path: root/lib/sqlalchemy/sql/roles.py

# sql/roles.py
# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: https://www.opensource.org/licenses/mit-license.php
from __future__ import annotations

from typing import Any
from typing import Generic
from typing import Iterable
from typing import List
from typing import Optional
from typing import TYPE_CHECKING
from typing import TypeVar

from .. import util
from ..util.typing import Literal

if TYPE_CHECKING:
    from ._typing import _PropagateAttrsType
    from .base import _EntityNamespace
    from .base import ColumnCollection
    from .base import ReadOnlyColumnCollection
    from .elements import ClauseElement
    from .elements import ColumnClause
    from .elements import ColumnElement
    from .elements import Label
    from .elements import NamedColumn
    from .selectable import _SelectIterable
    from .selectable import FromClause
    from .selectable import Subquery

_T = TypeVar("_T", bound=Any)


class SQLRole:
    """Define a "role" within a SQL statement structure.

    Classes within SQL Core participate within SQLRole hierarchies in order
    to more accurately indicate where they may be used within SQL statements
    of all types.

    .. versionadded:: 1.4

    """

    __slots__ = ()
    allows_lambda = False
    uses_inspection = False


class UsesInspection:
    __slots__ = ()
    _post_inspect: Literal[None] = None
    uses_inspection = True


class AllowsLambdaRole:
    __slots__ = ()
    allows_lambda = True


class HasCacheKeyRole(SQLRole):
    __slots__ = ()
    _role_name = "Cacheable Core or ORM object"


class ExecutableOptionRole(SQLRole):
    __slots__ = ()
    _role_name = "ExecutionOption Core or ORM object"


class LiteralValueRole(SQLRole):
    __slots__ = ()
    _role_name = "Literal Python value"


class ColumnArgumentRole(SQLRole):
    __slots__ = ()
    _role_name = "Column expression"


class ColumnArgumentOrKeyRole(ColumnArgumentRole):
    __slots__ = ()
    _role_name = "Column expression or string key"


class StrAsPlainColumnRole(ColumnArgumentRole):
    __slots__ = ()
    _role_name = "Column expression or string key"


class ColumnListRole(SQLRole):
    """Elements suitable for forming comma separated lists of expressions."""

    __slots__ = ()


class StringRole(SQLRole):
    """mixin indicating a role that results in strings"""

    __slots__ = ()


class TruncatedLabelRole(StringRole, SQLRole):
    __slots__ = ()
    _role_name = "String SQL identifier"


class ColumnsClauseRole(AllowsLambdaRole, UsesInspection, ColumnListRole):
    __slots__ = ()
    _role_name = "Column expression or FROM clause"

    @property
    def _select_iterable(self) -> _SelectIterable:
        raise NotImplementedError()


class LimitOffsetRole(SQLRole):
    __slots__ = ()
    _role_name = "LIMIT / OFFSET expression"


class ByOfRole(ColumnListRole):
    __slots__ = ()
    _role_name = "GROUP BY / OF / etc. expression"


class GroupByRole(AllowsLambdaRole, UsesInspection, ByOfRole):
    __slots__ = ()
    # note there's a special case right now where you can pass a whole
    # ORM entity to group_by() and it splits out.   we may not want to keep
    # this around

    _role_name = "GROUP BY expression"


class OrderByRole(AllowsLambdaRole, ByOfRole):
    __slots__ = ()
    _role_name = "ORDER BY expression"


class StructuralRole(SQLRole):
    __slots__ = ()


class StatementOptionRole(StructuralRole):
    __slots__ = ()
    _role_name = "statement sub-expression element"


class OnClauseRole(AllowsLambdaRole, StructuralRole):
    __slots__ = ()
    _role_name = (
        "ON clause, typically a SQL expression or "
        "ORM relationship attribute"
    )


class WhereHavingRole(OnClauseRole):
    __slots__ = ()
    _role_name = "SQL expression for WHERE/HAVING role"


class ExpressionElementRole(Generic[_T], SQLRole):
    # note when using generics for ExpressionElementRole,
    # the generic type needs to be in
    # sqlalchemy.sql.coercions._impl_lookup mapping also.
    # these are set up for basic types like int, bool, str, float
    # right now

    __slots__ = ()
    _role_name = "SQL expression element"

    def label(self, name: Optional[str]) -> Label[_T]:
        raise NotImplementedError()


class ConstExprRole(ExpressionElementRole[_T]):
    __slots__ = ()
    _role_name = "Constant True/False/None expression"


class LabeledColumnExprRole(ExpressionElementRole[_T]):
    __slots__ = ()


class BinaryElementRole(ExpressionElementRole[_T]):
    __slots__ = ()
    _role_name = "SQL expression element or literal value"


class InElementRole(SQLRole):
    __slots__ = ()
    _role_name = (
        "IN expression list, SELECT construct, or bound parameter object"
    )


class JoinTargetRole(AllowsLambdaRole, UsesInspection, StructuralRole):
    __slots__ = ()
    _role_name = (
        "Join target, typically a FROM expression, or ORM "
        "relationship attribute"
    )


class FromClauseRole(ColumnsClauseRole, JoinTargetRole):
    __slots__ = ()
    _role_name = "FROM expression, such as a Table or alias() object"

    _is_subquery = False

    named_with_column: bool

    if TYPE_CHECKING:

        @util.ro_non_memoized_property
        def c(self) -> ReadOnlyColumnCollection[str, ColumnClause[Any]]:
            ...

        @util.ro_non_memoized_property
        def columns(self) -> ReadOnlyColumnCollection[str, ColumnClause[Any]]:
            ...

        @util.ro_non_memoized_property
        def entity_namespace(self) -> _EntityNamespace:
            ...

        @util.ro_non_memoized_property
        def _hide_froms(self) -> Iterable[FromClause]:
            ...

        @util.ro_non_memoized_property
        def _from_objects(self) -> List[FromClause]:
            ...


class StrictFromClauseRole(FromClauseRole):
    __slots__ = ()
    # does not allow text() or select() objects

    if TYPE_CHECKING:

        @util.ro_non_memoized_property
        def description(self) -> str:
            ...


class AnonymizedFromClauseRole(StrictFromClauseRole):
    __slots__ = ()

    if TYPE_CHECKING:

        def _anonymous_fromclause(
            self, name: Optional[str] = None, flat: bool = False
        ) -> FromClause:
            ...


class ReturnsRowsRole(SQLRole):
    __slots__ = ()
    _role_name = (
        "Row returning expression such as a SELECT, a FROM clause, or an "
        "INSERT/UPDATE/DELETE with RETURNING"
    )


class StatementRole(SQLRole):
    __slots__ = ()
    _role_name = "Executable SQL or text() construct"

    _propagate_attrs: _PropagateAttrsType = util.immutabledict()


class SelectStatementRole(StatementRole, ReturnsRowsRole):
    __slots__ = ()
    _role_name = "SELECT construct or equivalent text() construct"

    def subquery(self) -> Subquery:
        raise NotImplementedError(
            "All SelectStatementRole objects should implement a "
            ".subquery() method."
        )


class HasCTERole(ReturnsRowsRole):
    __slots__ = ()


class IsCTERole(SQLRole):
    __slots__ = ()
    _role_name = "CTE object"


class CompoundElementRole(AllowsLambdaRole, SQLRole):
    """SELECT statements inside a CompoundSelect, e.g. UNION, EXTRACT, etc."""

    __slots__ = ()
    _role_name = (
        "SELECT construct for inclusion in a UNION or other set construct"
    )


# TODO: are we using this?
class DMLRole(StatementRole):
    __slots__ = ()


class DMLTableRole(FromClauseRole):
    __slots__ = ()
    _role_name = "subject table for an INSERT, UPDATE or DELETE"

    if TYPE_CHECKING:

        @util.ro_non_memoized_property
        def primary_key(self) -> Iterable[NamedColumn[Any]]:
            ...

        @util.ro_non_memoized_property
        def columns(self) -> ReadOnlyColumnCollection[str, ColumnClause[Any]]:
            ...


class DMLColumnRole(SQLRole):
    __slots__ = ()
    _role_name = "SET/VALUES column expression or string key"


class DMLSelectRole(SQLRole):
    """A SELECT statement embedded in DML, typically INSERT from SELECT"""

    __slots__ = ()
    _role_name = "SELECT statement or equivalent textual object"


class DDLRole(StatementRole):
    __slots__ = ()


class DDLExpressionRole(StructuralRole):
    __slots__ = ()
    _role_name = "SQL expression element for DDL constraint"


class DDLConstraintColumnRole(SQLRole):
    __slots__ = ()
    _role_name = "String column name or column expression for DDL constraint"


class DDLReferredColumnRole(DDLConstraintColumnRole):
    __slots__ = ()
    _role_name = (
        "String column name or Column object for DDL foreign key constraint"
    )