Django Tests: setUpTestData on Postgres throws: "Duplicate key value violates unique constraint"

Question

I am running into a database issue in my unit tests. I think it has something to do with the way I am using TestCase and setUpData.

When I try to set up my test data with certain values, the tests throw the following error:

django.db.utils.IntegrityError: duplicate key value violates unique constraint 

...

psycopg2.IntegrityError: duplicate key value violates unique constraint "InventoryLogs_productgroup_product_name_48ec6f8d_uniq"
DETAIL:  Key (product_name)=(Almonds) already exists.

I changed all of my primary keys and it seems to be running fine. It doesn't seem to affect any of the tests.

However, I'm concerned that I am doing something wrong. When it first happened, I reversed about an hour's worth of work on my app (not that much code for a noob), which corrected the problem.

Then when I wrote the changes back in, the same issue presented itself again. TestCase is pasted below. The issue seems to occur after I add the sortrecord items, but corresponds with the items above it.

I don't want to keep going through and changing primary keys and urls in my tests, so if anyone sees something wrong with the way I am using this, please help me out. Thanks!

TestCase

class DetailsPageTest(TestCase):


@classmethod
def setUpTestData(cls):

    cls.product1 = ProductGroup.objects.create(
                        product_name="Almonds"
                        )
    cls.variety1 = Variety.objects.create(
                        product_group = cls.product1,
                        variety_name = "non pareil",
                        husked = False,
                        finished = False,
                        )

    cls.supplier1 = Supplier.objects.create(
                        company_name = "Acme",
                        company_location = "Acme Acres",
                        contact_info = "Call me!"
                        )

    cls.shipment1 = Purchase.objects.create(
                        tag=9,
                        shipment_id=9999,
                        supplier_id = cls.supplier1,
                        purchase_date='2015-01-09',
                        purchase_price=9.99,
                        product_name=cls.variety1,
                        pieces=99,
                        kgs=999,
                        crackout_estimate=99.9
                        )
    cls.shipment2 = Purchase.objects.create(
                        tag=8,
                        shipment_id=8888,
                        supplier_id=cls.supplier1,
                        purchase_date='2015-01-08',
                        purchase_price=8.88,
                        product_name=cls.variety1,
                        pieces=88,
                        kgs=888,
                        crackout_estimate=88.8
                        )
    cls.shipment3 = Purchase.objects.create(
                        tag=7,
                        shipment_id=7777,
                        supplier_id=cls.supplier1,
                        purchase_date='2014-01-07',
                        purchase_price=7.77,
                        product_name=cls.variety1,
                        pieces=77,
                        kgs=777,
                        crackout_estimate=77.7
                        )

    cls.sortrecord1 = SortingRecords.objects.create(
                        tag=cls.shipment1,
                        date="2015-02-05",
                        bags_sorted=20,
                        turnout=199,
                        )

    cls.sortrecord2 = SortingRecords.objects.create(
                        tag=cls.shipment1,
                        date="2015-02-07",
                        bags_sorted=40,
                        turnout=399,
                        )
    cls.sortrecord3 = SortingRecords.objects.create(
                        tag=cls.shipment1,
                        date='2015-02-09',
                        bags_sorted=30,
                        turnout=299,
                        )

Models

from datetime import datetime

from django.db import models
from django.db.models import Q


class ProductGroup(models.Model):
    product_name = models.CharField(max_length=140, primary_key=True)

    def __str__(self):
        return self.product_name

    class Meta:
        verbose_name = "Product"

class Supplier(models.Model):
    company_name = models.CharField(max_length=45)
    company_location = models.CharField(max_length=45)
    contact_info = models.CharField(max_length=256)

    class Meta:
        ordering = ["company_name"]

    def __str__(self):
        return self.company_name

class Variety(models.Model):
    product_group = models.ForeignKey(ProductGroup)
    variety_name = models.CharField(max_length=140)
    husked = models.BooleanField()
    finished = models.BooleanField()
    description = models.CharField(max_length=500, blank=True)

    class Meta:
        ordering = ["product_group_id"]
        verbose_name_plural = "Varieties"

    def __str__(self):
        return self.variety_name


class PurchaseYears(models.Manager):

    def purchase_years_list(self):
        unique_years = Purchase.objects.dates('purchase_date', 'year')
        results_list = []
        for p in unique_years:
            results_list.append(p.year)
        return results_list


class Purchase(models.Model):
    tag = models.IntegerField(primary_key=True)
    product_name = models.ForeignKey(Variety, related_name='purchases')
    shipment_id = models.CharField(max_length=24)
    supplier_id = models.ForeignKey(Supplier)
    purchase_date = models.DateField()
    estimated_delivery = models.DateField(null=True, blank=True)
    purchase_price = models.DecimalField(max_digits=6, decimal_places=3)
    pieces = models.IntegerField()
    kgs = models.IntegerField()
    crackout_estimate = models.DecimalField(max_digits=6,decimal_places=3, null=True)
    crackout_actual = models.DecimalField(max_digits=6,decimal_places=3, null=True)
    objects = models.Manager()
    purchase_years = PurchaseYears()
    # Keep manager as "objects" in case admin, etc. needs it. Filter can be called like so:
    # Purchase.objects.purchase_years_list()
    # Managers in docs: https://docs.djangoproject.com/en/1.8/intro/tutorial01/

    class Meta:
        ordering = ["purchase_date"]

    def __str__(self):
        return self.shipment_id

    def _weight_conversion(self):
        return round(self.kgs * 2.20462)
    lbs = property(_weight_conversion)

class SortingModelsBagsCalulator(models.Manager):

    def total_sorted(self, record_date, current_set):
        sorted = [SortingRecords['bags_sorted'] for SortingRecords in current_set if
                  SortingRecords['date'] <= record_date]
        return sum(sorted)


class SortingRecords(models.Model):
    tag = models.ForeignKey(Purchase, related_name='sorting_record')
    date = models.DateField()
    bags_sorted = models.IntegerField()
    turnout = models.IntegerField()
    objects = models.Manager()

    def __str__(self):
        return "%s  [%s]" % (self.date, self.tag.tag)

    class Meta:
        ordering = ["date"]
        verbose_name_plural = "Sorting Records"

    def _calculate_kgs_sorted(self):
        kg_per_bag = self.tag.kgs / self.tag.pieces
        kgs_sorted = kg_per_bag * self.bags_sorted
        return (round(kgs_sorted, 2))
    kgs_sorted = property(_calculate_kgs_sorted)

    def _byproduct(self):
        waste = self.kgs_sorted - self.turnout
        return  (round(waste, 2))
    byproduct = property(_byproduct)

    def _bags_remaining(self):
        current_set = SortingRecords.objects.values().filter(~Q(id=self.id), tag=self.tag)
        sorted = [SortingRecords['bags_sorted'] for SortingRecords in current_set if
                  SortingRecords['date'] <= self.date]
        remaining = self.tag.pieces - sum(sorted) - self.bags_sorted
        return remaining
    bags_remaining = property(_bags_remaining)

EDIT

It also fails with integers, like so.

django.db.utils.IntegrityError: duplicate key value violates unique constraint "InventoryLogs_purchase_pkey"
DETAIL:  Key (tag)=(9) already exists.

UDPATE

So I should have mentioned this earlier, but I completely forgot. I have two unit test files that use the same data. Just for kicks, I matched a primary key in both instances of setUpTestData() to a different value and sure enough, I got the same error.

These two setups were working fine side-by-side before I added more data to one of them. Now, it appears that they need different values. I guess you can only get away with using repeat data for so long.

Answer 1

I continued to get this error without having any duplicate data but I was able to resolve the issue by initializing the object and calling the save() method rather than creating the object via Model.objects.create()

In other words, I did this:

@classmethod
def setUpTestData(cls):
    cls.person = Person(first_name="Jane", last_name="Doe")
    cls.person.save()

Instead of this:

@classmethod
def setUpTestData(cls):
    cls.person = Person.objects.create(first_name="Jane", last_name="Doe")

Answer 2

I've been running into this issue sporadically for months now. I believe I just figured out the root cause and a couple solutions.

Summary For whatever reason, it seems like the Django test case base classes aren't removing the database records created by let's just call it TestCase1 before running TestCase2. Which, in TestCase2 when it tries to create records in the database using the same IDs as TestCase1 the database raises a DuplicateKey exception because those IDs already exists in the database. And even saying the magic word "please" won't help with database duplicate key errors.

Good news is, there are multiple ways to solve this problem! Here are a couple...

Solution 1

Make sure if you are overriding the class method tearDownClass that you call super().tearDownClass(). If you override tearDownClass() without calling its super, it will in turn never call TransactionTestCase._post_teardown() nor TransactionTestCase._fixture_teardown(). Quoting from the doc string in TransactionTestCase._post_teardown()`:

    def _post_teardown(self):
        """
        Perform post-test things:
        * Flush the contents of the database to leave a clean slate. If the
          class has an 'available_apps' attribute, don't fire post_migrate.
        * Force-close the connection so the next test gets a clean cursor.
        """

If TestCase.tearDownClass() is not called via super() then the database is not reset in between test cases and you will get the dreaded duplicate key exception.

Solution 2

Override TransactionTestCase and set the class variable serialized_rollback = True, like this:

class MyTestCase(TransactionTestCase):
    fixtures = ['test-data.json']
    serialized_rollback = True

    def test_name_goes_here(self):
        pass

Quoting from the source:

class TransactionTestCase(SimpleTestCase):

    ...

    # If transactions aren't available, Django will serialize the database
    # contents into a fixture during setup and flush and reload them
    # during teardown (as flush does not restore data from migrations).
    # This can be slow; this flag allows enabling on a per-case basis.
    serialized_rollback = False

When serialized_rollback is set to True, Django test runner rolls back any transactions inserted into the database beween test cases. And batta bing, batta bang... no more duplicate key errors!

Conclusion

There are probably many more ways to implement a solution for the OP's issue, but these two should work nicely. Would definitely love to have more solutions added by others for clarity sake and a deeper understanding of the underlying Django test case base classes. Phew, say that last line real fast three times and you could win a pony!

Answer 3

The log you provided states DETAIL: Key (product_name)=(Almonds) already exists. Did you verify in your db?

To prevent such errors in the future, you should prefix all your test data string by test_

Answer 4

I discovered the issue, as noted at the bottom of the question.

From what I can tell, the database didn't like me using duplicate data in the setUpTestData() methods of two different tests. Changing the primary key values in the second test corrected the problem.

Answer 5

I think the problem here is that you had a tearDownClass method in your TestCase without the call to super method. In this way the django TestCase lost the transactional functionalities behind the setUpTestData so it doesn't clean your test db after a TestCase is finished.

Check warning in django docs here: https://docs.djangoproject.com/en/1.10/topics/testing/tools/#django.test.SimpleTestCase.allow_database_queries

Answer 6

I had similar problem that had been caused by providing the primary key value to a test case explicitly.

As discussed in the Django documentation, manually assigning a value to an auto-incrementing field doesn’t update the field’s sequence, which might later cause a conflict.

I have solved it by altering the sequence manually:

from django.db import connection


class MyTestCase(TestCase):
    @classmethod
    def setUpTestData(cls):
        Model.objects.create(id=1)

        with connection.cursor() as c:
            c.execute(
                """
                ALTER SEQUENCE "app_model_id_seq" RESTART WITH 2;
                """
            )