Re: Migrating to BTrees 4.x

On 1/5/17 11:18 AM, Jim Fulton wrote:
>
>
> On Thu, Jan 5, 2017 at 1:11 PM, David Glick (Glick Software) 
> <[email protected] <mailto:[email protected]>> wrote:
>
>     On 1/5/17 10:01 AM, Jim Fulton wrote:
>
>         So, now the problem will move up through the application stack. :)
>
>         And perhaps become harder.
>
>         But surely people have built apps with BTrees 4, because
>         BTrees 4 was released a loooooooong time ago (late 2012), and
>         this seatbelt was introduced in BTrees 4.0.
>
>         When indexing content, you will very often encounter content
>         without a value set, typically defaulting to None.
>
>         When such values are indexed, you'll get an error.  I don't
>         see any guard against this error in, for example, zope.index.
>
>         Have people built newer apps with indexing on BTrees 4? If so,
>         how have you dealt with this issue?
>
>     Thanks for the release.
>
>     Products.ZCatalog was updated some time ago to work with BTrees 4.
>     It explictly checks for None and silently skips indexing it, to
>     avoid erroring in that scenario:
>     https://github.com/zopefoundation/Products.ZCatalog/blob/master/src/Products/PluginIndexes/unindex.py#L246
>     <https://github.com/zopefoundation/Products.ZCatalog/blob/master/src/Products/PluginIndexes/unindex.py#L246>
>
>
>
> Thanks David (and Hanno).
>
> Good to know. It's sad that zope.index hasn't gotten a fix.
>
> In Postgres (and I assume other RDBMSs), you can specify how nulls are 
> handled, so null values are still handled.
>
> I wonder if that's something that should be done here as well.  That 
> is, I wonder if indexes should have some special None accommodation.

It certainly seems like a valid use case to support querying for items 
that don't have a value set. That could be done by storing a separate 
treeset of ids with no value, outside the BTree, of course.

-- 
You received this message because you are subscribed to the Google Groups "zodb" group.
To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
For more options, visit https://groups.google.com/d/optout.