Commit 2ceb10f3 authored by Claude Paroz's avatar Claude Paroz
Browse files

Fixed #14180 -- Prevented unneeded index creation on MySQL-InnoDB 

Thanks zimnyx for the report and Simon Charette, Tim Graham for
the reviews.
parent 47182965

django/db/backends/mysql/introspection.py

+6 −2
Original line number Diff line number Diff line
@@ -142,13 +142,17 @@ class DatabaseIntrospection(BaseDatabaseIntrospection): 


    def get_storage_engine(self, cursor, table_name):

        """

        Retrieves the storage engine for a given table.

        Retrieves the storage engine for a given table. Returns the default

        storage engine if the table doesn't exist.

        """

        cursor.execute(

            "SELECT engine "

            "FROM information_schema.tables "

            "WHERE table_name = %s", [table_name])

        return cursor.fetchone()[0]

        result = cursor.fetchone()

        if not result:

            return self.connection.features._mysql_storage_engine

        return result[0]



    def get_constraints(self, cursor, table_name):

        """

django/db/backends/mysql/schema.py

+12 −0
Original line number Diff line number Diff line
@@ -51,3 +51,15 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor): 
                'table': self.quote_name(model._meta.db_table),

                'column': self.quote_name(field.column),

            }, [effective_default])



    def _model_indexes_sql(self, model):

        storage = self.connection.introspection.get_storage_engine(

            self.connection.cursor(), model._meta.db_table

        )

        if storage == "InnoDB":

            for field in model._meta.local_fields:

                if field.db_index and not field.unique and field.get_internal_type() == "ForeignKey":

                    # Temporary setting db_index to False (in memory) to disable

                    # index creation for FKs (index automatically created by MySQL)

                    field.db_index = False

        return super(DatabaseSchemaEditor, self)._model_indexes_sql(model)

docs/releases/1.8.txt

+3 −0
Original line number Diff line number Diff line
@@ -249,6 +249,9 @@ Database backends 
  and up will support microseconds. See the :ref:`MySQL database notes

  <mysql-fractional-seconds>` for more details.



* The MySQL backend no longer creates explicit indexes for foreign keys when

  using the InnoDB storage engine, as MySQL already creates them automatically.



Email

^^^^^

tests/commands_sql/tests.py

+6 −6
Original line number Diff line number Diff line
@@ -72,14 +72,14 @@ class SQLCommandsTestCase(TestCase): 
        with warnings.catch_warnings():

            warnings.simplefilter("ignore", category=RemovedInDjango20Warning)

            output = sql_indexes(app_config, no_style(), connections[DEFAULT_DB_ALIAS])

        # PostgreSQL creates one additional index for CharField

        self.assertIn(self.count_ddl(output, 'CREATE INDEX'), [3, 4])

        # Number of indexes is backend-dependent

        self.assertTrue(1 <= self.count_ddl(output, 'CREATE INDEX') <= 4)



    def test_sql_destroy_indexes(self):

        app_config = apps.get_app_config('commands_sql')

        output = sql_destroy_indexes(app_config, no_style(), connections[DEFAULT_DB_ALIAS])

        # PostgreSQL creates one additional index for CharField

        self.assertIn(self.count_ddl(output, 'DROP INDEX'), [3, 4])

        # Number of indexes is backend-dependent

        self.assertTrue(1 <= self.count_ddl(output, 'DROP INDEX') <= 4)



    def test_sql_all(self):

        app_config = apps.get_app_config('commands_sql')
@@ -88,8 +88,8 @@ class SQLCommandsTestCase(TestCase): 
            output = sql_all(app_config, no_style(), connections[DEFAULT_DB_ALIAS])



        self.assertEqual(self.count_ddl(output, 'CREATE TABLE'), 3)

        # PostgreSQL creates one additional index for CharField

        self.assertIn(self.count_ddl(output, 'CREATE INDEX'), [3, 4])

        # Number of indexes is backend-dependent

        self.assertTrue(1 <= self.count_ddl(output, 'CREATE INDEX') <= 4)





class TestRouter(object):

tests/indexes/tests.py

+15 −1
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ from django.db import connection 
from django.test import TestCase

from django.test.utils import IgnorePendingDeprecationWarningsMixin



from .models import Article, IndexTogetherSingleList

from .models import Article, ArticleTranslation, IndexTogetherSingleList





class CreationIndexesTests(IgnorePendingDeprecationWarningsMixin, TestCase):
@@ -82,3 +82,17 @@ class SchemaIndexesTests(TestCase): 
        """Test indexes are not created for related objects"""

        index_sql = connection.schema_editor()._model_indexes_sql(Article)

        self.assertEqual(len(index_sql), 1)



    @skipUnless(connection.vendor == 'mysql', "This is a mysql-specific issue")

    def test_no_index_for_foreignkey(self):

        """

        MySQL on InnoDB already creates indexes automatically for foreign keys.

        (#14180).

        """

        storage = connection.introspection.get_storage_engine(

            connection.cursor(), ArticleTranslation._meta.db_table

        )

        if storage != "InnoDB":

            self.skip("This test only applies to the InnoDB storage engine")

        index_sql = connection.schema_editor()._model_indexes_sql(ArticleTranslation)

        self.assertEqual(index_sql, [])