[elephant-devel] garbage collection

[Ian Eslick]

Dmitri,

The latest version in CVS does export a compact function that works  
on BDB stores, but it only truncates the end of the %ELEPHANT file  
and isn't very reliable because if you haven't dropped the last  
object added then it can't truncate at all.

If you do drop objects, BDB should reuse the pages that were  
allocated to those objects so it should grow more slowly, but it  
doesn't reorganize to optimize space so fragmentation can lead to an  
inefficient use of space.

However, the best way to reclaim disk space today is to migrate from  
your current BDB store to a new one.  This will copy over only those  
objects that are globally reachable; namely anything reachable from  
the controller-root and all indexed instances.

At some point I'll finish a wrapper function for this (currently a  
sketch is in src/elephant/gc.lisp and called via elephant::stop-and- 
copy-gc) but you are better off doing the copy manually for now.

If the documentation doesn't make this process clear, please write  
back to us.

Good luck,
Ian


On Jul 10, 2007, at 7:19 PM, Dmitri V. Gorbatovsky wrote:

> Hello, from grateful user.
> I find that size of %ELEPHANT file (BDB) only grows with
> time and transactions. No matter how many objects I delete.
> Is there are any conventional way to shrink it?
> Sorry if the question is stupid, Iam not really advanced
> in Berkeley db usage.
>
> Thanks, DG
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