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147 lines
4.5 KiB
147 lines
4.5 KiB
# -*- coding: utf-8 -*- |
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""" |
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14. Using a custom primary key |
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By default, Django adds an ``"id"`` field to each model. But you can override |
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this behavior by explicitly adding ``primary_key=True`` to a field. |
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""" |
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from django.conf import settings |
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from django.db import models, transaction, IntegrityError |
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class Employee(models.Model): |
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employee_code = models.IntegerField(primary_key=True, db_column = 'code') |
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first_name = models.CharField(max_length=20) |
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last_name = models.CharField(max_length=20) |
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class Meta: |
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ordering = ('last_name', 'first_name') |
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def __unicode__(self): |
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return u"%s %s" % (self.first_name, self.last_name) |
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class Business(models.Model): |
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name = models.CharField(max_length=20, primary_key=True) |
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employees = models.ManyToManyField(Employee) |
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class Meta: |
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verbose_name_plural = 'businesses' |
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def __unicode__(self): |
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return self.name |
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__test__ = {'API_TESTS':""" |
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>>> dan = Employee(employee_code=123, first_name='Dan', last_name='Jones') |
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>>> dan.save() |
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>>> Employee.objects.all() |
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[<Employee: Dan Jones>] |
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>>> fran = Employee(employee_code=456, first_name='Fran', last_name='Bones') |
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>>> fran.save() |
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>>> Employee.objects.all() |
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[<Employee: Fran Bones>, <Employee: Dan Jones>] |
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>>> Employee.objects.get(pk=123) |
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<Employee: Dan Jones> |
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>>> Employee.objects.get(pk=456) |
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<Employee: Fran Bones> |
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>>> Employee.objects.get(pk=42) |
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Traceback (most recent call last): |
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... |
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DoesNotExist: Employee matching query does not exist. |
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# Use the name of the primary key, rather than pk. |
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>>> Employee.objects.get(employee_code__exact=123) |
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<Employee: Dan Jones> |
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# pk can be used as a substitute for the primary key. |
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>>> Employee.objects.filter(pk__in=[123, 456]) |
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[<Employee: Fran Bones>, <Employee: Dan Jones>] |
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# The primary key can be accessed via the pk property on the model. |
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>>> e = Employee.objects.get(pk=123) |
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>>> e.pk |
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123 |
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# Or we can use the real attribute name for the primary key: |
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>>> e.employee_code |
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123 |
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# Fran got married and changed her last name. |
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>>> fran = Employee.objects.get(pk=456) |
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>>> fran.last_name = 'Jones' |
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>>> fran.save() |
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>>> Employee.objects.filter(last_name__exact='Jones') |
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[<Employee: Dan Jones>, <Employee: Fran Jones>] |
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>>> emps = Employee.objects.in_bulk([123, 456]) |
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>>> emps[123] |
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<Employee: Dan Jones> |
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>>> b = Business(name='Sears') |
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>>> b.save() |
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>>> b.employees.add(dan, fran) |
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>>> b.employees.all() |
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[<Employee: Dan Jones>, <Employee: Fran Jones>] |
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>>> fran.business_set.all() |
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[<Business: Sears>] |
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>>> Business.objects.in_bulk(['Sears']) |
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{u'Sears': <Business: Sears>} |
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>>> Business.objects.filter(name__exact='Sears') |
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[<Business: Sears>] |
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>>> Business.objects.filter(pk='Sears') |
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[<Business: Sears>] |
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# Queries across tables, involving primary key |
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>>> Employee.objects.filter(business__name__exact='Sears') |
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[<Employee: Dan Jones>, <Employee: Fran Jones>] |
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>>> Employee.objects.filter(business__pk='Sears') |
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[<Employee: Dan Jones>, <Employee: Fran Jones>] |
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>>> Business.objects.filter(employees__employee_code__exact=123) |
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[<Business: Sears>] |
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>>> Business.objects.filter(employees__pk=123) |
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[<Business: Sears>] |
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>>> Business.objects.filter(employees__first_name__startswith='Fran') |
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[<Business: Sears>] |
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# Primary key may be unicode string |
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>>> bus = Business(name=u'jaźń') |
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>>> bus.save() |
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# The primary key must also obviously be unique, so trying to create a new |
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# object with the same primary key will fail. |
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>>> try: |
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... sid = transaction.savepoint() |
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... Employee.objects.create(employee_code=123, first_name='Fred', last_name='Jones') |
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... transaction.savepoint_commit(sid) |
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... except Exception, e: |
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... if isinstance(e, IntegrityError): |
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... transaction.savepoint_rollback(sid) |
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... print "Pass" |
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... else: |
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... print "Fail with %s" % type(e) |
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Pass |
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"""} |
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# SQLite lets objects be saved with an empty primary key, even though an |
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# integer is expected. So we can't check for an error being raised in that case |
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# for SQLite. Remove it from the suite for this next bit. |
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if settings.DATABASE_ENGINE != 'sqlite3': |
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__test__["API_TESTS"] += """ |
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# The primary key must be specified, so an error is raised if you try to create |
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# an object without it. |
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>>> try: |
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... sid = transaction.savepoint() |
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... Employee.objects.create(first_name='Tom', last_name='Smith') |
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... print 'hello' |
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... transaction.savepoint_commit(sid) |
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... print 'hello2' |
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... except Exception, e: |
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... if isinstance(e, IntegrityError): |
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... transaction.savepoint_rollback(sid) |
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... print "Pass" |
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... else: |
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... print "Fail with %s" % type(e) |
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Pass |
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"""
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