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From Emmanuel Lécharny <elecha...@gmail.com>
Subject Re: [ApacheDS] how can a partition return more than one result ?
Date Fri, 08 Jun 2012 11:58:17 GMT
Le 6/8/12 1:49 PM, Garbage a écrit :
> I learned a lot about the implementation of custom partitions and see the changes in
the API from search and lookup returning an Entry in 1.5.x and an EntryFilteringCursor later
on.
> I even was able to change an existing partition (shame on me: based on the 1.5.5 example,
but I will switch to 2.0 soon) in a way that lets it return a fake group object that was created
in my custom POJO.
>
> But I am only able to return ONE entry, I didn't find or understand the concept how MULTIPLE
entries can be returned. Can someone show me the right direction ?
The idea is to use a Cursor that maps around the partition and fetch the 
entries one by one.

The way the server works is that based on your filter, you select the 
right index to use to fetch the entries. There are may possibilities here :
- first, you may have to do a full scan (the filter is not selective 
enough, for instance). In this case, you don't use any index, you just 
use the MasterTable to get the entries. Now, for each entry you fetch, 
you'll have to filter them to see if it's a valid entry - or not.
- or you can select an index. You will fetch the index elements, and for 
each of them, fetch the associated entry.  Once done, you can check 
against the filter if the entry is valid - or not

In any case, the cursor is your friend here : it maps the next() 
operation on top of your index.

Now, if your Partition is a Btree, it's easier, as the 
AbstractBTreePartition class already handles everyting for you. If you 
don't inherit from this Abstract class, then it's way more complicated. 
I'll suggest you have a look at the AbstractBTreePartition to get a clue 
about how we process a search over a BTree based partition.

-- 
Regards,
Cordialement,
Emmanuel Lécharny
www.iktek.com


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