Commit 6bf79640 authored by Aaron Elliot Ross's avatar Aaron Elliot Ross Committed by Tim Graham
Browse files

Fixed #26171 -- Made MySQL create an index on ForeignKeys with db_contraint=False. 

Refactored "Prevented unneeded index creation on MySQL-InnoDB" (2ceb10f3)
to avoid setting db_index=False.
parent 5fe1c922

django/db/backends/base/schema.py

+4 −1
Original line number Diff line number Diff line
@@ -884,7 +884,7 @@ class BaseDatabaseSchemaEditor(object): 
            return []

        output = []

        for field in model._meta.local_fields:

            if field.db_index and not field.unique:

            if self._field_should_be_indexed(model, field):

                output.append(self._create_index_sql(model, [field], suffix=""))



        for field_names in model._meta.index_together:
@@ -892,6 +892,9 @@ class BaseDatabaseSchemaEditor(object): 
            output.append(self._create_index_sql(model, fields, suffix="_idx"))

        return output



    def _field_should_be_indexed(self, model, field):

        return field.db_index and not field.unique



    def _rename_field_sql(self, table, old_field, new_field, new_type):

        return self.sql_rename_column % {

            "table": self.quote_name(table),

django/db/backends/mysql/schema.py

+11 −8
Original line number Diff line number Diff line
@@ -51,17 +51,20 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor): 
                'column': self.quote_name(field.column),

            }, [effective_default])



    def _model_indexes_sql(self, model):

    def _field_should_be_indexed(self, model, field):

        create_index = super(DatabaseSchemaEditor, self)._field_should_be_indexed(model, field)

        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)

        # No need to create an index for ForeignKey fields except if

        # db_constraint=False because the index from that constraint won't be

        # created.

        if (storage == "InnoDB" and

                create_index and

                field.get_internal_type() == 'ForeignKey' and

                field.db_constraint):

            return False

        return create_index



    def _delete_composed_index(self, model, fields, *args):

        """

tests/indexes/models.py

+1 −0
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ class CurrentTranslation(models.ForeignObject): 
class ArticleTranslation(models.Model):



    article = models.ForeignKey('indexes.Article', models.CASCADE)

    article_no_constraint = models.ForeignKey('indexes.Article', models.CASCADE, db_constraint=False)

    language = models.CharField(max_length=10, unique=True)

    content = models.TextField()

tests/indexes/tests.py

+5 −2
Original line number Diff line number Diff line
@@ -62,7 +62,7 @@ class SchemaIndexesTests(TestCase): 
    def test_no_index_for_foreignkey(self):

        """

        MySQL on InnoDB already creates indexes automatically for foreign keys.

        (#14180).

        (#14180). An index should be created if db_constraint=False (#26171).

        """

        storage = connection.introspection.get_storage_engine(

            connection.cursor(), ArticleTranslation._meta.db_table
@@ -70,4 +70,7 @@ class SchemaIndexesTests(TestCase): 
        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, [])
 
        self.assertEqual(index_sql, [

            'CREATE INDEX `indexes_articletranslation_99fb53c2` '

            'ON `indexes_articletranslation` (`article_no_constraint_id`)'

        ])