Re: BUG #15182: Canceling authentication due to timeout aka Denial of Service Attack

On July 23, 2018 9:50:10 PM PDT, Michael Paquier <michael@paquier.xyz> wrote:
>On Mon, Jul 23, 2018 at 09:17:53PM -0700, Andres Freund wrote:
>> I might be mis-parsing this due to typos. Are you actually suggesting
>> vacuum on system tables should depend on that GUC? If so, why? That's
>> seems like a terrible idea.  It's pretty normal to occasionally have
>> to vacuum them?
>
>Oh, yes, that would be bad.  My mind has slipped here.  I have seen
>manual VACUUMs on system catalogs for applications using many temp
>tables...  So we would want to have only VACUUM FULL being
>conditionally
>happening?  The question comes then about what to do when a VACUUM FULL
>is run without a list of relations because expand_vacuum_rel() is not
>actually the only problem.  Would we want to ignore system tables as
>well except if allow_system_table_mods is on?  When no relation list is
>specified, get_all_vacuum_rels() builds the list of relations which
>causes vacuum_rel() to complain on try_relation_open(), so patching
>just expand_vacuum_rel() solves only half of the problem for manual
>VACUUMs.

I think any such restriction is entirely unacceptable. FULL or not.

Andres
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