AFAIK, the only systems supported by Postgres that this patch won't work on are NetBSD and OpenBSD.

The POSIX calls free the user from the SHMMAX and SHMALL limitations of the SysV shared memory calls on platforms that support it. Since this still takes one SysV segment, SHMMNI can still be reached on some platforms if a ton of databases are opened simultaneously (i.e. 256 on Linux and Solaris, 100 on SCO Unix, 512 on HP-UX, 32 on Mac OS X, unlimited on FreeBSD). This is the case without the patch anyhow.

Chris Marcellino

On Mar 3, 2007, at 9:09 AM, Joshua D. Drake wrote:

If you have the need to ship a product with Postgres embedded in it and are unable to change kernel settings (like myself), this might be of use to you. I have tested all of the failure situations I could think of by
various combinations of deleting lockfiles while in use, changing the
PID inside the lockfile and trying to restart and run more than one
postmaster simultaneously.

Of course, this since this requires both POSIX and SysV shared memory,
this doesn't increase the portability of Postgres which might make it
less appropriate for mass distribution; I thought I would put it out
there for any feedback either way.

Well that depends, what systems don't use (or have) POSIX shared memory?
This sounds very interesting to me. Oddly enough I went to do some
digging on what various differences and I came up with:

Which happens to be you ;)


Joshua D. Drake

Thanks again,
Chris Marcellino

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