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From Stefan Seelmann <seelm...@apache.org>
Subject Re: Alias cycle detection
Date Tue, 14 Jun 2011 13:26:05 GMT
On Tue, Jun 14, 2011 at 2:29 PM, Emmanuel L├ęcharny <elecharny@apache.org> wrote:
> On 6/13/11 11:19 PM, Stefan Seelmann wrote:
>>>>
>>>> It's actually quite simple and quite fast. Using the objectclass index
>>>> it's trivial to obtain the list of all alias entries within the
>>>> database, so
>>>> from the outset you already know the maximum size of what you're dealing
>>>> with.
>>>
>>> We already have a cache that is constructed at startup, gathering all the
>>> aliases from the backend, using the OC index. This cache is of course
>>> updated on the fly, if one alias is added or removed.
>>>
>>> I don't think it should take more than one day to fix this issue.
>>
>> In that case we can also get rid of all the alias indices (aliasIdx,
>> oneAliasIdx, subAliasIdx).
>
> Yes absolutely.
>
> There are a few steps we also have to fulfill :
> - create an Alias cache ( I thought we had one, but in fact, we have the
> opposite : a notAliasCache in the ExceptionInterceptor)

I wonder why we need an alias cache? For fast lookup of the search
base in case the "find" bit is set?

> - create an AliasInterceptor to manage the Add and Delete operations done on
> alias entries (and also move, rename and combined ops)

You mean that interceptor is used to update the cache, right?

> - modify the Search to handle a set of met aliases.

Yep.

> I'll proceed by creating the alias interceptor first, and Ill remove the
> part that handle Aliases in ExceptionInterceptor
>
> The Alias index removal will be done at the end.

Ok.


Two other issues I see with the new algorighm:
- It is efficient if there are only few aliases. But if a user adds
million of alias entries we may get a memory problem. I just want to
mention that to make clear that such an issue may occur. I don't think
it makes sense to create so many alias entries, but I saw an example
where group membership was implemented using aliases...
- It is possible that duplicates occur, for example if an alias
enlarges the initial search scope by pointing to a parent of the
initial search base. I think duplicates can be avoided by tracking
each search base and filter result enties within already processed
search bases.

Kind Regards,
Stefan

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