On Tue, Aug 16, 2011 at 10:53 AM, Emmanuel Lécharny <email@example.com>
On 8/15/11 5:59 PM, Stefan Seelmann wrote:
Some toughts about this one-level/sub-level index.
Now I have to update the parts that are a bit special, let me explain:
In HBase partition I didn't use one-level and sub-level indices, but
use the RDN index table instead. I also extended the search engine in
that way that one-level and sub-level cursors get the search filter in
order to perform filtering within the store instead of returning all
candidates and evaluate them.
Using the Rdn index makes perfect sense : we have the Rdn -> parent relation plus the parent -> children relation in this index, so there is no need to have a one level index (all the children are already listed in the RDN index for a specific entry). I'm a bit more concerned about the sub-level processing : we have to recurse on all the children to get all the candidates. That's fine, we can easily implement that (and you already did), but what concerns me is that we don't have the count of all the entries, we will have to compute them. This count is necessary in the search engine to select the index we will use to walk the entries.
One solution would be to store two more elements in the ParentIdAndRdn data structure : the number of children directly below the RDN, and the number of children and descendant. That would probably solve the issue I'm mentioning. Of course, that also means we wil have to update all the RDN hierarchy from top to bottom (but affecting only the RDN part of the entry DN) each time we add/move/delete an entry. Note that we already do that for the oneLevel and Sublevel index.
Good idea Emmanuel.
This would be a neat solution to handling the sub level count problem. Let's experiment with this and see if it does intact lead to a speedup which I think it should but it's good to just see. I wish we had a nice lab for this.
Also we need to update the docs a bit to show all the changes that took place. We still show the old upon and ndn indices of old. Something at the heart of the server like this should always be in sync with the documentation.