Thread: Is necessary to use SEQ_MAXVALUE in pg_dump?

I'm trying fix independence of pg_dump.c on postgres.h. And I found 
following construct in dumpSequence function:



09391     snprintf(bufm, sizeof(bufm), INT64_FORMAT, SEQ_MINVALUE);
09392     snprintf(bufx, sizeof(bufx), INT64_FORMAT, SEQ_MAXVALUE);
09393
09394     appendPQExpBuffer(query,
09395                       "SELECT sequence_name, last_value, 
increment_by, "
09396                    "CASE WHEN increment_by > 0 AND max_value = %s 
THEN NULL "
09397                    "     WHEN increment_by < 0 AND max_value = -1 
THEN NULL "
09398                       "     ELSE max_value "
09399                       "END AS max_value, "
09400                     "CASE WHEN increment_by > 0 AND min_value = 1 
THEN NULL "
09401                    "     WHEN increment_by < 0 AND min_value = %s 
THEN NULL "
09402                       "     ELSE min_value "
09403                       "END AS min_value, "
09404                       "cache_value, is_cycled, is_called from %s",
09405                       bufx, bufm,
09406                       fmtId(tbinfo->dobj.name));


This construct is used to determine if max_value/min_value is used and 
after that pg_dump add NO MAXVALUE to the output instead of the value. 
If I compare it with manual documentation NO MAXVALUE uses default value 
and I do not see any reason to have this code there. I think we can 
remove this code and release dependency on sequence.h.
    Any comments?
        Zdenek

Zdenek Kotala <Zdenek.Kotala@Sun.COM> writes:
> This construct is used to determine if max_value/min_value is used and 
> after that pg_dump add NO MAXVALUE to the output instead of the value. 
> If I compare it with manual documentation NO MAXVALUE uses default value 
> and I do not see any reason to have this code there. I think we can 
> remove this code and release dependency on sequence.h.

IIUC you are proposing that it's okay to print random-huge-values in
the dumped CREATE SEQUENCE commands.  I don't agree with that.
In particular it would make for a legacy/compatibility issue for
INT64_IS_BROKEN platforms.

A better solution might be to move the declarations of
SEQ_MINVALUE/SEQ_MAXVALUE someplace else.
        regards, tom lane

Tom Lane wrote:

> 
> A better solution might be to move the declarations of
> SEQ_MINVALUE/SEQ_MAXVALUE someplace else.

Hmm. It seems better, but it is also hard to find correct place. :( I'm 
thinking put it into c.h.

Another question why sequence does not have separate flag which 
determines if it is default/no max value or predefined?
Any comments, better ideas?
    Zdenek

Zdenek Kotala <Zdenek.Kotala@Sun.COM> writes:
> Tom Lane wrote:
>> A better solution might be to move the declarations of
>> SEQ_MINVALUE/SEQ_MAXVALUE someplace else.

> Hmm. It seems better, but it is also hard to find correct place. :( I'm 
> thinking put it into c.h.

The idea that was in the back of my mind was pg_config_manual.h,
since these numbers could be seen as configuration constants if
you hold your head at the right angle ...
        regards, tom lane