[ZODB-Dev] create unique container keys

[Jim Fulton]

On Apr 2, 2009, at 4:19 AM, Adam GROSZER wrote:

> Hello,
>
> What's a good practice to create unique container keys for a heavily
> loaded application? (I mean lots of writes to the same container)
> Obviously having a counter on the container and incrementing and using
> that for key gives write conflicts.
>
> What do the experts use?


Assuming that ordering of the keys isn't important, my favorite  
strategy is to:

- use integer keys, which saves memory and makes lookup faster if you  
use an IOBTree.
- assign keys sequentially with random starting points, using a _v_  
variable to keep track of the index. The idea is that instances in  
separate threads/processes use different random starting points, to  
avoid conflicts, but assign keys sequentially to update the btree  
efficiently.

See for example _generateId in:
http://svn.zope.org/zope.intid/trunk/src/zope/intid/__init__.py?rev=95793&view=auto

Jim

--
Jim Fulton
Zope Corporation