On 30.10.2013 18:52, Robert Haas wrote:
> Here's a short summary of what I posted back in August: at system
> startup time, the postmaster creates one dynamic shared segment,
> called the control segment. That segment sticks around for the
> lifetime of the server and records the identity of any *other* dynamic
> shared memory segments that are subsequently created. If the server
> dies a horrible death (e.g. kill -9), the next postmaster will find
> the previous control segment (whose ID is written to a file in the
> data directory) and remove any leftover shared memory segments from
> the previous run; without this, such segments would live until the
> next server reboot unless manually removed by the user (which isn't
> even practical on all platforms; e.g. there doesn't seem to be any way
> to list all exstant POSIX shared memory segments on MacOS X, so a user
> wouldn't know which segments to remove).
Wait, that sounds horrible. If you kill -9 the server, and then rm -rf
$PGDATA, the shared memory segment is leaked until next reboot? I find
that unacceptable. There are many scenarios where you never restart
postmaster after a crash. For example, if you have an automatic failover
setup; you fail over to the standby in case of crash, and re-initialize
the old master with e.g rsync.
- Heikki
