Function set_output_count

src/backend/executor/nodeSetOp.c:149–182

* We've completed processing a tuple group. Decide how many copies (if any) * of its representative row to emit, and store the count into numOutput. * This logic is straight from the SQL92 specification. */

 * This logic is straight from the SQL92 specification.
 */
static void
set_output_count(SetOpState *setopstate, SetOpStatePerGroup pergroup)
{
	SetOp	   *plannode = (SetOp *) setopstate->ps.plan;

	switch (plannode->cmd)
	{
		case SETOPCMD_INTERSECT:
			if (pergroup->numLeft > 0 && pergroup->numRight > 0)
				setopstate->numOutput = 1;
			else
				setopstate->numOutput = 0;
			break;
		case SETOPCMD_INTERSECT_ALL:
			setopstate->numOutput =
				(pergroup->numLeft < pergroup->numRight) ?
				pergroup->numLeft : pergroup->numRight;
			break;
		case SETOPCMD_EXCEPT:
			if (pergroup->numLeft > 0 && pergroup->numRight == 0)
				setopstate->numOutput = 1;
			else
				setopstate->numOutput = 0;
			break;
		case SETOPCMD_EXCEPT_ALL:
			setopstate->numOutput =
				(pergroup->numLeft < pergroup->numRight) ?
				0 : (pergroup->numLeft - pergroup->numRight);
			break;
		default:
			elog(ERROR, "unrecognized set op: %d", (int) plannode->cmd);
			break;
	}
}


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