Re: Issues arising from creating powerdns backend based on LMDB

[Mark Zealey <spam@markandruth.co.uk>]

On 23/08/13 17:08, Howard Chu wrote:
> Mark Zealey wrote:
> > > > I've found another weird - I have now converted the database to use
> > > > duplicates. Typically when I do mdb_cursor_get(... MDB_NEXT ) it will
> > > > set the key and value but I've found 1 place so far where I do it 
> > > > and on
> > > > the duplicate's second entry the value is set but the key is empty.
> > >
> > > I don't see how this can happen; the only time we don't return the key
> > > is if some operation actually failed. Can you send test code to
> > > reproduce this?
> >
> > Attached .c shows it - create 3 keys with 5 entries under each. Actually
> > my report was incorrect - cursor_get() with MDB_NEXT or MDB_NEXT_DUP
> > never seems to set the key unless it is the first entry read... Perhaps
> > this is intended?!
>
> Yes and no. It was intended for NEXT_DUP because, since it's a 
> duplicate, you already know what the key is. It is unintended for 
> NEXT, for the opposite reason, and in this case it's a bug.

It would be nice to have it for NEXT_DUP as well to be honest - I have a 
function that gets called for each record and it would be good not have 
to save state between calls.

Mark