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Editing: selectable.py
# sql/selectable.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 """The :class:`_expression.FromClause` class of SQL expression elements, representing SQL tables and derived rowsets. """ import collections import itertools import operator from operator import attrgetter from sqlalchemy.sql.visitors import Visitable from . import operators from . import type_api from .annotation import Annotated from .base import _from_objects from .base import _generative from .base import ColumnCollection from .base import ColumnSet from .base import Executable from .base import Generative from .base import Immutable from .elements import _anonymous_label from .elements import _clause_element_as_expr from .elements import _clone from .elements import _cloned_difference from .elements import _cloned_intersection from .elements import _document_text_coercion from .elements import _expand_cloned from .elements import _interpret_as_column_or_from from .elements import _literal_and_labels_as_label_reference from .elements import _literal_as_label_reference from .elements import _literal_as_text from .elements import _no_text_coercion from .elements import _select_iterables from .elements import and_ from .elements import BindParameter from .elements import ClauseElement from .elements import ClauseList from .elements import Grouping from .elements import literal_column from .elements import True_ from .elements import UnaryExpression from .. import exc from .. import inspection from .. import util def _interpret_as_from(element): insp = inspection.inspect(element, raiseerr=False) if insp is None: if isinstance(element, util.string_types): _no_text_coercion(element) try: return insp.selectable except AttributeError as err: util.raise_( exc.ArgumentError("FROM expression expected"), replace_context=err ) def _interpret_as_select(element): element = _interpret_as_from(element) if isinstance(element, Alias): element = element.original if not isinstance(element, SelectBase): element = element.select() return element class _OffsetLimitParam(BindParameter): @property def _limit_offset_value(self): return self.effective_value def _offset_or_limit_clause(element, name=None, type_=None): """Convert the given value to an "offset or limit" clause. This handles incoming integers and converts to an expression; if an expression is already given, it is passed through. """ if element is None: return None elif hasattr(element, "__clause_element__"): return element.__clause_element__() elif isinstance(element, Visitable): return element else: value = util.asint(element) return _OffsetLimitParam(name, value, type_=type_, unique=True) def _offset_or_limit_clause_asint(clause, attrname): """Convert the "offset or limit" clause of a select construct to an integer. This is only possible if the value is stored as a simple bound parameter. Otherwise, a compilation error is raised. """ if clause is None: return None try: value = clause._limit_offset_value except AttributeError as err: util.raise_( exc.CompileError( "This SELECT structure does not use a simple " "integer value for %s" % attrname ), replace_context=err, ) else: return util.asint(value) def subquery(alias, *args, **kwargs): r"""Return an :class:`_expression.Alias` object derived from a :class:`_expression.Select`. :param alias: the alias name :param \*args, \**kwargs: all other arguments are delivered to the :func:`_expression.select` function. """ return Select(*args, **kwargs).alias(alias) class Selectable(ClauseElement): """Mark a class as being selectable.""" __visit_name__ = "selectable" is_selectable = True @property def selectable(self): return self class HasPrefixes(object): _prefixes = () @_generative @_document_text_coercion( "expr", ":meth:`_expression.HasPrefixes.prefix_with`", ":paramref:`.HasPrefixes.prefix_with.*expr`", ) def prefix_with(self, *expr, **kw): r"""Add one or more expressions following the statement keyword, i.e. SELECT, INSERT, UPDATE, or DELETE. Generative. This is used to support backend-specific prefix keywords such as those provided by MySQL. E.g.:: stmt = table.insert().prefix_with("LOW_PRIORITY", dialect="mysql") # MySQL 5.7 optimizer hints stmt = select([table]).prefix_with( "/*+ BKA(t1) */", dialect="mysql") Multiple prefixes can be specified by multiple calls to :meth:`_expression.HasPrefixes.prefix_with`. :param \*expr: textual or :class:`_expression.ClauseElement` construct which will be rendered following the INSERT, UPDATE, or DELETE keyword. :param \**kw: A single keyword 'dialect' is accepted. This is an optional string dialect name which will limit rendering of this prefix to only that dialect. """ dialect = kw.pop("dialect", None) if kw: raise exc.ArgumentError( "Unsupported argument(s): %s" % ",".join(kw) ) self._setup_prefixes(expr, dialect) def _setup_prefixes(self, prefixes, dialect=None): self._prefixes = self._prefixes + tuple( [ (_literal_as_text(p, allow_coercion_to_text=True), dialect) for p in prefixes ] ) class HasSuffixes(object): _suffixes = () @_generative @_document_text_coercion( "expr", ":meth:`_expression.HasSuffixes.suffix_with`", ":paramref:`.HasSuffixes.suffix_with.*expr`", ) def suffix_with(self, *expr, **kw): r"""Add one or more expressions following the statement as a whole. This is used to support backend-specific suffix keywords on certain constructs. E.g.:: stmt = select([col1, col2]).cte().suffix_with( "cycle empno set y_cycle to 1 default 0", dialect="oracle") Multiple suffixes can be specified by multiple calls to :meth:`_expression.HasSuffixes.suffix_with`. :param \*expr: textual or :class:`_expression.ClauseElement` construct which will be rendered following the target clause. :param \**kw: A single keyword 'dialect' is accepted. This is an optional string dialect name which will limit rendering of this suffix to only that dialect. """ dialect = kw.pop("dialect", None) if kw: raise exc.ArgumentError( "Unsupported argument(s): %s" % ",".join(kw) ) self._setup_suffixes(expr, dialect) def _setup_suffixes(self, suffixes, dialect=None): self._suffixes = self._suffixes + tuple( [ (_literal_as_text(p, allow_coercion_to_text=True), dialect) for p in suffixes ] ) class FromClause(Selectable): """Represent an element that can be used within the ``FROM`` clause of a ``SELECT`` statement. The most common forms of :class:`_expression.FromClause` are the :class:`_schema.Table` and the :func:`_expression.select` constructs. Key features common to all :class:`_expression.FromClause` objects include: * a :attr:`.c` collection, which provides per-name access to a collection of :class:`_expression.ColumnElement` objects. * a :attr:`.primary_key` attribute, which is a collection of all those :class:`_expression.ColumnElement` objects that indicate the ``primary_key`` flag. * Methods to generate various derivations of a "from" clause, including :meth:`_expression.FromClause.alias`, :meth:`_expression.FromClause.join`, :meth:`_expression.FromClause.select`. """ __visit_name__ = "fromclause" named_with_column = False _hide_froms = [] _is_join = False _is_select = False _is_from_container = False _is_lateral = False _textual = False """A marker that allows us to easily distinguish a :class:`.TextAsFrom` or similar object from other kinds of :class:`_expression.FromClause` objects.""" schema = None """Define the 'schema' attribute for this :class:`_expression.FromClause`. This is typically ``None`` for most objects except that of :class:`_schema.Table`, where it is taken as the value of the :paramref:`_schema.Table.schema` argument. """ def _translate_schema(self, effective_schema, map_): return effective_schema _memoized_property = util.group_expirable_memoized_property(["_columns"]) @util.deprecated( "1.1", message="The :meth:`.FromClause.count` method is deprecated, " "and will be removed in a future release. Please use the " ":class:`_functions.count` function available from the " ":attr:`.func` namespace.", ) @util.dependencies("sqlalchemy.sql.functions") def count(self, functions, whereclause=None, **params): """Return a SELECT COUNT generated against this :class:`_expression.FromClause`. .. seealso:: :class:`_functions.count` """ if self.primary_key: col = list(self.primary_key)[0] else: col = list(self.columns)[0] return Select( [functions.func.count(col).label("tbl_row_count")], whereclause, from_obj=[self], **params ) def select(self, whereclause=None, **params): """Return a SELECT of this :class:`_expression.FromClause`. .. seealso:: :func:`_expression.select` - general purpose method which allows for arbitrary column lists. """ return Select([self], whereclause, **params) def join(self, right, onclause=None, isouter=False, full=False): """Return a :class:`_expression.Join` from this :class:`_expression.FromClause` to another :class:`_expression.FromClause`. E.g.:: from sqlalchemy import join j = user_table.join(address_table, user_table.c.id == address_table.c.user_id) stmt = select([user_table]).select_from(j) would emit SQL along the lines of:: SELECT user.id, user.name FROM user JOIN address ON user.id = address.user_id :param right: the right side of the join; this is any :class:`_expression.FromClause` object such as a :class:`_schema.Table` object, and may also be a selectable-compatible object such as an ORM-mapped class. :param onclause: a SQL expression representing the ON clause of the join. If left at ``None``, :meth:`_expression.FromClause.join` will attempt to join the two tables based on a foreign key relationship. :param isouter: if True, render a LEFT OUTER JOIN, instead of JOIN. :param full: if True, render a FULL OUTER JOIN, instead of LEFT OUTER JOIN. Implies :paramref:`.FromClause.join.isouter`. .. versionadded:: 1.1 .. seealso:: :func:`_expression.join` - standalone function :class:`_expression.Join` - the type of object produced """ return Join(self, right, onclause, isouter, full) def outerjoin(self, right, onclause=None, full=False): """Return a :class:`_expression.Join` from this :class:`_expression.FromClause` to another :class:`FromClause`, with the "isouter" flag set to True. E.g.:: from sqlalchemy import outerjoin j = user_table.outerjoin(address_table, user_table.c.id == address_table.c.user_id) The above is equivalent to:: j = user_table.join( address_table, user_table.c.id == address_table.c.user_id, isouter=True) :param right: the right side of the join; this is any :class:`_expression.FromClause` object such as a :class:`_schema.Table` object, and may also be a selectable-compatible object such as an ORM-mapped class. :param onclause: a SQL expression representing the ON clause of the join. If left at ``None``, :meth:`_expression.FromClause.join` will attempt to join the two tables based on a foreign key relationship. :param full: if True, render a FULL OUTER JOIN, instead of LEFT OUTER JOIN. .. versionadded:: 1.1 .. seealso:: :meth:`_expression.FromClause.join` :class:`_expression.Join` """ return Join(self, right, onclause, True, full) def alias(self, name=None, flat=False): """Return an alias of this :class:`_expression.FromClause`. E.g.:: a2 = some_table.alias('a2') The above code creates an :class:`_expression.Alias` object which can be used as a FROM clause in any SELECT statement. .. seealso:: :ref:`core_tutorial_aliases` :func:`_expression.alias` """ return Alias._construct(self, name) def lateral(self, name=None): """Return a LATERAL alias of this :class:`_expression.FromClause`. The return value is the :class:`_expression.Lateral` construct also provided by the top-level :func:`_expression.lateral` function. .. versionadded:: 1.1 .. seealso:: :ref:`lateral_selects` - overview of usage. """ return Lateral._construct(self, name) def tablesample(self, sampling, name=None, seed=None): """Return a TABLESAMPLE alias of this :class:`_expression.FromClause`. The return value is the :class:`_expression.TableSample` construct also provided by the top-level :func:`_expression.tablesample` function. .. versionadded:: 1.1 .. seealso:: :func:`_expression.tablesample` - usage guidelines and parameters """ return TableSample._construct(self, sampling, name, seed) def is_derived_from(self, fromclause): """Return ``True`` if this :class:`_expression.FromClause` is 'derived' from the given ``FromClause``. An example would be an Alias of a Table is derived from that Table. """ # this is essentially an "identity" check in the base class. # Other constructs override this to traverse through # contained elements. return fromclause in self._cloned_set def _is_lexical_equivalent(self, other): """Return ``True`` if this :class:`_expression.FromClause` and the other represent the same lexical identity. This tests if either one is a copy of the other, or if they are the same via annotation identity. """ return self._cloned_set.intersection(other._cloned_set) @util.dependencies("sqlalchemy.sql.util") def replace_selectable(self, sqlutil, old, alias): """Replace all occurrences of FromClause 'old' with the given Alias object, returning a copy of this :class:`_expression.FromClause`. """ return sqlutil.ClauseAdapter(alias).traverse(self) def correspond_on_equivalents(self, column, equivalents): """Return corresponding_column for the given column, or if None search for a match in the given dictionary. """ col = self.corresponding_column(column, require_embedded=True) if col is None and col in equivalents: for equiv in equivalents[col]: nc = self.corresponding_column(equiv, require_embedded=True) if nc: return nc return col def corresponding_column(self, column, require_embedded=False): """Given a :class:`_expression.ColumnElement`, return the exported :class:`_expression.ColumnElement` object from this :class:`expression.Selectable` which corresponds to that original :class:`~sqlalchemy.schema.Column` via a common ancestor column. :param column: the target :class:`_expression.ColumnElement` to be matched :param require_embedded: only return corresponding columns for the given :class:`_expression.ColumnElement`, if the given :class:`_expression.ColumnElement` is actually present within a sub-element of this :class:`_expression.FromClause`. Normally the column will match if it merely shares a common ancestor with one of the exported columns of this :class:`_expression.FromClause`. """ def embedded(expanded_proxy_set, target_set): for t in target_set.difference(expanded_proxy_set): if not set(_expand_cloned([t])).intersection( expanded_proxy_set ): return False return True # don't dig around if the column is locally present if self.c.contains_column(column): return column col, intersect = None, None target_set = column.proxy_set cols = self.c._all_columns for c in cols: expanded_proxy_set = set(_expand_cloned(c.proxy_set)) i = target_set.intersection(expanded_proxy_set) if i and ( not require_embedded or embedded(expanded_proxy_set, target_set) ): if col is None: # no corresponding column yet, pick this one. col, intersect = c, i elif len(i) > len(intersect): # 'c' has a larger field of correspondence than # 'col'. i.e. selectable.c.a1_x->a1.c.x->table.c.x # matches a1.c.x->table.c.x better than # selectable.c.x->table.c.x does. col, intersect = c, i elif i == intersect: # they have the same field of correspondence. see # which proxy_set has fewer columns in it, which # indicates a closer relationship with the root # column. Also take into account the "weight" # attribute which CompoundSelect() uses to give # higher precedence to columns based on vertical # position in the compound statement, and discard # columns that have no reference to the target # column (also occurs with CompoundSelect) col_distance = util.reduce( operator.add, [ sc._annotations.get("weight", 1) for sc in col._uncached_proxy_set() if sc.shares_lineage(column) ], ) c_distance = util.reduce( operator.add, [ sc._annotations.get("weight", 1) for sc in c._uncached_proxy_set() if sc.shares_lineage(column) ], ) if c_distance < col_distance: col, intersect = c, i return col @property def description(self): """A brief description of this :class:`_expression.FromClause`. Used primarily for error message formatting. """ return getattr(self, "name", self.__class__.__name__ + " object") def _reset_exported(self): """Delete memoized collections when a FromClause is cloned.""" self._memoized_property.expire_instance(self) @_memoized_property def columns(self): """A named-based collection of :class:`_expression.ColumnElement` objects maintained by this :class:`_expression.FromClause`. The :attr:`.columns`, or :attr:`.c` collection, is the gateway to the construction of SQL expressions using table-bound or other selectable-bound columns:: select([mytable]).where(mytable.c.somecolumn == 5) """ if "_columns" not in self.__dict__: self._init_collections() self._populate_column_collection() return self._columns.as_immutable() @_memoized_property def primary_key(self): """Return the collection of :class:`_schema.Column` objects which comprise the primary key of this FromClause. """ self._init_collections() self._populate_column_collection() return self.primary_key @_memoized_property def foreign_keys(self): """Return the collection of :class:`_schema.ForeignKey` objects which this FromClause references. """ self._init_collections() self._populate_column_collection() return self.foreign_keys c = property( attrgetter("columns"), doc="An alias for the :attr:`.columns` attribute.", ) _select_iterable = property(attrgetter("columns")) def _init_collections(self): assert "_columns" not in self.__dict__ assert "primary_key" not in self.__dict__ assert "foreign_keys" not in self.__dict__ self._columns = ColumnCollection() self.primary_key = ColumnSet() self.foreign_keys = set() @property def _cols_populated(self): return "_columns" in self.__dict__ def _populate_column_collection(self): """Called on subclasses to establish the .c collection. Each implementation has a different way of establishing this collection. """ def _refresh_for_new_column(self, column): """Given a column added to the .c collection of an underlying selectable, produce the local version of that column, assuming this selectable ultimately should proxy this column. this is used to "ping" a derived selectable to add a new column to its .c. collection when a Column has been added to one of the Table objects it ultimtely derives from. If the given selectable hasn't populated its .c. collection yet, it should at least pass on the message to the contained selectables, but it will return None. This method is currently used by Declarative to allow Table columns to be added to a partially constructed inheritance mapping that may have already produced joins. The method isn't public right now, as the full span of implications and/or caveats aren't yet clear. It's also possible that this functionality could be invoked by default via an event, which would require that selectables maintain a weak referencing collection of all derivations. """ if not self._cols_populated: return None elif column.key in self.columns and self.columns[column.key] is column: return column else: return None class Join(FromClause): """Represent a ``JOIN`` construct between two :class:`_expression.FromClause` elements. The public constructor function for :class:`_expression.Join` is the module-level :func:`_expression.join()` function, as well as the :meth:`_expression.FromClause.join` method of any :class:`_expression.FromClause` (e.g. such as :class:`_schema.Table`). .. seealso:: :func:`_expression.join` :meth:`_expression.FromClause.join` """ __visit_name__ = "join" _is_join = True def __init__(self, left, right, onclause=None, isouter=False, full=False): """Construct a new :class:`_expression.Join`. The usual entrypoint here is the :func:`_expression.join` function or the :meth:`_expression.FromClause.join` method of any :class:`_expression.FromClause` object. """ self.left = _interpret_as_from(left) self.right = _interpret_as_from(right).self_group() if onclause is None: self.onclause = self._match_primaries(self.left, self.right) else: self.onclause = onclause self.isouter = isouter self.full = full @classmethod def _create_outerjoin(cls, left, right, onclause=None, full=False): """Return an ``OUTER JOIN`` clause element. The returned object is an instance of :class:`_expression.Join`. Similar functionality is also available via the :meth:`_expression.FromClause.outerjoin` method on any :class:`_expression.FromClause`. :param left: The left side of the join. :param right: The right side of the join. :param onclause: Optional criterion for the ``ON`` clause, is derived from foreign key relationships established between left and right otherwise. To chain joins together, use the :meth:`_expression.FromClause.join` or :meth:`_expression.FromClause.outerjoin` methods on the resulting :class:`_expression.Join` object. """ return cls(left, right, onclause, isouter=True, full=full) @classmethod def _create_join( cls, left, right, onclause=None, isouter=False, full=False ): """Produce a :class:`_expression.Join` object, given two :class:`_expression.FromClause` expressions. E.g.:: j = join(user_table, address_table, user_table.c.id == address_table.c.user_id) stmt = select([user_table]).select_from(j) would emit SQL along the lines of:: SELECT user.id, user.name FROM user JOIN address ON user.id = address.user_id Similar functionality is available given any :class:`_expression.FromClause` object (e.g. such as a :class:`_schema.Table`) using the :meth:`_expression.FromClause.join` method. :param left: The left side of the join. :param right: the right side of the join; this is any :class:`_expression.FromClause` object such as a :class:`_schema.Table` object, and may also be a selectable-compatible object such as an ORM-mapped class. :param onclause: a SQL expression representing the ON clause of the join. If left at ``None``, :meth:`_expression.FromClause.join` will attempt to join the two tables based on a foreign key relationship. :param isouter: if True, render a LEFT OUTER JOIN, instead of JOIN. :param full: if True, render a FULL OUTER JOIN, instead of JOIN. .. versionadded:: 1.1 .. seealso:: :meth:`_expression.FromClause.join` - method form, based on a given left side. :class:`_expression.Join` - the type of object produced. """ return cls(left, right, onclause, isouter, full) @property def description(self): return "Join object on %s(%d) and %s(%d)" % ( self.left.description, id(self.left), self.right.description, id(self.right), ) def is_derived_from(self, fromclause): return ( fromclause is self or self.left.is_derived_from(fromclause) or self.right.is_derived_from(fromclause) ) def self_group(self, against=None): return FromGrouping(self) @util.dependencies("sqlalchemy.sql.util") def _populate_column_collection(self, sqlutil): columns = [c for c in self.left.columns] + [ c for c in self.right.columns ] self.primary_key.extend( sqlutil.reduce_columns( (c for c in columns if c.primary_key), self.onclause ) ) self._columns.update((col._label, col) for col in columns) self.foreign_keys.update( itertools.chain(*[col.foreign_keys for col in columns]) ) def _refresh_for_new_column(self, column): col = self.left._refresh_for_new_column(column) if col is None: col = self.right._refresh_for_new_column(column) if col is not None: if self._cols_populated: self._columns[col._label] = col self.foreign_keys.update(col.foreign_keys) if col.primary_key: self.primary_key.add(col) return col return None def _copy_internals(self, clone=_clone, **kw): self._reset_exported() self.left = clone(self.left, **kw) self.right = clone(self.right, **kw) self.onclause = clone(self.onclause, **kw) def get_children(self, **kwargs): return self.left, self.right, self.onclause def _match_primaries(self, left, right): if isinstance(left, Join): left_right = left.right else: left_right = None return self._join_condition(left, right, a_subset=left_right) @classmethod @util.deprecated_params( ignore_nonexistent_tables=( "0.9", "The :paramref:`.join_condition.ignore_nonexistent_tables` " "parameter is deprecated and will be removed in a future " "release. Tables outside of the two tables being handled " "are no longer considered.", ) ) def _join_condition( cls, a, b, ignore_nonexistent_tables=False, a_subset=None, consider_as_foreign_keys=None, ): """Create a join condition between two tables or selectables. e.g.:: join_condition(tablea, tableb) would produce an expression along the lines of:: tablea.c.id==tableb.c.tablea_id The join is determined based on the foreign key relationships between the two selectables. If there are multiple ways to join, or no way to join, an error is raised. :param ignore_nonexistent_tables: unused - tables outside of the two tables being handled are not considered. :param a_subset: An optional expression that is a sub-component of ``a``. An attempt will be made to join to just this sub-component first before looking at the full ``a`` construct, and if found will be successful even if there are other ways to join to ``a``. This allows the "right side" of a join to be passed thereby providing a "natural join". """ constraints = cls._joincond_scan_left_right( a, a_subset, b, consider_as_foreign_keys ) if len(constraints) > 1: cls._joincond_trim_constraints( a, b, constraints, consider_as_foreign_keys ) if len(constraints) == 0: if isinstance(b, FromGrouping): hint = ( " Perhaps you meant to convert the right side to a " "subquery using alias()?" ) else: hint = "" raise exc.NoForeignKeysError( "Can't find any foreign key relationships " "between '%s' and '%s'.%s" % (a.description, b.description, hint) ) crit = [(x == y) for x, y in list(constraints.values())[0]] if len(crit) == 1: return crit[0] else: return and_(*crit) @classmethod def _can_join(cls, left, right, consider_as_foreign_keys=None): if isinstance(left, Join): left_right = left.right else: left_right = None constraints = cls._joincond_scan_left_right( a=left, b=right, a_subset=left_right, consider_as_foreign_keys=consider_as_foreign_keys, ) return bool(constraints) @classmethod @util.dependencies("sqlalchemy.sql.util") def _joincond_scan_left_right( cls, sql_util, a, a_subset, b, consider_as_foreign_keys ): constraints = collections.defaultdict(list) for left in (a_subset, a): if left is None: continue for fk in sorted( b.foreign_keys, key=lambda fk: fk.parent._creation_order ): if ( consider_as_foreign_keys is not None and fk.parent not in consider_as_foreign_keys ): continue try: col = fk.get_referent(left) except exc.NoReferenceError as nrte: table_names = {t.name for t in sql_util.find_tables(left)} if nrte.table_name in table_names: raise else: continue if col is not None: constraints[fk.constraint].append((col, fk.parent)) if left is not b: for fk in sorted( left.foreign_keys, key=lambda fk: fk.parent._creation_order ): if ( consider_as_foreign_keys is not None and fk.parent not in consider_as_foreign_keys ): continue try: col = fk.get_referent(b) except exc.NoReferenceError as nrte: table_names = {t.name for t in sql_util.find_tables(b)} if nrte.table_name in table_names: raise else: continue if col is not None: constraints[fk.constraint].append((col, fk.parent)) if constraints: break return constraints @classmethod def _joincond_trim_constraints( cls, a, b, constraints, consider_as_foreign_keys ): # more than one constraint matched. narrow down the list # to include just those FKCs that match exactly to # "consider_as_foreign_keys". if consider_as_foreign_keys: for const in list(constraints): if set(f.parent for f in const.elements) != set( consider_as_foreign_keys ): del constraints[const] # if still multiple constraints, but # they all refer to the exact same end result, use it. if len(constraints) > 1: dedupe = set(tuple(crit) for crit in constraints.values()) if len(dedupe) == 1: key = list(constraints)[0] constraints = {key: constraints[key]} if len(constraints) != 1: raise exc.AmbiguousForeignKeysError( "Can't determine join between '%s' and '%s'; " "tables have more than one foreign key " "constraint relationship between them. " "Please specify the 'onclause' of this " "join explicitly." % (a.description, b.description) ) def select(self, whereclause=None, **kwargs): r"""Create a :class:`_expression.Select` from this :class:`_expression.Join`. The equivalent long-hand form, given a :class:`_expression.Join` object ``j``, is:: from sqlalchemy import select j = select([j.left, j.right], **kw).\ where(whereclause).\ select_from(j) :param whereclause: the WHERE criterion that will be sent to the :func:`select()` function :param \**kwargs: all other kwargs are sent to the underlying :func:`select()` function. """ collist = [self.left, self.right] return Select(collist, whereclause, from_obj=[self], **kwargs) @property def bind(self): return self.left.bind or self.right.bind @util.dependencies("sqlalchemy.sql.util") def alias(self, sqlutil, name=None, flat=False): r"""Return an alias of this :class:`_expression.Join`. The default behavior here is to first produce a SELECT construct from this :class:`_expression.Join`, then to produce an :class:`_expression.Alias` from that. So given a join of the form:: j = table_a.join(table_b, table_a.c.id == table_b.c.a_id) The JOIN by itself would look like:: table_a JOIN table_b ON table_a.id = table_b.a_id Whereas the alias of the above, ``j.alias()``, would in a SELECT context look like:: (SELECT table_a.id AS table_a_id, table_b.id AS table_b_id, table_b.a_id AS table_b_a_id FROM table_a JOIN table_b ON table_a.id = table_b.a_id) AS anon_1 The equivalent long-hand form, given a :class:`_expression.Join` object ``j``, is:: from sqlalchemy import select, alias j = alias( select([j.left, j.right]).\ select_from(j).\ with_labels(True).\ correlate(False), name=name ) The selectable produced by :meth:`_expression.Join.alias` features the same columns as that of the two individual selectables presented under a single name - the individual columns are "auto-labeled", meaning the ``.c.`` collection of the resulting :class:`_expression.Alias` represents the names of the individual columns using a ``<tablename>_<columname>`` scheme:: j.c.table_a_id j.c.table_b_a_id :meth:`_expression.Join.alias` also features an alternate option for aliasing joins which produces no enclosing SELECT and does not normally apply labels to the column names. The ``flat=True`` option will call :meth:`_expression.FromClause.alias` against the left and right sides individually. Using this option, no new ``SELECT`` is produced; we instead, from a construct as below:: j = table_a.join(table_b, table_a.c.id == table_b.c.a_id) j = j.alias(flat=True) we get a result like this:: table_a AS table_a_1 JOIN table_b AS table_b_1 ON table_a_1.id = table_b_1.a_id The ``flat=True`` argument is also propagated to the contained selectables, so that a composite join such as:: j = table_a.join( table_b.join(table_c, table_b.c.id == table_c.c.b_id), table_b.c.a_id == table_a.c.id ).alias(flat=True) Will produce an expression like:: table_a AS table_a_1 JOIN ( table_b AS table_b_1 JOIN table_c AS table_c_1 ON table_b_1.id = table_c_1.b_id ) ON table_a_1.id = table_b_1.a_id The standalone :func:`_expression.alias` function as well as the base :meth:`_expression.FromClause.alias` method also support the ``flat=True`` argument as a no-op, so that the argument can be passed to the ``alias()`` method of any selectable. .. versionadded:: 0.9.0 Added the ``flat=True`` option to create "aliases" of joins without enclosing inside of a SELECT subquery. :param name: name given to the alias. :param flat: if True, produce an alias of the left and right sides of this :class:`_expression.Join` and return the join of those two selectables. This produces join expression that does not include an enclosing SELECT. .. versionadded:: 0.9.0 .. seealso:: :ref:`core_tutorial_aliases` :func:`_expression.alias` """ if flat: assert name is None, "Can't send name argument with flat" left_a, right_a = ( self.left.alias(flat=True), self.right.alias(flat=True), ) adapter = sqlutil.ClauseAdapter(left_a).chain( sqlutil.ClauseAdapter(right_a) ) return left_a.join( right_a, adapter.traverse(self.onclause), isouter=self.isouter, full=self.full, ) else: return self.select(use_labels=True, correlate=False).alias(name) @property def _hide_froms(self): return itertools.chain( *[_from_objects(x.left, x.right) for x in self._cloned_set] ) @property def _from_objects(self): return ( [self] + self.onclause._from_objects + self.left._from_objects + self.right._from_objects ) class Alias(FromClause): """Represents an table or selectable alias (AS). Represents an alias, as typically applied to any table or sub-select within a SQL statement using the ``AS`` keyword (or without the keyword on certain databases such as Oracle). This object is constructed from the :func:`_expression.alias` module level function as well as the :meth:`_expression.FromClause.alias` method available on all :class:`_expression.FromClause` subclasses. """ __visit_name__ = "alias" named_with_column = True _is_from_container = True def __init__(self, *arg, **kw): raise NotImplementedError( "The %s class is not intended to be constructed " "directly. Please use the %s() standalone " "function or the %s() method available from appropriate " "selectable objects." % ( self.__class__.__name__, self.__class__.__name__.lower(), self.__class__.__name__.lower(), ) ) @classmethod def _construct(cls, *arg, **kw): obj = cls.__new__(cls) obj._init(*arg, **kw) return obj @classmethod def _factory(cls, selectable, name=None, flat=False): """Return an :class:`_expression.Alias` object. An :class:`_expression.Alias` represents any :class:`_expression.FromClause` with an alternate name assigned within SQL, typically using the ``AS`` clause when generated, e.g. ``SELECT * FROM table AS aliasname``. Similar functionality is available via the :meth:`_expression.FromClause.alias` method available on all :class:`_expression.FromClause` subclasses. In terms of a SELECT object as generated from the :func:`_expression.select` function, the :meth:`_expression.SelectBase.alias` method returns an :class:`_expression.Alias` or similar object which represents a named, parenthesized subquery. When an :class:`_expression.Alias` is created from a :class:`_schema.Table` object, this has the effect of the table being rendered as ``tablename AS aliasname`` in a SELECT statement. For :func:`_expression.select` objects, the effect is that of creating a named subquery, i.e. ``(select ...) AS aliasname``. The ``name`` parameter is optional, and provides the name to use in the rendered SQL. If blank, an "anonymous" name will be deterministically generated at compile time. Deterministic means the name is guaranteed to be unique against other constructs used in the same statement, and will also be the same name for each successive compilation of the same statement object. :param selectable: any :class:`_expression.FromClause` subclass, such as a table, select statement, etc. :param name: string name to be assigned as the alias. If ``None``, a name will be deterministically generated at compile time. :param flat: Will be passed through to if the given selectable is an instance of :class:`_expression.Join` - see :meth:`_expression.Join.alias` for details. .. versionadded:: 0.9.0 """ return _interpret_as_from(selectable).alias(name=name, flat=flat) def _init(self, selectable, name=None): baseselectable = selectable while isinstance(baseselectable, Alias): baseselectable = baseselectable.element self.original = baseselectable self.supports_execution = baseselectable.supports_execution if self.supports_execution: self._execution_options = baseselectable._execution_options self.element = selectable if name is None: if self.original.named_with_column: name = getattr(self.original, "name", None) name = _anonymous_label("%%(%d %s)s" % (id(self), name or "anon")) self.name = name def self_group(self, against=None): if ( isinstance(against, CompoundSelect) and isinstance(self.original, Select) and self.original._needs_parens_for_grouping() ): return FromGrouping(self) return super(Alias, self).self_group(against=against) @property def description(self): if util.py3k: return self.name else: return self.name.encode("ascii", "backslashreplace") def as_scalar(self): try: return self.element.as_scalar() except AttributeError as err: util.raise_( AttributeError( "Element %s does not support " "'as_scalar()'" % self.element ), replace_context=err, ) def is_derived_from(self, fromclause): if fromclause in self._cloned_set: return True return self.element.is_derived_from(fromclause) def _populate_column_collection(self): for col in self.element.columns._all_columns: col._make_proxy(self) def _refresh_for_new_column(self, column): col = self.element._refresh_for_new_column(column) if col is not None: if not self._cols_populated: return None else: return col._make_proxy(self) else: return None def _copy_internals(self, clone=_clone, **kw): # don't apply anything to an aliased Table # for now. May want to drive this from # the given **kw. if isinstance(self.element, TableClause): return self._reset_exported() self.element = clone(self.element, **kw) baseselectable = self.element while isinstance(baseselectable, Alias): baseselectable = baseselectable.element self.original = baseselectable def get_children(self, column_collections=True, **kw): if column_collections: for c in self.c: yield c yield self.element @property def _from_objects(self): return [self] @property def bind(self): return self.element.bind class Lateral(Alias): """Represent a LATERAL subquery. This object is constructed from the :func:`_expression.lateral` module level function as well as the :meth:`_expression.FromClause.lateral` method available on all :class:`_expression.FromClause` subclasses. While LATERAL is part of the SQL standard, currently only more recent PostgreSQL versions provide support for this keyword. .. versionadded:: 1.1 .. seealso:: :ref:`lateral_selects` - overview of usage. """ __visit_name__ = "lateral" _is_lateral = True @classmethod def _factory(cls, selectable, name=None): """Return a :class:`_expression.Lateral` object. :class:`_expression.Lateral` is an :class:`_expression.Alias` subclass that represents a subquery with the LATERAL keyword applied to it. The special behavior of a LATERAL subquery is that it appears in the FROM clause of an enclosing SELECT, but may correlate to other FROM clauses of that SELECT. It is a special case of subquery only supported by a small number of backends, currently more recent PostgreSQL versions. .. versionadded:: 1.1 .. seealso:: :ref:`lateral_selects` - overview of usage. """ return _interpret_as_from(selectable).lateral(name=name) class TableSample(Alias): """Represent a TABLESAMPLE clause. This object is constructed from the :func:`_expression.tablesample` module level function as well as the :meth:`_expression.FromClause.tablesample` method available on all :class:`_expression.FromClause` subclasses. .. versionadded:: 1.1 .. seealso:: :func:`_expression.tablesample` """ __visit_name__ = "tablesample" @classmethod def _factory(cls, selectable, sampling, name=None, seed=None): """Return a :class:`_expression.TableSample` object. :class:`_expression.TableSample` is an :class:`_expression.Alias` subclass that represents a table with the TABLESAMPLE clause applied to it. :func:`_expression.tablesample` is also available from the :class:`_expression.FromClause` class via the :meth:`_expression.FromClause.tablesample` method. The TABLESAMPLE clause allows selecting a randomly selected approximate percentage of rows from a table. It supports multiple sampling methods, most commonly BERNOULLI and SYSTEM. e.g.:: from sqlalchemy import func selectable = people.tablesample( func.bernoulli(1), name='alias', seed=func.random()) stmt = select([selectable.c.people_id]) Assuming ``people`` with a column ``people_id``, the above statement would render as:: SELECT alias.people_id FROM people AS alias TABLESAMPLE bernoulli(:bernoulli_1) REPEATABLE (random()) .. versionadded:: 1.1 :param sampling: a ``float`` percentage between 0 and 100 or :class:`_functions.Function`. :param name: optional alias name :param seed: any real-valued SQL expression. When specified, the REPEATABLE sub-clause is also rendered. """ return _interpret_as_from(selectable).tablesample( sampling, name=name, seed=seed ) def _init(self, selectable, sampling, name=None, seed=None): self.sampling = sampling self.seed = seed super(TableSample, self)._init(selectable, name=name) @util.dependencies("sqlalchemy.sql.functions") def _get_method(self, functions): if isinstance(self.sampling, functions.Function): return self.sampling else: return functions.func.system(self.sampling) class CTE(Generative, HasPrefixes, HasSuffixes, Alias): """Represent a Common Table Expression. The :class:`_expression.CTE` object is obtained using the :meth:`_expression.SelectBase.cte` method from any selectable. See that method for complete examples. """ __visit_name__ = "cte" @classmethod def _factory(cls, selectable, name=None, recursive=False): r"""Return a new :class:`_expression.CTE`, or Common Table Expression instance. Please see :meth:`_expression.HasCTE.cte` for detail on CTE usage. """ return _interpret_as_from(selectable).cte( name=name, recursive=recursive ) def _init( self, selectable, name=None, recursive=False, _cte_alias=None, _restates=frozenset(), _prefixes=None, _suffixes=None, ): self.recursive = recursive self._cte_alias = _cte_alias self._restates = _restates if _prefixes: self._prefixes = _prefixes if _suffixes: self._suffixes = _suffixes super(CTE, self)._init(selectable, name=name) def _copy_internals(self, clone=_clone, **kw): super(CTE, self)._copy_internals(clone, **kw) if self._cte_alias is not None: self._cte_alias = clone(self._cte_alias, **kw) self._restates = frozenset( [clone(elem, **kw) for elem in self._restates] ) @util.dependencies("sqlalchemy.sql.dml") def _populate_column_collection(self, dml): if isinstance(self.element, dml.UpdateBase): for col in self.element._returning: col._make_proxy(self) else: for col in self.element.columns._all_columns: col._make_proxy(self) def alias(self, name=None, flat=False): """Return an :class:`_expression.Alias` of this :class:`_expression.CTE`. This method is a CTE-specific specialization of the :meth:`_expression.FromClause.alias` method. .. seealso:: :ref:`core_tutorial_aliases` :func:`_expression.alias` """ return CTE._construct( self.original, name=name, recursive=self.recursive, _cte_alias=self, _prefixes=self._prefixes, _suffixes=self._suffixes, ) def union(self, other): return CTE._construct( self.original.union(other), name=self.name, recursive=self.recursive, _restates=self._restates.union([self]), _prefixes=self._prefixes, _suffixes=self._suffixes, ) def union_all(self, other): return CTE._construct( self.original.union_all(other), name=self.name, recursive=self.recursive, _restates=self._restates.union([self]), _prefixes=self._prefixes, _suffixes=self._suffixes, ) class HasCTE(object): """Mixin that declares a class to include CTE support. .. versionadded:: 1.1 """ def cte(self, name=None, recursive=False): r"""Return a new :class:`_expression.CTE`, or Common Table Expression instance. Common table expressions are a SQL standard whereby SELECT statements can draw upon secondary statements specified along with the primary statement, using a clause called "WITH". Special semantics regarding UNION can also be employed to allow "recursive" queries, where a SELECT statement can draw upon the set of rows that have previously been selected. CTEs can also be applied to DML constructs UPDATE, INSERT and DELETE on some databases, both as a source of CTE rows when combined with RETURNING, as well as a consumer of CTE rows. .. versionchanged:: 1.1 Added support for UPDATE/INSERT/DELETE as CTE, CTEs added to UPDATE/INSERT/DELETE. SQLAlchemy detects :class:`_expression.CTE` objects, which are treated similarly to :class:`_expression.Alias` objects, as special elements to be delivered to the FROM clause of the statement as well as to a WITH clause at the top of the statement. For special prefixes such as PostgreSQL "MATERIALIZED" and "NOT MATERIALIZED", the :meth:`_expression.CTE.prefix_with` method may be used to establish these. .. versionchanged:: 1.3.13 Added support for prefixes. In particular - MATERIALIZED and NOT MATERIALIZED. :param name: name given to the common table expression. Like :meth:`_expression.FromClause.alias`, the name can be left as ``None`` in which case an anonymous symbol will be used at query compile time. :param recursive: if ``True``, will render ``WITH RECURSIVE``. A recursive common table expression is intended to be used in conjunction with UNION ALL in order to derive rows from those already selected. The following examples include two from PostgreSQL's documentation at http://www.postgresql.org/docs/current/static/queries-with.html, as well as additional examples. Example 1, non recursive:: from sqlalchemy import (Table, Column, String, Integer, MetaData, select, func) metadata = MetaData() orders = Table('orders', metadata, Column('region', String), Column('amount', Integer), Column('product', String), Column('quantity', Integer) ) regional_sales = select([ orders.c.region, func.sum(orders.c.amount).label('total_sales') ]).group_by(orders.c.region).cte("regional_sales") top_regions = select([regional_sales.c.region]).\ where( regional_sales.c.total_sales > select([ func.sum(regional_sales.c.total_sales)/10 ]) ).cte("top_regions") statement = select([ orders.c.region, orders.c.product, func.sum(orders.c.quantity).label("product_units"), func.sum(orders.c.amount).label("product_sales") ]).where(orders.c.region.in_( select([top_regions.c.region]) )).group_by(orders.c.region, orders.c.product) result = conn.execute(statement).fetchall() Example 2, WITH RECURSIVE:: from sqlalchemy import (Table, Column, String, Integer, MetaData, select, func) metadata = MetaData() parts = Table('parts', metadata, Column('part', String), Column('sub_part', String), Column('quantity', Integer), ) included_parts = select([ parts.c.sub_part, parts.c.part, parts.c.quantity]).\ where(parts.c.part=='our part').\ cte(recursive=True) incl_alias = included_parts.alias() parts_alias = parts.alias() included_parts = included_parts.union_all( select([ parts_alias.c.sub_part, parts_alias.c.part, parts_alias.c.quantity ]). where(parts_alias.c.part==incl_alias.c.sub_part) ) statement = select([ included_parts.c.sub_part, func.sum(included_parts.c.quantity). label('total_quantity') ]).\ group_by(included_parts.c.sub_part) result = conn.execute(statement).fetchall() Example 3, an upsert using UPDATE and INSERT with CTEs:: from datetime import date from sqlalchemy import (MetaData, Table, Column, Integer, Date, select, literal, and_, exists) metadata = MetaData() visitors = Table('visitors', metadata, Column('product_id', Integer, primary_key=True), Column('date', Date, primary_key=True), Column('count', Integer), ) # add 5 visitors for the product_id == 1 product_id = 1 day = date.today() count = 5 update_cte = ( visitors.update() .where(and_(visitors.c.product_id == product_id, visitors.c.date == day)) .values(count=visitors.c.count + count) .returning(literal(1)) .cte('update_cte') ) upsert = visitors.insert().from_select( [visitors.c.product_id, visitors.c.date, visitors.c.count], select([literal(product_id), literal(day), literal(count)]) .where(~exists(update_cte.select())) ) connection.execute(upsert) .. seealso:: :meth:`.orm.query.Query.cte` - ORM version of :meth:`_expression.HasCTE.cte`. """ return CTE._construct(self, name=name, recursive=recursive) class FromGrouping(FromClause): """Represent a grouping of a FROM clause""" __visit_name__ = "grouping" def __init__(self, element): self.element = element def _init_collections(self): pass @property def columns(self): return self.element.columns @property def primary_key(self): return self.element.primary_key @property def foreign_keys(self): return self.element.foreign_keys def is_derived_from(self, element): return self.element.is_derived_from(element) def alias(self, **kw): return FromGrouping(self.element.alias(**kw)) @property def _hide_froms(self): return self.element._hide_froms def get_children(self, **kwargs): return (self.element,) def _copy_internals(self, clone=_clone, **kw): self.element = clone(self.element, **kw) @property def _from_objects(self): return self.element._from_objects def __getattr__(self, attr): return getattr(self.element, attr) def __getstate__(self): return {"element": self.element} def __setstate__(self, state): self.element = state["element"] class TableClause(Immutable, FromClause): """Represents a minimal "table" construct. This is a lightweight table object that has only a name, a collection of columns, which are typically produced by the :func:`_expression.column` function, and a schema:: from sqlalchemy import table, column user = table("user", column("id"), column("name"), column("description"), ) The :class:`_expression.TableClause` construct serves as the base for the more commonly used :class:`_schema.Table` object, providing the usual set of :class:`_expression.FromClause` services including the ``.c.`` collection and statement generation methods. It does **not** provide all the additional schema-level services of :class:`_schema.Table`, including constraints, references to other tables, or support for :class:`_schema.MetaData`-level services. It's useful on its own as an ad-hoc construct used to generate quick SQL statements when a more fully fledged :class:`_schema.Table` is not on hand. """ __visit_name__ = "table" named_with_column = True implicit_returning = False """:class:`_expression.TableClause` doesn't support having a primary key or column -level defaults, so implicit returning doesn't apply.""" _autoincrement_column = None """No PK or default support so no autoincrement column.""" def __init__(self, name, *columns, **kw): """Produce a new :class:`_expression.TableClause`. The object returned is an instance of :class:`_expression.TableClause`, which represents the "syntactical" portion of the schema-level :class:`_schema.Table` object. It may be used to construct lightweight table constructs. .. versionchanged:: 1.0.0 :func:`_expression.table` can now be imported from the plain ``sqlalchemy`` namespace like any other SQL element. :param name: Name of the table. :param columns: A collection of :func:`_expression.column` constructs. :param schema: The schema name for this table. .. versionadded:: 1.3.18 :func:`_expression.table` can now accept a ``schema`` argument. """ super(TableClause, self).__init__() self.name = self.fullname = name self._columns = ColumnCollection() self.primary_key = ColumnSet() self.foreign_keys = set() for c in columns: self.append_column(c) schema = kw.pop("schema", None) if schema is not None: self.schema = schema if kw: raise exc.ArgumentError("Unsupported argument(s): %s" % list(kw)) def _init_collections(self): pass @util.memoized_property def description(self): if util.py3k: return self.name else: return self.name.encode("ascii", "backslashreplace") def append_column(self, c): existing = c.table if existing is not None and existing is not self: raise exc.ArgumentError( "column object '%s' already assigned to table %r" % (c.key, getattr(existing, "description", existing)) ) self._columns[c.key] = c c.table = self def get_children(self, column_collections=True, **kwargs): if column_collections: return [c for c in self.c] else: return [] @util.dependencies("sqlalchemy.sql.dml") def insert(self, dml, values=None, inline=False, **kwargs): """Generate an :func:`_expression.insert` construct against this :class:`_expression.TableClause`. E.g.:: table.insert().values(name='foo') See :func:`_expression.insert` for argument and usage information. """ return dml.Insert(self, values=values, inline=inline, **kwargs) @util.dependencies("sqlalchemy.sql.dml") def update( self, dml, whereclause=None, values=None, inline=False, **kwargs ): """Generate an :func:`_expression.update` construct against this :class:`_expression.TableClause`. E.g.:: table.update().where(table.c.id==7).values(name='foo') See :func:`_expression.update` for argument and usage information. """ return dml.Update( self, whereclause=whereclause, values=values, inline=inline, **kwargs ) @util.dependencies("sqlalchemy.sql.dml") def delete(self, dml, whereclause=None, **kwargs): """Generate a :func:`_expression.delete` construct against this :class:`_expression.TableClause`. E.g.:: table.delete().where(table.c.id==7) See :func:`_expression.delete` for argument and usage information. """ return dml.Delete(self, whereclause, **kwargs) @property def _from_objects(self): return [self] class ForUpdateArg(ClauseElement): @classmethod def parse_legacy_select(self, arg): """Parse the for_update argument of :func:`_expression.select`. :param mode: Defines the lockmode to use. ``None`` - translates to no lockmode ``'update'`` - translates to ``FOR UPDATE`` (standard SQL, supported by most dialects) ``'nowait'`` - translates to ``FOR UPDATE NOWAIT`` (supported by Oracle, PostgreSQL 8.1 upwards) ``'read'`` - translates to ``LOCK IN SHARE MODE`` (for MySQL), and ``FOR SHARE`` (for PostgreSQL) ``'read_nowait'`` - translates to ``FOR SHARE NOWAIT`` (supported by PostgreSQL). ``FOR SHARE`` and ``FOR SHARE NOWAIT`` (PostgreSQL). """ if arg in (None, False): return None nowait = read = False if arg == "nowait": nowait = True elif arg == "read": read = True elif arg == "read_nowait": read = nowait = True elif arg is not True: raise exc.ArgumentError("Unknown for_update argument: %r" % arg) return ForUpdateArg(read=read, nowait=nowait) @property def legacy_for_update_value(self): if self.read and not self.nowait: return "read" elif self.read and self.nowait: return "read_nowait" elif self.nowait: return "nowait" else: return True def __eq__(self, other): return ( isinstance(other, ForUpdateArg) and other.nowait == self.nowait and other.read == self.read and other.skip_locked == self.skip_locked and other.key_share == self.key_share and other.of is self.of ) def __hash__(self): return id(self) def _copy_internals(self, clone=_clone, **kw): if self.of is not None: self.of = [clone(col, **kw) for col in self.of] def __init__( self, nowait=False, read=False, of=None, skip_locked=False, key_share=False, ): """Represents arguments specified to :meth:`_expression.Select.for_update`. .. versionadded:: 0.9.0 """ self.nowait = nowait self.read = read self.skip_locked = skip_locked self.key_share = key_share if of is not None: self.of = [ _interpret_as_column_or_from(elem) for elem in util.to_list(of) ] else: self.of = None class SelectBase(HasCTE, Executable, FromClause): """Base class for SELECT statements. This includes :class:`_expression.Select`, :class:`_selectable.CompoundSelect` and :class:`.TextAsFrom`. """ def as_scalar(self): """Return a 'scalar' representation of this selectable, which can be used as a column expression. Typically, a select statement which has only one column in its columns clause is eligible to be used as a scalar expression. The returned object is an instance of :class:`ScalarSelect`. """ return ScalarSelect(self) def label(self, name): """Return a 'scalar' representation of this selectable, embedded as a subquery with a label. .. seealso:: :meth:`_expression.SelectBase.as_scalar`. """ return self.as_scalar().label(name) @_generative @util.deprecated( "0.6", message="The :meth:`.SelectBase.autocommit` method is deprecated, " "and will be removed in a future release. Please use the " "the :paramref:`.Connection.execution_options.autocommit` " "parameter in conjunction with the " ":meth:`.Executable.execution_options` method.", ) def autocommit(self): """Return a new selectable with the 'autocommit' flag set to True. """ self._execution_options = self._execution_options.union( {"autocommit": True} ) def _generate(self): """Override the default _generate() method to also clear out exported collections.""" s = self.__class__.__new__(self.__class__) s.__dict__ = self.__dict__.copy() s._reset_exported() return s @property def _from_objects(self): return [self] class GenerativeSelect(SelectBase): """Base class for SELECT statements where additional elements can be added. This serves as the base for :class:`_expression.Select` and :class:`_selectable.CompoundSelect` where elements such as ORDER BY, GROUP BY can be added and column rendering can be controlled. Compare to :class:`.TextAsFrom`, which, while it subclasses :class:`_expression.SelectBase` and is also a SELECT construct, represents a fixed textual string which cannot be altered at this level, only wrapped as a subquery. .. versionadded:: 0.9.0 :class:`_expression.GenerativeSelect` was added to provide functionality specific to :class:`_expression.Select` and :class:`_selectable.CompoundSelect` while allowing :class:`_expression.SelectBase` to be used for other SELECT-like objects, e.g. :class:`.TextAsFrom`. """ _order_by_clause = ClauseList() _group_by_clause = ClauseList() _limit_clause = None _offset_clause = None _for_update_arg = None def __init__( self, use_labels=False, for_update=False, limit=None, offset=None, order_by=None, group_by=None, bind=None, autocommit=None, ): self.use_labels = use_labels if for_update is not False: self._for_update_arg = ForUpdateArg.parse_legacy_select(for_update) if autocommit is not None: util.warn_deprecated( "The select.autocommit parameter is deprecated and will be " "removed in a future release. Please refer to the " "Select.execution_options.autocommit` parameter." ) self._execution_options = self._execution_options.union( {"autocommit": autocommit} ) if limit is not None: self._limit_clause = _offset_or_limit_clause(limit) if offset is not None: self._offset_clause = _offset_or_limit_clause(offset) self._bind = bind if order_by is not None: self._order_by_clause = ClauseList( *util.to_list(order_by), _literal_as_text=_literal_and_labels_as_label_reference ) if group_by is not None: self._group_by_clause = ClauseList( *util.to_list(group_by), _literal_as_text=_literal_as_label_reference ) @property def for_update(self): """Provide legacy dialect support for the ``for_update`` attribute.""" if self._for_update_arg is not None: return self._for_update_arg.legacy_for_update_value else: return None @for_update.setter def for_update(self, value): self._for_update_arg = ForUpdateArg.parse_legacy_select(value) @_generative def with_for_update( self, nowait=False, read=False, of=None, skip_locked=False, key_share=False, ): """Specify a ``FOR UPDATE`` clause for this :class:`_expression.GenerativeSelect`. E.g.:: stmt = select([table]).with_for_update(nowait=True) On a database like PostgreSQL or Oracle, the above would render a statement like:: SELECT table.a, table.b FROM table FOR UPDATE NOWAIT on other backends, the ``nowait`` option is ignored and instead would produce:: SELECT table.a, table.b FROM table FOR UPDATE When called with no arguments, the statement will render with the suffix ``FOR UPDATE``. Additional arguments can then be provided which allow for common database-specific variants. :param nowait: boolean; will render ``FOR UPDATE NOWAIT`` on Oracle and PostgreSQL dialects. :param read: boolean; will render ``LOCK IN SHARE MODE`` on MySQL, ``FOR SHARE`` on PostgreSQL. On PostgreSQL, when combined with ``nowait``, will render ``FOR SHARE NOWAIT``. :param of: SQL expression or list of SQL expression elements (typically :class:`_schema.Column` objects or a compatible expression) which will render into a ``FOR UPDATE OF`` clause; supported by PostgreSQL and Oracle. May render as a table or as a column depending on backend. :param skip_locked: boolean, will render ``FOR UPDATE SKIP LOCKED`` on Oracle and PostgreSQL dialects or ``FOR SHARE SKIP LOCKED`` if ``read=True`` is also specified. .. versionadded:: 1.1.0 :param key_share: boolean, will render ``FOR NO KEY UPDATE``, or if combined with ``read=True`` will render ``FOR KEY SHARE``, on the PostgreSQL dialect. .. versionadded:: 1.1.0 """ self._for_update_arg = ForUpdateArg( nowait=nowait, read=read, of=of, skip_locked=skip_locked, key_share=key_share, ) @_generative def apply_labels(self): """Return a new selectable with the 'use_labels' flag set to True. This will result in column expressions being generated using labels against their table name, such as "SELECT somecolumn AS tablename_somecolumn". This allows selectables which contain multiple FROM clauses to produce a unique set of column names regardless of name conflicts among the individual FROM clauses. """ self.use_labels = True @property def _limit(self): """Get an integer value for the limit. This should only be used by code that cannot support a limit as a BindParameter or other custom clause as it will throw an exception if the limit isn't currently set to an integer. """ return _offset_or_limit_clause_asint(self._limit_clause, "limit") @property def _simple_int_limit(self): """True if the LIMIT clause is a simple integer, False if it is not present or is a SQL expression. """ return isinstance(self._limit_clause, _OffsetLimitParam) @property def _simple_int_offset(self): """True if the OFFSET clause is a simple integer, False if it is not present or is a SQL expression. """ return isinstance(self._offset_clause, _OffsetLimitParam) @property def _offset(self): """Get an integer value for the offset. This should only be used by code that cannot support an offset as a BindParameter or other custom clause as it will throw an exception if the offset isn't currently set to an integer. """ return _offset_or_limit_clause_asint(self._offset_clause, "offset") @_generative def limit(self, limit): """Return a new selectable with the given LIMIT criterion applied. This is a numerical value which usually renders as a ``LIMIT`` expression in the resulting select. Backends that don't support ``LIMIT`` will attempt to provide similar functionality. .. versionchanged:: 1.0.0 - :meth:`_expression.Select.limit` can now accept arbitrary SQL expressions as well as integer values. :param limit: an integer LIMIT parameter, or a SQL expression that provides an integer result. """ self._limit_clause = _offset_or_limit_clause(limit) @_generative def offset(self, offset): """Return a new selectable with the given OFFSET criterion applied. This is a numeric value which usually renders as an ``OFFSET`` expression in the resulting select. Backends that don't support ``OFFSET`` will attempt to provide similar functionality. .. versionchanged:: 1.0.0 - :meth:`_expression.Select.offset` can now accept arbitrary SQL expressions as well as integer values. :param offset: an integer OFFSET parameter, or a SQL expression that provides an integer result. """ self._offset_clause = _offset_or_limit_clause(offset) @_generative def order_by(self, *clauses): r"""Return a new selectable with the given list of ORDER BY criterion applied. e.g.:: stmt = select([table]).order_by(table.c.id, table.c.name) :param \*clauses: a series of :class:`_expression.ColumnElement` constructs which will be used to generate an ORDER BY clause. .. seealso:: :ref:`core_tutorial_ordering` """ self.append_order_by(*clauses) @_generative def group_by(self, *clauses): r"""Return a new selectable with the given list of GROUP BY criterion applied. e.g.:: stmt = select([table.c.name, func.max(table.c.stat)]).\ group_by(table.c.name) :param \*clauses: a series of :class:`_expression.ColumnElement` constructs which will be used to generate an GROUP BY clause. .. seealso:: :ref:`core_tutorial_ordering` """ self.append_group_by(*clauses) def append_order_by(self, *clauses): """Append the given ORDER BY criterion applied to this selectable. The criterion will be appended to any pre-existing ORDER BY criterion. This is an **in-place** mutation method; the :meth:`_expression.GenerativeSelect.order_by` method is preferred, as it provides standard :term:`method chaining`. .. seealso:: :meth:`_expression.GenerativeSelect.order_by` """ if len(clauses) == 1 and clauses[0] is None: self._order_by_clause = ClauseList() else: if getattr(self, "_order_by_clause", None) is not None: clauses = list(self._order_by_clause) + list(clauses) self._order_by_clause = ClauseList( *clauses, _literal_as_text=_literal_and_labels_as_label_reference ) def append_group_by(self, *clauses): """Append the given GROUP BY criterion applied to this selectable. The criterion will be appended to any pre-existing GROUP BY criterion. This is an **in-place** mutation method; the :meth:`_expression.GenerativeSelect.group_by` method is preferred, as it provides standard :term:`method chaining`. .. seealso:: :meth:`_expression.GenerativeSelect.group_by` """ if len(clauses) == 1 and clauses[0] is None: self._group_by_clause = ClauseList() else: if getattr(self, "_group_by_clause", None) is not None: clauses = list(self._group_by_clause) + list(clauses) self._group_by_clause = ClauseList( *clauses, _literal_as_text=_literal_as_label_reference ) @property def _label_resolve_dict(self): raise NotImplementedError() def _copy_internals(self, clone=_clone, **kw): if self._limit_clause is not None: self._limit_clause = clone(self._limit_clause, **kw) if self._offset_clause is not None: self._offset_clause = clone(self._offset_clause, **kw) class CompoundSelect(GenerativeSelect): """Forms the basis of ``UNION``, ``UNION ALL``, and other SELECT-based set operations. .. seealso:: :func:`_expression.union` :func:`_expression.union_all` :func:`_expression.intersect` :func:`_expression.intersect_all` :func:`_expression.except` :func:`_expression.except_all` """ __visit_name__ = "compound_select" UNION = util.symbol("UNION") UNION_ALL = util.symbol("UNION ALL") EXCEPT = util.symbol("EXCEPT") EXCEPT_ALL = util.symbol("EXCEPT ALL") INTERSECT = util.symbol("INTERSECT") INTERSECT_ALL = util.symbol("INTERSECT ALL") _is_from_container = True def __init__(self, keyword, *selects, **kwargs): self._auto_correlate = kwargs.pop("correlate", False) self.keyword = keyword self.selects = [] numcols = None # some DBs do not like ORDER BY in the inner queries of a UNION, etc. for n, s in enumerate(selects): s = _clause_element_as_expr(s) if not numcols: numcols = len(s.c._all_columns) elif len(s.c._all_columns) != numcols: raise exc.ArgumentError( "All selectables passed to " "CompoundSelect must have identical numbers of " "columns; select #%d has %d columns, select " "#%d has %d" % ( 1, len(self.selects[0].c._all_columns), n + 1, len(s.c._all_columns), ) ) self.selects.append(s.self_group(against=self)) GenerativeSelect.__init__(self, **kwargs) @property def _label_resolve_dict(self): d = dict((c.key, c) for c in self.c) return d, d, d @classmethod def _create_union(cls, *selects, **kwargs): r"""Return a ``UNION`` of multiple selectables. The returned object is an instance of :class:`_selectable.CompoundSelect`. A similar :func:`union()` method is available on all :class:`_expression.FromClause` subclasses. :param \*selects: a list of :class:`_expression.Select` instances. :param \**kwargs: available keyword arguments are the same as those of :func:`select`. """ return CompoundSelect(CompoundSelect.UNION, *selects, **kwargs) @classmethod def _create_union_all(cls, *selects, **kwargs): r"""Return a ``UNION ALL`` of multiple selectables. The returned object is an instance of :class:`_selectable.CompoundSelect`. A similar :func:`union_all()` method is available on all :class:`_expression.FromClause` subclasses. :param \*selects: a list of :class:`_expression.Select` instances. :param \**kwargs: available keyword arguments are the same as those of :func:`select`. """ return CompoundSelect(CompoundSelect.UNION_ALL, *selects, **kwargs) @classmethod def _create_except(cls, *selects, **kwargs): r"""Return an ``EXCEPT`` of multiple selectables. The returned object is an instance of :class:`_selectable.CompoundSelect`. :param \*selects: a list of :class:`_expression.Select` instances. :param \**kwargs: available keyword arguments are the same as those of :func:`select`. """ return CompoundSelect(CompoundSelect.EXCEPT, *selects, **kwargs) @classmethod def _create_except_all(cls, *selects, **kwargs): r"""Return an ``EXCEPT ALL`` of multiple selectables. The returned object is an instance of :class:`_selectable.CompoundSelect`. :param \*selects: a list of :class:`_expression.Select` instances. :param \**kwargs: available keyword arguments are the same as those of :func:`select`. """ return CompoundSelect(CompoundSelect.EXCEPT_ALL, *selects, **kwargs) @classmethod def _create_intersect(cls, *selects, **kwargs): r"""Return an ``INTERSECT`` of multiple selectables. The returned object is an instance of :class:`_selectable.CompoundSelect`. :param \*selects: a list of :class:`_expression.Select` instances. :param \**kwargs: available keyword arguments are the same as those of :func:`select`. """ return CompoundSelect(CompoundSelect.INTERSECT, *selects, **kwargs) @classmethod def _create_intersect_all(cls, *selects, **kwargs): r"""Return an ``INTERSECT ALL`` of multiple selectables. The returned object is an instance of :class:`_selectable.CompoundSelect`. :param \*selects: a list of :class:`_expression.Select` instances. :param \**kwargs: available keyword arguments are the same as those of :func:`select`. """ return CompoundSelect(CompoundSelect.INTERSECT_ALL, *selects, **kwargs) def _scalar_type(self): return self.selects[0]._scalar_type() def self_group(self, against=None): return FromGrouping(self) def is_derived_from(self, fromclause): for s in self.selects: if s.is_derived_from(fromclause): return True return False def _populate_column_collection(self): for cols in zip(*[s.c._all_columns for s in self.selects]): # this is a slightly hacky thing - the union exports a # column that resembles just that of the *first* selectable. # to get at a "composite" column, particularly foreign keys, # you have to dig through the proxies collection which we # generate below. We may want to improve upon this, such as # perhaps _make_proxy can accept a list of other columns # that are "shared" - schema.column can then copy all the # ForeignKeys in. this would allow the union() to have all # those fks too. proxy = cols[0]._make_proxy( self, name=cols[0]._label if self.use_labels else None, key=cols[0]._key_label if self.use_labels else None, ) # hand-construct the "_proxies" collection to include all # derived columns place a 'weight' annotation corresponding # to how low in the list of select()s the column occurs, so # that the corresponding_column() operation can resolve # conflicts proxy._proxies = [ c._annotate({"weight": i + 1}) for (i, c) in enumerate(cols) ] def _refresh_for_new_column(self, column): for s in self.selects: s._refresh_for_new_column(column) if not self._cols_populated: return None raise NotImplementedError( "CompoundSelect constructs don't support " "addition of columns to underlying " "selectables" ) def _copy_internals(self, clone=_clone, **kw): super(CompoundSelect, self)._copy_internals(clone, **kw) self._reset_exported() self.selects = [clone(s, **kw) for s in self.selects] if hasattr(self, "_col_map"): del self._col_map for attr in ( "_order_by_clause", "_group_by_clause", "_for_update_arg", ): if getattr(self, attr) is not None: setattr(self, attr, clone(getattr(self, attr), **kw)) def get_children(self, column_collections=True, **kwargs): return ( (column_collections and list(self.c) or []) + [self._order_by_clause, self._group_by_clause] + list(self.selects) ) def bind(self): if self._bind: return self._bind for s in self.selects: e = s.bind if e: return e else: return None def _set_bind(self, bind): self._bind = bind bind = property(bind, _set_bind) class Select(HasPrefixes, HasSuffixes, GenerativeSelect): """Represents a ``SELECT`` statement.""" __visit_name__ = "select" _prefixes = () _suffixes = () _hints = util.immutabledict() _statement_hints = () _distinct = False _from_cloned = None _correlate = () _correlate_except = None _memoized_property = SelectBase._memoized_property _is_select = True @util.deprecated_params( autocommit=( "0.6", "The :paramref:`_expression.select.autocommit` " "parameter is deprecated " "and will be removed in a future release. Please refer to " "the :paramref:`.Connection.execution_options.autocommit` " "parameter in conjunction with the the " ":meth:`.Executable.execution_options` method in order to " "affect the autocommit behavior for a statement.", ), for_update=( "0.9", "The :paramref:`_expression.select.for_update` " "parameter is deprecated and " "will be removed in a future release. Please refer to the " ":meth:`_expression.Select.with_for_update` to specify the " "structure of the ``FOR UPDATE`` clause.", ), ) def __init__( self, columns=None, whereclause=None, from_obj=None, distinct=False, having=None, correlate=True, prefixes=None, suffixes=None, **kwargs ): """Construct a new :class:`_expression.Select`. Similar functionality is also available via the :meth:`_expression.FromClause.select` method on any :class:`_expression.FromClause`. All arguments which accept :class:`_expression.ClauseElement` arguments also accept string arguments, which will be converted as appropriate into either :func:`_expression.text` or :func:`_expression.literal_column` constructs. .. seealso:: :ref:`coretutorial_selecting` - Core Tutorial description of :func:`_expression.select`. :param columns: A list of :class:`_expression.ColumnElement` or :class:`_expression.FromClause` objects which will form the columns clause of the resulting statement. For those objects that are instances of :class:`_expression.FromClause` (typically :class:`_schema.Table` or :class:`_expression.Alias` objects), the :attr:`_expression.FromClause.c` collection is extracted to form a collection of :class:`_expression.ColumnElement` objects. This parameter will also accept :class:`_expression.TextClause` constructs as given, as well as ORM-mapped classes. .. note:: The :paramref:`_expression.select.columns` parameter is not available in the method form of :func:`_expression.select`, e.g. :meth:`_expression.FromClause.select`. .. seealso:: :meth:`_expression.Select.column` :meth:`_expression.Select.with_only_columns` :param whereclause: A :class:`_expression.ClauseElement` expression which will be used to form the ``WHERE`` clause. It is typically preferable to add WHERE criterion to an existing :class:`_expression.Select` using method chaining with :meth:`_expression.Select.where`. .. seealso:: :meth:`_expression.Select.where` :param from_obj: A list of :class:`_expression.ClauseElement` objects which will be added to the ``FROM`` clause of the resulting statement. This is equivalent to calling :meth:`_expression.Select.select_from` using method chaining on an existing :class:`_expression.Select` object. .. seealso:: :meth:`_expression.Select.select_from` - full description of explicit FROM clause specification. :param autocommit: legacy autocommit parameter. :param bind=None: an :class:`_engine.Engine` or :class:`_engine.Connection` instance to which the resulting :class:`_expression.Select` object will be bound. The :class:`_expression.Select` object will otherwise automatically bind to whatever :class:`~.base.Connectable` instances can be located within its contained :class:`_expression.ClauseElement` members. :param correlate=True: indicates that this :class:`_expression.Select` object should have its contained :class:`_expression.FromClause` elements "correlated" to an enclosing :class:`_expression.Select` object. It is typically preferable to specify correlations on an existing :class:`_expression.Select` construct using :meth:`_expression.Select.correlate`. .. seealso:: :meth:`_expression.Select.correlate` - full description of correlation. :param distinct=False: when ``True``, applies a ``DISTINCT`` qualifier to the columns clause of the resulting statement. The boolean argument may also be a column expression or list of column expressions - this is a special calling form which is understood by the PostgreSQL dialect to render the ``DISTINCT ON (<columns>)`` syntax. ``distinct`` is also available on an existing :class:`_expression.Select` object via the :meth:`_expression.Select.distinct` method. .. seealso:: :meth:`_expression.Select.distinct` :param for_update=False: when ``True``, applies ``FOR UPDATE`` to the end of the resulting statement. ``for_update`` accepts various string values interpreted by specific backends, including: * ``"read"`` - on MySQL, translates to ``LOCK IN SHARE MODE``; on PostgreSQL, translates to ``FOR SHARE``. * ``"nowait"`` - on PostgreSQL and Oracle, translates to ``FOR UPDATE NOWAIT``. * ``"read_nowait"`` - on PostgreSQL, translates to ``FOR SHARE NOWAIT``. .. seealso:: :meth:`_expression.Select.with_for_update` - improved API for specifying the ``FOR UPDATE`` clause. :param group_by: a list of :class:`_expression.ClauseElement` objects which will comprise the ``GROUP BY`` clause of the resulting select. This parameter is typically specified more naturally using the :meth:`_expression.Select.group_by` method on an existing :class:`_expression.Select`. .. seealso:: :meth:`_expression.Select.group_by` :param having: a :class:`_expression.ClauseElement` that will comprise the ``HAVING`` clause of the resulting select when ``GROUP BY`` is used. This parameter is typically specified more naturally using the :meth:`_expression.Select.having` method on an existing :class:`_expression.Select`. .. seealso:: :meth:`_expression.Select.having` :param limit=None: a numerical value which usually renders as a ``LIMIT`` expression in the resulting select. Backends that don't support ``LIMIT`` will attempt to provide similar functionality. This parameter is typically specified more naturally using the :meth:`_expression.Select.limit` method on an existing :class:`_expression.Select`. .. seealso:: :meth:`_expression.Select.limit` :param offset=None: a numeric value which usually renders as an ``OFFSET`` expression in the resulting select. Backends that don't support ``OFFSET`` will attempt to provide similar functionality. This parameter is typically specified more naturally using the :meth:`_expression.Select.offset` method on an existing :class:`_expression.Select`. .. seealso:: :meth:`_expression.Select.offset` :param order_by: a scalar or list of :class:`_expression.ClauseElement` objects which will comprise the ``ORDER BY`` clause of the resulting select. This parameter is typically specified more naturally using the :meth:`_expression.Select.order_by` method on an existing :class:`_expression.Select`. .. seealso:: :meth:`_expression.Select.order_by` :param use_labels=False: when ``True``, the statement will be generated using labels for each column in the columns clause, which qualify each column with its parent table's (or aliases) name so that name conflicts between columns in different tables don't occur. The format of the label is ``<tablename>_<column>``. The "c" collection of the resulting :class:`_expression.Select` object will use these names as well for targeting column members. This parameter can also be specified on an existing :class:`_expression.Select` object using the :meth:`_expression.Select.apply_labels` method. .. seealso:: :meth:`_expression.Select.apply_labels` """ self._auto_correlate = correlate if distinct is not False: if distinct is True: self._distinct = True else: self._distinct = [ _literal_as_label_reference(e) for e in util.to_list(distinct) ] if from_obj is not None: self._from_obj = util.OrderedSet( _interpret_as_from(f) for f in util.to_list(from_obj) ) else: self._from_obj = util.OrderedSet() try: cols_present = bool(columns) except TypeError as err: util.raise_( exc.ArgumentError( "columns argument to select() must " "be a Python list or other iterable" ), replace_context=err, ) if cols_present: self._raw_columns = [] for c in columns: c = _interpret_as_column_or_from(c) if isinstance(c, ScalarSelect): c = c.self_group(against=operators.comma_op) self._raw_columns.append(c) else: self._raw_columns = [] if whereclause is not None: self._whereclause = _literal_as_text(whereclause).self_group( against=operators._asbool ) else: self._whereclause = None if having is not None: self._having = _literal_as_text(having).self_group( against=operators._asbool ) else: self._having = None if prefixes: self._setup_prefixes(prefixes) if suffixes: self._setup_suffixes(suffixes) GenerativeSelect.__init__(self, **kwargs) @property def _froms(self): # would love to cache this, # but there's just enough edge cases, particularly now that # declarative encourages construction of SQL expressions # without tables present, to just regen this each time. froms = [] seen = set() translate = self._from_cloned for item in itertools.chain( _from_objects(*self._raw_columns), _from_objects(self._whereclause) if self._whereclause is not None else (), self._from_obj, ): if item is self: raise exc.InvalidRequestError( "select() construct refers to itself as a FROM" ) if translate and item in translate: item = translate[item] if not seen.intersection(item._cloned_set): froms.append(item) seen.update(item._cloned_set) return froms def _get_display_froms( self, explicit_correlate_froms=None, implicit_correlate_froms=None ): """Return the full list of 'from' clauses to be displayed. Takes into account a set of existing froms which may be rendered in the FROM clause of enclosing selects; this Select may want to leave those absent if it is automatically correlating. """ froms = self._froms toremove = set( itertools.chain(*[_expand_cloned(f._hide_froms) for f in froms]) ) if toremove: # if we're maintaining clones of froms, # add the copies out to the toremove list. only include # clones that are lexical equivalents. if self._from_cloned: toremove.update( self._from_cloned[f] for f in toremove.intersection(self._from_cloned) if self._from_cloned[f]._is_lexical_equivalent(f) ) # filter out to FROM clauses not in the list, # using a list to maintain ordering froms = [f for f in froms if f not in toremove] if self._correlate: to_correlate = self._correlate if to_correlate: froms = [ f for f in froms if f not in _cloned_intersection( _cloned_intersection( froms, explicit_correlate_froms or () ), to_correlate, ) ] if self._correlate_except is not None: froms = [ f for f in froms if f not in _cloned_difference( _cloned_intersection( froms, explicit_correlate_froms or () ), self._correlate_except, ) ] if ( self._auto_correlate and implicit_correlate_froms and len(froms) > 1 ): froms = [ f for f in froms if f not in _cloned_intersection(froms, implicit_correlate_froms) ] if not len(froms): raise exc.InvalidRequestError( "Select statement '%s" "' returned no FROM clauses " "due to auto-correlation; " "specify correlate(<tables>) " "to control correlation " "manually." % self ) return froms def _scalar_type(self): elem = self._raw_columns[0] cols = list(elem._select_iterable) return cols[0].type @property def froms(self): """Return the displayed list of FromClause elements.""" return self._get_display_froms() def with_statement_hint(self, text, dialect_name="*"): """Add a statement hint to this :class:`_expression.Select`. This method is similar to :meth:`_expression.Select.with_hint` except that it does not require an individual table, and instead applies to the statement as a whole. Hints here are specific to the backend database and may include directives such as isolation levels, file directives, fetch directives, etc. .. versionadded:: 1.0.0 .. seealso:: :meth:`_expression.Select.with_hint` :meth:`.Select.prefix_with` - generic SELECT prefixing which also can suit some database-specific HINT syntaxes such as MySQL optimizer hints """ return self.with_hint(None, text, dialect_name) @_generative def with_hint(self, selectable, text, dialect_name="*"): r"""Add an indexing or other executional context hint for the given selectable to this :class:`_expression.Select`. The text of the hint is rendered in the appropriate location for the database backend in use, relative to the given :class:`_schema.Table` or :class:`_expression.Alias` passed as the ``selectable`` argument. The dialect implementation typically uses Python string substitution syntax with the token ``%(name)s`` to render the name of the table or alias. E.g. when using Oracle, the following:: select([mytable]).\ with_hint(mytable, "index(%(name)s ix_mytable)") Would render SQL as:: select /*+ index(mytable ix_mytable) */ ... from mytable The ``dialect_name`` option will limit the rendering of a particular hint to a particular backend. Such as, to add hints for both Oracle and Sybase simultaneously:: select([mytable]).\ with_hint(mytable, "index(%(name)s ix_mytable)", 'oracle').\ with_hint(mytable, "WITH INDEX ix_mytable", 'sybase') .. seealso:: :meth:`_expression.Select.with_statement_hint` """ if selectable is None: self._statement_hints += ((dialect_name, text),) else: self._hints = self._hints.union({(selectable, dialect_name): text}) @property def type(self): raise exc.InvalidRequestError( "Select objects don't have a type. " "Call as_scalar() on this Select " "object to return a 'scalar' version " "of this Select." ) @_memoized_property.method def locate_all_froms(self): """Return a Set of all :class:`_expression.FromClause` elements referenced by this Select. This set is a superset of that returned by the ``froms`` property, which is specifically for those FromClause elements that would actually be rendered. """ froms = self._froms return froms + list(_from_objects(*froms)) @property def inner_columns(self): """An iterator of all :class:`_expression.ColumnElement` expressions which would be rendered into the columns clause of the resulting SELECT statement. """ return _select_iterables(self._raw_columns) @_memoized_property def _label_resolve_dict(self): with_cols = dict( (c._resolve_label or c._label or c.key, c) for c in _select_iterables(self._raw_columns) if c._allow_label_resolve ) only_froms = dict( (c.key, c) for c in _select_iterables(self.froms) if c._allow_label_resolve ) only_cols = with_cols.copy() for key, value in only_froms.items(): with_cols.setdefault(key, value) return with_cols, only_froms, only_cols def is_derived_from(self, fromclause): if self in fromclause._cloned_set: return True for f in self.locate_all_froms(): if f.is_derived_from(fromclause): return True return False def _copy_internals(self, clone=_clone, **kw): super(Select, self)._copy_internals(clone, **kw) # Select() object has been cloned and probably adapted by the # given clone function. Apply the cloning function to internal # objects # 1. keep a dictionary of the froms we've cloned, and what # they've become. This is consulted later when we derive # additional froms from "whereclause" and the columns clause, # which may still reference the uncloned parent table. # as of 0.7.4 we also put the current version of _froms, which # gets cleared on each generation. previously we were "baking" # _froms into self._from_obj. self._from_cloned = from_cloned = dict( (f, clone(f, **kw)) for f in self._from_obj.union(self._froms) ) # 3. update persistent _from_obj with the cloned versions. self._from_obj = util.OrderedSet( from_cloned[f] for f in self._from_obj ) # the _correlate collection is done separately, what can happen # here is the same item is _correlate as in _from_obj but the # _correlate version has an annotation on it - (specifically # RelationshipProperty.Comparator._criterion_exists() does # this). Also keep _correlate liberally open with its previous # contents, as this set is used for matching, not rendering. self._correlate = set(clone(f, **kw) for f in self._correlate).union( self._correlate ) # do something similar for _correlate_except - this is a more # unusual case but same idea applies if self._correlate_except: self._correlate_except = set( clone(f, **kw) for f in self._correlate_except ).union(self._correlate_except) # 4. clone other things. The difficulty here is that Column # objects are not actually cloned, and refer to their original # .table, resulting in the wrong "from" parent after a clone # operation. Hence _from_cloned and _from_obj supersede what is # present here. self._raw_columns = [clone(c, **kw) for c in self._raw_columns] for attr in ( "_whereclause", "_having", "_order_by_clause", "_group_by_clause", "_for_update_arg", ): if getattr(self, attr) is not None: setattr(self, attr, clone(getattr(self, attr), **kw)) # erase exported column list, _froms collection, # etc. self._reset_exported() def get_children(self, column_collections=True, **kwargs): """Return child elements as per the ClauseElement specification.""" return ( (column_collections and list(self.columns) or []) + self._raw_columns + list(self._froms) + [ x for x in ( self._whereclause, self._having, self._order_by_clause, self._group_by_clause, ) if x is not None ] ) @_generative def column(self, column): """Return a new :func:`_expression.select` construct with the given column expression added to its columns clause. E.g.:: my_select = my_select.column(table.c.new_column) See the documentation for :meth:`_expression.Select.with_only_columns` for guidelines on adding /replacing the columns of a :class:`_expression.Select` object. """ self.append_column(column) @util.dependencies("sqlalchemy.sql.util") def reduce_columns(self, sqlutil, only_synonyms=True): """Return a new :func:`_expression.select` construct with redundantly named, equivalently-valued columns removed from the columns clause. "Redundant" here means two columns where one refers to the other either based on foreign key, or via a simple equality comparison in the WHERE clause of the statement. The primary purpose of this method is to automatically construct a select statement with all uniquely-named columns, without the need to use table-qualified labels as :meth:`_expression.Select.apply_labels` does. When columns are omitted based on foreign key, the referred-to column is the one that's kept. When columns are omitted based on WHERE equivalence, the first column in the columns clause is the one that's kept. :param only_synonyms: when True, limit the removal of columns to those which have the same name as the equivalent. Otherwise, all columns that are equivalent to another are removed. """ return self.with_only_columns( sqlutil.reduce_columns( self.inner_columns, only_synonyms=only_synonyms, *(self._whereclause,) + tuple(self._from_obj) ) ) @_generative def with_only_columns(self, columns): r"""Return a new :func:`_expression.select` construct with its columns clause replaced with the given columns. This method is exactly equivalent to as if the original :func:`_expression.select` had been called with the given columns clause. I.e. a statement:: s = select([table1.c.a, table1.c.b]) s = s.with_only_columns([table1.c.b]) should be exactly equivalent to:: s = select([table1.c.b]) This means that FROM clauses which are only derived from the column list will be discarded if the new column list no longer contains that FROM:: >>> table1 = table('t1', column('a'), column('b')) >>> table2 = table('t2', column('a'), column('b')) >>> s1 = select([table1.c.a, table2.c.b]) >>> print(s1) SELECT t1.a, t2.b FROM t1, t2 >>> s2 = s1.with_only_columns([table2.c.b]) >>> print(s2) SELECT t2.b FROM t1 The preferred way to maintain a specific FROM clause in the construct, assuming it won't be represented anywhere else (i.e. not in the WHERE clause, etc.) is to set it using :meth:`_expression.Select.select_from`:: >>> s1 = select([table1.c.a, table2.c.b]).\ ... select_from(table1.join(table2, ... table1.c.a==table2.c.a)) >>> s2 = s1.with_only_columns([table2.c.b]) >>> print(s2) SELECT t2.b FROM t1 JOIN t2 ON t1.a=t2.a Care should also be taken to use the correct set of column objects passed to :meth:`_expression.Select.with_only_columns`. Since the method is essentially equivalent to calling the :func:`_expression.select` construct in the first place with the given columns, the columns passed to :meth:`_expression.Select.with_only_columns` should usually be a subset of those which were passed to the :func:`_expression.select` construct, not those which are available from the ``.c`` collection of that :func:`_expression.select`. That is:: s = select([table1.c.a, table1.c.b]).select_from(table1) s = s.with_only_columns([table1.c.b]) and **not**:: # usually incorrect s = s.with_only_columns([s.c.b]) The latter would produce the SQL:: SELECT b FROM (SELECT t1.a AS a, t1.b AS b FROM t1), t1 Since the :func:`_expression.select` construct is essentially being asked to select both from ``table1`` as well as itself. """ self._reset_exported() rc = [] for c in columns: c = _interpret_as_column_or_from(c) if isinstance(c, ScalarSelect): c = c.self_group(against=operators.comma_op) rc.append(c) self._raw_columns = rc @_generative def where(self, whereclause): """Return a new :func:`_expression.select` construct with the given expression added to its WHERE clause, joined to the existing clause via AND, if any. """ self.append_whereclause(whereclause) @_generative def having(self, having): """Return a new :func:`_expression.select` construct with the given expression added to its HAVING clause, joined to the existing clause via AND, if any. """ self.append_having(having) @_generative def distinct(self, *expr): r"""Return a new :func:`_expression.select` construct which will apply DISTINCT to its columns clause. :param \*expr: optional column expressions. When present, the PostgreSQL dialect will render a ``DISTINCT ON (<expressions>>)`` construct. """ if expr: expr = [_literal_as_label_reference(e) for e in expr] if isinstance(self._distinct, list): self._distinct = self._distinct + expr else: self._distinct = expr else: self._distinct = True @_generative def select_from(self, fromclause): r"""Return a new :func:`_expression.select` construct with the given FROM expression(s) merged into its list of FROM objects. E.g.:: table1 = table('t1', column('a')) table2 = table('t2', column('b')) s = select([table1.c.a]).\ select_from( table1.join(table2, table1.c.a==table2.c.b) ) The "from" list is a unique set on the identity of each element, so adding an already present :class:`_schema.Table` or other selectable will have no effect. Passing a :class:`_expression.Join` that refers to an already present :class:`_schema.Table` or other selectable will have the effect of concealing the presence of that selectable as an individual element in the rendered FROM list, instead rendering it into a JOIN clause. While the typical purpose of :meth:`_expression.Select.select_from` is to replace the default, derived FROM clause with a join, it can also be called with individual table elements, multiple times if desired, in the case that the FROM clause cannot be fully derived from the columns clause:: select([func.count('*')]).select_from(table1) """ self.append_from(fromclause) @_generative def correlate(self, *fromclauses): r"""Return a new :class:`_expression.Select` which will correlate the given FROM clauses to that of an enclosing :class:`_expression.Select`. Calling this method turns off the :class:`_expression.Select` object's default behavior of "auto-correlation". Normally, FROM elements which appear in a :class:`_expression.Select` that encloses this one via its :term:`WHERE clause`, ORDER BY, HAVING or :term:`columns clause` will be omitted from this :class:`_expression.Select` object's :term:`FROM clause`. Setting an explicit correlation collection using the :meth:`_expression.Select.correlate` method provides a fixed list of FROM objects that can potentially take place in this process. When :meth:`_expression.Select.correlate` is used to apply specific FROM clauses for correlation, the FROM elements become candidates for correlation regardless of how deeply nested this :class:`_expression.Select` object is, relative to an enclosing :class:`_expression.Select` which refers to the same FROM object. This is in contrast to the behavior of "auto-correlation" which only correlates to an immediate enclosing :class:`_expression.Select`. Multi-level correlation ensures that the link between enclosed and enclosing :class:`_expression.Select` is always via at least one WHERE/ORDER BY/HAVING/columns clause in order for correlation to take place. If ``None`` is passed, the :class:`_expression.Select` object will correlate none of its FROM entries, and all will render unconditionally in the local FROM clause. :param \*fromclauses: a list of one or more :class:`_expression.FromClause` constructs, or other compatible constructs (i.e. ORM-mapped classes) to become part of the correlate collection. .. seealso:: :meth:`_expression.Select.correlate_except` :ref:`correlated_subqueries` """ self._auto_correlate = False if fromclauses and fromclauses[0] is None: self._correlate = () else: self._correlate = set(self._correlate).union( _interpret_as_from(f) for f in fromclauses ) @_generative def correlate_except(self, *fromclauses): r"""Return a new :class:`_expression.Select` which will omit the given FROM clauses from the auto-correlation process. Calling :meth:`_expression.Select.correlate_except` turns off the :class:`_expression.Select` object's default behavior of "auto-correlation" for the given FROM elements. An element specified here will unconditionally appear in the FROM list, while all other FROM elements remain subject to normal auto-correlation behaviors. If ``None`` is passed, the :class:`_expression.Select` object will correlate all of its FROM entries. :param \*fromclauses: a list of one or more :class:`_expression.FromClause` constructs, or other compatible constructs (i.e. ORM-mapped classes) to become part of the correlate-exception collection. .. seealso:: :meth:`_expression.Select.correlate` :ref:`correlated_subqueries` """ self._auto_correlate = False if fromclauses and fromclauses[0] is None: self._correlate_except = () else: self._correlate_except = set(self._correlate_except or ()).union( _interpret_as_from(f) for f in fromclauses ) def append_correlation(self, fromclause): """Append the given correlation expression to this :func:`_expression.select` construct. This is an **in-place** mutation method; the :meth:`_expression.Select.correlate` method is preferred, as it provides standard :term:`method chaining`. """ self._auto_correlate = False self._correlate = set(self._correlate).union( _interpret_as_from(f) for f in fromclause ) def append_column(self, column): """Append the given column expression to the columns clause of this :func:`_expression.select` construct. E.g.:: my_select.append_column(some_table.c.new_column) This is an **in-place** mutation method; the :meth:`_expression.Select.column` method is preferred, as it provides standard :term:`method chaining`. See the documentation for :meth:`_expression.Select.with_only_columns` for guidelines on adding /replacing the columns of a :class:`_expression.Select` object. """ self._reset_exported() column = _interpret_as_column_or_from(column) if isinstance(column, ScalarSelect): column = column.self_group(against=operators.comma_op) self._raw_columns = self._raw_columns + [column] def append_prefix(self, clause): """Append the given columns clause prefix expression to this :func:`_expression.select` construct. This is an **in-place** mutation method; the :meth:`_expression.Select.prefix_with` method is preferred, as it provides standard :term:`method chaining`. """ clause = _literal_as_text(clause) self._prefixes = self._prefixes + (clause,) def append_whereclause(self, whereclause): """Append the given expression to this :func:`_expression.select` construct's WHERE criterion. The expression will be joined to existing WHERE criterion via AND. This is an **in-place** mutation method; the :meth:`_expression.Select.where` method is preferred, as it provides standard :term:`method chaining`. """ self._reset_exported() self._whereclause = and_(True_._ifnone(self._whereclause), whereclause) def append_having(self, having): """Append the given expression to this :func:`_expression.select` construct's HAVING criterion. The expression will be joined to existing HAVING criterion via AND. This is an **in-place** mutation method; the :meth:`_expression.Select.having` method is preferred, as it provides standard :term:`method chaining`. """ self._reset_exported() self._having = and_(True_._ifnone(self._having), having) def append_from(self, fromclause): """Append the given FromClause expression to this :func:`_expression.select` construct's FROM clause. This is an **in-place** mutation method; the :meth:`_expression.Select.select_from` method is preferred, as it provides standard :term:`method chaining`. """ self._reset_exported() fromclause = _interpret_as_from(fromclause) self._from_obj = self._from_obj.union([fromclause]) @_memoized_property def _columns_plus_names(self): if self.use_labels: names = set() def name_for_col(c): if c._label is None or not c._render_label_in_columns_clause: return (None, c) name = c._label if name in names: name = c.anon_label else: names.add(name) return name, c return [ name_for_col(c) for c in util.unique_list(_select_iterables(self._raw_columns)) ] else: return [ (None, c) for c in util.unique_list(_select_iterables(self._raw_columns)) ] def _populate_column_collection(self): for name, c in self._columns_plus_names: if not hasattr(c, "_make_proxy"): continue if name is None: key = None elif self.use_labels: key = c._key_label if key is not None and key in self.c: key = c.anon_label else: key = None c._make_proxy(self, key=key, name=name, name_is_truncatable=True) def _refresh_for_new_column(self, column): for fromclause in self._froms: col = fromclause._refresh_for_new_column(column) if col is not None: if col in self.inner_columns and self._cols_populated: our_label = col._key_label if self.use_labels else col.key if our_label not in self.c: return col._make_proxy( self, name=col._label if self.use_labels else None, key=col._key_label if self.use_labels else None, name_is_truncatable=True, ) return None return None def _needs_parens_for_grouping(self): return ( self._limit_clause is not None or self._offset_clause is not None or bool(self._order_by_clause.clauses) ) def self_group(self, against=None): """Return a 'grouping' construct as per the :class:`_expression.ClauseElement` specification. This produces an element that can be embedded in an expression. Note that this method is called automatically as needed when constructing expressions and should not require explicit use. """ if ( isinstance(against, CompoundSelect) and not self._needs_parens_for_grouping() ): return self return FromGrouping(self) def union(self, other, **kwargs): """Return a SQL ``UNION`` of this select() construct against the given selectable. """ return CompoundSelect._create_union(self, other, **kwargs) def union_all(self, other, **kwargs): """Return a SQL ``UNION ALL`` of this select() construct against the given selectable. """ return CompoundSelect._create_union_all(self, other, **kwargs) def except_(self, other, **kwargs): """Return a SQL ``EXCEPT`` of this select() construct against the given selectable. """ return CompoundSelect._create_except(self, other, **kwargs) def except_all(self, other, **kwargs): """Return a SQL ``EXCEPT ALL`` of this select() construct against the given selectable. """ return CompoundSelect._create_except_all(self, other, **kwargs) def intersect(self, other, **kwargs): """Return a SQL ``INTERSECT`` of this select() construct against the given selectable. """ return CompoundSelect._create_intersect(self, other, **kwargs) def intersect_all(self, other, **kwargs): """Return a SQL ``INTERSECT ALL`` of this select() construct against the given selectable. """ return CompoundSelect._create_intersect_all(self, other, **kwargs) def bind(self): if self._bind: return self._bind froms = self._froms if not froms: for c in self._raw_columns: e = c.bind if e: self._bind = e return e else: e = list(froms)[0].bind if e: self._bind = e return e return None def _set_bind(self, bind): self._bind = bind bind = property(bind, _set_bind) class ScalarSelect(Generative, Grouping): _from_objects = [] _is_from_container = True _is_implicitly_boolean = False def __init__(self, element): self.element = element self.type = element._scalar_type() @property def columns(self): raise exc.InvalidRequestError( "Scalar Select expression has no " "columns; use this object directly " "within a column-level expression." ) c = columns @_generative def where(self, crit): """Apply a WHERE clause to the SELECT statement referred to by this :class:`_expression.ScalarSelect`. """ self.element = self.element.where(crit) def self_group(self, **kwargs): return self class Exists(UnaryExpression): """Represent an ``EXISTS`` clause.""" __visit_name__ = UnaryExpression.__visit_name__ _from_objects = [] def __init__(self, *args, **kwargs): """Construct a new :class:`_expression.Exists` against an existing :class:`_expression.Select` object. Calling styles are of the following forms:: # use on an existing select() s = select([table.c.col1]).where(table.c.col2==5) s_e = exists(s) # an exists is usually used in a where of another select # to produce a WHERE EXISTS (SELECT ... ) select([table.c.col1]).where(s_e) # but can also be used in a select to produce a # SELECT EXISTS (SELECT ... ) query select([s_e]) # construct a select() at once exists(['*'], **select_arguments).where(criterion) # columns argument is optional, generates "EXISTS (SELECT *)" # by default. exists().where(table.c.col2==5) """ if args and isinstance(args[0], (SelectBase, ScalarSelect)): s = args[0] else: if not args: args = ([literal_column("*")],) s = Select(*args, **kwargs).as_scalar().self_group() UnaryExpression.__init__( self, s, operator=operators.exists, type_=type_api.BOOLEANTYPE, wraps_column_expression=True, ) def select(self, whereclause=None, **params): return Select([self], whereclause, **params) def correlate(self, *fromclause): e = self._clone() e.element = self.element.correlate(*fromclause).self_group() return e def correlate_except(self, *fromclause): e = self._clone() e.element = self.element.correlate_except(*fromclause).self_group() return e def select_from(self, clause): """Return a new :class:`_expression.Exists` construct, applying the given expression to the :meth:`_expression.Select.select_from` method of the select statement contained. """ e = self._clone() e.element = self.element.select_from(clause).self_group() return e def where(self, clause): """Return a new :func:`_expression.exists` construct with the given expression added to its WHERE clause, joined to the existing clause via AND, if any. """ e = self._clone() e.element = self.element.where(clause).self_group() return e class TextAsFrom(SelectBase): """Wrap a :class:`_expression.TextClause` construct within a :class:`_expression.SelectBase` interface. This allows the :class:`_expression.TextClause` object to gain a ``.c`` collection and other FROM-like capabilities such as :meth:`_expression.FromClause.alias`, :meth:`_expression.SelectBase.cte`, etc. The :class:`.TextAsFrom` construct is produced via the :meth:`_expression.TextClause.columns` method - see that method for details. .. versionadded:: 0.9.0 .. seealso:: :func:`_expression.text` :meth:`_expression.TextClause.columns` """ __visit_name__ = "text_as_from" _textual = True def __init__(self, text, columns, positional=False): self.element = text self.column_args = columns self.positional = positional @property def _bind(self): return self.element._bind @_generative def bindparams(self, *binds, **bind_as_values): self.element = self.element.bindparams(*binds, **bind_as_values) def _populate_column_collection(self): for c in self.column_args: c._make_proxy(self) def _copy_internals(self, clone=_clone, **kw): self._reset_exported() self.element = clone(self.element, **kw) def _scalar_type(self): return self.column_args[0].type class AnnotatedFromClause(Annotated): def __init__(self, element, values): # force FromClause to generate their internal # collections into __dict__ element.c Annotated.__init__(self, element, values)
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