[Zope3-dev] Queries (was Re: personal conceptual questions)

[Jeffrey P Shell]

Whee!  Happy to pop back in for a moment.  I'll try to find time to 
follow up on all the relations discussions because I still find myself 
caring about that a lot.  Queries are the other big thing.

I really like the concept of APE, but found that I couldn't use it with 
my existing database application (instead, I'm ending up with something 
that's halfway between APE and Modeling, using a lot of Table Gateway 
pattern based objects).  The main reason that I couldn't go with APE 
was that I couldn't find an easy way to pull objects out of a 
relational storage (since APE is so transparent) according to a set of 
criteria, such as "Get me all Shows between May 5 2003 and June 6 
2003".  If I had written the application for Zope, I would have had one 
or more catalogs that I could query with the catalog query language.  
But since it's in an RDBMS, I already have this all set up with SQL.

What would be nice is to be able to have some sort of query language 
that could go down closer to the storage level and not the application 
level (where catalog is).  This would make working with and querying 
other storage types easier.

The Modeling framework (an Enterprise Objects Framework inspired O-R 
framework for Python) has fetch specifications:

     from Modeling.FetchSpecification import FetchSpecification
     from Modeling.Qualifier import qualifierWithQualifierFormat

     qualifier=qualifierWithQualifierFormat('lastName=="Hugo"')
     fetchSpec=FetchSpecification(entityName='Writer', 
qualifier=qualifier)
     objects=ec.objectsWithFetchSpecification(fetchSpec)

http://modeling.sourceforge.net/UserGuide/ec-simple-fetch.html

It can even do complex queries like:

qual=qualifierWithQualifierFormat('author.pygmalion.lastName 
caseInsensitiveLike 'r*')
fetchSpec=FetchSpecification(entityName='Book', qualifier=qual)
objects=ec.objectsWithFetchSpecification(fetchSpec)

Which generates SQL like:
SELECT t0.id, t0.title, t0.FK_WRITER_ID, t0.PRICE
FROM BOOK t0
   INNER JOIN  ( WRITER t1
                 INNER JOIN WRITER t2
                 ON t1.FK_WRITER_ID=t2.ID )
   ON t0.FK_WRITER_ID=t1.ID
WHERE t2.LAST_NAME LIKE 'R%'

http://modeling.sourceforge.net/UserGuide/node54.html

This returns book objects, but based on the value of a sub-subobject's 
attribute match of the query.

I'd be happy with something like this that could query ZODB, and could 
query other storages (via APE or something else) in the same manner.  
Not sure if it can happen, but it's another little dream of mine.  
Another dream I have no time to do anything about.