Re: [HACKERS] [COMMITTERS] pgsql: Fix freezing of a dead HOT-updatedtuple

Wood, Dan wrote:

> There is a tangled web of issues here.  With the community fix we get a corrupted page(invalid redirect ptr from
indexeditem).  The cause of that is:
 
> pruneheap.c:
> 
>                   /*
>                    * Check the tuple XMIN against prior XMAX, if any
>                    */
>                   if (TransactionIdIsValid(priorXmax) &&
>                           !TransactionIdEquals(HeapTupleHeaderGetXmin(htup), priorXmax))
>                           break;
> 
>     chainitems[nchain++] = offnum;
> 
> The priorXmax is a multixact key share lock,

Uhh, what?  That certainly shouldn't happen -- the priorXmax comes from
        priorXmax = HeapTupleHeaderGetUpdateXid(htup);

so only the XID of the update itself should be reported, not a multixact
and certainly not just a tuple lock XID.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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