[Zope-dev] Sorting for zope.index

[Chris McDonough]

Chris McDonough wrote:
> Dan Korostelev wrote:
>> 2008/12/27 Chris McDonough <chrism at plope.com>:
>>> Dan Korostelev wrote:
>>>> I also made an implementation for the FieldIndex that may not be too
>>>> optimal, but I'm currently most interested in clean and universal
>>>> IIndexSort definition that any index could efficiently implement.
>>> I've done this work too... but outside zope.index... please see (for example):
>>>
>>> http://svn.repoze.org/repoze.catalog/trunk/repoze/catalog/indexes/field.py
>>>
>>> It's reasonably optimized.
>> Thanks for the point. That's something I was going to write to add
>> optimizations for FieldIndex sorting, now I only need to adapt your
>> code and that's great! :-)
> 
> There are many tests in there too.  Note that the algorithms came mostly from
> the Zope 2 Catalog code.  The only things I'm less than sure about in there is:
> 
> - the computation of when to use n-best and lazy (there are constants in there
>   stolen from Zope 2).
> 
> - The fact that when we need to sort in reverse order we can't be lazy.
>   I.e. in the branch that reads:
> 
>      # If the result set is not much larger than the number
>      # of documents in this index, or if we need to sort in
>      # reverse order, use a non-lazy sort.
> 
>   BTree values can't be iterated in reverse order, that's why we don't try
>   the lazy case here if it's a reverse sort.  There may be a better way to
>   do this.
> 
> 
>> However, the more important thing for now is the IIndexSort interface
>> declaration. Is it okay and fits any possible sortable index? ;-)
>>
> 
> It looks like we came up with the same interface independently; I think that's a
> good sign.

One difference is that the repoze.catalog implementation skips docids that
aren't in the index rather than raising a KeyError.  I think I like the KeyError
better.

> 
> - C
>