Re: pg_dump -Fd and compression level

On 07/27/2015 03:52 AM, Marc Mamin wrote:
>>>> As per attached patch.
>>>>
>>>> Comments?
>>> It seems that the first test on the compression in pg_backup_tar.c is now obsolete.
>>> It didn't make much sense anyway.
>>>
>>>
>>>
>>>     211         if (AH->compression < 0 || AH->compression > 9)
>>>     212             AH->compression = Z_DEFAULT_COMPRESSION;
>>>     213
>>>     214         /* Don't compress into tar files unless asked to do so */
>>>     215         if (AH->compression == Z_DEFAULT_COMPRESSION)
>>>     216             AH->compression = 0;
>>>     217
>>>     218         /*
>>>     219          * We don't support compression because reading the files back is not
>>>     220          * possible since gzdopen uses buffered IO which totally screws file
>>>     221          * positioning.
>>>     222          */
>>>     223         if (AH->compression != 0)
>>>     224             exit_horribly(modulename,
>>>     225                      "compression is not supported by tar archive format\n");
>>>     226     }
>>>     
>>>     
>> In fact, the first two tests look unnecessary. Neither condition should
>> be possible now.
>>
> Hello,
>
> Isn't the second test still required if you call pg_dump -Ft without setting -Z0 explicitly ?
> (=> AH->compression == Z_DEFAULT_COMPRESSION)



No. Z_DEFAULT_COMPRESSION is only set for directory and custom archive 
types. See pg_dump.c at lines 578-592.


cheers

andrew