2014-02-12 12:52 GMT+09:00 Craig Ringer <cr...@2ndquadrant.com>: > Hi all > > I've just seen another case of data loss due to misuse of / > misunderstanding of tablespaces: > > http://dba.stackexchange.com/questions/58704/how-do-i-access-a-old-saved-tablespace-after-reinstalling-postgres > > and it's prompted me to write some docs amendments to make it more > obvious that *you shouldn't do that*. > > Not that it'll stop people, but it'll at least mean they can't say we > didn't warn them. > > This is actually quite important, because many users are used to MySQL's > MyISAM, where each table contains its own metadata and is readable by > simply copying the table into a different MySQL install's data > directory. It doesn't even have to be the same version! Users are > clearly surprised that PostgreSQL tablespaces don't have the same > properties. > > Thoughts?
People still use MyISAM!? I had a similar issue pop up at work a while back, having something explicit to point to is definitely a good idea. Suggestion for the first paragraph of the patch (sorry I can't provide it in patch form right now): Even if they are located outside the main PostgreSQL data directory, tablespaces are an integral part of the database cluster and <emphasis>cannot</emphasis> be treated as an autonomous collection of data files. They rely on metadata contained in the main data directory, without which they are useless. In particular, tablespaces cannot be reattached to a different database cluster, and backing up individual tablespaces makes no sense as a backup/redundancy method. Similarly, if you lose a tablespace (file deletion, disk failure, etc) the main database may become unreadable or fail to start. Regards Ian Barwick -- Sent via pgsql-docs mailing list (pgsql-docs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-docs
