executor/nodeTidrangescan.c:132–205

---------------------------------------------------------------- * TidRangeEval * * Compute and set node's block and offset range to scan by evaluating * the trss_tidexprs. Returns false if we detect the range cannot * contain any tuples. Returns true if it's possible for the range to * contain tuples. * ---------------------------------------------------------------- */

 * ----------------------------------------------------------------
 */
static bool
TidRangeEval(TidRangeScanState *node)
{
	ExprContext *econtext = node->ss.ps.ps_ExprContext;
	ItemPointerData lowerBound;
	ItemPointerData upperBound;
	ListCell   *l;

	/*
	 * Set the upper and lower bounds to the absolute limits of the range of
	 * the ItemPointer type.  Below we'll try to narrow this range on either
	 * side by looking at the TidOpExprs.
	 */
	ItemPointerSet(&lowerBound, 0, 0);
	ItemPointerSet(&upperBound, InvalidBlockNumber, PG_UINT16_MAX);

	foreach(l, node->trss_tidexprs)
	{
		TidOpExpr  *tidopexpr = (TidOpExpr *) lfirst(l);
		ItemPointer itemptr;
		bool		isNull;

		/* Evaluate this bound. */
		itemptr = (ItemPointer)
			DatumGetPointer(ExecEvalExprSwitchContext(tidopexpr->exprstate,
													  econtext,
													  &isNull));

		/* If the bound is NULL, *nothing* matches the qual. */
		if (isNull)
			return false;

		if (tidopexpr->exprtype == TIDEXPR_LOWER_BOUND)
		{
			ItemPointerData lb;

			ItemPointerCopy(itemptr, &lb);

			/*
			 * Normalize non-inclusive ranges to become inclusive.  The
			 * resulting ItemPointer here may not be a valid item pointer.
			 */
			if (!tidopexpr->inclusive)
				ItemPointerInc(&lb);

			/* Check if we can narrow the range using this qual */
			if (ItemPointerCompare(&lb, &lowerBound) > 0)
				ItemPointerCopy(&lb, &lowerBound);
		}

		else if (tidopexpr->exprtype == TIDEXPR_UPPER_BOUND)
		{
			ItemPointerData ub;

			ItemPointerCopy(itemptr, &ub);

			/*
			 * Normalize non-inclusive ranges to become inclusive.  The