from collections import namedtuple
# Structure returned by DatabaseIntrospection.get_table_list()
TableInfo = namedtuple('TableInfo', ['name', 'type'])
# Structure returned by the DB-API cursor.description interface (PEP 249)
FieldInfo = namedtuple('FieldInfo', 'name type_code display_size internal_size precision scale null_ok default')
class BaseDatabaseIntrospection:
"""Encapsulate backend-specific introspection utilities."""
data_types_reverse = {}
def __init__(self, connection):
self.connection = connection
def get_field_type(self, data_type, description):
"""
Hook for a database backend to use the cursor description to
match a Django field type to a database column.
For Oracle, the column data_type on its own is insufficient to
distinguish between a FloatField and IntegerField, for example.
"""
return self.data_types_reverse[data_type]
def table_name_converter(self, name):
"""
Apply a conversion to the name for the purposes of comparison.
The default table name converter is for case sensitive comparison.
"""
return name
def column_name_converter(self, name):
"""
Apply a conversion to the column name for the purposes of comparison.
Use table_name_converter() by default.
"""
return self.table_name_converter(name)
def table_names(self, cursor=None, include_views=False):
"""
Return a list of names of all tables that exist in the database.
Sort the returned table list by Python's default sorting. Do NOT use
the database's ORDER BY here to avoid subtle differences in sorting
order between databases.
"""
def get_names(cursor):
return sorted(ti.name for ti in self.get_table_list(cursor)
if include_views or ti.type == 't')
if cursor is None:
with self.connection.cursor() as cursor:
return get_names(cursor)
return get_names(cursor)
def get_table_list(self, cursor):
"""
Return an unsorted list of TableInfo named tuples of all tables and
views that exist in the database.
"""
raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_table_list() method')
def django_table_names(self, only_existing=False, include_views=True):
"""
Return a list of all table names that have associated Django models and
are in INSTALLED_APPS.
If only_existing is True, include only the tables in the database.
"""
from django.apps import apps
from django.db import router
tables = set()
for app_config in apps.get_app_configs():
for model in router.get_migratable_models(app_config, self.connection.alias):
if not model._meta.managed:
continue
tables.add(model._meta.db_table)
tables.update(
f.m2m_db_table() for f in model._meta.local_many_to_many
if f.remote_field.through._meta.managed
)
tables = list(tables)
if only_existing:
existing_tables = self.table_names(include_views=include_views)
tables = [
t
for t in tables
if self.table_name_converter(t) in existing_tables
]
return tables
def installed_models(self, tables):
"""
Return a set of all models represented by the provided list of table
names.
"""
from django.apps import apps
from django.db import router
all_models = []
for app_config in apps.get_app_configs():
all_models.extend(router.get_migratable_models(app_config, self.connection.alias))
tables = list(map(self.table_name_converter, tables))
return {
m for m in all_models
if self.table_name_converter(m._meta.db_table) in tables
}
def sequence_list(self):
"""
Return a list of information about all DB sequences for all models in
all apps.
"""
from django.apps import apps
from django.db import router
sequence_list = []
cursor = self.connection.cursor()
for app_config in apps.get_app_configs():
for model in router.get_migratable_models(app_config, self.connection.alias):
if not model._meta.managed:
continue
if model._meta.swapped:
continue
sequence_list.extend(self.get_sequences(cursor, model._meta.db_table, model._meta.local_fields))
for f in model._meta.local_many_to_many:
# If this is an m2m using an intermediate table,
# we don't need to reset the sequence.
if f.remote_field.through is None:
sequence = self.get_sequences(cursor, f.m2m_db_table())
sequence_list.extend(sequence if sequence else [{'table': f.m2m_db_table(), 'column': None}])
return sequence_list
def get_sequences(self, cursor, table_name, table_fields=()):
"""
Return a list of introspected sequences for table_name. Each sequence
is a dict: {'table': <table_name>, 'column': <column_name>}. An optional
'name' key can be added if the backend supports named sequences.
"""
raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_sequences() method')
def get_key_columns(self, cursor, table_name):
"""
Backends can override this to return a list of:
(column_name, referenced_table_name, referenced_column_name)
for all key columns in given table.
"""
raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_key_columns() method')
def get_primary_key_column(self, cursor, table_name):
"""
Return the name of the primary key column for the given table.
"""
for constraint in self.get_constraints(cursor, table_name).values():
if constraint['primary_key']:
return constraint['columns'][0]
return None
def get_indexes(self, cursor, table_name):
"""
Deprecated in Django 1.11, use get_constraints instead.
Return a dictionary of indexed fieldname -> infodict for the given
table, where each infodict is in the format:
{'primary_key': boolean representing whether it's the primary key,
'unique': boolean representing whether it's a unique index}
Only single-column indexes are introspected.
"""
raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_indexes() method')
def get_constraints(self, cursor, table_name):
"""
Retrieve any constraints or keys (unique, pk, fk, check, index)
across one or more columns.
Return a dict mapping constraint names to their attributes,
where attributes is a dict with keys:
* columns: List of columns this covers
* primary_key: True if primary key, False otherwise
* unique: True if this is a unique constraint, False otherwise
* foreign_key: (table, column) of target, or None
* check: True if check constraint, False otherwise
* index: True if index, False otherwise.
* orders: The order (ASC/DESC) defined for the columns of indexes
* type: The type of the index (btree, hash, etc.)
Some backends may return special constraint names that don't exist
if they don't name constraints of a certain type (e.g. SQLite)
"""
raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_constraints() method')