Re: [Patch] pg_rewind: options to use restore_command fromrecovery.conf or command line

On 2020-03-02 07:53, Michael Paquier wrote:

> 
>> + * For fixed-size files, the caller may pass the expected size as an
>> + * additional crosscheck on successful recovery.  If the file size is 
>> not
>> + * known, set expectedSize = 0.
>> + */
>> +int
>> +RestoreArchivedWALFile(const char *path, const char *xlogfname,
>> +                       off_t expectedSize, const char *restoreCommand)
> 
> Actually, expectedSize is IMO a bad idea, because any caller of this
> routine passing down zero could be trapped with an incorrect file
> size.  So let's remove the behavior where it is possible to bypass
> this sanity check.  We don't need it in pg_rewind either.
> 

OK, sounds reasonable, but just to be clear. I will remove only a 
possibility to bypass this sanity check (with 0), but leave expectedSize 
argument intact. We still need it, since pg_rewind takes WalSegSz from 
ControlFile and should pass it further, am I right?

> 
>> +        /* Remove trailing newline */
>> +        if (strchr(cmd_output, '\n') != NULL)
>> +            *strchr(cmd_output, '\n') = '\0';
> 
> It seems to me that what you are looking here is to use
> pg_strip_crlf().  Thinking harder, we have pipe_read_line() in
> src/common/exec.c which does the exact same job..
> 

pg_strip_crlf fits well, but would you mind if I also make 
pipe_read_line external in this patch?

> 
>> -    /*
>> -     * construct the command to be executed
>> -     */
> 
> Perhaps you meant "build" here.
> 

Actually, the verb 'construct' is used historically applied to 
archive/restore commands (see also xlogarchive.c and pgarch.c), but it 
should be 'build' in (fe_)archive.c, since we have BuildRestoreCommand 
there now.

All other remarks look clear for me, so I fix them in the next patch 
version, thanks.


Regards
--
Alexey Kondratov

Postgres Professional https://www.postgrespro.com
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