Re: Somebody has not thought through subscription locking considerations

On 31/03/17 21:00, Tom Lane wrote:
> Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com> writes:
>> On 31/03/17 20:23, Tom Lane wrote:
>>> No, the problematic part is that there is any heap_open happening at
>>> all. That open could very easily result in a recursive attempt to read
>>> pg_class, for example, which is going to be fatal if we're in the midst
>>> of vacuum full'ing or reindex'ing pg_class. It's frankly astonishing
>>> to me that this patch seems to have survived testing under
>>> CLOBBER_CACHE_ALWAYS, because it's only the catalog caches that are
>>> preventing such recursive lookups.
>
>> Hmm okay, so the solution is to either use standard dependency info for
>> this so that it's only called for tables that are actually know to be
>> subscribed or have some exceptions in the current code to call the
>> function only for user catalogs. Any preferences?
>
> Looking at dependency info isn't going to fix this, it only moves the
> unsafe catalog access somewhere else (ie pg_depend instead of
> pg_subscription_rel). I suspect the only safe solution is doing an
> IsCatalogRelation or similar test pretty early in the logical replication
> code paths.
>

I don't follow, everything else does dependency info check in this
situation, how is this any different?

--
Petr Jelinek http://www.2ndQuadrant.com/
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