import keyword import re from collections import OrderedDict from django.core.management.base import BaseCommand, CommandError from django.db import DEFAULT_DB_ALIAS, connections from django.db.models.constants import LOOKUP_SEP class Command(BaseCommand): help = "Introspects the database tables in the given database and outputs a Django model module." requires_system_checks = False stealth_options = ('table_name_filter',) db_module = 'django.db' def add_arguments(self, parser): parser.add_argument( 'table', nargs='*', type=str, help='Selects what tables or views should be introspected.', ) parser.add_argument( '--database', default=DEFAULT_DB_ALIAS, help='Nominates a database to introspect. Defaults to using the "default" database.', ) parser.add_argument( '--include-views', action='store_true', help='Also output models for database views.', ) def handle(self, **options): try: for line in self.handle_inspection(options): self.stdout.write("%s\n" % line) except NotImplementedError: raise CommandError("Database inspection isn't supported for the currently selected database backend.") def handle_inspection(self, options): connection = connections[options['database']] # 'table_name_filter' is a stealth option table_name_filter = options.get('table_name_filter') def table2model(table_name): return re.sub(r'[^a-zA-Z0-9]', '', table_name.title()) with connection.cursor() as cursor: yield "# This is an auto-generated Django model module." yield "# You'll have to do the following manually to clean this up:" yield "# * Rearrange models' order" yield "# * Make sure each model has one field with primary_key=True" yield "# * Make sure each ForeignKey has `on_delete` set to the desired behavior." yield ( "# * Remove `managed = False` lines if you wish to allow " "Django to create, modify, and delete the table" ) yield "# Feel free to rename the models, but don't rename db_table values or field names." yield 'from %s import models' % self.db_module known_models = [] table_info = connection.introspection.get_table_list(cursor) tables_to_introspect = ( options['table'] or sorted(info.name for info in table_info if options['include_views'] or info.type == 't') ) for table_name in tables_to_introspect: if table_name_filter is not None and callable(table_name_filter): if not table_name_filter(table_name): continue try: try: relations = connection.introspection.get_relations(cursor, table_name) except NotImplementedError: relations = {} try: constraints = connection.introspection.get_constraints(cursor, table_name) except NotImplementedError: constraints = {} primary_key_column = connection.introspection.get_primary_key_column(cursor, table_name) unique_columns = [ c['columns'][0] for c in constraints.values() if c['unique'] and len(c['columns']) == 1 ] table_description = connection.introspection.get_table_description(cursor, table_name) except Exception as e: yield "# Unable to inspect table '%s'" % table_name yield "# The error was: %s" % e continue yield '' yield '' yield 'class %s(models.Model):' % table2model(table_name) known_models.append(table2model(table_name)) used_column_names = [] # Holds column names used in the table so far column_to_field_name = {} # Maps column names to names of model fields for row in table_description: comment_notes = [] # Holds Field notes, to be displayed in a Python comment. extra_params = OrderedDict() # Holds Field parameters such as 'db_column'. column_name = row.name is_relation = column_name in relations att_name, params, notes = self.normalize_col_name( column_name, used_column_names, is_relation) extra_params.update(params) comment_notes.extend(notes) used_column_names.append(att_name) column_to_field_name[column_name] = att_name # Add primary_key and unique, if necessary. if column_name == primary_key_column: extra_params['primary_key'] = True elif column_name in unique_columns: extra_params['unique'] = True if is_relation: rel_to = ( "self" if relations[column_name][1] == table_name else table2model(relations[column_name][1]) ) if rel_to in known_models: field_type = 'ForeignKey(%s' % rel_to else: field_type = "ForeignKey('%s'" % rel_to else: # Calling `get_field_type` to get the field type string and any # additional parameters and notes. field_type, field_params, field_notes = self.get_field_type(connection, table_name, row) extra_params.update(field_params) comment_notes.extend(field_notes) field_type += '(' # Don't output 'id = meta.AutoField(primary_key=True)', because # that's assumed if it doesn't exist. if att_name == 'id' and extra_params == {'primary_key': True}: if field_type == 'AutoField(': continue elif field_type == 'IntegerField(' and not connection.features.can_introspect_autofield: comment_notes.append('AutoField?') # Add 'null' and 'blank', if the 'null_ok' flag was present in the # table description. if row.null_ok: # If it's NULL... extra_params['blank'] = True extra_params['null'] = True field_desc = '%s = %s%s' % ( att_name, # Custom fields will have a dotted path '' if '.' in field_type else 'models.', field_type, ) if field_type.startswith('ForeignKey('): field_desc += ', models.DO_NOTHING' if extra_params: if not field_desc.endswith('('): field_desc += ', ' field_desc += ', '.join('%s=%r' % (k, v) for k, v in extra_params.items()) field_desc += ')' if comment_notes: field_desc += ' # ' + ' '.join(comment_notes) yield ' %s' % field_desc is_view = any(info.name == table_name and info.type == 'v' for info in table_info) for meta_line in self.get_meta(table_name, constraints, column_to_field_name, is_view): yield meta_line def normalize_col_name(self, col_name, used_column_names, is_relation): """ Modify the column name to make it Python-compatible as a field name """ field_params = {} field_notes = [] new_name = col_name.lower() if new_name != col_name: field_notes.append('Field name made lowercase.') if is_relation: if new_name.endswith('_id'): new_name = new_name[:-3] else: field_params['db_column'] = col_name new_name, num_repl = re.subn(r'\W', '_', new_name) if num_repl > 0: field_notes.append('Field renamed to remove unsuitable characters.') if new_name.find(LOOKUP_SEP) >= 0: while new_name.find(LOOKUP_SEP) >= 0: new_name = new_name.replace(LOOKUP_SEP, '_') if col_name.lower().find(LOOKUP_SEP) >= 0: # Only add the comment if the double underscore was in the original name field_notes.append("Field renamed because it contained more than one '_' in a row.") if new_name.startswith('_'): new_name = 'field%s' % new_name field_notes.append("Field renamed because it started with '_'.") if new_name.endswith('_'): new_name = '%sfield' % new_name field_notes.append("Field renamed because it ended with '_'.") if keyword.iskeyword(new_name): new_name += '_field' field_notes.append('Field renamed because it was a Python reserved word.') if new_name[0].isdigit(): new_name = 'number_%s' % new_name field_notes.append("Field renamed because it wasn't a valid Python identifier.") if new_name in used_column_names: num = 0 while '%s_%d' % (new_name, num) in used_column_names: num += 1 new_name = '%s_%d' % (new_name, num) field_notes.append('Field renamed because of name conflict.') if col_name != new_name and field_notes: field_params['db_column'] = col_name return new_name, field_params, field_notes def get_field_type(self, connection, table_name, row): """ Given the database connection, the table name, and the cursor row description, this routine will return the given field type name, as well as any additional keyword parameters and notes for the field. """ field_params = OrderedDict() field_notes = [] try: field_type = connection.introspection.get_field_type(row.type_code, row) except KeyError: field_type = 'TextField' field_notes.append('This field type is a guess.') # This is a hook for data_types_reverse to return a tuple of # (field_type, field_params_dict). if type(field_type) is tuple: field_type, new_params = field_type field_params.update(new_params) # Add max_length for all CharFields. if field_type == 'CharField' and row.internal_size: field_params['max_length'] = int(row.internal_size) if field_type == 'DecimalField': if row.precision is None or row.scale is None: field_notes.append( 'max_digits and decimal_places have been guessed, as this ' 'database handles decimal fields as float') field_params['max_digits'] = row.precision if row.precision is not None else 10 field_params['decimal_places'] = row.scale if row.scale is not None else 5 else: field_params['max_digits'] = row.precision field_params['decimal_places'] = row.scale return field_type, field_params, field_notes def get_meta(self, table_name, constraints, column_to_field_name, is_view): """ Return a sequence comprising the lines of code necessary to construct the inner Meta class for the model corresponding to the given database table name. """ unique_together = [] has_unsupported_constraint = False for params in constraints.values(): if params['unique']: columns = params['columns'] if None in columns: has_unsupported_constraint = True columns = [x for x in columns if x is not None] if len(columns) > 1: unique_together.append(str(tuple(column_to_field_name[c] for c in columns))) managed_comment = " # Created from a view. Don't remove." if is_view else "" meta = [''] if has_unsupported_constraint: meta.append(' # A unique constraint could not be introspected.') meta += [ ' class Meta:', ' managed = False%s' % managed_comment, ' db_table = %r' % table_name ] if unique_together: tup = '(' + ', '.join(unique_together) + ',)' meta += [" unique_together = %s" % tup] return meta