Function SS_identify_outer_params

src/backend/optimizer/plan/subselect.c:2514–2560

* SS_identify_outer_params - identify the Params available from outer levels * * This must be run after SS_replace_correlation_vars and SS_process_sublinks * processing is complete in a given query level as well as all of its * descendant levels (which means it's most practical to do it at the end of * processing the query level). We compute the set of paramIds that outer * levels will make

 * 	plan->extParam and plan->allParam - attach params to top of the plan
 */
void
SS_identify_outer_params(PlannerInfo *root)
{
	Bitmapset  *outer_params;
	PlannerInfo *proot;
	ListCell   *l;

	/*
	 * If no parameters have been assigned anywhere in the tree, we certainly
	 * don't need to do anything here.
	 */
	if (root->glob->paramExecTypes == NIL)
		return;

	/*
	 * Scan all query levels above this one to see which parameters are due to
	 * be available from them, either because lower query levels have
	 * requested them (via plan_params) or because they will be available from
	 * initPlans of those levels.
	 */
	outer_params = NULL;
	for (proot = root->parent_root; proot != NULL; proot = proot->parent_root)
	{
		/* Include ordinary Var/PHV/Aggref/GroupingFunc params */
		foreach(l, proot->plan_params)
		{
			PlannerParamItem *pitem = (PlannerParamItem *) lfirst(l);

			outer_params = bms_add_member(outer_params, pitem->paramId);
		}
		/* Include any outputs of outer-level initPlans */
		foreach(l, proot->init_plans)
		{
			SubPlan    *initsubplan = (SubPlan *) lfirst(l);
			ListCell   *l2;

			foreach(l2, initsubplan->setParam)
			{
				outer_params = bms_add_member(outer_params, lfirst_int(l2));
			}
		}
		/* Include worktable ID, if a recursive query is being planned */
		if (proot->wt_param_id >= 0)
			outer_params = bms_add_member(outer_params, proot->wt_param_id);
	}
	root->outer_params = outer_params;
}

/*
 * SS_charge_for_initplans - account for initplans in Path costs & parallelism