Re: [HACKERS] Tablespaces

From: tswan(at)idigx(dot)com
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Zeugswetter Andreas SB SD" <zeugswettera(at)spardat(dot)at>, "Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us>, "Greg Stark" <gsstark(at)mit(dot)edu>, pgsql-hackers(at)postgresql(dot)org, "PostgreSQL Win32 port list" <pgsql-hackers-win32(at)postgresql(dot)org>
Subject: Re: [HACKERS] Tablespaces
Date: 2004-03-04 17:50:11
Message-ID: 32004.199.222.14.2.1078422611.squirrel@www.idigx.com
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> "Zeugswetter Andreas SB SD" <ZeugswetterA(at)spardat(dot)at> writes:
>>>> My feeling is that we need not support tablespaces on OS's without
>>>> symlinks.
>
>> To create symlinked directories on Win2k NTFS see:
>> http://www.sysinternals.com/ntw2k/source/misc.shtml#junction
>> I think Win2000 or XP would be a reasonable restriction for Win32 PG
>> installations that want tablespaces.
>
> Oh, good --- symlinks for directories are all that we need for this
> design. I think that settles it then.
>

What archival tools are there that would restore this to this back to the
filesystem: tar? zip? What would happen if a symlink were removed or
pointed to an invalid location while the postmaste was running?

I think the catalog approach would future proof yourself; think about the
possibility of new filesystems, table storage mechanisms, or devices.
There may be a raw disk system in the future. With that you could point
to a block device instead of a filesystem directory. Symlinks seem like a
simple solution but will it be complete enough? A meta file or catalog
entry could store more than just the location of the tablespace: max/min
space allocation, vacuum frequencies, storage type (maybe in-place
updates), locking schemes (in case someome had a wild hair to customize
NFS operations).

That meta/configuration file with a summary or one that is generated for a
summary could be useful.

I just can't help but state that "I've got a bad feeling about this."

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