[Zope3-Users] zql

[Andreas Jung]

--On 23. April 2006 14:57:52 -0400 Pete Taylor <baldtrol at gmail.com> wrote:

> hmmm...  i don't guess i disagree with those contentions directly, as
> they apply to sql.  but i do think that a query language of some kind
> for the zodb would be beneficial.  i have already encounted user-realm
> questions on applications i've built that would be more easily
> answered with a query language, rather than specific python scripts or
> catalogs.  the trouble with catalogs is that until you know you're
> going to want to index on and query certain information, you probably
> won't build an index for it in the catalog...  and it's a non-trivial
> amount of work to make querying the zodb, even with hurry.query, work
> the right way.

In reality you don't want to search inside a RDBMS for unindexed data
for performance reasons. This is even more true for Zope since you have to 
read all data of the ZODB..this will be totally inefficient especially
for large installations. Zope object can be very complex: attributes can be
basic Python types, Zope BTrees, hierarchial data etc...how will you define
a query language that covers all use cases? In Zope 2 we have something 
like AdvancedQuery to specify almost generic queries for the ZCatalog..I 
think hurry was inspired by AdvancedQuery. Of course you can define 
something that implements a particular subset of all possibile types and 
query types . But when it comes to the point where the functionality is too 
limited you end up writing you queries based on the functionality the core 
engine gives you.

-aj


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