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# engine/reflection.py
# Copyright (C) 2005-2016 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Provides an abstraction for obtaining database schema information.
Usage Notes:
Here are some general conventions when accessing the low level inspector
methods such as get_table_names, get_columns, etc.
1. Inspector methods return lists of dicts in most cases for the following
reasons:
* They're both standard types that can be serialized.
* Using a dict instead of a tuple allows easy expansion of attributes.
* Using a list for the outer structure maintains order and is easy to work
with (e.g. list comprehension [d['name'] for d in cols]).
2. Records that contain a name, such as the column name in a column record
use the key 'name'. So for most return values, each record will have a
'name' attribute..
"""
from .. import exc, sql
from ..sql import schema as sa_schema
from .. import util
from ..sql.type_api import TypeEngine
from ..util import deprecated
from ..util import topological
from .. import inspection
from .base import Connectable
@util.decorator
def cache(fn, self, con, *args, **kw):
info_cache = kw.get('info_cache', None)
if info_cache is None:
return fn(self, con, *args, **kw)
key = (
fn.__name__,
tuple(a for a in args if isinstance(a, util.string_types)),
tuple((k, v) for k, v in kw.items() if
isinstance(v,
util.string_types + util.int_types + (float, )
)
)
)
ret = info_cache.get(key)
if ret is None:
ret = fn(self, con, *args, **kw)
info_cache[key] = ret
return ret
class Inspector(object):
"""Performs database schema inspection.
The Inspector acts as a proxy to the reflection methods of the
:class:`~sqlalchemy.engine.interfaces.Dialect`, providing a
consistent interface as well as caching support for previously
fetched metadata.
A :class:`.Inspector` object is usually created via the
:func:`.inspect` function::
from sqlalchemy import inspect, create_engine
engine = create_engine('...')
insp = inspect(engine)
The inspection method above is equivalent to using the
:meth:`.Inspector.from_engine` method, i.e.::
engine = create_engine('...')
insp = Inspector.from_engine(engine)
Where above, the :class:`~sqlalchemy.engine.interfaces.Dialect` may opt
to return an :class:`.Inspector` subclass that provides additional
methods specific to the dialect's target database.
"""
def __init__(self, bind):
"""Initialize a new :class:`.Inspector`.
:param bind: a :class:`~sqlalchemy.engine.Connectable`,
which is typically an instance of
:class:`~sqlalchemy.engine.Engine` or
:class:`~sqlalchemy.engine.Connection`.
For a dialect-specific instance of :class:`.Inspector`, see
:meth:`.Inspector.from_engine`
"""
# this might not be a connection, it could be an engine.
self.bind = bind
# set the engine
if hasattr(bind, 'engine'):
self.engine = bind.engine
else:
self.engine = bind
if self.engine is bind:
# if engine, ensure initialized
bind.connect().close()
self.dialect = self.engine.dialect
self.info_cache = {}
@classmethod
def from_engine(cls, bind):
"""Construct a new dialect-specific Inspector object from the given
engine or connection.
:param bind: a :class:`~sqlalchemy.engine.Connectable`,
which is typically an instance of
:class:`~sqlalchemy.engine.Engine` or
:class:`~sqlalchemy.engine.Connection`.
This method differs from direct a direct constructor call of
:class:`.Inspector` in that the
:class:`~sqlalchemy.engine.interfaces.Dialect` is given a chance to
provide a dialect-specific :class:`.Inspector` instance, which may
provide additional methods.
See the example at :class:`.Inspector`.
"""
if hasattr(bind.dialect, 'inspector'):
return bind.dialect.inspector(bind)
return Inspector(bind)
@inspection._inspects(Connectable)
def _insp(bind):
return Inspector.from_engine(bind)
@property
def default_schema_name(self):
"""Return the default schema name presented by the dialect
for the current engine's database user.
E.g. this is typically ``public`` for Postgresql and ``dbo``
for SQL Server.
"""
return self.dialect.default_schema_name
def get_schema_names(self):
"""Return all schema names.
"""
if hasattr(self.dialect, 'get_schema_names'):
return self.dialect.get_schema_names(self.bind,
info_cache=self.info_cache)
return []
def get_table_names(self, schema=None, order_by=None):
"""Return all table names in referred to within a particular schema.
The names are expected to be real tables only, not views.
Views are instead returned using the :meth:`.Inspector.get_view_names`
method.
:param schema: Schema name. If ``schema`` is left at ``None``, the
database's default schema is
used, else the named schema is searched. If the database does not
support named schemas, behavior is undefined if ``schema`` is not
passed as ``None``. For special quoting, use :class:`.quoted_name`.
:param order_by: Optional, may be the string "foreign_key" to sort
the result on foreign key dependencies. Does not automatically
resolve cycles, and will raise :class:`.CircularDependencyError`
if cycles exist.
.. deprecated:: 1.0.0 - see
:meth:`.Inspector.get_sorted_table_and_fkc_names` for a version
of this which resolves foreign key cycles between tables
automatically.
.. versionchanged:: 0.8 the "foreign_key" sorting sorts tables
in order of dependee to dependent; that is, in creation
order, rather than in drop order. This is to maintain
consistency with similar features such as
:attr:`.MetaData.sorted_tables` and :func:`.util.sort_tables`.
.. seealso::
:meth:`.Inspector.get_sorted_table_and_fkc_names`
:attr:`.MetaData.sorted_tables`
"""
if hasattr(self.dialect, 'get_table_names'):
tnames = self.dialect.get_table_names(
self.bind, schema, info_cache=self.info_cache)
else:
tnames = self.engine.table_names(schema)
if order_by == 'foreign_key':
tuples = []
for tname in tnames:
for fkey in self.get_foreign_keys(tname, schema):
if tname != fkey['referred_table']:
tuples.append((fkey['referred_table'], tname))
tnames = list(topological.sort(tuples, tnames))
return tnames
def get_sorted_table_and_fkc_names(self, schema=None):
"""Return dependency-sorted table and foreign key constraint names in
referred to within a particular schema.
This will yield 2-tuples of
``(tablename, [(tname, fkname), (tname, fkname), ...])``
consisting of table names in CREATE order grouped with the foreign key
constraint names that are not detected as belonging to a cycle.
The final element
will be ``(None, [(tname, fkname), (tname, fkname), ..])``
which will consist of remaining
foreign key constraint names that would require a separate CREATE
step after-the-fact, based on dependencies between tables.
.. versionadded:: 1.0.-
.. seealso::
:meth:`.Inspector.get_table_names`
:func:`.sort_tables_and_constraints` - similar method which works
with an already-given :class:`.MetaData`.
"""
if hasattr(self.dialect, 'get_table_names'):
tnames = self.dialect.get_table_names(
self.bind, schema, info_cache=self.info_cache)
else:
tnames = self.engine.table_names(schema)
tuples = set()
remaining_fkcs = set()
fknames_for_table = {}
for tname in tnames:
fkeys = self.get_foreign_keys(tname, schema)
fknames_for_table[tname] = set(
[fk['name'] for fk in fkeys]
)
for fkey in fkeys:
if tname != fkey['referred_table']:
tuples.add((fkey['referred_table'], tname))
try:
candidate_sort = list(topological.sort(tuples, tnames))
except exc.CircularDependencyError as err:
for edge in err.edges:
tuples.remove(edge)
remaining_fkcs.update(
(edge[1], fkc)
for fkc in fknames_for_table[edge[1]]
)
candidate_sort = list(topological.sort(tuples, tnames))
return [
(tname, fknames_for_table[tname].difference(remaining_fkcs))
for tname in candidate_sort
] + [(None, list(remaining_fkcs))]
def get_temp_table_names(self):
"""return a list of temporary table names for the current bind.
This method is unsupported by most dialects; currently
only SQLite implements it.
.. versionadded:: 1.0.0
"""
return self.dialect.get_temp_table_names(
self.bind, info_cache=self.info_cache)
def get_temp_view_names(self):
"""return a list of temporary view names for the current bind.
This method is unsupported by most dialects; currently
only SQLite implements it.
.. versionadded:: 1.0.0
"""
return self.dialect.get_temp_view_names(
self.bind, info_cache=self.info_cache)
def get_table_options(self, table_name, schema=None, **kw):
"""Return a dictionary of options specified when the table of the
given name was created.
This currently includes some options that apply to MySQL tables.
:param table_name: string name of the table. For special quoting,
use :class:`.quoted_name`.
:param schema: string schema name; if omitted, uses the default schema
of the database connection. For special quoting,
use :class:`.quoted_name`.
"""
if hasattr(self.dialect, 'get_table_options'):
return self.dialect.get_table_options(
self.bind, table_name, schema,
info_cache=self.info_cache, **kw)
return {}
def get_view_names(self, schema=None):
"""Return all view names in `schema`.
:param schema: Optional, retrieve names from a non-default schema.
For special quoting, use :class:`.quoted_name`.
"""
return self.dialect.get_view_names(self.bind, schema,
info_cache=self.info_cache)
def get_view_definition(self, view_name, schema=None):
"""Return definition for `view_name`.
:param schema: Optional, retrieve names from a non-default schema.
For special quoting, use :class:`.quoted_name`.
"""
return self.dialect.get_view_definition(
self.bind, view_name, schema, info_cache=self.info_cache)
def get_columns(self, table_name, schema=None, **kw):
"""Return information about columns in `table_name`.
Given a string `table_name` and an optional string `schema`, return
column information as a list of dicts with these keys:
name
the column's name
type
:class:`~sqlalchemy.types.TypeEngine`
nullable
boolean
default
the column's default value
attrs
dict containing optional column attributes
:param table_name: string name of the table. For special quoting,
use :class:`.quoted_name`.
:param schema: string schema name; if omitted, uses the default schema
of the database connection. For special quoting,
use :class:`.quoted_name`.
"""
col_defs = self.dialect.get_columns(self.bind, table_name, schema,
info_cache=self.info_cache,
**kw)
for col_def in col_defs:
# make this easy and only return instances for coltype
coltype = col_def['type']
if not isinstance(coltype, TypeEngine):
col_def['type'] = coltype()
return col_defs
@deprecated('0.7', 'Call to deprecated method get_primary_keys.'
' Use get_pk_constraint instead.')
def get_primary_keys(self, table_name, schema=None, **kw):
"""Return information about primary keys in `table_name`.
Given a string `table_name`, and an optional string `schema`, return
primary key information as a list of column names.
"""
return self.dialect.get_pk_constraint(self.bind, table_name, schema,
info_cache=self.info_cache,
**kw)['constrained_columns']
def get_pk_constraint(self, table_name, schema=None, **kw):
"""Return information about primary key constraint on `table_name`.
Given a string `table_name`, and an optional string `schema`, return
primary key information as a dictionary with these keys:
constrained_columns
a list of column names that make up the primary key
name
optional name of the primary key constraint.
:param table_name: string name of the table. For special quoting,
use :class:`.quoted_name`.
:param schema: string schema name; if omitted, uses the default schema
of the database connection. For special quoting,
use :class:`.quoted_name`.
"""
return self.dialect.get_pk_constraint(self.bind, table_name, schema,
info_cache=self.info_cache,
**kw)
def get_foreign_keys(self, table_name, schema=None, **kw):
"""Return information about foreign_keys in `table_name`.
Given a string `table_name`, and an optional string `schema`, return
foreign key information as a list of dicts with these keys:
constrained_columns
a list of column names that make up the foreign key
referred_schema
the name of the referred schema
referred_table
the name of the referred table
referred_columns
a list of column names in the referred table that correspond to
constrained_columns
name
optional name of the foreign key constraint.
:param table_name: string name of the table. For special quoting,
use :class:`.quoted_name`.
:param schema: string schema name; if omitted, uses the default schema
of the database connection. For special quoting,
use :class:`.quoted_name`.
"""
return self.dialect.get_foreign_keys(self.bind, table_name, schema,
info_cache=self.info_cache,
**kw)
def get_indexes(self, table_name, schema=None, **kw):
"""Return information about indexes in `table_name`.
Given a string `table_name` and an optional string `schema`, return
index information as a list of dicts with these keys:
name
the index's name
column_names
list of column names in order
unique
boolean
dialect_options
dict of dialect-specific index options. May not be present
for all dialects.
.. versionadded:: 1.0.0
:param table_name: string name of the table. For special quoting,
use :class:`.quoted_name`.
:param schema: string schema name; if omitted, uses the default schema
of the database connection. For special quoting,
use :class:`.quoted_name`.
"""
return self.dialect.get_indexes(self.bind, table_name,
schema,
info_cache=self.info_cache, **kw)
def get_unique_constraints(self, table_name, schema=None, **kw):
"""Return information about unique constraints in `table_name`.
Given a string `table_name` and an optional string `schema`, return
unique constraint information as a list of dicts with these keys:
name
the unique constraint's name
column_names
list of column names in order
:param table_name: string name of the table. For special quoting,
use :class:`.quoted_name`.
:param schema: string schema name; if omitted, uses the default schema
of the database connection. For special quoting,
use :class:`.quoted_name`.
.. versionadded:: 0.8.4
"""
return self.dialect.get_unique_constraints(
self.bind, table_name, schema, info_cache=self.info_cache, **kw)
def reflecttable(self, table, include_columns, exclude_columns=()):
"""Given a Table object, load its internal constructs based on
introspection.
This is the underlying method used by most dialects to produce
table reflection. Direct usage is like::
from sqlalchemy import create_engine, MetaData, Table
from sqlalchemy.engine import reflection
engine = create_engine('...')
meta = MetaData()
user_table = Table('user', meta)
insp = Inspector.from_engine(engine)
insp.reflecttable(user_table, None)
:param table: a :class:`~sqlalchemy.schema.Table` instance.
:param include_columns: a list of string column names to include
in the reflection process. If ``None``, all columns are reflected.
"""
dialect = self.bind.dialect
schema = table.schema
table_name = table.name
# get table-level arguments that are specifically
# intended for reflection, e.g. oracle_resolve_synonyms.
# these are unconditionally passed to related Table
# objects
reflection_options = dict(
(k, table.dialect_kwargs.get(k))
for k in dialect.reflection_options
if k in table.dialect_kwargs
)
# reflect table options, like mysql_engine
tbl_opts = self.get_table_options(
table_name, schema, **table.dialect_kwargs)
if tbl_opts:
# add additional kwargs to the Table if the dialect
# returned them
table._validate_dialect_kwargs(tbl_opts)
if util.py2k:
if isinstance(schema, str):
schema = schema.decode(dialect.encoding)
if isinstance(table_name, str):
table_name = table_name.decode(dialect.encoding)
found_table = False
cols_by_orig_name = {}
for col_d in self.get_columns(
table_name, schema, **table.dialect_kwargs):
found_table = True
self._reflect_column(
table, col_d, include_columns,
exclude_columns, cols_by_orig_name)
if not found_table:
raise exc.NoSuchTableError(table.name)
self._reflect_pk(
table_name, schema, table, cols_by_orig_name, exclude_columns)
self._reflect_fk(
table_name, schema, table, cols_by_orig_name,
exclude_columns, reflection_options)
self._reflect_indexes(
table_name, schema, table, cols_by_orig_name,
include_columns, exclude_columns, reflection_options)
self._reflect_unique_constraints(
table_name, schema, table, cols_by_orig_name,
include_columns, exclude_columns, reflection_options)
def _reflect_column(
self, table, col_d, include_columns,
exclude_columns, cols_by_orig_name):
orig_name = col_d['name']
table.dispatch.column_reflect(self, table, col_d)
# fetch name again as column_reflect is allowed to
# change it
name = col_d['name']
if (include_columns and name not in include_columns) \
or (exclude_columns and name in exclude_columns):
return
coltype = col_d['type']
col_kw = dict(
(k, col_d[k])
for k in ['nullable', 'autoincrement', 'quote', 'info', 'key']
if k in col_d
)
colargs = []
if col_d.get('default') is not None:
# the "default" value is assumed to be a literal SQL
# expression, so is wrapped in text() so that no quoting
# occurs on re-issuance.
colargs.append(
sa_schema.DefaultClause(
sql.text(col_d['default']), _reflected=True
)
)
if 'sequence' in col_d:
self._reflect_col_sequence(col_d, colargs)
cols_by_orig_name[orig_name] = col = \
sa_schema.Column(name, coltype, *colargs, **col_kw)
if col.key in table.primary_key:
col.primary_key = True
table.append_column(col)
def _reflect_col_sequence(self, col_d, colargs):
if 'sequence' in col_d:
# TODO: mssql and sybase are using this.
seq = col_d['sequence']
sequence = sa_schema.Sequence(seq['name'], 1, 1)
if 'start' in seq:
sequence.start = seq['start']
if 'increment' in seq:
sequence.increment = seq['increment']
colargs.append(sequence)
def _reflect_pk(
self, table_name, schema, table,
cols_by_orig_name, exclude_columns):
pk_cons = self.get_pk_constraint(
table_name, schema, **table.dialect_kwargs)
if pk_cons:
pk_cols = [
cols_by_orig_name[pk]
for pk in pk_cons['constrained_columns']
if pk in cols_by_orig_name and pk not in exclude_columns
]
# update pk constraint name
table.primary_key.name = pk_cons.get('name')
# tell the PKConstraint to re-initialize
# its column collection
table.primary_key._reload(pk_cols)
def _reflect_fk(
self, table_name, schema, table, cols_by_orig_name,
exclude_columns, reflection_options):
fkeys = self.get_foreign_keys(
table_name, schema, **table.dialect_kwargs)
for fkey_d in fkeys:
conname = fkey_d['name']
# look for columns by orig name in cols_by_orig_name,
# but support columns that are in-Python only as fallback
constrained_columns = [
cols_by_orig_name[c].key
if c in cols_by_orig_name else c
for c in fkey_d['constrained_columns']
]
if exclude_columns and set(constrained_columns).intersection(
exclude_columns):
continue
referred_schema = fkey_d['referred_schema']
referred_table = fkey_d['referred_table']
referred_columns = fkey_d['referred_columns']
refspec = []
if referred_schema is not None:
sa_schema.Table(referred_table, table.metadata,
autoload=True, schema=referred_schema,
autoload_with=self.bind,
**reflection_options
)
for column in referred_columns:
refspec.append(".".join(
[referred_schema, referred_table, column]))
else:
sa_schema.Table(referred_table, table.metadata, autoload=True,
autoload_with=self.bind,
schema=sa_schema.BLANK_SCHEMA,
**reflection_options
)
for column in referred_columns:
refspec.append(".".join([referred_table, column]))
if 'options' in fkey_d:
options = fkey_d['options']
else:
options = {}
table.append_constraint(
sa_schema.ForeignKeyConstraint(constrained_columns, refspec,
conname, link_to_name=True,
**options))
def _reflect_indexes(
self, table_name, schema, table, cols_by_orig_name,
include_columns, exclude_columns, reflection_options):
# Indexes
indexes = self.get_indexes(table_name, schema)
for index_d in indexes:
name = index_d['name']
columns = index_d['column_names']
unique = index_d['unique']
flavor = index_d.get('type', 'index')
dialect_options = index_d.get('dialect_options', {})
duplicates = index_d.get('duplicates_constraint')
if include_columns and \
not set(columns).issubset(include_columns):
util.warn(
"Omitting %s key for (%s), key covers omitted columns." %
(flavor, ', '.join(columns)))
continue
if duplicates:
continue
# look for columns by orig name in cols_by_orig_name,
# but support columns that are in-Python only as fallback
idx_cols = []
for c in columns:
try:
idx_col = cols_by_orig_name[c] \
if c in cols_by_orig_name else table.c[c]
except KeyError:
util.warn(
"%s key '%s' was not located in "
"columns for table '%s'" % (
flavor, c, table_name
))
else:
idx_cols.append(idx_col)
sa_schema.Index(
name, *idx_cols,
**dict(list(dialect_options.items()) + [('unique', unique)])
)
def _reflect_unique_constraints(
self, table_name, schema, table, cols_by_orig_name,
include_columns, exclude_columns, reflection_options):
# Unique Constraints
try:
constraints = self.get_unique_constraints(table_name, schema)
except NotImplementedError:
# optional dialect feature
return
for const_d in constraints:
conname = const_d['name']
columns = const_d['column_names']
duplicates = const_d.get('duplicates_index')
if include_columns and \
not set(columns).issubset(include_columns):
util.warn(
"Omitting unique constraint key for (%s), "
"key covers omitted columns." %
', '.join(columns))
continue
if duplicates:
continue
# look for columns by orig name in cols_by_orig_name,
# but support columns that are in-Python only as fallback
constrained_cols = []
for c in columns:
try:
constrained_col = cols_by_orig_name[c] \
if c in cols_by_orig_name else table.c[c]
except KeyError:
util.warn(
"unique constraint key '%s' was not located in "
"columns for table '%s'" % (c, table_name))
else:
constrained_cols.append(constrained_col)
table.append_constraint(
sa_schema.UniqueConstraint(*constrained_cols, name=conname))
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