diff options
Diffstat (limited to 'django/db/backends/mysql/compiler.py')
| -rw-r--r-- | django/db/backends/mysql/compiler.py | 22 |
1 files changed, 12 insertions, 10 deletions
diff --git a/django/db/backends/mysql/compiler.py b/django/db/backends/mysql/compiler.py index 1b4d583fb0..da02c1fd73 100644 --- a/django/db/backends/mysql/compiler.py +++ b/django/db/backends/mysql/compiler.py @@ -16,13 +16,15 @@ class SQLInsertCompiler(compiler.SQLInsertCompiler, SQLCompiler): class SQLDeleteCompiler(compiler.SQLDeleteCompiler, SQLCompiler): def as_sql(self): - if self.connection.features.update_can_self_select or self.single_alias: + # Prefer the non-standard DELETE FROM syntax over the SQL generated by + # the SQLDeleteCompiler's default implementation when multiple tables + # are involved since MySQL/MariaDB will generate a more efficient query + # plan than when using a subquery. + where, having = self.query.where.split_having() + if self.single_alias or having: + # DELETE FROM cannot be used when filtering against aggregates + # since it doesn't allow for GROUP BY and HAVING clauses. return super().as_sql() - # MySQL and MariaDB < 10.3.2 doesn't support deletion with a subquery - # which is what the default implementation of SQLDeleteCompiler uses - # when multiple tables are involved. Use the MySQL/MariaDB specific - # DELETE table FROM table syntax instead to avoid performing the - # operation in two queries. result = [ 'DELETE %s FROM' % self.quote_name_unless_alias( self.query.get_initial_alias() @@ -30,10 +32,10 @@ class SQLDeleteCompiler(compiler.SQLDeleteCompiler, SQLCompiler): ] from_sql, from_params = self.get_from_clause() result.extend(from_sql) - where, params = self.compile(self.query.where) - if where: - result.append('WHERE %s' % where) - return ' '.join(result), tuple(from_params) + tuple(params) + where_sql, where_params = self.compile(where) + if where_sql: + result.append('WHERE %s' % where_sql) + return ' '.join(result), tuple(from_params) + tuple(where_params) class SQLUpdateCompiler(compiler.SQLUpdateCompiler, SQLCompiler): |