Re: Tablespaces in the data directory

On 12/02/2012 07:50 PM, Magnus Hagander wrote:
> On Sat, Dec 1, 2012 at 6:56 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Magnus Hagander <magnus@hagander.net> writes:
>>> Someone just reported a problem when they had created a new tablespace
>>> inside the old data directory. I'm sure there can be other issues
>>> caused by this as well, but this is mainly a confusing scenario for
>>> people now.
>>> As there isn't (as far as I know at least) any actual *point* in
>>> creating a tablespace inside the main data directory, should we
>>> perhaps disallow this in CREATE TABLESPACE? Or at least throw a
>>> WARNING if one does it?
>> It could be pretty hard to detect that in general (think symlinks
>> and such).  I guess if we're just trying to print a helpful warning,
>> we don't have to worry about extreme corner cases.  But what exactly
>> do you have in mind --- complain about any relative path?  Complain
>> about absolute paths that have a prefix matching the DataDir?
> Oh, I hadn't thought quite so far as the implementation :) Was looking
> to see if there were going to be some major objections before I even
> started thinking about that.
>
> But for the implementation, I'd say any absolute path that have a
> prefix matching DataDir. Tablespaces cannot be created using relative
> paths, so we don't have to deal with that.
>

I have been known to symlink a tablespace on a replica back to a 
directory in the datadir, while on the primary it points elsewhere. What 
exactly is the problem?

cheers

andrew