Fixed #11863: added a `Model.objects.raw()` method for executing raw SQL queries and yield models.

See `docs/topics/db/raw.txt` for details.

Thanks to seanoc for getting the ball rolling, and to Russ for wrapping things up.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@11921 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/manager.py

@@ -1,5 +1,5 @@
 import django.utils.copycompat as copy
-from django.db.models.query import QuerySet, EmptyQuerySet, insert_query
+from django.db.models.query import QuerySet, EmptyQuerySet, insert_query, RawQuerySet
 from django.db.models import signals
 from django.db.models.fields import FieldDoesNotExist
 
@@ -181,6 +181,9 @@ class Manager(object):
     def _update(self, values, **kwargs):
         return self.get_query_set()._update(values, **kwargs)
 
+    def raw(self, query, params=None, *args, **kwargs):
+        return RawQuerySet(model=self.model, query=query, params=params, *args, **kwargs)
+
 class ManagerDescriptor(object):
     # This class ensures managers aren't accessible via model instances.
     # For example, Poll.objects works, but poll_obj.objects raises AttributeError.

django/db/models/query.py

@@ -5,7 +5,7 @@ The main QuerySet implementation. This provides the public API for the ORM.
 from django.db import connection, transaction, IntegrityError
 from django.db.models.aggregates import Aggregate
 from django.db.models.fields import DateField
-from django.db.models.query_utils import Q, select_related_descend, CollectedObjects, CyclicDependency, deferred_class_factory
+from django.db.models.query_utils import Q, select_related_descend, CollectedObjects, CyclicDependency, deferred_class_factory, InvalidQuery
 from django.db.models import signals, sql
 from django.utils.copycompat import deepcopy
 
@@ -287,7 +287,7 @@ class QuerySet(object):
         Returns a dictionary containing the calculations (aggregation)
         over the current queryset
 
-        If args is present the expression is passed as a kwarg ussing
+        If args is present the expression is passed as a kwarg using
         the Aggregate object's default alias.
         """
         for arg in args:
@@ -1107,6 +1107,89 @@ def delete_objects(seen_objs):
         if forced_managed:
             transaction.leave_transaction_management()
 
+class RawQuerySet(object):
+    """
+    Provides an iterator which converts the results of raw SQL queries into
+    annotated model instances.
+    """
+    def __init__(self, query, model=None, query_obj=None, params=None, translations=None):
+        self.model = model
+        self.query = query_obj or sql.RawQuery(sql=query, connection=connection, params=params)
+        self.params = params or ()
+        self.translations = translations or {}
+
+    def __iter__(self):
+        for row in self.query:
+            yield self.transform_results(row)
+
+    def __repr__(self):
+        return "<RawQuerySet: %r>" % (self.query.sql % self.params)
+
+    @property
+    def columns(self):
+        """
+        A list of model field names in the order they'll appear in the
+        query results.
+        """
+        if not hasattr(self, '_columns'):
+            self._columns = self.query.get_columns()
+
+            # Adjust any column names which don't match field names
+            for (query_name, model_name) in self.translations.items():
+                try:
+                    index = self._columns.index(query_name)
+                    self._columns[index] = model_name
+                except ValueError:
+                    # Ignore translations for non-existant column names
+                    pass
+
+        return self._columns
+
+    @property
+    def model_fields(self):
+        """
+        A dict mapping column names to model field names.
+        """
+        if not hasattr(self, '_model_fields'):
+            self._model_fields = {}
+            for field in self.model._meta.fields:
+                name, column = field.get_attname_column()
+                self._model_fields[column] = name
+        return self._model_fields
+
+    def transform_results(self, values):
+        model_init_kwargs = {}
+        annotations = ()
+
+        # Associate fields to values
+        for pos, value in enumerate(values):
+            column = self.columns[pos]
+
+            # Separate properties from annotations
+            if column in self.model_fields.keys():
+                model_init_kwargs[self.model_fields[column]] = value
+            else:
+                annotations += (column, value),
+
+        # Construct model instance and apply annotations
+        skip = set()
+        for field in self.model._meta.fields:
+            if field.name not in model_init_kwargs.keys():
+                skip.add(field.attname)
+
+        if skip:
+            if self.model._meta.pk.attname in skip:
+                raise InvalidQuery('Raw query must include the primary key')
+            model_cls = deferred_class_factory(self.model, skip)
+        else:
+            model_cls = self.model
+
+        instance = model_cls(**model_init_kwargs)
+
+        for field, value in annotations:
+            setattr(instance, field, value)
+
+        return instance
 
 def insert_query(model, values, return_id=False, raw_values=False):
     """

django/db/models/query_utils.py

@@ -20,6 +20,13 @@ class CyclicDependency(Exception):
     """
     pass
 
+class InvalidQuery(Exception):
+    """
+    The query passed to raw isn't a safe query to use with raw.
+    """
+    pass
+
+
 class CollectedObjects(object):
     """
     A container that stores keys and lists of values along with remembering the

django/db/models/sql/query.py

@@ -15,7 +15,7 @@ from django.db.backends.util import truncate_name
 from django.db import connection
 from django.db.models import signals
 from django.db.models.fields import FieldDoesNotExist
-from django.db.models.query_utils import select_related_descend
+from django.db.models.query_utils import select_related_descend, InvalidQuery
 from django.db.models.sql import aggregates as base_aggregates_module
 from django.db.models.sql.expressions import SQLEvaluator
 from django.db.models.sql.where import WhereNode, Constraint, EverythingNode, AND, OR
@@ -23,7 +23,42 @@ from django.core.exceptions import FieldError
 from datastructures import EmptyResultSet, Empty, MultiJoin
 from constants import *
 
-__all__ = ['Query', 'BaseQuery']
+__all__ = ['Query', 'BaseQuery', 'RawQuery']
+
+class RawQuery(object):
+    """
+    A single raw SQL query
+    """
+
+    def __init__(self, sql, connection, params=None):
+        self.validate_sql(sql)
+        self.params = params or ()
+        self.sql = sql
+        self.connection = connection
+        self.cursor = None
+
+    def get_columns(self):
+        if self.cursor is None:
+            self._execute_query()
+        return [column_meta[0] for column_meta in self.cursor.description]
+
+    def validate_sql(self, sql):
+        if not sql.lower().strip().startswith('select'):
+            raise InvalidQuery('Raw queries are limited to SELECT queries. Use '
+                               'connection.cursor directly for types of queries.')
+
+    def __iter__(self):
+        # Always execute a new query for a new iterator.
+        # This could be optomized with a cache at the expense of RAM.
+        self._execute_query()
+        return self.cursor
+
+    def __repr__(self):
+        return "<RawQuery: %r>" % (self.sql % self.params)
+
+    def _execute_query(self):
+        self.cursor = self.connection.cursor()
+        self.cursor.execute(self.sql, self.params)
 
 class BaseQuery(object):
     """

docs/topics/db/queries.txt

@@ -1059,14 +1059,9 @@ Falling back to raw SQL
 =======================
 
 If you find yourself needing to write an SQL query that is too complex for
-Django's database-mapper to handle, you can fall back into raw-SQL statement
+Django's database-mapper to handle, you can fall back on writing SQL by hand.
-mode.
+Django has a couple of options for writing raw SQL queries; see
-
+:ref:`topics-db-sql`.
-The preferred way to do this is by giving your model custom methods or custom
-manager methods that execute queries. Although there's nothing in Django that
-*requires* database queries to live in the model layer, this approach keeps all
-your data-access logic in one place, which is smart from an code-organization
-standpoint. For instructions, see :ref:`topics-db-sql`.
 
 Finally, it's important to note that the Django database layer is merely an
 interface to your database. You can access your database via other tools,

docs/topics/db/sql.txt

@@ -1,10 +1,183 @@
 .. _topics-db-sql:
 
+==========================
 Performing raw SQL queries
 ==========================
 
-Feel free to write custom SQL statements in custom model methods and
+.. currentmodule:: django.db.models
-module-level methods. The object ``django.db.connection`` represents the
+
+When the :ref:`model query APIs <topics-db-queries>` don't go far enough, you
+can fall back to writing raw SQL. Django gives you two ways of performing raw
+SQL queries: you can use :meth:`Manager.raw()` to `perform raw queries and
+return model instances`__, or you can avoid the model layer entirely and
+`execute custom SQL directly`__.
+
+__ `performing raw queries`_
+__ `executing custom SQL directly`_
+
+Performing raw queries
+======================
+
+.. versionadded:: 1.2
+
+The ``raw()`` manager method can be used to perform raw SQL queries that
+return model instances:
+
+.. method:: Manager.raw(query, params=None, translations=None)
+
+This method method takes a raw SQL query, executes it, and returns model
+instances.
+
+This is best illustrated with an example. Suppose you've got the following model::
+
+    class Person(models.Model):
+        first_name = models.CharField(...)
+        last_name = models.CharField(...)
+        birth_date = models.DateField(...)
+
+You could then execute custom SQL like so::
+
+    >>> Person.objects.raw('SELECT * from myapp_person')
+    [<Person: John Doe>, <Person: Jane Doe>, ...]
+
+.. admonition:: Model table names
+
+    Where'd the name of the ``Person`` table come from in that example?
+
+    By default, Django figures out a database table name by joining the
+    model's "app label" -- the name you used in ``manage.py startapp`` -- to
+    the model's class name, with an underscore between them. In the example
+    we've assumed that the ``Person`` model lives in an app named ``myapp``,
+    so its table would be ``myapp_person``.
+
+    For more details check out the documentation for the
+    :attr:`~Options.db_table` option, which also lets you manually set the
+    database table name.
+
+Of course, this example isn't very exciting -- it's exactly the same as
+running ``Person.objects.all()``. However, ``raw()`` has a bunch of other
+options that make it very powerful.
+
+Mapping query fields to model fields
+------------------------------------
+
+``raw()`` automatically maps fields in the query to fields on the model.
+
+The order of fields in your query doesn't matter. In other words, both
+of the following queries work identically::
+
+    >>> Person.objects.raw('SELECT id, first_name, last_name, birth_date FROM myapp_person')
+    ...
+    >>> Person.objects.raw('SELECT last_name, birth_date, first_name, id FROM myapp_person')
+    ...
+
+Matching is done by name. This means that you can use SQL's ``AS`` clauses to
+map fields in the query to model fields. So if you had some other table that
+had ``Person`` data in it, you could easily map it into ``Person`` instances::
+
+    >>> Person.objects.raw('''SELECT first AS first_name,
+    ...                              last AS last_name,
+    ...                              bd AS birth_date,
+    ...                              pk as id,
+    ...                       FROM some_other_table)
+
+As long as the names match, the model instances will be created correctly.
+
+Alternatively, you can map fields in the query to model fields using the
+``translations`` argument to ``raw()``. This is a dictionary mapping names of
+fields in the query to names of fields on the model. For example, the above
+query could also be written::
+
+    >>> name_map = {'first': 'first_name', 'last': 'last_name', 'bd': 'birth_date', 'pk': 'id'}
+    >>> Person.objects.raw('SELECT * FROM some_other_table', translations=name_map)
+
+Deferring model fields
+----------------------
+
+Fields may also be left out::
+
+    >>> people = Person.objects.raw('SELECT id, first_name FROM myapp_person'):
+
+The ``Person`` objects returned by this query will be :ref:`deferred
+<queryset-defer>` model instances. This means that the fields that are omitted
+from the query will be loaded on demand. For example::
+
+    >>> for p in Person.objects.raw('SELECT id, first_name FROM myapp_person'):
+    ...     print p.first_name, # This will be retrieved by the original query
+    ...     print p.last_name # This will be retrieved on demand
+    ...
+    John Smith
+    Jane Jones
+
+From outward appearances, this looks like the query has retrieved both
+the first name and last name. However, this example actually issued 3
+queries. Only the first names were retrieved by the raw() query -- the
+last names were both retrieved on demand when they were printed.
+
+There is only one field that you can't leave out - the primary key
+field. Django uses the primary key to identify model instances, so it
+must always be included in a raw query. An ``InvalidQuery`` exception
+will be raised if you forget to include the primary key.
+
+Adding annotations
+------------------
+
+You can also execute queries containing fields that aren't defined on the
+model. For example, we could use `PostgreSQL's age() function`__ to get a list
+of people with their ages calculated by the database::
+
+    >>> people = Person.objects.raw('SELECT *, age(birth_date) AS age FROM myapp_person')
+    >>> for p in people:
+    ...   print "%s is %s." % (p.first_name, p.age)
+    John is 37.
+    Jane is 42.
+    ...
+
+__ http://www.postgresql.org/docs/8.4/static/functions-datetime.html
+
+Passing parameters into ``raw()``
+---------------------------------
+
+If you need to perform parameterized queries, you can use the ``params``
+argument to ``raw()``::
+
+    >>> lname = 'Doe'
+    >>> Person.objects.raw('SELECT * FROM myapp_person WHERE last_name = %s', [lname])
+
+``params`` is a list of parameters. You'll use ``%s`` placeholders in the
+query string (regardless of your database engine); they'll be replaced with
+parameters from the ``params`` list.
+
+.. warning::
+
+    **Do not use string formatting on raw queries!**
+
+    It's tempting to write the above query as::
+
+        >>> query = 'SELECT * FROM myapp_person WHERE last_name = %s', % lname
+        >>> Person.objects.raw(query)
+
+    **Don't.**
+
+    Using the ``params`` list completely protects you from `SQL injection
+    attacks`__`, a common exploit where attackers inject arbitrary SQL into
+    your database. If you use string interpolation, sooner or later you'll
+    fall victim to SQL injection. As long as you remember to always use the
+    ``params`` list you'll be protected.
+
+__ http://en.wikipedia.org/wiki/SQL_injection
+
+Executing custom SQL directly
+=============================
+
+Sometimes even :meth:`Manager.raw` isn't quite enough: you might need to
+perform queries that don't map cleanly to models, or directly execute
+``UPDATE``, ``INSERT``, or ``DELETE`` queries.
+
+In these cases, you can always access the database directly, routing around
+the model layer entirely.
+
+The object ``django.db.connection`` represents the
 current database connection, and ``django.db.transaction`` represents the
 current database transaction. To use the database connection, call
 ``connection.cursor()`` to get a cursor object. Then, call
@@ -15,7 +188,7 @@ changing operation, you should then call
 to the database. If your query is purely a data retrieval operation, no commit
 is required. For example::
 
-    def my_custom_sql(self):
+    def my_custom_sql():
         from django.db import connection, transaction
         cursor = connection.cursor()
 
@@ -78,12 +251,5 @@ necessary. (Also note that Django expects the ``"%s"`` placeholder, *not* the
 ``"?"`` placeholder, which is used by the SQLite Python bindings. This is for
 the sake of consistency and sanity.)
 
-An easier option?
------------------
-
-A final note: If all you want to do is a custom ``WHERE`` clause, you can just
-use the ``where``, ``tables`` and ``params`` arguments to the
-:ref:`extra clause <extra>` in the standard queryset API.
-
 .. _Python DB-API: http://www.python.org/peps/pep-0249.html
 

tests/modeltests/raw_query/fixtures/initial_data.json

@@ -0,0 +1,102 @@
+[
+    {
+        "pk": 1,
+        "model": "raw_query.author",
+        "fields": {
+            "dob": "1950-09-20",
+            "first_name": "Joe",
+            "last_name": "Smith"
+        }
+    },
+    {
+        "pk": 2,
+        "model": "raw_query.author",
+        "fields": {
+            "dob": "1920-04-02",
+            "first_name": "Jill",
+            "last_name": "Doe"
+        }
+    },
+    {
+        "pk": 3,
+        "model": "raw_query.author",
+        "fields": {
+            "dob": "1986-01-25",
+            "first_name": "Bob",
+            "last_name": "Smith"
+        }
+    },
+    {
+        "pk": 4,
+        "model": "raw_query.author",
+        "fields": {
+            "dob": "1932-05-10",
+            "first_name": "Bill",
+            "last_name": "Jones"
+        }
+    },
+    {
+        "pk": 1,
+        "model": "raw_query.book",
+        "fields": {
+            "author": 1,
+            "title": "The awesome book"
+        }
+    },
+    {
+        "pk": 2,
+        "model": "raw_query.book",
+        "fields": {
+            "author": 1,
+            "title": "The horrible book"
+        }
+    },
+    {
+        "pk": 3,
+        "model": "raw_query.book",
+        "fields": {
+            "author": 1,
+            "title": "Another awesome book"
+        }
+    },
+    {
+        "pk": 4,
+        "model": "raw_query.book",
+        "fields": {
+            "author": 3,
+            "title": "Some other book"
+        }
+    },
+    {
+        "pk": 1,
+        "model": "raw_query.coffee",
+        "fields": {
+            "brand": "dunkin doughnuts"
+        }
+    },
+    {
+        "pk": 2,
+        "model": "raw_query.coffee",
+        "fields": {
+            "brand": "starbucks"
+        }
+    },
+    {
+        "pk": 1,
+        "model": "raw_query.reviewer",
+        "fields": {
+            "reviewed": [
+                2,
+                3,
+                4
+            ]
+        }
+    },
+    {
+        "pk": 2,
+        "model": "raw_query.reviewer",
+        "fields": {
+            "reviewed": []
+        }
+    }
+]

tests/modeltests/raw_query/models.py

@@ -0,0 +1,25 @@
+from django.db import models
+
+class Author(models.Model):
+    first_name = models.CharField(max_length=255)
+    last_name = models.CharField(max_length=255)
+    dob = models.DateField()
+
+    def __init__(self, *args, **kwargs):
+        super(Author, self).__init__(*args, **kwargs)
+        # Protect against annotations being passed to __init__ --
+        # this'll make the test suite get angry if annotations aren't
+        # treated differently than fields.
+        for k in kwargs:
+            assert k in [f.attname for f in self._meta.fields], \
+                "Author.__init__ got an unexpected paramater: %s" % k
+
+class Book(models.Model):
+    title = models.CharField(max_length=255)
+    author = models.ForeignKey(Author)
+
+class Coffee(models.Model):
+    brand = models.CharField(max_length=255, db_column="name")
+
+class Reviewer(models.Model):
+    reviewed = models.ManyToManyField(Book)

tests/modeltests/raw_query/tests.py

@@ -0,0 +1,188 @@
+from django.test import TestCase
+from datetime import datetime
+from models import Author, Book, Coffee, Reviewer
+from django.db.models.sql.query import InvalidQuery
+
+class RawQueryTests(TestCase):
+
+    def assertSuccessfulRawQuery(self, model, query, expected_results,
+            expected_annotations=(), params=[], translations=None):
+        """
+        Execute the passed query against the passed model and check the output
+        """
+        results = list(model.objects.raw(query=query, params=params, translations=translations))
+        self.assertProcessed(results, expected_results, expected_annotations)
+        self.assertAnnotations(results, expected_annotations)
+
+    def assertProcessed(self, results, orig, expected_annotations=()):
+        """
+        Compare the results of a raw query against expected results
+        """
+        self.assertEqual(len(results), len(orig))
+        for index, item in enumerate(results):
+            orig_item = orig[index]
+            for annotation in expected_annotations:
+                setattr(orig_item, *annotation)
+
+            self.assertEqual(item.id, orig_item.id)
+
+    def assertNoAnnotations(self, results):
+        """
+        Check that the results of a raw query contain no annotations
+        """
+        self.assertAnnotations(results, ())
+
+    def assertAnnotations(self, results, expected_annotations):
+        """
+        Check that the passed raw query results contain the expected
+        annotations
+        """
+        if expected_annotations:
+            for index, result in enumerate(results):
+                annotation, value = expected_annotations[index]
+                self.assertTrue(hasattr(result, annotation))
+                self.assertEqual(getattr(result, annotation), value)
+
+    def testSimpleRawQuery(self):
+        """
+        Basic test of raw query with a simple database query
+        """
+        query = "SELECT * FROM raw_query_author"
+        authors = Author.objects.all()
+        self.assertSuccessfulRawQuery(Author, query, authors)
+
+    def testRawQueryLazy(self):
+        """
+        Raw queries are lazy: they aren't actually executed until they're
+        iterated over.
+        """
+        q = Author.objects.raw('SELECT * FROM raw_query_author')
+        self.assert_(q.query.cursor is None)
+        list(q)
+        self.assert_(q.query.cursor is not None)
+
+    def testFkeyRawQuery(self):
+        """
+        Test of a simple raw query against a model containing a foreign key
+        """
+        query = "SELECT * FROM raw_query_book"
+        books = Book.objects.all()
+        self.assertSuccessfulRawQuery(Book, query, books)
+
+    def testDBColumnHandler(self):
+        """
+        Test of a simple raw query against a model containing a field with
+        db_column defined.
+        """
+        query = "SELECT * FROM raw_query_coffee"
+        coffees = Coffee.objects.all()
+        self.assertSuccessfulRawQuery(Coffee, query, coffees)
+
+    def testOrderHandler(self):
+        """
+        Test of raw raw query's tolerance for columns being returned in any
+        order
+        """
+        selects = (
+            ('dob, last_name, first_name, id'),
+            ('last_name, dob, first_name, id'),
+            ('first_name, last_name, dob, id'),
+        )
+
+        for select in selects:
+            query = "SELECT %s FROM raw_query_author" % select
+            authors = Author.objects.all()
+            self.assertSuccessfulRawQuery(Author, query, authors)
+
+    def testTranslations(self):
+        """
+        Test of raw query's optional ability to translate unexpected result
+        column names to specific model fields
+        """
+        query = "SELECT first_name AS first, last_name AS last, dob, id FROM raw_query_author"
+        translations = {'first': 'first_name', 'last': 'last_name'}
+        authors = Author.objects.all()
+        self.assertSuccessfulRawQuery(Author, query, authors, translations=translations)
+
+    def testParams(self):
+        """
+        Test passing optional query parameters
+        """
+        query = "SELECT * FROM raw_query_author WHERE first_name = %s"
+        author = Author.objects.all()[2]
+        params = [author.first_name]
+        results = list(Author.objects.raw(query=query, params=params))
+        self.assertProcessed(results, [author])
+        self.assertNoAnnotations(results)
+        self.assertEqual(len(results), 1)
+
+    def testManyToMany(self):
+        """
+        Test of a simple raw query against a model containing a m2m field
+        """
+        query = "SELECT * FROM raw_query_reviewer"
+        reviewers = Reviewer.objects.all()
+        self.assertSuccessfulRawQuery(Reviewer, query, reviewers)
+
+    def testExtraConversions(self):
+        """
+        Test to insure that extra translations are ignored.
+        """
+        query = "SELECT * FROM raw_query_author"
+        translations = {'something': 'else'}
+        authors = Author.objects.all()
+        self.assertSuccessfulRawQuery(Author, query, authors, translations=translations)
+
+    def testMissingFields(self):
+        query = "SELECT id, first_name, dob FROM raw_query_author"
+        for author in Author.objects.raw(query):
+            self.assertNotEqual(author.first_name, None)
+            # last_name isn't given, but it will be retrieved on demand
+            self.assertNotEqual(author.last_name, None)
+
+    def testMissingFieldsWithoutPK(self):
+        query = "SELECT first_name, dob FROM raw_query_author"
+        try:
+            list(Author.objects.raw(query))
+            self.fail('Query without primary key should fail')
+        except InvalidQuery:
+            pass
+
+    def testAnnotations(self):
+        query = "SELECT a.*, count(b.id) as book_count FROM raw_query_author a LEFT JOIN raw_query_book b ON a.id = b.author_id GROUP BY a.id, a.first_name, a.last_name, a.dob ORDER BY a.id"
+        expected_annotations = (
+            ('book_count', 3),
+            ('book_count', 0),
+            ('book_count', 1),
+            ('book_count', 0),
+        )
+        authors = Author.objects.all()
+        self.assertSuccessfulRawQuery(Author, query, authors, expected_annotations)
+
+    def testInvalidQuery(self):
+        query = "UPDATE raw_query_author SET first_name='thing' WHERE first_name='Joe'"
+        self.assertRaises(InvalidQuery, Author.objects.raw, query)
+
+    def testWhiteSpaceQuery(self):
+        query = "    SELECT * FROM raw_query_author"
+        authors = Author.objects.all()
+        self.assertSuccessfulRawQuery(Author, query, authors)
+
+    def testMultipleIterations(self):
+        query = "SELECT * FROM raw_query_author"
+        normal_authors = Author.objects.all()
+        raw_authors = Author.objects.raw(query)
+
+        # First Iteration
+        first_iterations = 0
+        for index, raw_author in enumerate(raw_authors):
+            self.assertEqual(normal_authors[index], raw_author)
+            first_iterations += 1
+
+        # Second Iteration
+        second_iterations = 0
+        for index, raw_author in enumerate(raw_authors):
+            self.assertEqual(normal_authors[index], raw_author)
+            second_iterations += 1
+
+        self.assertEqual(first_iterations, second_iterations)