| From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
|---|---|
| To: | "Wood, Dan" <hexpert(at)amazon(dot)com> |
| Cc: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, "Wong, Yi Wen" <yiwong(at)amazon(dot)com> |
| Subject: | Re: [COMMITTERS] pgsql: Fix freezing of a dead HOT-updated tuple |
| Date: | 2017-10-04 09:51:59 |
| Message-ID: | 20171004095159.wi277fwlmky6ymmz@alvherre.pgsql |
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| Lists: | pgsql-committers pgsql-hackers |
Wood, Dan wrote:
> There is a tangled web of issues here. With the community fix we get a corrupted page(invalid redirect ptr from indexed item). 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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