starting to write the QuerySet class

cqlengine/exceptions.py

@@ -1,4 +1,6 @@
 #cqlengine exceptions
-class ModelException(BaseException): pass
-class ValidationError(BaseException): pass
+class CQLEngineException(BaseException): pass
+class ModelException(CQLEngineException): pass
+class ValidationError(CQLEngineException): pass
 
+class QueryException(CQLEngineException): pass

cqlengine/query.py

@@ -1,18 +1,58 @@
+from collections import namedtuple
 import copy
 
 from cqlengine.connection import get_connection
+from cqlengine.exceptions import QueryException
 
 #CQL 3 reference:
 #http://www.datastax.com/docs/1.1/references/cql/index
 
-class Query(object):
+WhereFilter = namedtuple('WhereFilter', ['column', 'operator', 'value'])
 
-    pass
+class QueryOperatorException(QueryException): pass
+
+class QueryOperator(object):
+    symbol = None
+
+    @classmethod
+    def get_operator(cls, symbol):
+        if not hasattr(cls, 'opmap'):
+            QueryOperator.opmap = {}
+            def _recurse(klass):
+                if klass.symbol:
+                    QueryOperator.opmap[klass.symbol.upper()] = klass
+                for subklass in klass.__subclasses__():
+                    _recurse(subklass)
+                pass
+            _recurse(QueryOperator)
+        try:
+            return QueryOperator.opmap[symbol.upper()]
+        except KeyError:
+            raise QueryOperatorException("{} doesn't map to a QueryOperator".format(symbol))
+
+class EqualsOperator(QueryOperator):
+    symbol = 'EQ'
+
+class InOperator(QueryOperator):
+    symbol = 'IN'
+
+class GreaterThanOperator(QueryOperator):
+    symbol = "GT"
+
+class GreaterThanOrEqualOperator(QueryOperator):
+    symbol = "GTE"
+
+class LessThanOperator(QueryOperator):
+    symbol = "LT"
+
+class LessThanOrEqualOperator(QueryOperator):
+    symbol = "LTE"
 
 class QuerySet(object):
     #TODO: querysets should be immutable
     #TODO: querysets should be executed lazily
-    #TODO: conflicting filter args should raise exception unless a force kwarg is supplied
+    #TODO: support specifying offset and limit (use slice) (maybe return a mutated queryset)
+    #TODO: support specifying columns to exclude or select only
 
     #CQL supports ==, >, >=, <, <=, IN (a,b,c,..n)
     #REVERSE, LIMIT
@@ -21,9 +61,22 @@ class QuerySet(object):
     def __init__(self, model, query_args={}):
         super(QuerySet, self).__init__()
         self.model = model
-        self.query_args = query_args
         self.column_family_name = self.model.objects.column_family_name
 
+        #Where clause filters
+        self._where = []
+
+        #ordering arguments
+        self._order = []
+
+        #subset selection
+        self._limit = None
+        self._start = None
+
+        #see the defer and only methods
+        self._defer_fields = []
+        self._only_fields = []
+
         self._cursor = None
 
     #----query generation / execution----
@@ -31,7 +84,16 @@ class QuerySet(object):
         conn = get_connection()
         self._cursor = conn.cursor()
 
-    def _generate_querystring(self):
+    def _where_clause(self):
+        """
+        Returns a where clause based on the given filter args
+        """
+        pass
+
+    def _select_query(self):
+        """
+        Returns a select clause based on the given filter args
+        """
         pass
 
     @property
@@ -67,16 +129,36 @@ class QuerySet(object):
         pass
 
     def all(self):
-        return QuerySet(self.model)
+        clone = copy.deepcopy(self)
+        clone._where = []
+        return clone
+
+    def _parse_filter_arg(self, arg, val):
+        statement = arg.split('__')
+        if len(statement) == 1:
+            return WhereFilter(arg, None, val)
+        elif len(statement) == 2:
+            return WhereFilter(statement[0], statement[1], val)
+        else:
+            raise QueryException("Can't parse '{}'".format(arg))
 
     def filter(self, **kwargs):
-        qargs = copy.deepcopy(self.query_args)
-        qargs.update(kwargs)
-        return QuerySet(self.model, query_args=qargs)
+        #add arguments to the where clause filters
+        clone = copy.deepcopy(self)
+        for arg, val in kwargs.items():
+            raw_statement = self._parse_filter_arg(arg, val)
+            #resolve column and operator
+            try:
+                column = self.model._columns[raw_statement.column]
+            except KeyError:
+                raise QueryException("Can't resolve column name: '{}'".format(raw_statement.column))
 
-    def exclude(self, **kwargs):
-        """ Need to invert the logic for all kwargs """
-        pass
+            operator = QueryOperator.get_operator(raw_statement.operator)
+
+            statement = WhereFilter(column, operator, val)
+            clone._where.append(statement)
+
+        return clone
 
     def count(self):
         """ Returns the number of rows matched by this query """
@@ -95,6 +177,32 @@ class QuerySet(object):
         self._cursor.execute(qs, {self.model._pk_name:pk})
         return self._get_next()
 
+    def _only_or_defer(self, action, fields):
+        clone = copy.deepcopy(self)
+        if clone._defer_fields or clone._only_fields:
+            raise QueryException("QuerySet alread has only or defer fields defined")
+
+        #check for strange fields
+        missing_fields = [f for f in fields if f not in self.model._columns.keys()]
+        if missing_fields:
+            raise QueryException("Can't resolve fields {} in {}".format(', '.join(missing_fields), self.model.__name__))
+
+        if action == 'defer':
+            clone._defer_fields = fields
+        elif action == 'only':
+            clone._only_fields = fields
+        else:
+            raise ValueError
+
+        return clone
+
+    def only(self, fields):
+        """ Load only these fields for the returned query """
+        return self._only_or_defer('only', fields)
+
+    def defer(self, fields):
+        """ Don't load these fields for the returned query """
+        return self._only_or_defer('defer', fields)
 
     #----writes----
     def save(self, instance):
@@ -137,7 +245,7 @@ class QuerySet(object):
         cur.execute(qs, field_values)
 
     #----delete---
-    def delete(self):
+    def delete(self, columns=[]):
         """
         Deletes the contents of a query
         """

cqlengine/tests/query/test_queryset.py

@@ -0,0 +1,52 @@
+from cqlengine.tests.base import BaseCassEngTestCase
+
+from cqlengine.exceptions import ModelException
+from cqlengine.models import Model
+from cqlengine import columns
+
+class TestQuerySet(BaseCassEngTestCase):
+
+    def test_query_filter_parsing(self):
+        """
+        Tests the queryset filter method
+        """
+
+    def test_where_clause_generation(self):
+        """
+        Tests the where clause creation
+        """
+
+    def test_querystring_generation(self):
+        """
+        Tests the select querystring creation
+        """
+
+    def test_queryset_is_immutable(self):
+        """
+        Tests that calling a queryset function that changes it's state returns a new queryset
+        """
+
+    def test_queryset_slicing(self):
+        """
+        Check that the limit and start is implemented as iterator slices
+        """
+
+    def test_proper_delete_behavior(self):
+        """
+        Tests that deleting the contents of a queryset works properly
+        """
+
+    def test_the_all_method_clears_where_filter(self):
+        """
+        Tests that calling all on a queryset with previously defined filters returns a queryset with no filters
+        """
+
+    def test_defining_only_and_defer_fails(self):
+        """
+        Tests that trying to add fields to either only or defer, or doing so more than once fails
+        """
+
+    def test_defining_only_or_defer_fields_fails(self):
+        """
+        Tests that setting only or defer fields that don't exist raises an exception
+        """