id,summary,reporter,owner,description,type,status,component,version,severity,resolution,keywords,cc,stage,has_patch,needs_docs,needs_tests,needs_better_patch,easy,ui_ux 31731,Dead code in the sequence_reset_sql for postgres and oracle,axil,Ravindar Sharma,"In the definition of `sequence_reset_sql` function in `django/db/backends/postgresql/operations.py` and `django/db/backends/oracle/operations.py` files {{{ def sequence_reset_sql(self, style, model_list): from django.db import models output = [] qn = self.quote_name for model in model_list: # Use `coalesce` to set the sequence for each model to the max pk value if there are records, # or 1 if there are none. Set the `is_called` property (the third argument to `setval`) to true # if there are records (as the max pk value is already in use), otherwise set it to false. # Use pg_get_serial_sequence to get the underlying sequence name from the table name # and column name (available since PostgreSQL 8) for f in model._meta.local_fields: if isinstance(f, models.AutoField): output.append( ""%s setval(pg_get_serial_sequence('%s','%s'), "" ""coalesce(max(%s), 1), max(%s) %s null) %s %s;"" % ( style.SQL_KEYWORD('SELECT'), style.SQL_TABLE(qn(model._meta.db_table)), style.SQL_FIELD(f.column), style.SQL_FIELD(qn(f.column)), style.SQL_FIELD(qn(f.column)), style.SQL_KEYWORD('IS NOT'), style.SQL_KEYWORD('FROM'), style.SQL_TABLE(qn(model._meta.db_table)), ) ) break # Only one AutoField is allowed per model, so don't bother continuing. for f in model._meta.many_to_many: if not f.remote_field.through: ## output.append( ## ""%s setval(pg_get_serial_sequence('%s','%s'), "" ## ""coalesce(max(%s), 1), max(%s) %s null) %s %s;"" % ( ## style.SQL_KEYWORD('SELECT'), ## style.SQL_TABLE(qn(f.m2m_db_table())), ## style.SQL_FIELD('id'), ## style.SQL_FIELD(qn('id')), ## style.SQL_FIELD(qn('id')), ## style.SQL_KEYWORD('IS NOT'), ## style.SQL_KEYWORD('FROM'), ## style.SQL_TABLE(qn(f.m2m_db_table())) ## ) ## ) return output }}} The statement marked with ## never executes. 11 years ago when this code was written (ticket #11107) this `if not f.remote_field.through:` was a valid way to check if the `ManyToManyField` uses the user-provided intermediate `through` table or not. Nowadays `bool(f.remote_field.through)` always evaluates to `True`, no matter if it is a user-provided or an automatic table. But actually it is not necessary anymore. This function is used in three places in django code: 1) `manage.py sqlsequencereset` uses {{{ models = app_config.get_models(include_auto_created=True) }}} instead of the original {{{ models = app_config.get_models() }}} which was there when this ticket 11107 was merged. So now it fetches both automatic and user-defined intermediate tables at the ealier stage, before going. 2) loaddata is unaffected by this branch of execution because it needs to reset the sequences solely of the models that are being loaded and not of any others. To be 100% sure I created a project reproduced the models.py from 11107 and loaded the fixture provided there with `manage.py loaddata` - it succeeded without entering into that execution branch. 3) `django.contrib.sites.management.create_default_site` applies it to the Site model {{{ sequence_sql = connections[using].ops.sequence_reset_sql(no_style(), [Site]) }}} which has no manytomany keys, so it is unaffected. I would suggest to remove the code marked with ""##"" and check for other usages of `f.remote_field.through` for similar issues.",Cleanup/optimization,closed,"Database layer (models, ORM)",3.0,Normal,fixed,sql sequence reset postgres oracle,,Ready for checkin,1,0,0,0,0,0