[WIP][PATCH] GUID index for LDB

[Andrew Bartlett]

On Tue, 2017-08-15 at 10:55 +0200, Volker Lendecke wrote:
> On Tue, Aug 15, 2017 at 08:21:25PM +1200, Andrew Bartlett via samba-technical wrote:
> > This is a heads-up about a work I have in progress.
> 
> When doing format changes I'd recommend taking a look at Chapter 7 of
> http://shop.oreilly.com/product/0636920023913.do which has a hint how
> stuff might be stored in AD. Also, when talking to Metze I learn that
> there are some optimizations possible in the way we store attributes.
> 
> The problem with format changes is that any time we do that we have to
> be backwards compatible and have upgrade code. Just take a look at
> pdb_tdb.c. We should be careful to not accumulate too much of those
> versions, so some good consideration is due here I guess.

I do agree.  It would be the hight of irony if ldb, designed in
response to the inflexibility of tdb_pack based formats, was caught
needing multiple version upgrade handlers.

Thankfully in this case I confine myself to the index code and index
records.  The actual packed objects are not changed.  An upgrade will
trigger a re-index without changing the objects, and a downgrade will
(when I'm finished) simply detect a corrupt index and fall back to a
full scan and then re-index.

I'll write more of a compare and contrast with AD and OpenLDAP when I
get a working prototype, but I do hope this will be a practical and
useful incremental change. 

(Previous research by Garming has showed that for performance we do
need to change the packed objects, at least by sorting them, but
thankfully that is not required to take on these changes.)

Thanks!

Andrew Bartlett
-- 
Andrew Bartlett
https://samba.org/~abartlet/
Authentication Developer, Samba Team         https://samba.org
Samba Development and Support, Catalyst IT   
https://catalyst.net.nz/services/samba