Function ExecProjectSet

src/backend/executor/nodeProjectSet.c:42–117

---------------------------------------------------------------- * ExecProjectSet(node) * * Return tuples after evaluating the targetlist (which contains set * returning functions). * ---------------------------------------------------------------- */

 * ----------------------------------------------------------------
 */
static TupleTableSlot *
ExecProjectSet(PlanState *pstate)
{
	ProjectSetState *node = castNode(ProjectSetState, pstate);
	TupleTableSlot *outerTupleSlot;
	TupleTableSlot *resultSlot;
	PlanState  *outerPlan;
	ExprContext *econtext;

	CHECK_FOR_INTERRUPTS();

	econtext = node->ps.ps_ExprContext;

	/*
	 * Reset per-tuple context to free expression-evaluation storage allocated
	 * for a potentially previously returned tuple. Note that the SRF argument
	 * context has a different lifetime and is reset below.
	 */
	ResetExprContext(econtext);

	/*
	 * Check to see if we're still projecting out tuples from a previous scan
	 * tuple (because there is a function-returning-set in the projection
	 * expressions).  If so, try to project another one.
	 */
	if (node->pending_srf_tuples)
	{
		resultSlot = ExecProjectSRF(node, true);

		if (resultSlot != NULL)
			return resultSlot;
	}

	/*
	 * Reset argument context to free any expression evaluation storage
	 * allocated in the previous tuple cycle.  Note this can't happen until
	 * we're done projecting out tuples from a scan tuple, as ValuePerCall
	 * functions are allowed to reference the arguments for each returned
	 * tuple.
	 */
	MemoryContextReset(node->argcontext);

	/*
	 * Get another input tuple and project SRFs from it.
	 */
	for (;;)
	{
		/*
		 * Retrieve tuples from the outer plan until there are no more.
		 */
		outerPlan = outerPlanState(node);
		outerTupleSlot = ExecProcNode(outerPlan);

		if (TupIsNull(outerTupleSlot))
			return NULL;

		/*
		 * Prepare to compute projection expressions, which will expect to