Function set_tablefunction_pathlist

src/backend/optimizer/path/allpaths.c:2776–2857

* set_tablefunction_pathlist * Build the (single) access path for a table function RTE */

 *		Build the (single) access path for a table function RTE
 */
static void
set_tablefunction_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
	PlannerConfig *config;
	RangeTblFunction *rtfunc;
	FuncExpr   *fexpr;
	ListCell   *arg;
	RelOptInfo *sub_final_rel;
	Relids		required_outer;
	ListCell   *lc;

	/* Cannot be a preplanned subquery from window_planner. */
	Assert(!rte->subquery_root);

	Assert(list_length(rte->functions) == 1);
	rtfunc = (RangeTblFunction *) linitial(rte->functions);
	Assert(rtfunc->funcexpr && IsA(rtfunc->funcexpr, FuncExpr));
	fexpr= (FuncExpr *) rtfunc->funcexpr;

	/*
	 * We don't support pushing join clauses into the quals of a function
	 * scan, but it could still have required parameterization due to LATERAL
	 * refs in the function expression.
	 */
	required_outer = rel->lateral_relids;

	config = CopyPlannerConfig(root->config);
	config->honor_order_by = false;		/* partial order is enough */

	/* Plan input subquery */
	rel->subroot = subquery_planner(root->glob, rte->subquery, root,
									false,
									0.0, //tuple_fraction
									config);

	/*
	 * It's possible that constraint exclusion proved the subquery empty. If
	 * so, it's desirable to produce an unadorned dummy path so that we will
	 * recognize appropriate optimizations at this query level.
	 */
	sub_final_rel = fetch_upper_rel(rel->subroot, UPPERREL_FINAL, NULL);

	/*
	 * With the subquery planned we now need to clear the subquery from the
	 * TableValueExpr nodes, otherwise preprocess_expression will trip over
	 * it.
	 */
	foreach(arg, fexpr->args)
	{
		if (IsA(arg, TableValueExpr))
		{
			TableValueExpr *tve = (TableValueExpr *) arg;

			tve->subquery = NULL;
		}
	}

	/* Mark rel with estimated output rows, width, etc */