Invalid Path with UpperRel

Hi, hackers!

I recently encountered strange behavior when, after running the
create_ms.sql test, I ran the last query from this test. In general, the
playback looks like this:

\i src/test/regress/sql/create_misc.sql

I added Assert(0) in create_sort_plan() before calling
create_plan_recurse and restarted postgres. After that I run query:

SELECT relname, reltoastrelid <> 0 AS has_toast_table
   FROM pg_class
   WHERE oid::regclass IN ('a_star', 'c_star')
   ORDER BY 1;

I found Invalid_path in cheapest_startup_path:

 (gdb) p *(IndexPath *)((SortPath
*)best_path)->subpath->parent->cheapest_startup_path
$12 = {path = {type = T_Invalid, pathtype = T_Invalid, parent =
0x7f7f7f7f7f7f7f7f, pathtarget = 0x7f7f7f7f7f7f7f7f, param_info =
0x7f7f7f7f7f7f7f7f,
    parallel_aware = 127, parallel_safe = 127, parallel_workers =
2139062143 <tel:2139062143>, rows = 1.3824172084878715e+306,
startup_cost = 1.3824172084878715e+306,
    total_cost = 1.3824172084878715e+306, pathkeys =
0x7f7f7f7f7f7f7f7f}, indexinfo = 0x7f7f7f7f7f7f7f7f, indexclauses =
0x7f7f7f7f7f7f7f7f,
  indexorderbys = 0x7f7f7f7f7f7f7f7f, indexorderbycols =
0x7f7f7f7f7f7f7f7f, indexscandir = 2139062143 <tel:2139062143>,
indextotalcost = 1.3824172084878715e+306,
  indexselectivity = 1.3824172084878715e+306}

(gdb) p (IndexPath *)((SortPath
*)best_path)->subpath->parent->cheapest_startup_path
$11 = (IndexPath *) 0x555febc66160

I found that this beginning since creation upperrel (fetch_upper_rel
function):

/* primary planning entry point (may recurse for subqueries) */  root =
subquery_planner(glob, parse, NULL,        false, tuple_fraction);  /*
Select best Path and turn it into a Plan */ * final_rel =
fetch_upper_rel(root, UPPERREL_FINAL, NULL);*  best_path =
get_cheapest_fractional_path(final_rel, tuple_fraction);
Red Heart

(gdb) p *(IndexPath *)((SortPath *)final_rel->cheapest_total_path
)->subpath->parent->cheapest_startup_path
$15 = {path = {type = T_Invalid, pathtype = T_Invalid, parent =
0x7f7f7f7f7f7f7f7f, pathtarget = 0x7f7f7f7f7f7f7f7f, param_info =
0x7f7f7f7f7f7f7f7f,
    parallel_aware = 127, parallel_safe = 127, parallel_workers =
2139062143 <tel:2139062143>, rows = 1.3824172084878715e+306,
startup_cost = 1.3824172084878715e+306,
    total_cost = 1.3824172084878715e+306, pathkeys =
0x7f7f7f7f7f7f7f7f}, indexinfo = 0x7f7f7f7f7f7f7f7f, indexclauses =
0x7f7f7f7f7f7f7f7f,
  indexorderbys = 0x7f7f7f7f7f7f7f7f, indexorderbycols =
0x7f7f7f7f7f7f7f7f, indexscandir = 2139062143 <tel:2139062143>,
indextotalcost = 1.3824172084878715e+306,
  indexselectivity = 1.3824172084878715e+306}
(gdb) p (IndexPath *)((SortPath *)final_rel->cheapest_total_path
)->subpath->parent->cheapest_startup_path
$16 = (IndexPath *) 0x555febc66160

I know it doesn't cause a crash anywhere, but can anybody explain me
what's going on here and why Invalid Path appears?

--
Regards,
Alena Rybakina