From: Tomas Vondra [mailto:tomas.von...@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 item would 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 system catalogs. That may result in OOM, and this patch can rescue it. Regards Takayuki Tsunakawa
