Function ExecTupleSplit

src/backend/executor/nodeTupleSplit.c:169–247

* ExecTupleSplit - * * ExecTupleSplit receives tuples from its outer subplan. Every * input tuple will generate n output tuples (n is the number of * the DQAs exprs). Each output tuple only contain one DQA expr and * all GROUP BY exprs. */

 *      all GROUP BY exprs.
 */
static TupleTableSlot *
ExecTupleSplit(PlanState *pstate)
{
	TupleSplitState *node = castNode(TupleSplitState, pstate);
	TupleTableSlot  *result;
	ExprContext     *econtext;
	TupleSplit      *plan;
	bool             filter_out = false;

	econtext = node->ss.ps.ps_ExprContext;
	plan = (TupleSplit *)node->ss.ps.plan;

	do {
		/* if all DQAs of the last slot were processed, get a new slot */
		if (node->currentExprId == 0)
		{
			node->outerslot = ExecProcNode(outerPlanState(node));

			if (TupIsNull(node->outerslot))
				return NULL;

			slot_getsomeattrs(node->outerslot, node->maxAttrNum);

			/* store original tupleslot isnull array */
			memcpy(node->isnull_orig, node->outerslot->tts_isnull,
		           node->outerslot->tts_nvalid * sizeof(bool));
		}

		econtext->ecxt_outertuple = node->outerslot;

		/* The filter is pushed down from relative DQA */
		ExprState * filter = NULL;
		if (node->currentExprId < node->numDisDQAs)
			filter = node->agg_filter_array[node->currentExprId];

		if (filter)
		{
			Datum		res;
			bool		isnull;

			res = ExecEvalExprSwitchContext(filter, econtext, &isnull);

			if (isnull || !DatumGetBool(res))
			{
				/* skip tuple split once, if the tuple filter out */
				node->currentExprId = (node->currentExprId + 1) % node->numDisDQAs;
				filter_out = true;
			}
			else
				filter_out = false;
		}
		else
			filter_out = false;

	} while(filter_out);

	/* reset the isnull array to the original state */
	bool *isnull = node->outerslot->tts_isnull;