gocept.objectquery 0.1b1

A framework for indexing and querying the ZODB

Some example usecases

Root joins:

>>> r = query('/PersistentList/Library')
>>> sorted(elem.location for elem in r)
['Berlin', 'Chester', 'Halle']

Search for the authors of all Books named "Faust":

>>> r = query('/PersistentList/Library/Book[@title="Faust"]/Person')
>>> sorted(elem.name for elem in r)
['Johann Wolfgang von Goethe']

Search for all books written after year 2000:

>>> r = query('/PersistentList/Library/Book[@written>=2000]')
>>> len(r)
3
>>> pprint(sorted(elem.title for elem in r))
['Farm der Tiere',
'Plone-Benutzerhandbuch',
'Web Component Development with Zope 3']

Search for all authors of books written after year 2000:

>>> r = query('/PersistentList/Library/Book[@written>=2000]/Person')
>>> len(r)
3
>>> pprint(sorted(elem.name for elem in r))
['George Orwell', 'Philipp von Weitershausen', 'Thomas Lotze']

Search for all Books, that have are located in Halle and have been written in 2007:

>>> r = query('/PersistentList/Library[@location="Halle"]/Book[@written==2007]')
>>> sorted((elem.title, elem.isbn) for elem in r)
[('Web Component Development with Zope 3', 3540338071L)]

Handle Wildcards correctly:

>>> r = query('/PersistentList/Library/_/Person')
>>> pprint(sorted(elem.name for elem in r))
['George Orwell',
'Johann Wolfgang von Goethe',
'Philipp von Weitershausen',
'Thomas Lotze']

Instead of only providing the classname, it is also possible to provide the class with its full module:

>>> r = query('/PersistentList/gocept.objectquery.tests.objects.Library')
>>> pprint([library.location for library in r])
['Halle', 'Berlin', 'Chester']
>>> query('/PersistentList/gocept.objectquery.tests.objects2.Library')
[]

What about precedence:

>>> r = query('/PersistentList/Library[@location="Halle"]/Book/Person')
>>> pprint(sorted(elem.name for elem in r))
['George Orwell', 'Philipp von Weitershausen', 'Thomas Lotze']

>>> r = query('(/PersistentList/Library[@location="Halle"]/Book)/Person')
>>> pprint(sorted(elem.name for elem in r))
['George Orwell', 'Philipp von Weitershausen', 'Thomas Lotze']

>>> r = query('/PersistentList/Library[@location="Halle"]/(Book/Person)')
>>> len(r)
0
>>> r = query('(/PersistentList/Library/Book[@title="Faust"])/(Book/Person)')
>>> sorted(elem.name for elem in r)
['Johann Wolfgang von Goethe']

But pay attention. If you change the query from .."]/(Book.. to .."](/Book.. you get an Library-Result with location in "Halle". This is, because the subquery (in brakets) returns no results:

>>> r = query('/PersistentList/Library[@location="Halle"](/Book/Person)')
>>> len(r)
1
>>> r[0].location
'Halle'

Unions:

>>> r = query('(/PersistentList/Library[@location="Halle"])|(Book/Person)')
>>> len(r)
5
>>> pprint(sorted(elem for elem in r))
[<gocept.objectquery.tests.objects.Library object at 0x...>,
<gocept.objectquery.tests.objects.Person object at 0x...>,
<gocept.objectquery.tests.objects.Person object at 0x...>,
<gocept.objectquery.tests.objects.Person object at 0x...>,
<gocept.objectquery.tests.objects.Person object at 0x...>]

>>> r = query('(/PersistentList/Library)|(Book[@written=1990])')
>>> len(r)
4
>>> pprint(sorted(elem for elem in r))
[<gocept.objectquery.tests.objects.Book object at 0x...>,
<gocept.objectquery.tests.objects.Library object at 0x...>,
<gocept.objectquery.tests.objects.Library object at 0x...>,
<gocept.objectquery.tests.objects.Library object at 0x...>]

>>> transaction.commit()

Kleene Closure

First we need a new database:

>>> doc1 = Document()
>>> doc2 = Document()
>>> doc3 = Document()
>>> fol4 = Folder([doc2])
>>> fol3 = Folder([doc1])
>>> fol2 = Folder([fol3])
>>> fol1 = Folder([fol2])
>>> plo1 = Plone([fol1, fol4, doc3])
>>> root = Root([plo1])

>>> dbroot['test'] = root
>>> transaction.commit()

Now there should be one Plone object under root:

>>> r = query('/Root/Plone')
>>> len(r) == 1 and r[0] == plo1
True

>>> r = query('/Root/Plone/Folder/Document')
>>> len(r)
1
>>> r[0] == doc2
True

Get all Documents which are under any number of Folders:

>>> r = query('/Root/Plone/Folder*/Document')
>>> r[0] != r[1] != r[2] and isinstance(r[0], Document)
True

>>> r = query('Plone/Folder*/Document')
>>> r[0] != r[1] != r[2] and isinstance(r[0], Document)
True

>>> r = query('Folder*/Document')
>>> r[0] != r[1] != r[2] and isinstance(r[0], Document)
True

Get all Documents which are under one or zero number of Folders:

>>> r = query('/Root/Plone/Folder?/Document')
>>> len(r) == 2 and (r[0] == doc2 or r[1] == doc2) and (r[0] == doc3 or r[1] == doc3) and r[0] != r[1]
True

>>> r = query('Folder?/Document')
>>> len(r) == 3 and r[0] != r[1] != r[2]
True

Get all Documents which are under one or more number of Folders:

>>> r = query('/Root/Plone/Folder+/Document')
>>> len(r) == 2 and (r[0] == doc1 or r[1] == doc1) and (r[0] == doc2 or r[1] == doc2) and r[0] != r[1]
True

>>> r = query('Folder+/Document')
>>> len(r) == 2 and (r[0] == doc1 or r[1] == doc1) and (r[0] == doc2 or r[1] == doc2) and r[0] != r[1]
True

You may also query absolute path lengths:

>>> len(query('Plone/Document'))
1
>>> len(query('Plone/Folder/Document'))
1
>>> len(query('Plone/Folder/Folder/Document'))
0
>>> len(query('Plone/Folder/Folder/Folder/Document'))
1

Furthermore, it is possible to query all Documents, which are located under 2 or more Folders:

>>> r = query('Plone/Folder+/Folder/Document')
>>> len(r) == 1 and r[0] == doc1
True

>>> r = query('Plone/Folder/Folder+/Document')
>>> len(r) == 1 and r[0] == doc1
True

A special case is the combination of wildcard and '*' closure:

>>> r = query('Plone/_*/Document')
>>> len(r) == 3
True