Re: pg14b1 stuck in lazy_scan_prune/heap_page_prune of pg_statistic

From: Andres Freund <andres(at)anarazel(dot)de>
To: Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>
Cc: Michael Paquier <michael(at)paquier(dot)xyz>, Peter Geoghegan <pg(at)bowt(dot)ie>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: pg14b1 stuck in lazy_scan_prune/heap_page_prune of pg_statistic
Date: 2021-06-09 18:45:06
Views: Raw Message | Whole Thread | Download mbox | Resend email
Lists: pgsql-hackers


Good find!

On 2021-06-09 17:42:34 +0200, Matthias van de Meent wrote:
> I believe that I've found the culprit:
> GetOldestNonRemovableTransactionId(rel) does not use the exact same
> conditions for returning OldestXmin as GlobalVisTestFor(rel) does.
> This results in different minimal XIDs, and subsequently this failure.

Specifically, the issue is that it uses the innocuous looking

else if (RelationIsAccessibleInLogicalDecoding(rel))
return horizons.catalog_oldest_nonremovable;

but that's not sufficient, because

#define RelationIsAccessibleInLogicalDecoding(relation) \
(XLogLogicalInfoActive() && \
RelationNeedsWAL(relation) && \
(IsCatalogRelation(relation) || RelationIsUsedAsCatalogTable(relation)))

it is never true if wal_level < logical. So what it is missing is the
IsCatalogRelation(rel) || bit.

> The attached patch fixes this inconsistency

I think I prefer applying the fix and the larger changes separately.

> Another approach might be changing GlobalVisTestFor(rel) instead to
> reflect the conditions in GetOldestNonRemovableTransactionId.

No, that'd not be correct, afaict.


Andres Freund

In response to


Browse pgsql-hackers by date

  From Date Subject
Next Message Vijaykumar Jain 2021-06-09 18:45:40 Re: Estimating HugePages Requirements?
Previous Message Jonathan S. Katz 2021-06-09 18:33:56 unnesting multirange data types