Re: HOT chain validation in verify_heapam() - Mailing list pgsql-hackers

> +             }
> +
> +             /* Loop over offsets and validate the data in the predecessor array. */
> +             for (OffsetNumber currentoffnum = FirstOffsetNumber; currentoffnum <= maxoff;
> +                      currentoffnum = OffsetNumberNext(currentoffnum))
> +             {
> +                     HeapTupleHeader pred_htup;
> +                     HeapTupleHeader curr_htup;
> +                     TransactionId pred_xmin;
> +                     TransactionId curr_xmin;
> +                     ItemId          pred_lp;
> +                     ItemId          curr_lp;
> +
> +                     ctx.offnum = predecessor[currentoffnum];
> +                     ctx.attnum = -1;
> +
> +                     if (ctx.offnum == 0)
> +                     {
> +                             /*
> +                              * Either the root of the chain or an xmin-aborted tuple from
> +                              * an abandoned portion of the HOT chain.
> +                              */

Hm - couldn't we check that the tuple could conceivably be at the root of a
chain? I.e. isn't HEAP_HOT_UPDATED? Or alternatively has an aborted xmin?

 

 I don't see a way to check if tuple is at the root of HOT chain because predecessor array will always be having either xmin from non-abandoned transaction or it will be zero. We can't differentiate root or tuple inserted via abandoned transaction.