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import keyword
import re
from collections import OrderedDict
from 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):
'table', action='store', nargs='*', type=str,
help='Selects what tables or views should be introspected.',
'--database', action='store', dest='database', default=DEFAULT_DB_ALIAS,
help='Nominates a database to introspect. Defaults to using the "default" database.',
'--include-views', action='store_true', help='Also output models for database views.',
def handle(self, **options):
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())
def strip_prefix(s):
return s[1:] if s.startswith("u'") else s
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( 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):
relations = connection.introspection.get_relations(cursor, table_name)
except NotImplementedError:
relations = {}
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
yield ''
yield ''
yield 'class %s(models.Model):' % 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[0]
is_relation = column_name in relations
att_name, params, notes = self.normalize_col_name(
column_name, used_column_names, is_relation)
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
field_type = "ForeignKey('%s'" % rel_to
# 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)
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(':
elif field_type == 'IntegerField(' and not connection.features.can_introspect_autofield:
# Add 'null' and 'blank', if the 'null_ok' flag was present in the
# table description.
if row[6]: # If it's NULL...
extra_params['blank'] = True
extra_params['null'] = True
field_desc = '%s = %s%s' % (
# Custom fields will have a dotted path
'' if '.' in field_type else 'models.',
if field_type.startswith('ForeignKey('):
field_desc += ', models.DO_NOTHING'
if extra_params:
if not field_desc.endswith('('):
field_desc += ', '
field_desc += ', '.join(
'%s=%s' % (k, strip_prefix(repr(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( == 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]
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 = []
field_type = connection.introspection.get_field_type(row[1], 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
# Add max_length for all CharFields.
if field_type == 'CharField' and row[3]:
field_params['max_length'] = int(row[3])
if field_type == 'DecimalField':
if row[4] is None or row[5] is None:
'max_digits and decimal_places have been guessed, as this '
'database handles decimal fields as float')
field_params['max_digits'] = row[4] if row[4] is not None else 10
field_params['decimal_places'] = row[5] if row[5] is not None else 5
field_params['max_digits'] = row[4]
field_params['decimal_places'] = row[5]
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