Hello Christian, Christian Tacke [2014-02-17 13:14 +0100]: > PGDATA/pg_stat_tmp/* is written to a lot, even on a > completely idle system. This is not good if running on an > SSD or alike. That's for my motivation. > > This directory is only needed at runtime, so putting it in > /var/run seems more appropiate also. The manual even > recommends using a RAM based filesystem for this directory.
Indeed, this is recommended here: http://www.postgresql.org/docs/8.4/static/runtime-config-statistics.html I think configuring a tmpfs dir by default is a good idea, thanks for pointing that out. > === modified file 'createcluster.conf' > --- createcluster.conf 2013-04-12 12:32:08 +0000 > +++ createcluster.conf 2014-02-17 11:26:47 +0000 > @@ -23,3 +23,6 @@ > # All other options are copied into the new cluster's postgresql.conf > > log_line_prefix = '%%t ' > + > +# Starting at version 8.4 one can move the pg_stat_tmp dir > +stats_temp_directory = '/var/run/postgresql/%v-%c_stat_tmp' Note that this is a little too simplistic. This directory is only writable to clusters owned by postgres. While that is the default, you can assign any other owner, and you can even call pg_createcluster as a normal user and put everything into your $HOME; in those cases, /tmp/ will be used for the Unix socket, and we can't use /var/run/postgresql/. One idea is to add a new "%s" macro to the evaluation of createcluster.conf which expands to the used socket dir, and set stats_temp_directory = '%s/%v-%c_stat_tmp'. That's a little more complex, but always ought to work since we know that the socket dir is writable. A simpler solution might be to use /var/run/lock/ instead, which is world-writable (same permissions as /tmp/). It's just a bit of an abuse as these are not really lock files. A third option would be to not put this into createcluster.conf, but dynamically set it up in pg_createcluster; i. e. only postgres-owned clusters would configure this (more specifically, add the option if /var/run/postgresql is writable for the owner, so that admins could put other users into the postgres group). Christian, Christoph, What do you think? Thanks, Martin -- Martin Pitt | http://www.piware.de Ubuntu Developer (www.ubuntu.com) | Debian Developer (www.debian.org)
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