From: Tomas Vondra [mailto:tomas.vondra@2ndquadrant.com]
> > I didin't consider planning that happen within a function. If
> > 5min is the default for catalog_cache_prune_min_age, 10% of it
> > (30s) seems enough and gettieofday() with such intervals wouldn't
> > affect forground jobs. I'd choose catalog_c_p_m_age/10 rather
> > than fixed value 30s and 1s as the minimal.
> >
>
> Actually, I see CatCacheCleanupOldEntries contains this comment:
>
> /*
> * Calculate the duration from the time of the last access to the
> * "current" time. Since catcacheclock is not advanced within a
> * transaction, the entries that are accessed within the current
> * transaction won't be pruned.
> */
>
> which I think is pretty much what I've been saying ... But the question
> is whether we need to do something about it.
Hmm, I'm surprised at v14 patch about this. I remember that previous patches renewed the cache clock on every
statement,and it is correct. If the cache clock is only updated at the beginning of a transaction, the following TODO
itemwould not be solved:
https://wiki.postgresql.org/wiki/Todo
" Reduce memory use when analyzing many tables in a single command by making catcache and syscache flushable or
bounded."
Also, Tom mentioned pg_dump in this thread (protect syscache...). pg_dump runs in a single transaction, touching all
systemcatalogs. That may result in OOM, and this patch can rescue it.
Regards
Takayuki Tsunakawa
