Function cost_tablefunction

src/backend/optimizer/path/costsize.c:1646–1687

* cost_tablefunction * Determines and returns the cost of scanning a table function RTE. */

 *	  Determines and returns the cost of scanning a table function RTE.
 */
void
cost_tablefunction(TableFunctionScanPath *path, PlannerInfo *root, RelOptInfo *baserel_orig,
				   ParamPathInfo *param_info_orig)
{
	ADJUST_BASESCAN(baserel_orig, baserel, param_info_orig, param_info);
	Cost		startup_cost;
	Cost		run_cost;
	QualCost	qpqual_cost;
	Cost		cpu_per_tuple;

	/* Should only be applied to base relations that are functions */
	Assert(baserel->relid > 0);
	Assert(baserel->rtekind == RTE_TABLEFUNCTION);

	/* Mark the path with the correct row estimate */
	if (param_info)
		path->path.rows = param_info->ppi_rows;
	else
		path->path.rows = baserel->rows;

	/* Initialize cost of the subquery input */
	path->path.startup_cost = path->subpath->startup_cost;
	path->path.total_cost   = path->subpath->total_cost;

	/*
	 * For now, estimate function's cost at one operator eval per function
	 * call.  Someday we should revive the function cost estimate columns in
	 * pg_proc...  (see cost_functionscan above)
	 */
	cpu_per_tuple = cpu_operator_cost;

	/* Calculate additional cost of the table function node */
	get_restriction_qual_cost(root, baserel_orig, param_info_orig, &qpqual_cost);

	startup_cost = qpqual_cost.startup;
	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
	run_cost = cpu_per_tuple * baserel->tuples;

	/* Add in the additional cost */
	path->path.startup_cost += startup_cost;
	path->path.total_cost   += startup_cost + run_cost;
}

/*
 * cost_tablefuncscan