Re: Damage control for planner's get_actual_variable_endpoint() runaway

Hi,

On 2022-11-21 17:06:16 +0100, Jakub Wartak wrote:
> @@ -6213,14 +6216,26 @@ get_actual_variable_endpoint(Relation heapRel,
>      /* Fetch first/next tuple in specified direction */
>      while ((tid = index_getnext_tid(index_scan, indexscandir)) != NULL)
>      {
> +        BlockNumber block = ItemPointerGetBlockNumber(tid);
>          if (!VM_ALL_VISIBLE(heapRel,
> -                            ItemPointerGetBlockNumber(tid),
> +                            block,
>                              &vmbuffer))
>          {
>              /* Rats, we have to visit the heap to check visibility */
>              if (!index_fetch_heap(index_scan, tableslot))
>                  continue;        /* no visible tuple, try next index entry */
>  
> +            {
> +                CHECK_FOR_INTERRUPTS();
> +                if (block != last_block)
> +                    visited_pages++;
> +#define VISITED_PAGES_LIMIT 100
> +                if (visited_pages > VISITED_PAGES_LIMIT)
> +                    break;
> +                else
> +                    continue; /* no visible tuple, try next index entry */
> +            }
> +
>              /* We don't actually need the heap tuple for anything */
>              ExecClearTuple(tableslot);
>  
> -- 
> 2.30.2

This can't quite be right - isn't this only applying the limit if we found a
visible tuple?

Greetings,

Andres Freund