# sql/base.py # Copyright (C) 2005-2014 the SQLAlchemy authors and contributors # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """Foundational utilities common to many sql modules. """ from .. import util, exc import itertools from .visitors import ClauseVisitor import re import collections PARSE_AUTOCOMMIT = util.symbol('PARSE_AUTOCOMMIT') NO_ARG = util.symbol('NO_ARG') class Immutable(object): """mark a ClauseElement as 'immutable' when expressions are cloned.""" def unique_params(self, *optionaldict, **kwargs): raise NotImplementedError("Immutable objects do not support copying") def params(self, *optionaldict, **kwargs): raise NotImplementedError("Immutable objects do not support copying") def _clone(self): return self def _from_objects(*elements): return itertools.chain(*[element._from_objects for element in elements]) @util.decorator def _generative(fn, *args, **kw): """Mark a method as generative.""" self = args[0]._generate() fn(self, *args[1:], **kw) return self class _DialectArgView(collections.MutableMapping): """A dictionary view of dialect-level arguments in the form _. """ def __init__(self, obj): self.obj = obj def _key(self, key): try: dialect, value_key = key.split("_", 1) except ValueError: raise KeyError(key) else: return dialect, value_key def __getitem__(self, key): dialect, value_key = self._key(key) try: opt = self.obj.dialect_options[dialect] except exc.NoSuchModuleError: raise KeyError(key) else: return opt[value_key] def __setitem__(self, key, value): try: dialect, value_key = self._key(key) except KeyError: raise exc.ArgumentError( "Keys must be of the form _") else: self.obj.dialect_options[dialect][value_key] = value def __delitem__(self, key): dialect, value_key = self._key(key) del self.obj.dialect_options[dialect][value_key] def __len__(self): return sum(len(args._non_defaults) for args in self.obj.dialect_options.values()) def __iter__(self): return ( "%s_%s" % (dialect_name, value_name) for dialect_name in self.obj.dialect_options for value_name in self.obj.dialect_options[dialect_name]._non_defaults ) class _DialectArgDict(collections.MutableMapping): """A dictionary view of dialect-level arguments for a specific dialect. Maintains a separate collection of user-specified arguments and dialect-specified default arguments. """ def __init__(self): self._non_defaults = {} self._defaults = {} def __len__(self): return len(set(self._non_defaults).union(self._defaults)) def __iter__(self): return iter(set(self._non_defaults).union(self._defaults)) def __getitem__(self, key): if key in self._non_defaults: return self._non_defaults[key] else: return self._defaults[key] def __setitem__(self, key, value): self._non_defaults[key] = value def __delitem__(self, key): del self._non_defaults[key] class DialectKWArgs(object): """Establish the ability for a class to have dialect-specific arguments with defaults and constructor validation. The :class:`.DialectKWArgs` interacts with the :attr:`.DefaultDialect.construct_arguments` present on a dialect. .. seealso:: :attr:`.DefaultDialect.construct_arguments` """ @classmethod def argument_for(cls, dialect_name, argument_name, default): """Add a new kind of dialect-specific keyword argument for this class. E.g.:: Index.argument_for("mydialect", "length", None) some_index = Index('a', 'b', mydialect_length=5) The :meth:`.DialectKWArgs.argument_for` method is a per-argument way adding extra arguments to the :attr:`.DefaultDialect.construct_arguments` dictionary. This dictionary provides a list of argument names accepted by various schema-level constructs on behalf of a dialect. New dialects should typically specify this dictionary all at once as a data member of the dialect class. The use case for ad-hoc addition of argument names is typically for end-user code that is also using a custom compilation scheme which consumes the additional arguments. :param dialect_name: name of a dialect. The dialect must be locatable, else a :class:`.NoSuchModuleError` is raised. The dialect must also include an existing :attr:`.DefaultDialect.construct_arguments` collection, indicating that it participates in the keyword-argument validation and default system, else :class:`.ArgumentError` is raised. If the dialect does not include this collection, then any keyword argument can be specified on behalf of this dialect already. All dialects packaged within SQLAlchemy include this collection, however for third party dialects, support may vary. :param argument_name: name of the parameter. :param default: default value of the parameter. .. versionadded:: 0.9.4 """ construct_arg_dictionary = DialectKWArgs._kw_registry[dialect_name] if construct_arg_dictionary is None: raise exc.ArgumentError("Dialect '%s' does have keyword-argument " "validation and defaults enabled configured" % dialect_name) if cls not in construct_arg_dictionary: construct_arg_dictionary[cls] = {} construct_arg_dictionary[cls][argument_name] = default @util.memoized_property def dialect_kwargs(self): """A collection of keyword arguments specified as dialect-specific options to this construct. The arguments are present here in their original ``_`` format. Only arguments that were actually passed are included; unlike the :attr:`.DialectKWArgs.dialect_options` collection, which contains all options known by this dialect including defaults. The collection is also writable; keys are accepted of the form ``_`` where the value will be assembled into the list of options. .. versionadded:: 0.9.2 .. versionchanged:: 0.9.4 The :attr:`.DialectKWArgs.dialect_kwargs` collection is now writable. .. seealso:: :attr:`.DialectKWArgs.dialect_options` - nested dictionary form """ return _DialectArgView(self) @property def kwargs(self): """A synonym for :attr:`.DialectKWArgs.dialect_kwargs`.""" return self.dialect_kwargs @util.dependencies("sqlalchemy.dialects") def _kw_reg_for_dialect(dialects, dialect_name): dialect_cls = dialects.registry.load(dialect_name) if dialect_cls.construct_arguments is None: return None return dict(dialect_cls.construct_arguments) _kw_registry = util.PopulateDict(_kw_reg_for_dialect) def _kw_reg_for_dialect_cls(self, dialect_name): construct_arg_dictionary = DialectKWArgs._kw_registry[dialect_name] d = _DialectArgDict() if construct_arg_dictionary is None: d._defaults.update({"*": None}) else: for cls in reversed(self.__class__.__mro__): if cls in construct_arg_dictionary: d._defaults.update(construct_arg_dictionary[cls]) return d @util.memoized_property def dialect_options(self): """A collection of keyword arguments specified as dialect-specific options to this construct. This is a two-level nested registry, keyed to ```` and ````. For example, the ``postgresql_where`` argument would be locatable as:: arg = my_object.dialect_options['postgresql']['where'] .. versionadded:: 0.9.2 .. seealso:: :attr:`.DialectKWArgs.dialect_kwargs` - flat dictionary form """ return util.PopulateDict( util.portable_instancemethod(self._kw_reg_for_dialect_cls) ) def _validate_dialect_kwargs(self, kwargs): # validate remaining kwargs that they all specify DB prefixes if not kwargs: return for k in kwargs: m = re.match('^(.+?)_(.+)$', k) if not m: raise TypeError("Additional arguments should be " "named _, got '%s'" % k) dialect_name, arg_name = m.group(1, 2) try: construct_arg_dictionary = self.dialect_options[dialect_name] except exc.NoSuchModuleError: util.warn( "Can't validate argument %r; can't " "locate any SQLAlchemy dialect named %r" % (k, dialect_name)) self.dialect_options[dialect_name] = d = _DialectArgDict() d._defaults.update({"*": None}) d._non_defaults[arg_name] = kwargs[k] else: if "*" not in construct_arg_dictionary and \ arg_name not in construct_arg_dictionary: raise exc.ArgumentError( "Argument %r is not accepted by " "dialect %r on behalf of %r" % ( k, dialect_name, self.__class__ )) else: construct_arg_dictionary[arg_name] = kwargs[k] class Generative(object): """Allow a ClauseElement to generate itself via the @_generative decorator. """ def _generate(self): s = self.__class__.__new__(self.__class__) s.__dict__ = self.__dict__.copy() return s class Executable(Generative): """Mark a ClauseElement as supporting execution. :class:`.Executable` is a superclass for all "statement" types of objects, including :func:`select`, :func:`delete`, :func:`update`, :func:`insert`, :func:`text`. """ supports_execution = True _execution_options = util.immutabledict() _bind = None @_generative def execution_options(self, **kw): """ Set non-SQL options for the statement which take effect during execution. Execution options can be set on a per-statement or per :class:`.Connection` basis. Additionally, the :class:`.Engine` and ORM :class:`~.orm.query.Query` objects provide access to execution options which they in turn configure upon connections. The :meth:`execution_options` method is generative. A new instance of this statement is returned that contains the options:: statement = select([table.c.x, table.c.y]) statement = statement.execution_options(autocommit=True) Note that only a subset of possible execution options can be applied to a statement - these include "autocommit" and "stream_results", but not "isolation_level" or "compiled_cache". See :meth:`.Connection.execution_options` for a full list of possible options. .. seealso:: :meth:`.Connection.execution_options()` :meth:`.Query.execution_options()` """ if 'isolation_level' in kw: raise exc.ArgumentError( "'isolation_level' execution option may only be specified " "on Connection.execution_options(), or " "per-engine using the isolation_level " "argument to create_engine()." ) if 'compiled_cache' in kw: raise exc.ArgumentError( "'compiled_cache' execution option may only be specified " "on Connection.execution_options(), not per statement." ) self._execution_options = self._execution_options.union(kw) def execute(self, *multiparams, **params): """Compile and execute this :class:`.Executable`.""" e = self.bind if e is None: label = getattr(self, 'description', self.__class__.__name__) msg = ('This %s is not directly bound to a Connection or Engine.' 'Use the .execute() method of a Connection or Engine ' 'to execute this construct.' % label) raise exc.UnboundExecutionError(msg) return e._execute_clauseelement(self, multiparams, params) def scalar(self, *multiparams, **params): """Compile and execute this :class:`.Executable`, returning the result's scalar representation. """ return self.execute(*multiparams, **params).scalar() @property def bind(self): """Returns the :class:`.Engine` or :class:`.Connection` to which this :class:`.Executable` is bound, or None if none found. This is a traversal which checks locally, then checks among the "from" clauses of associated objects until a bound engine or connection is found. """ if self._bind is not None: return self._bind for f in _from_objects(self): if f is self: continue engine = f.bind if engine is not None: return engine else: return None class SchemaEventTarget(object): """Base class for elements that are the targets of :class:`.DDLEvents` events. This includes :class:`.SchemaItem` as well as :class:`.SchemaType`. """ def _set_parent(self, parent): """Associate with this SchemaEvent's parent object.""" raise NotImplementedError() def _set_parent_with_dispatch(self, parent): self.dispatch.before_parent_attach(self, parent) self._set_parent(parent) self.dispatch.after_parent_attach(self, parent) class SchemaVisitor(ClauseVisitor): """Define the visiting for ``SchemaItem`` objects.""" __traverse_options__ = {'schema_visitor': True} class ColumnCollection(util.OrderedProperties): """An ordered dictionary that stores a list of ColumnElement instances. Overrides the ``__eq__()`` method to produce SQL clauses between sets of correlated columns. """ def __init__(self): super(ColumnCollection, self).__init__() self.__dict__['_all_col_set'] = util.column_set() self.__dict__['_all_columns'] = [] def __str__(self): return repr([str(c) for c in self]) def replace(self, column): """add the given column to this collection, removing unaliased versions of this column as well as existing columns with the same key. e.g.:: t = Table('sometable', metadata, Column('col1', Integer)) t.columns.replace(Column('col1', Integer, key='columnone')) will remove the original 'col1' from the collection, and add the new column under the name 'columnname'. Used by schema.Column to override columns during table reflection. """ remove_col = None if column.name in self and column.key != column.name: other = self[column.name] if other.name == other.key: remove_col = other self._all_col_set.remove(other) del self._data[other.key] if column.key in self._data: remove_col = self._data[column.key] self._all_col_set.remove(remove_col) self._all_col_set.add(column) self._data[column.key] = column if remove_col is not None: self._all_columns[:] = [column if c is remove_col else c for c in self._all_columns] else: self._all_columns.append(column) def add(self, column): """Add a column to this collection. The key attribute of the column will be used as the hash key for this dictionary. """ if not column.key: raise exc.ArgumentError( "Can't add unnamed column to column collection") self[column.key] = column def __delitem__(self, key): raise NotImplementedError() def __setattr__(self, key, object): raise NotImplementedError() def __setitem__(self, key, value): if key in self: # this warning is primarily to catch select() statements # which have conflicting column names in their exported # columns collection existing = self[key] if not existing.shares_lineage(value): util.warn('Column %r on table %r being replaced by ' '%r, which has the same key. Consider ' 'use_labels for select() statements.' % (key, getattr(existing, 'table', None), value)) # pop out memoized proxy_set as this # operation may very well be occurring # in a _make_proxy operation util.memoized_property.reset(value, "proxy_set") self._all_col_set.add(value) self._all_columns.append(value) self._data[key] = value def clear(self): raise NotImplementedError() def remove(self, column): del self._data[column.key] self._all_col_set.remove(column) self._all_columns[:] = [c for c in self._all_columns if c is not column] def update(self, iter): cols = list(iter) self._all_columns.extend(c for label, c in cols if c not in self._all_col_set) self._all_col_set.update(c for label, c in cols) self._data.update((label, c) for label, c in cols) def extend(self, iter): cols = list(iter) self._all_columns.extend(c for c in cols if c not in self._all_col_set) self._all_col_set.update(cols) self._data.update((c.key, c) for c in cols) __hash__ = None @util.dependencies("sqlalchemy.sql.elements") def __eq__(self, elements, other): l = [] for c in getattr(other, "_all_columns", other): for local in self._all_columns: if c.shares_lineage(local): l.append(c == local) return elements.and_(*l) def __contains__(self, other): if not isinstance(other, util.string_types): raise exc.ArgumentError("__contains__ requires a string argument") return util.OrderedProperties.__contains__(self, other) def __getstate__(self): return {'_data': self.__dict__['_data'], '_all_columns': self.__dict__['_all_columns']} def __setstate__(self, state): self.__dict__['_data'] = state['_data'] self.__dict__['_all_columns'] = state['_all_columns'] self.__dict__['_all_col_set'] = util.column_set(state['_all_columns']) def contains_column(self, col): # this has to be done via set() membership return col in self._all_col_set def as_immutable(self): return ImmutableColumnCollection(self._data, self._all_col_set, self._all_columns) class ImmutableColumnCollection(util.ImmutableProperties, ColumnCollection): def __init__(self, data, colset, all_columns): util.ImmutableProperties.__init__(self, data) self.__dict__['_all_col_set'] = colset self.__dict__['_all_columns'] = all_columns extend = remove = util.ImmutableProperties._immutable class ColumnSet(util.ordered_column_set): def contains_column(self, col): return col in self def extend(self, cols): for col in cols: self.add(col) def __add__(self, other): return list(self) + list(other) @util.dependencies("sqlalchemy.sql.elements") def __eq__(self, elements, other): l = [] for c in other: for local in self: if c.shares_lineage(local): l.append(c == local) return elements.and_(*l) def __hash__(self): return hash(tuple(x for x in self)) def _bind_or_error(schemaitem, msg=None): bind = schemaitem.bind if not bind: name = schemaitem.__class__.__name__ label = getattr(schemaitem, 'fullname', getattr(schemaitem, 'name', None)) if label: item = '%s object %r' % (name, label) else: item = '%s object' % name if msg is None: msg = "%s is not bound to an Engine or Connection. "\ "Execution can not proceed without a database to execute "\ "against." % item raise exc.UnboundExecutionError(msg) return bind