From: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | bz(at)mailinator(dot)com, PostgreSQL Bugs List <pgsql-bugs(at)postgresql(dot)org> |
Subject: | Re: BUG #13442: ISBN doesn't always roundtrip with text |
Date: | 2015-06-15 18:34:18 |
Message-ID: | alpine.DEB.2.10.1506152026520.26470@sto |
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Lists: | pgsql-bugs |
>> I have a table containing ISBNs stored as the isbn type provided by the isn
>> extension. In certain cases an ISBN in ISBN10 form is considered unequal to
>> the same ISBN in ISBN13 form.
>
> I poked at this a little bit. I think the issue may be that this bit
> at line 832 in isn.c:
>
> case ISBN:
> memcpy(buf, "978", 3);
>
> supposes that all ISBNs should have prefix 978, whereas your example is
> using prefix 979, which seems to be also valid according to code a few
> lines above. I don't know enough about the whole ISBN/EAN mess to
> understand what this should be doing instead, though.
Hmmm. ISBN-10 -> ISBN-13 is really just adding "978" in front, so there is
no casted ISBN-10 number starting with 979. ISTM that "979" is just a
recorded prefix for books, just as "978", for ISBN-13. AFAICR the prefix
was chosen so that the checksum digit can be kept in the conversion.
SELECT '9791020902573'::isbn = '10-209-0257-4'::isbn; -- Returns f
Indeed, but this one should return true:
SELECT '9781020902574'::isbn = '10-209-0257-4'::isbn;
So I would say there is no bug as the number are indeed different, or that
I missed something.
--
Fabien.
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