On Wed, Apr 15, 2015 at 9:20 PM, Michael Paquier <michael.paqu...@gmail.com> wrote: > On Wed, Apr 15, 2015 at 2:22 PM, Fujii Masao wrote: >> On Wed, Apr 15, 2015 at 11:55 AM, Michael Paquier wrote: >>> 1) Doc patch to mention that it is possible that compression can give >>> hints to attackers when working on sensible fields that have a >>> non-fixed size. >> >> I think that this patch is enough as the first step. > > I'll get something done for that at least, a big warning below the > description of wal_compression would do it. > >>> 2) Switch at relation level to control wal_compression. >> >> ALTER TABLE SET is not allowed on system catalog like pg_authid. So should we >> change it so that a user can change the flag even on system catalog? I'm >> afraid >> that the change might cause another problem, though. Probably we can disable >> the compression on every system catalogs by default. But I can imagine that >> someone wants to enable the compression even on system catalog. For example, >> pg_largeobject may cause lots of FPW. > > We could enforce a value directly in pg_class.h for only pg_authid if > we think that it is a problem that bad, and rely on the default system > value for the rest. That's a hacky-ugly approach though...
Something else that I recalled and has not yet been mentioned on this thread. Even if the server-wide wal_compression is off, any user can change its value because it is PGC_USERSET, hence I think that we had better make it at least PGC_SUSET. -- Michael -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
