Hi,
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.
Greetings,
Andres Freund
