Re: Re: [COMMITTERS] pgsql: Map basebackup tablespaces using a tablespace_map file

On 06/05/2015 11:08 PM, Amit Kapila wrote:
> On Fri, Jun 5, 2015 at 10:51 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com
> <mailto:amit(dot)kapila16(at)gmail(dot)com>> wrote:
>
> On Fri, Jun 5, 2015 at 9:57 AM, Andrew Dunstan
> <andrew(at)dunslane(dot)net <mailto:andrew(at)dunslane(dot)net>> wrote:
>
>
> On 06/04/2015 11:35 PM, Amit Kapila wrote:
>
>
> Theoretically, I don't see much problem by changing the checks
> way you have done in patch, but it becomes different than what
> we have in destroy_tablespace_directories() and it is slightly
> changing the way check was originally done in
> create_tablespace_directories(), basically original check
> will try
> unlink if lstat returns non-zero return code. If you want
> to proceed
> with the changed checks as in v3, then may be we can modify
> comments on top of function remove_tablespace_symlink() which
> indicates that it works like destroy_tablespace_directories().
>
>
>
> The difference is that here we're getting the list from a base
> backup and it seems to me the risk of having a file we don't
> really want to unlink is significantly greater.
>
>
> Okay, I think I can understand why you want to be cautious for
> having a different check for this path, but in that case there is a
> chance that recovery might fail when it will try to create a symlink
> for that file. Shouldn't we then try to call this new function only
> when we are trying to restore from tablespace_map file and also
> is there a need of ifdef S_ISLINK in remove_tablespace_link?
>
>
> Shall I send an updated patch on these lines or do you want to
> proceed with v3 version?
>
>

The point seems to me that we should not be removing anything that's not
an empty directory or symlink, and that nothing else has any business
being in pg_tblspc. If we encounter such a thing whose name conflicts
with the name of a tablespace link we wish to create, rather than
quietly blowing it away we should complain loudly, and error out, making
it the user's responsibility to clean up their mess. Am I missing something?

cheers

andrew