Re: New option for pg_basebackup, to specify a different directory for pg_xlog

On 20/11/13 23:43, Haribabu kommi wrote:
> On 19 November 2013 19:12 Fujii Masao wrote:
>> On Tue, Nov 19, 2013 at 9:14 PM, Haribabu kommi
>> <haribabu(dot)kommi(at)huawei(dot)com> wrote:
>>> On 18 November 2013 23:30 Fujii Masao wrote:
>>>> On Tue, Nov 19, 2013 at 12:01 AM, Haribabu kommi
>>>> <haribabu(dot)kommi(at)huawei(dot)com> wrote:
>>>>
>>>> Thanks for newer version of the patch!
>>>>
>>>> I found that the empty base directory is created and remains even
>>>> when the same directory is specified in both -D and --xlogdir and
>> the
>>>> error occurs.
>>>> I think that it's
>>>> better to throw an error in that case before creating any new
>> directory.
>>>> Thought?
>>> By creating the base directory only the patch finds whether provided
>>> base and Xlog directories are same or not? To solve this problem
>>> following options are possible
>>>
>>> 1. No problem as it is just an empty base directory, so it can be
>> reused in the next time
>>> Leave it as it is.
>>> 2. Once the error is identified, the base directory can be deleted.
>>> 3. write a new function to remove the parent references from the
>> provided path to identify
>>> the absolute path used for detecting base and Xlog directories are
>> same or not?
>>> Please provide your suggestions.
>>>
>>>> + xlogdir = get_absolute_path(xlog_dir);
>>>>
>>>> xlog_dir must be an absolute path. ISTM we don't do the above. No?
>>> It is required. As user can provide the path as
>> /home/installation/bin/../bin/data.
>>> The provided path is considered as absolute path only but while
>>> comparing the same With data directory path it will not match.
>> Okay, maybe I understand you. In order to know the real absolute path,
>> basically we need to create the directory specified in --xlogdir,
>> change the working directory to it and calculate the parent path.
>> You're worried about the cases as follows, for example.
>> Right?
>>
>> * path containing ".." like /aaa/bbb/../ccc is specified in --xlogdir
>> * symbolic link is specified in --xlogdir
>>
>> On the second thought, I'm thinking that it might be overkill to add
>> such not simple code for that small benefit.
> I tried using of stat'ing in two directories, which is having a problem in windows.
> So modified old approach to detect limited errors. Updated patch attached.
> This will detect and throw an error in the following scenarios.
> 1. pg_basebackup -D /home/data --xlogdir=/home/data
> 2. pg_basebackup -D data --xlogdir=/home/data -- home is the CWD
> 3. pg_basebackup -D ../data --xlogdir=/data -- home is the CWD
>
> Please let me know your suggestions.
>
> Regards,
> Hari babu.
>
>
I don't think Postgres on other systems should be hobbled by the
limitations of Microsoft software!

If certain features of Postgres are either not available, or are
available in a reduced form on Microsoft platforms, then this should be
documented - might provide subtle hints to upgrade to Linux.

Cheers,
Gavin