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

On Thu, Jun 4, 2015 at 1:52 AM, Andrew Dunstan <andrew@dunslane.net> wrote:

On 06/02/2015 11:55 PM, Amit Kapila wrote:

On Tue, Jun 2, 2015 at 10:26 PM, Andrew Dunstan <andrew@dunslane.net <mailto:andrew@dunslane.net>> wrote:

    Well, it seems to me the new function is being altogether way too
    trusting about the nature of what it's being asked to remove. In
    the first place, the S_ISDIR/rmdir branch should only be for
    Windows, and secondly in the other branch we should be checking
    that S_ISLNK is true. It would actually be nice if we could test
    for a junction point on Windows, but that seems to be a bit
    difficult.

I think during recovery for tablespace related operations, it is
quite possible to have a directory instead of symlink in some
special cases (see function TablespaceCreateDbspace() and comments
in destroy_tablespace_directories() { ..Try to remove the symlink..}).
Also this new function is being called from create_tablespace_directories()
which uses the code as written in new function, so it doesn't make much
sense to change it Windows and non-Windows specific code.

Looking at it again, this might be not as bad as I thought, but I do think we should probably call the function something other than rmsymlink(). That seems too generic, since it also tries to remove directories - albeit that this will fail if the directory isn't empty. And I still think we should add a test for S_ISLNK in the second branch. As it stands the function could try to unlink anything that's not a directory. That might be safe-ish in the context it's used in for the tablespace code, but it's far from safe enough for a function that's in src/common

Okay, as we both seem to agree that it can be mostly used in

tablespace symlinks context, so I have changed the name to

remove_tablespace_symlink() and moved the function to

tablespace.c.  S_ISLINK check is used for non-windows code,

so not sure adding it here makes any real difference now that

we have made it specific to tablespace and we might need to

write small port specific code if we want to add S_ISLINK check.

 

Given that the function raises an error on failure, I think it will otherwise be OK as is.

Please find an updated patch attached with this mail.