Re: [MacPerl] DB record size

[daver@idiom.com (David Ray)]

I think my bug was different. I was replacing the value with a
progressively larger value each time. Again, I saw this bug on Digital
Unix, not MacPerl.

-Dave

At 2:46 PM 11/26/96, Matthias Ulrich Neeracher wrote:
> daver@idiom.com (David Ray) writes:
> >I'm still using the Perl-4 style DB functions such as dbopen() for my Perl
> >DB work, and I just ran into a problem. It looks like there is a size
> >limitation of the key/value data. Above a certain size, trying to set the
> >DB record causes the script to return a DB error.
>
> Last week, I denied the existence of this bug, but it looks as if I'll have to
> recant. The following message appeared in the Perl5-porters mailing list, and
> I'll have to look into it. David, could the symptoms you're seeing possibly be
> caused by a bug as described below?
>
> Matthias
>
> -----
> Matthias Neeracher   <neeri@iis.ee.ethz.ch>   http://www.iis.ee.ethz.ch/~neeri
>    "One fine day in my odd past..." -- Pixies, _Planet of Sound_
>
> Subject: Bug in Berkeley DB 1.85
> Newsgroups: perl.porters-gw
> Date: Mon, 25 Nov 1996 13:00:02 -0800
> From: jon@sems.com (Jonathan Biggar)
>
> I thought some of you might be interested in this bug+patch I found
> in Berkeley DB v1.85 using the hash mode.
>
> The bug symptoms are if you store a large value in the database (where
> large means larger than the database page size), and then replace
> it will a value that is smaller than the page size, then the key for
> this value can grow in length by one as stored in the database.  This
> causes future lookups for the value to fail, and sequential access of
> the database to return a key that was never inserted into the database.
>
> This is caused by an off by one error when removing the old value from the
> database before inserting the new value.  I caught this by comparing the
> cleanup code patched below with the PAGE_INIT macro defined in hash_page.c.
>
> Jon
>
> Here is the patch:
>
>
> *** hash_bigkey.c.orig   Fri Jun 24 08:12:30 1994
> --- hash_bigkey.c        Sat Nov 23 11:08:52 1996
> ***************
> *** 244,250 ****
>          n -= 2;
>          bp[0] = n;
>          FREESPACE(bp) = hashp->BSIZE - PAGE_META(n);
> !        OFFSET(bp) = hashp->BSIZE - 1;
>
>          bufp->flags |= BUF_MOD;
>          if (rbufp)
> --- 244,250 ----
>          n -= 2;
>          bp[0] = n;
>          FREESPACE(bp) = hashp->BSIZE - PAGE_META(n);
> !        OFFSET(bp) = hashp->BSIZE;
>
>          bufp->flags |= BUF_MOD;
>          if (rbufp)