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Fixed #28816 -- Prevented silencing data loss when decreasing CharField.max_length on PostgreSQL.

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This commit is contained in:
Hasan Ramezani 2019-05-11 17:29:24 +02:00 committed by Mariusz Felisiak
parent 519016e5f2
commit 1378d665a1
2 changed files with 26 additions and 3 deletions
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13
django/db/backends/postgresql/schema.py
View File

@ -6,8 +6,6 @@ from django.db.backends.ddl_references import IndexColumns
class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
sql_alter_column_type = "ALTER COLUMN %(column)s TYPE %(type)s USING %(column)s::%(type)s"
sql_create_sequence = "CREATE SEQUENCE %(sequence)s"
sql_delete_sequence = "DROP SEQUENCE IF EXISTS %(sequence)s CASCADE"
sql_set_sequence_max = "SELECT setval('%(sequence)s', MAX(%(column)s)) FROM %(table)s"
@ -36,6 +34,11 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
output.append(like_index_statement)
return output
def _field_data_type(self, field):
if field.is_relation:
return field.rel_db_type(self.connection)
return self.connection.data_types[field.get_internal_type()]
def _create_like_index_sql(self, model, field):
"""
Return the statement to create an index with varchar operator pattern
@ -59,7 +62,11 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
return None
def _alter_column_type_sql(self, model, old_field, new_field, new_type):
"""Make ALTER TYPE with SERIAL make sense."""
self.sql_alter_column_type = 'ALTER COLUMN %(column)s TYPE %(type)s'
# Cast when data type changed.
if self._field_data_type(old_field) != self._field_data_type(new_field):
self.sql_alter_column_type += ' USING %(column)s::%(type)s'
# Make ALTER TYPE with SERIAL make sense.
table = model._meta.db_table
if new_type.lower() in ("serial", "bigserial"):
column = new_field.column

16
tests/schema/tests.py
View File

@ -21,6 +21,7 @@ from django.db.models.fields.related import (
)
from django.db.models.indexes import Index
from django.db.transaction import TransactionManagementError, atomic
from django.db.utils import DataError
from django.test import (
TransactionTestCase, skipIfDBFeature, skipUnlessDBFeature,
)
@ -803,6 +804,21 @@ class SchemaTests(TransactionTestCase):
with connection.schema_editor() as editor:
editor.alter_field(Author, old_field, new_field, strict=True)
@unittest.skipUnless(connection.vendor == 'postgresql', 'PostgreSQL specific')
def test_alter_char_field_decrease_length(self):
# Create the table.
with connection.schema_editor() as editor:
editor.create_model(Author)
Author.objects.create(name='x' * 255)
# Change max_length of CharField.
old_field = Author._meta.get_field('name')
new_field = CharField(max_length=254)
new_field.set_attributes_from_name('name')
with connection.schema_editor() as editor:
msg = 'value too long for type character varying(254)'
with self.assertRaisesMessage(DataError, msg):
editor.alter_field(Author, old_field, new_field, strict=True)
def test_alter_textfield_to_null(self):
"""
#24307 - Should skip an alter statement on databases with