Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Yes, that is true. My idea is that they may want to create loc1 and
> loc2 which initially point to the same location, but later may be moved.
> For example, one tablespace for tables, another for indexes. They may
> initially point to the same directory, but later be split.
Well, that opens up a completely different issue, which is what about
moving tables from one tablespace to another?
I think the way you appear to be implying above (shut down the server
so that you can rearrange subdirectories by hand) is the wrong way to
go about it. For one thing, lots of people don't want to shut down
their servers completely for that long, but it's difficult to avoid
doing so if you want to move files by filesystem commands. For another
thing, the above approach requires guessing in advance --- maybe long
in advance --- how you are going to want to repartition your database
when it gets too big for your existing storage.
The right way to address this problem is to invent a "move table to
new tablespace" command. This'd be pretty trivial to implement based
on a file-versioning approach: the new version of the pg_class tuple
has a new tablespace identifier in it.
regards, tom lane