Re: [HACKERS] open item: tablespace handing in pg_dump/pg_restore

Hi,

There are certainly cygwin-users trying out PostgreSQL on cygwin on WinXX. If the newest cygwin-version will suddenly stop working under WinXX, they will not be happy.

I've given consideration to the argument that you can no longer take data-directories from the cygwin-version to the native-version... And I think that there's not a *huge* loss there. For me, as an observer and occiasional user/developer, I think the loss of not running on cygwin+winXX is larger.

After all, the data can still be dumped / reloaded. And what gives me the certainty that the two versions of PostgreSQL, the cygwin and the native version, are not already compiled in such way that they're not binary compatible? (remember, I'm an outsider on this, with no knowledge of the binary formats, and I'm trying to remain in that perspective for this discussion)

I don't know what the failure will be when you now try to move a data-directory from the cygwin version to the native version, when cygwin uses a .lnk hack and native uses a junction. Did anyone try? What do the results look like? Is there an acceptable way to stop ppl from trying / give sensible errors without introducing too much crap in the code and without harming ppls data?

regards,

--Tim

-----Original Message-----
From: pgsql-cygwin-owner(at)postgresql(dot)org [mailto:pgsql-cygwin-owner(at)postgresql(dot)org]On Behalf Of Tom Lane
Sent: Tuesday, October 12, 2004 1:02 AM
To: Bruce Momjian
Cc: Reini Urban; PostgreSQL Developers; pgsql-cygwin(at)postgresql(dot)org
Subject: Re: [CYGWIN] [HACKERS] open item: tablespace handing in pg_dump/pg_restore

Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> OK, I have applied the following patch that uses Cygwin native symlink()
> instead of the Win32 junctions. The reason for this is that Cygwin
> symlinks work on Win95/98/ME where junction points do not and we have no
> way to know what system will be running the Cygwin binaries so the
> safest bet is to use the Cygwin versions. On Win32 native we only run
> on systems that support junctions.

I think this is probably a net loss, because what it will mean is that
you cannot take a data directory built under a Cygwin postmaster and use
it under a native postmaster, nor vice versa. Given the number of other
ways in which we do not support pre-NT4 Windows systems, what is the
benefit of allowing this one?

regards, tom lane

---------------------------(end of broadcast)---------------------------
TIP 4: Don't 'kill -9' the postmaster

Leeuw van der, Tim schrieb:
> There are certainly cygwin-users trying out PostgreSQL on cygwin on
>WinXX. If the newest cygwin-version will suddenly stop working under
>WinXX, they will not be happy.

That's why we use cygwin symlinks, not junctions.

> I've given consideration to the argument that you can no longer take
>data-directories from the cygwin-version to the native-version... And I
>think that there's not a *huge* loss there. For me, as an observer and
>occiasional user/developer, I think the loss of not running on
>cygwin+winXX is larger.
>
> After all, the data can still be dumped / reloaded. And what gives me
>the certainty that the two versions of PostgreSQL, the cygwin and the
>native version, are not already compiled in such way that they're not
>binary compatible? (remember, I'm an outsider on this, with no knowledge
>of the binary formats, and I'm trying to remain in that perspective for
>this discussion)

See below. Conflicting --enable-integer-datetimes and --enable-multibyte
would be an issue. I don't know if and how our converters handle
multibyte/non-multibyte, when the backend changes.

> I don't know what the failure will be when you now try to move a
>data-directory from the cygwin version to the native version, when
>cygwin uses a .lnk hack and native uses a junction. Did anyone try? What
>do the results look like? Is there an acceptable way to stop ppl from
>trying / give sensible errors without introducing too much crap in the
>code and without harming ppls data?

That's a non-critical issue. You can always replace the cygwin .lnk dir
with an actual junction on cygwin also. You'd need to be superuser and
use "ln -d" or get "junction" from sysinternals.com.
But than you must have NTFS4 (same drive) or NTFS5 (other local drive).

You can also replace the junction with a cygwin .lnk if you switch to
FAT, but then you MUST use the cygwin binaries on the data.
Or don't use tablespace at all. It's a pretty esoteric feature at all.

But it will get problematic on big/little endian machine changes, and
different integer sizes. Don't know if the data is converted on the fly
then. I only know of AutoCAD's DWG: they designed its data format and
accessors to be machine and CPU independent. And you usually don't copy
machine dependent /usr/share/postgresql trees to other machines.

> -----Original Message-----
> From: pgsql-cygwin-owner(at)postgresql(dot)org [mailto:pgsql-cygwin-owner(at)postgresql(dot)org]On Behalf Of Tom Lane
> Sent: Tuesday, October 12, 2004 1:02 AM
> To: Bruce Momjian
> Cc: Reini Urban; PostgreSQL Developers; pgsql-cygwin(at)postgresql(dot)org
> Subject: Re: [CYGWIN] [HACKERS] open item: tablespace handing in pg_dump/pg_restore
>
>
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
>
>>OK, I have applied the following patch that uses Cygwin native symlink()
>>instead of the Win32 junctions. The reason for this is that Cygwin
>>symlinks work on Win95/98/ME where junction points do not and we have no
>>way to know what system will be running the Cygwin binaries so the
>>safest bet is to use the Cygwin versions. On Win32 native we only run
>>on systems that support junctions.
>
> I think this is probably a net loss, because what it will mean is that
> you cannot take a data directory built under a Cygwin postmaster and use
> it under a native postmaster, nor vice versa. Given the number of other
> ways in which we do not support pre-NT4 Windows systems, what is the
> benefit of allowing this one?

--
Reini Urban
http://xarch.tu-graz.ac.at/home/rurban/