# engine/reflection.py # Copyright (C) 2005-2021 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 .base import Connectable from .. import exc from .. import inspection from .. import sql from .. import util from ..sql import operators from ..sql import schema as sa_schema from ..sql.type_api import TypeEngine from ..util import deprecated from ..util import topological @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 k != "info_cache"), ) 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:`_reflection.Inspector` object is usually created via the :func:`_sa.inspect` function:: from sqlalchemy import inspect, create_engine engine = create_engine('...') insp = inspect(engine) The inspection method above is equivalent to using the :meth:`_reflection.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:`_reflection.Inspector` subclass that provides additional methods specific to the dialect's target database. """ def __init__(self, bind): """Initialize a new :class:`_reflection.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:`_reflection.Inspector`, see :meth:`_reflection.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:`_reflection.Inspector` in that the :class:`~sqlalchemy.engine.interfaces.Dialect` is given a chance to provide a dialect-specific :class:`_reflection.Inspector` instance, which may provide additional methods. See the example at :class:`_reflection.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 [] @util.deprecated_params( order_by=( "1.0", "The :paramref:`get_table_names.order_by` parameter is deprecated " "and will be removed in a future release. Please refer to " ":meth:`_reflection.Inspector.get_sorted_table_and_fkc_names` " "for a " "more comprehensive solution to resolving foreign key cycles " "between tables.", ) ) 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:`_reflection.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. .. seealso:: :meth:`_reflection.Inspector.get_sorted_table_and_fkc_names` :attr:`_schema.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:`_reflection.Inspector.get_table_names` :func:`.sort_tables_and_constraints` - similar method which works with an already-given :class:`_schema.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`` - the type of this column; an instance of :class:`~sqlalchemy.types.TypeEngine` * ``nullable`` - boolean flag if the column is NULL or NOT NULL * ``default`` - the column's server default value - this is returned as a string SQL expression. * ``autoincrement`` - indicates that the column is auto incremented - this is returned as a boolean or 'auto' * ``comment`` - (optional) the comment on the column. Only some dialects return this key * ``computed`` - (optional) when present it indicates that this column is computed by the database. Only some dialects return this key. Returned as a dict with the keys: * ``sqltext`` - the expression used to generate this column returned as a string SQL expression * ``persisted`` - (optional) boolean that indicates if the column is stored in the table .. versionadded:: 1.3.16 - added support for computed reflection. * ``dialect_options`` - (optional) a dict with dialect specific options :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: list of dictionaries, each representing the definition of a database column. """ 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", "The :meth:`_reflection.Inspector.get_primary_keys` " "method is deprecated and " "will be removed in a future release. Please refer to the " ":meth:`_reflection.Inspector.get_pk_constraint` method.", ) 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 * ``column_sorting`` - optional dict mapping column names to tuple of sort keywords, which may include ``asc``, ``desc``, ``nullsfirst``, ``nullslast``. .. versionadded:: 1.3.5 * ``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`. """ return self.dialect.get_unique_constraints( self.bind, table_name, schema, info_cache=self.info_cache, **kw ) def get_table_comment(self, table_name, schema=None, **kw): """Return information about the table comment for ``table_name``. Given a string ``table_name`` and an optional string ``schema``, return table comment information as a dictionary with these keys: * ``text`` - text of the comment. Raises ``NotImplementedError`` for a dialect that does not support comments. .. versionadded:: 1.2 """ return self.dialect.get_table_comment( self.bind, table_name, schema, info_cache=self.info_cache, **kw ) def get_check_constraints(self, table_name, schema=None, **kw): """Return information about check constraints in `table_name`. Given a string `table_name` and an optional string `schema`, return check constraint information as a list of dicts with these keys: * ``name`` - the check constraint's name * ``sqltext`` - the check constraint's SQL expression * ``dialect_options`` - may or may not be present; a dictionary with additional dialect-specific options for this CHECK constraint .. versionadded:: 1.3.8 :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:: 1.1.0 """ return self.dialect.get_check_constraints( self.bind, table_name, schema, info_cache=self.info_cache, **kw ) def reflecttable( self, table, include_columns, exclude_columns=(), resolve_fks=True, _extend_on=None, ): """Given a :class:`_schema.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.reflection import Inspector 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. """ if _extend_on is not None: if table in _extend_on: return else: _extend_on.add(table) dialect = self.bind.dialect schema = self.bind.schema_for_object(table) 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, resolve_fks, _extend_on, 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, ) self._reflect_check_constraints( table_name, schema, table, cols_by_orig_name, include_columns, exclude_columns, reflection_options, ) self._reflect_table_comment( table_name, schema, table, 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", "comment", ] if k in col_d ) if "dialect_options" in col_d: col_kw.update(col_d["dialect_options"]) colargs = [] if col_d.get("default") is not None: default = col_d["default"] if isinstance(default, sql.elements.TextClause): default = sa_schema.DefaultClause(default, _reflected=True) elif not isinstance(default, sa_schema.FetchedValue): default = sa_schema.DefaultClause( sql.text(col_d["default"]), _reflected=True ) colargs.append(default) if "computed" in col_d: computed = sa_schema.Computed(**col_d["computed"]) colargs.append(computed) 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, resolve_fks, _extend_on, 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: if resolve_fks: sa_schema.Table( referred_table, table.metadata, autoload=True, schema=referred_schema, autoload_with=self.bind, _extend_on=_extend_on, **reflection_options ) for column in referred_columns: refspec.append( ".".join([referred_schema, referred_table, column]) ) else: if resolve_fks: sa_schema.Table( referred_table, table.metadata, autoload=True, autoload_with=self.bind, schema=sa_schema.BLANK_SCHEMA, _extend_on=_extend_on, **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 ) ) _index_sort_exprs = [ ("asc", operators.asc_op), ("desc", operators.desc_op), ("nullsfirst", operators.nullsfirst_op), ("nullslast", operators.nullslast_op), ] 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"] column_sorting = index_d.get("column_sorting", {}) 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) ) continue c_sorting = column_sorting.get(c, ()) for k, op in self._index_sort_exprs: if k in c_sorting: idx_col = op(idx_col) idx_cols.append(idx_col) sa_schema.Index( name, *idx_cols, _table=table, **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) ) def _reflect_check_constraints( self, table_name, schema, table, cols_by_orig_name, include_columns, exclude_columns, reflection_options, ): try: constraints = self.get_check_constraints(table_name, schema) except NotImplementedError: # optional dialect feature return for const_d in constraints: table.append_constraint(sa_schema.CheckConstraint(**const_d)) def _reflect_table_comment( self, table_name, schema, table, reflection_options ): try: comment_dict = self.get_table_comment(table_name, schema) except NotImplementedError: return else: table.comment = comment_dict.get("text", None)