[tpop3d-discuss] DBM file authenticator (was: mailspool_save_index() using STDIO)

[Chris Lightfoot]

On Mon, Jul 01, 2002 at 09:05:45PM +0100, Chris Elsworth wrote:
> On Mon, Jul 01, 2002 at 06:14:46PM +0100, Chris Lightfoot wrote:
> > On Mon, Jul 01, 2002 at 03:14:58PM +0100, Chris Elsworth wrote:
> > > 
> > > Ok, understood.. unrelated note.. has there been much call for a
> > > dbmfile authenticator? It would be very easy to replicate most of the
> > > flatfile authenticator, but simply checking a dbm file instead in the
> > > interest of speed where there are thousands of entries. If that would
> > > be welcome, I'll work on that..
> > 
> > Well... dbm files are particularly easy to do in perl.
> > Unless there's a really good reason, I'd have thought that
> > perl is a better option for it.
> 
> Just the one word required.. speed? :)

I'd be interested to see some bench marks. Sure the C one
will be faster, but by how much? Against this there's the
issue that you have to figure out which DBM driver to use.
(Not quite as bad as the RDBMS situation, but not great.)
You've got, at least,

    dbm, ndbm, gdbm, new Berkeley (SleepyCat) db, cdb

-- some of these are intercompatible (e.g. gdbm and ndbm)
but even so....

NB http://cr.yp.to/cdb.html if you have not seen it
before. There is (GPL) code in Exim to do the lookups with
mmap, which is probably the right way to go since tpop3d
doesn't run on systems without mmap anyway.

I was intrigued to see on the Bernstein page above a thing
called rdbm, which is designed as a sort of journalled
version of cdb. Apparently (see its page) it's horribly
broken, but a good idea nonetheless.

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