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File Content: `postgresql.py`

# mypy: allow-untyped-defs, allow-incomplete-defs, allow-untyped-calls
# mypy: no-warn-return-any, allow-any-generics

from __future__ import annotations

import logging
import re
from typing import Any
from typing import cast
from typing import Dict
from typing import List
from typing import Optional
from typing import Sequence
from typing import Tuple
from typing import TYPE_CHECKING
from typing import Union

from sqlalchemy import Column
from sqlalchemy import Float
from sqlalchemy import Identity
from sqlalchemy import literal_column
from sqlalchemy import Numeric
from sqlalchemy import select
from sqlalchemy import text
from sqlalchemy import types as sqltypes
from sqlalchemy.dialects.postgresql import BIGINT
from sqlalchemy.dialects.postgresql import ExcludeConstraint
from sqlalchemy.dialects.postgresql import INTEGER
from sqlalchemy.schema import CreateIndex
from sqlalchemy.sql.elements import ColumnClause
from sqlalchemy.sql.elements import TextClause
from sqlalchemy.sql.functions import FunctionElement
from sqlalchemy.types import NULLTYPE

from .base import alter_column
from .base import alter_table
from .base import AlterColumn
from .base import ColumnComment
from .base import format_column_name
from .base import format_table_name
from .base import format_type
from .base import IdentityColumnDefault
from .base import RenameTable
from .impl import ComparisonResult
from .impl import DefaultImpl
from .. import util
from ..autogenerate import render
from ..operations import ops
from ..operations import schemaobj
from ..operations.base import BatchOperations
from ..operations.base import Operations
from ..util import sqla_compat
from ..util.sqla_compat import compiles

if TYPE_CHECKING:
    from typing import Literal

    from sqlalchemy import Index
    from sqlalchemy import UniqueConstraint
    from sqlalchemy.dialects.postgresql.array import ARRAY
    from sqlalchemy.dialects.postgresql.base import PGDDLCompiler
    from sqlalchemy.dialects.postgresql.hstore import HSTORE
    from sqlalchemy.dialects.postgresql.json import JSON
    from sqlalchemy.dialects.postgresql.json import JSONB
    from sqlalchemy.sql.elements import ClauseElement
    from sqlalchemy.sql.elements import ColumnElement
    from sqlalchemy.sql.elements import quoted_name
    from sqlalchemy.sql.schema import MetaData
    from sqlalchemy.sql.schema import Table
    from sqlalchemy.sql.type_api import TypeEngine

    from .base import _ServerDefault
    from ..autogenerate.api import AutogenContext
    from ..autogenerate.render import _f_name
    from ..runtime.migration import MigrationContext


log = logging.getLogger(__name__)


class PostgresqlImpl(DefaultImpl):
    __dialect__ = "postgresql"
    transactional_ddl = True
    type_synonyms = DefaultImpl.type_synonyms + (
        {"FLOAT", "DOUBLE PRECISION"},
    )

    def create_index(self, index: Index, **kw: Any) -> None:
        # this likely defaults to None if not present, so get()
        # should normally not return the default value.  being
        # defensive in any case
        postgresql_include = index.kwargs.get("postgresql_include", None) or ()
        for col in postgresql_include:
            if col not in index.table.c:  # type: ignore[union-attr]
                index.table.append_column(  # type: ignore[union-attr]
                    Column(col, sqltypes.NullType)
                )
        self._exec(CreateIndex(index, **kw))

    def prep_table_for_batch(self, batch_impl, table):
        for constraint in table.constraints:
            if (
                constraint.name is not None
                and constraint.name in batch_impl.named_constraints
            ):
                self.drop_constraint(constraint)

    def compare_server_default(
        self,
        inspector_column,
        metadata_column,
        rendered_metadata_default,
        rendered_inspector_default,
    ):
        # don't do defaults for SERIAL columns
        if (
            metadata_column.primary_key
            and metadata_column is metadata_column.table._autoincrement_column
        ):
            return False

        conn_col_default = rendered_inspector_default

        defaults_equal = conn_col_default == rendered_metadata_default
        if defaults_equal:
            return False

        if None in (
            conn_col_default,
            rendered_metadata_default,
            metadata_column.server_default,
        ):
            return not defaults_equal

        metadata_default = metadata_column.server_default.arg

        if isinstance(metadata_default, str):
            if not isinstance(inspector_column.type, (Numeric, Float)):
                metadata_default = re.sub(r"^'|'$", "", metadata_default)
                metadata_default = f"'{metadata_default}'"

            metadata_default = literal_column(metadata_default)

        # run a real compare against the server
        conn = self.connection
        assert conn is not None
        return not conn.scalar(
            select(literal_column(conn_col_default) == metadata_default)
        )

    def alter_column(  # type:ignore[override]
        self,
        table_name: str,
        column_name: str,
        nullable: Optional[bool] = None,
        server_default: Union[_ServerDefault, Literal[False]] = False,
        name: Optional[str] = None,
        type_: Optional[TypeEngine] = None,
        schema: Optional[str] = None,
        autoincrement: Optional[bool] = None,
        existing_type: Optional[TypeEngine] = None,
        existing_server_default: Optional[_ServerDefault] = None,
        existing_nullable: Optional[bool] = None,
        existing_autoincrement: Optional[bool] = None,
        **kw: Any,
    ) -> None:
        using = kw.pop("postgresql_using", None)

        if using is not None and type_ is None:
            raise util.CommandError(
                "postgresql_using must be used with the type_ parameter"
            )

        if type_ is not None:
            self._exec(
                PostgresqlColumnType(
                    table_name,
                    column_name,
                    type_,
                    schema=schema,
                    using=using,
                    existing_type=existing_type,
                    existing_server_default=existing_server_default,
                    existing_nullable=existing_nullable,
                )
            )

        super().alter_column(
            table_name,
            column_name,
            nullable=nullable,
            server_default=server_default,
            name=name,
            schema=schema,
            autoincrement=autoincrement,
            existing_type=existing_type,
            existing_server_default=existing_server_default,
            existing_nullable=existing_nullable,
            existing_autoincrement=existing_autoincrement,
            **kw,
        )

    def autogen_column_reflect(self, inspector, table, column_info):
        if column_info.get("default") and isinstance(
            column_info["type"], (INTEGER, BIGINT)
        ):
            seq_match = re.match(
                r"nextval\('(.+?)'::regclass\)", column_info["default"]
            )
            if seq_match:
                info = sqla_compat._exec_on_inspector(
                    inspector,
                    text(
                        "select c.relname, a.attname "
                        "from pg_class as c join "
                        "pg_depend d on d.objid=c.oid and "
                        "d.classid='pg_class'::regclass and "
                        "d.refclassid='pg_class'::regclass "
                        "join pg_class t on t.oid=d.refobjid "
                        "join pg_attribute a on a.attrelid=t.oid and "
                        "a.attnum=d.refobjsubid "
                        "where c.relkind='S' and "
                        "c.oid=cast(:seqname as regclass)"
                    ),
                    seqname=seq_match.group(1),
                ).first()
                if info:
                    seqname, colname = info
                    if colname == column_info["name"]:
                        log.info(
                            "Detected sequence named '%s' as "
                            "owned by integer column '%s(%s)', "
                            "assuming SERIAL and omitting",
                            seqname,
                            table.name,
                            colname,
                        )
                        # sequence, and the owner is this column,
                        # its a SERIAL - whack it!
                        del column_info["default"]

    def correct_for_autogen_constraints(
        self,
        conn_unique_constraints,
        conn_indexes,
        metadata_unique_constraints,
        metadata_indexes,
    ):
        doubled_constraints = {
            index
            for index in conn_indexes
            if index.info.get("duplicates_constraint")
        }

        for ix in doubled_constraints:
            conn_indexes.remove(ix)

        if not sqla_compat.sqla_2:
            self._skip_functional_indexes(metadata_indexes, conn_indexes)

    # pg behavior regarding modifiers
    # | # | compiled sql     | returned sql     | regexp. group is removed |
    # | - | ---------------- | -----------------| ------------------------ |
    # | 1 | nulls first      | nulls first      | -                        |
    # | 2 | nulls last       |                  | (?<! desc)( nulls last)$ |
    # | 3 | asc              |                  | ( asc)$                  |
    # | 4 | asc nulls first  | nulls first      | ( asc) nulls first$      |
    # | 5 | asc nulls last   |                  | ( asc nulls last)$       |
    # | 6 | desc             | desc             | -                        |
    # | 7 | desc nulls first | desc             | desc( nulls first)$      |
    # | 8 | desc nulls last  | desc nulls last  | -                        |
    _default_modifiers_re = (  # order of case 2 and 5 matters
        re.compile("( asc nulls last)$"),  # case 5
        re.compile("(?<! desc)( nulls last)$"),  # case 2
        re.compile("( asc)$"),  # case 3
        re.compile("( asc) nulls first$"),  # case 4
        re.compile(" desc( nulls first)$"),  # case 7
    )

    def _cleanup_index_expr(self, index: Index, expr: str) -> str:
        expr = expr.lower().replace('"', "").replace("'", "")
        if index.table is not None:
            # should not be needed, since include_table=False is in compile
            expr = expr.replace(f"{index.table.name.lower()}.", "")

        if "::" in expr:
            # strip :: cast. types can have spaces in them
            expr = re.sub(r"(::[\w ]+\w)", "", expr)

        while expr and expr[0] == "(" and expr[-1] == ")":
            expr = expr[1:-1]

        # NOTE: when parsing the connection expression this cleanup could
        # be skipped
        for rs in self._default_modifiers_re:
            if match := rs.search(expr):
                start, end = match.span(1)
                expr = expr[:start] + expr[end:]
                break

        while expr and expr[0] == "(" and expr[-1] == ")":
            expr = expr[1:-1]

        # strip casts
        cast_re = re.compile(r"cast\s*\(")
        if cast_re.match(expr):
            expr = cast_re.sub("", expr)
            # remove the as type
            expr = re.sub(r"as\s+[^)]+\)", "", expr)
        # remove spaces
        expr = expr.replace(" ", "")
        return expr

    def _dialect_options(
        self, item: Union[Index, UniqueConstraint]
    ) -> Tuple[Any, ...]:
        # only the positive case is returned by sqlalchemy reflection so
        # None and False are threated the same
        if item.dialect_kwargs.get("postgresql_nulls_not_distinct"):
            return ("nulls_not_distinct",)
        return ()

    def compare_indexes(
        self,
        metadata_index: Index,
        reflected_index: Index,
    ) -> ComparisonResult:
        msg = []
        unique_msg = self._compare_index_unique(
            metadata_index, reflected_index
        )
        if unique_msg:
            msg.append(unique_msg)
        m_exprs = metadata_index.expressions
        r_exprs = reflected_index.expressions
        if len(m_exprs) != len(r_exprs):
            msg.append(f"expression number {len(r_exprs)} to {len(m_exprs)}")
        if msg:
            # no point going further, return early
            return ComparisonResult.Different(msg)
        skip = []
        for pos, (m_e, r_e) in enumerate(zip(m_exprs, r_exprs), 1):
            m_compile = self._compile_element(m_e)
            m_text = self._cleanup_index_expr(metadata_index, m_compile)
            # print(f"META ORIG: {m_compile!r} CLEANUP: {m_text!r}")
            r_compile = self._compile_element(r_e)
            r_text = self._cleanup_index_expr(metadata_index, r_compile)
            # print(f"CONN ORIG: {r_compile!r} CLEANUP: {r_text!r}")
            if m_text == r_text:
                continue  # expressions these are equal
            elif m_compile.strip().endswith("_ops") and (
                " " in m_compile or ")" in m_compile  # is an expression
            ):
                skip.append(
                    f"expression #{pos} {m_compile!r} detected "
                    "as including operator clause."
                )
                util.warn(
                    f"Expression #{pos} {m_compile!r} in index "
                    f"{reflected_index.name!r} detected to include "
                    "an operator clause. Expression compare cannot proceed. "
                    "Please move the operator clause to the "
                    "``postgresql_ops`` dict to enable proper compare "
                    "of the index expressions: "
                    "https://docs.sqlalchemy.org/en/latest/dialects/postgresql.html#operator-classes",  # noqa: E501
                )
            else:
                msg.append(f"expression #{pos} {r_compile!r} to {m_compile!r}")

        m_options = self._dialect_options(metadata_index)
        r_options = self._dialect_options(reflected_index)
        if m_options != r_options:
            msg.extend(f"options {r_options} to {m_options}")

        if msg:
            return ComparisonResult.Different(msg)
        elif skip:
            # if there are other changes detected don't skip the index
            return ComparisonResult.Skip(skip)
        else:
            return ComparisonResult.Equal()

    def compare_unique_constraint(
        self,
        metadata_constraint: UniqueConstraint,
        reflected_constraint: UniqueConstraint,
    ) -> ComparisonResult:
        metadata_tup = self._create_metadata_constraint_sig(
            metadata_constraint
        )
        reflected_tup = self._create_reflected_constraint_sig(
            reflected_constraint
        )

        meta_sig = metadata_tup.unnamed
        conn_sig = reflected_tup.unnamed
        if conn_sig != meta_sig:
            return ComparisonResult.Different(
                f"expression {conn_sig} to {meta_sig}"
            )

        metadata_do = self._dialect_options(metadata_tup.const)
        conn_do = self._dialect_options(reflected_tup.const)
        if metadata_do != conn_do:
            return ComparisonResult.Different(
                f"expression {conn_do} to {metadata_do}"
            )

        return ComparisonResult.Equal()

    def adjust_reflected_dialect_options(
        self, reflected_options: Dict[str, Any], kind: str
    ) -> Dict[str, Any]:
        options: Dict[str, Any]
        options = reflected_options.get("dialect_options", {}).copy()
        if not options.get("postgresql_include"):
            options.pop("postgresql_include", None)
        return options

    def _compile_element(self, element: Union[ClauseElement, str]) -> str:
        if isinstance(element, str):
            return element
        return element.compile(
            dialect=self.dialect,
            compile_kwargs={"literal_binds": True, "include_table": False},
        ).string

    def render_ddl_sql_expr(
        self,
        expr: ClauseElement,
        is_server_default: bool = False,
        is_index: bool = False,
        **kw: Any,
    ) -> str:
        """Render a SQL expression that is typically a server default,
        index expression, etc.

        """

        # apply self_group to index expressions;
        # see https://github.com/sqlalchemy/sqlalchemy/blob/
        # 82fa95cfce070fab401d020c6e6e4a6a96cc2578/
        # lib/sqlalchemy/dialects/postgresql/base.py#L2261
        if is_index and not isinstance(expr, ColumnClause):
            expr = expr.self_group()

        return super().render_ddl_sql_expr(
            expr, is_server_default=is_server_default, is_index=is_index, **kw
        )

    def render_type(
        self, type_: TypeEngine, autogen_context: AutogenContext
    ) -> Union[str, Literal[False]]:
        mod = type(type_).__module__
        if not mod.startswith("sqlalchemy.dialects.postgresql"):
            return False

        if hasattr(self, "_render_%s_type" % type_.__visit_name__):
            meth = getattr(self, "_render_%s_type" % type_.__visit_name__)
            return meth(type_, autogen_context)

        return False

    def _render_HSTORE_type(
        self, type_: HSTORE, autogen_context: AutogenContext
    ) -> str:
        return cast(
            str,
            render._render_type_w_subtype(
                type_, autogen_context, "text_type", r"(.+?\(.*text_type=)"
            ),
        )

    def _render_ARRAY_type(
        self, type_: ARRAY, autogen_context: AutogenContext
    ) -> str:
        return cast(
            str,
            render._render_type_w_subtype(
                type_, autogen_context, "item_type", r"(.+?\()"
            ),
        )

    def _render_JSON_type(
        self, type_: JSON, autogen_context: AutogenContext
    ) -> str:
        return cast(
            str,
            render._render_type_w_subtype(
                type_, autogen_context, "astext_type", r"(.+?\(.*astext_type=)"
            ),
        )

    def _render_JSONB_type(
        self, type_: JSONB, autogen_context: AutogenContext
    ) -> str:
        return cast(
            str,
            render._render_type_w_subtype(
                type_, autogen_context, "astext_type", r"(.+?\(.*astext_type=)"
            ),
        )


class PostgresqlColumnType(AlterColumn):
    def __init__(
        self, name: str, column_name: str, type_: TypeEngine, **kw
    ) -> None:
        using = kw.pop("using", None)
        super().__init__(name, column_name, **kw)
        self.type_ = sqltypes.to_instance(type_)
        self.using = using


@compiles(RenameTable, "postgresql")
def visit_rename_table(
    element: RenameTable, compiler: PGDDLCompiler, **kw
) -> str:
    return "%s RENAME TO %s" % (
        alter_table(compiler, element.table_name, element.schema),
        format_table_name(compiler, element.new_table_name, None),
    )


@compiles(PostgresqlColumnType, "postgresql")
def visit_column_type(
    element: PostgresqlColumnType, compiler: PGDDLCompiler, **kw
) -> str:
    return "%s %s %s %s" % (
        alter_table(compiler, element.table_name, element.schema),
        alter_column(compiler, element.column_name),
        "TYPE %s" % format_type(compiler, element.type_),
        "USING %s" % element.using if element.using else "",
    )


@compiles(ColumnComment, "postgresql")
def visit_column_comment(
    element: ColumnComment, compiler: PGDDLCompiler, **kw
) -> str:
    ddl = "COMMENT ON COLUMN {table_name}.{column_name} IS {comment}"
    comment = (
        compiler.sql_compiler.render_literal_value(
            element.comment, sqltypes.String()
        )
        if element.comment is not None
        else "NULL"
    )

    return ddl.format(
        table_name=format_table_name(
            compiler, element.table_name, element.schema
        ),
        column_name=format_column_name(compiler, element.column_name),
        comment=comment,
    )


@compiles(IdentityColumnDefault, "postgresql")
def visit_identity_column(
    element: IdentityColumnDefault, compiler: PGDDLCompiler, **kw
):
    text = "%s %s " % (
        alter_table(compiler, element.table_name, element.schema),
        alter_column(compiler, element.column_name),
    )
    if element.default is None:
        # drop identity
        text += "DROP IDENTITY"
        return text
    elif element.existing_server_default is None:
        # add identity options
        text += "ADD "
        text += compiler.visit_identity_column(element.default)
        return text
    else:
        # alter identity
        diff, _, _ = element.impl._compare_identity_default(
            element.default, element.existing_server_default
        )
        identity = element.default
        for attr in sorted(diff):
            if attr == "always":
                text += "SET GENERATED %s " % (
                    "ALWAYS" if identity.always else "BY DEFAULT"
                )
            else:
                text += "SET %s " % compiler.get_identity_options(
                    Identity(**{attr: getattr(identity, attr)})
                )
        return text


@Operations.register_operation("create_exclude_constraint")
@BatchOperations.register_operation(
    "create_exclude_constraint", "batch_create_exclude_constraint"
)
@ops.AddConstraintOp.register_add_constraint("exclude_constraint")
class CreateExcludeConstraintOp(ops.AddConstraintOp):
    """Represent a create exclude constraint operation."""

    constraint_type = "exclude"

    def __init__(
        self,
        constraint_name: sqla_compat._ConstraintName,
        table_name: Union[str, quoted_name],
        elements: Union[
            Sequence[Tuple[str, str]],
            Sequence[Tuple[ColumnClause[Any], str]],
        ],
        where: Optional[Union[ColumnElement[bool], str]] = None,
        schema: Optional[str] = None,
        _orig_constraint: Optional[ExcludeConstraint] = None,
        **kw,
    ) -> None:
        self.constraint_name = constraint_name
        self.table_name = table_name
        self.elements = elements
        self.where = where
        self.schema = schema
        self._orig_constraint = _orig_constraint
        self.kw = kw

    @classmethod
    def from_constraint(  # type:ignore[override]
        cls, constraint: ExcludeConstraint
    ) -> CreateExcludeConstraintOp:
        constraint_table = sqla_compat._table_for_constraint(constraint)
        return cls(
            constraint.name,
            constraint_table.name,
            [  # type: ignore
                (expr, op) for expr, name, op in constraint._render_exprs
            ],
            where=cast("ColumnElement[bool] | None", constraint.where),
            schema=constraint_table.schema,
            _orig_constraint=constraint,
            deferrable=constraint.deferrable,
            initially=constraint.initially,
            using=constraint.using,
        )

    def to_constraint(
        self, migration_context: Optional[MigrationContext] = None
    ) -> ExcludeConstraint:
        if self._orig_constraint is not None:
            return self._orig_constraint
        schema_obj = schemaobj.SchemaObjects(migration_context)
        t = schema_obj.table(self.table_name, schema=self.schema)
        excl = ExcludeConstraint(
            *self.elements,
            name=self.constraint_name,
            where=self.where,
            **self.kw,
        )
        for (
            expr,
            name,
            oper,
        ) in excl._render_exprs:
            t.append_column(Column(name, NULLTYPE))
        t.append_constraint(excl)
        return excl

    @classmethod
    def create_exclude_constraint(
        cls,
        operations: Operations,
        constraint_name: str,
        table_name: str,
        *elements: Any,
        **kw: Any,
    ) -> Optional[Table]:
        """Issue an alter to create an EXCLUDE constraint using the
        current migration context.

        .. note::  This method is Postgresql specific, and additionally
           requires at least SQLAlchemy 1.0.

        e.g.::

            from alembic import op

            op.create_exclude_constraint(
                "user_excl",
                "user",
                ("period", "&&"),
                ("group", "="),
                where=("group != 'some group'"),
            )

        Note that the expressions work the same way as that of
        the ``ExcludeConstraint`` object itself; if plain strings are
        passed, quoting rules must be applied manually.

        :param name: Name of the constraint.
        :param table_name: String name of the source table.
        :param elements: exclude conditions.
        :param where: SQL expression or SQL string with optional WHERE
         clause.
        :param deferrable: optional bool. If set, emit DEFERRABLE or
         NOT DEFERRABLE when issuing DDL for this constraint.
        :param initially: optional string. If set, emit INITIALLY <value>
         when issuing DDL for this constraint.
        :param schema: Optional schema name to operate within.

        """
        op = cls(constraint_name, table_name, elements, **kw)
        return operations.invoke(op)

    @classmethod
    def batch_create_exclude_constraint(
        cls,
        operations: BatchOperations,
        constraint_name: str,
        *elements: Any,
        **kw: Any,
    ) -> Optional[Table]:
        """Issue a "create exclude constraint" instruction using the
        current batch migration context.

        .. note::  This method is Postgresql specific, and additionally
           requires at least SQLAlchemy 1.0.

        .. seealso::

            :meth:`.Operations.create_exclude_constraint`

        """
        kw["schema"] = operations.impl.schema
        op = cls(constraint_name, operations.impl.table_name, elements, **kw)
        return operations.invoke(op)


@render.renderers.dispatch_for(CreateExcludeConstraintOp)
def _add_exclude_constraint(
    autogen_context: AutogenContext, op: CreateExcludeConstraintOp
) -> str:
    return _exclude_constraint(op.to_constraint(), autogen_context, alter=True)


@render._constraint_renderers.dispatch_for(ExcludeConstraint)
def _render_inline_exclude_constraint(
    constraint: ExcludeConstraint,
    autogen_context: AutogenContext,
    namespace_metadata: MetaData,
) -> str:
    rendered = render._user_defined_render(
        "exclude", constraint, autogen_context
    )
    if rendered is not False:
        return rendered

    return _exclude_constraint(constraint, autogen_context, False)


def _postgresql_autogenerate_prefix(autogen_context: AutogenContext) -> str:
    imports = autogen_context.imports
    if imports is not None:
        imports.add("from sqlalchemy.dialects import postgresql")
    return "postgresql."


def _exclude_constraint(
    constraint: ExcludeConstraint,
    autogen_context: AutogenContext,
    alter: bool,
) -> str:
    opts: List[Tuple[str, Union[quoted_name, str, _f_name, None]]] = []

    has_batch = autogen_context._has_batch

    if constraint.deferrable:
        opts.append(("deferrable", str(constraint.deferrable)))
    if constraint.initially:
        opts.append(("initially", str(constraint.initially)))
    if constraint.using:
        opts.append(("using", str(constraint.using)))
    if not has_batch and alter and constraint.table.schema:
        opts.append(("schema", render._ident(constraint.table.schema)))
    if not alter and constraint.name:
        opts.append(
            ("name", render._render_gen_name(autogen_context, constraint.name))
        )

    def do_expr_where_opts():
        args = [
            "(%s, %r)"
            % (
                _render_potential_column(
                    sqltext,  # type:ignore[arg-type]
                    autogen_context,
                ),
                opstring,
            )
            for sqltext, name, opstring in constraint._render_exprs
        ]
        if constraint.where is not None:
            args.append(
                "where=%s"
                % render._render_potential_expr(
                    constraint.where, autogen_context
                )
            )
        args.extend(["%s=%r" % (k, v) for k, v in opts])
        return args

    if alter:
        args = [
            repr(render._render_gen_name(autogen_context, constraint.name))
        ]
        if not has_batch:
            args += [repr(render._ident(constraint.table.name))]
        args.extend(do_expr_where_opts())
        return "%(prefix)screate_exclude_constraint(%(args)s)" % {
            "prefix": render._alembic_autogenerate_prefix(autogen_context),
            "args": ", ".join(args),
        }
    else:
        args = do_expr_where_opts()
        return "%(prefix)sExcludeConstraint(%(args)s)" % {
            "prefix": _postgresql_autogenerate_prefix(autogen_context),
            "args": ", ".join(args),
        }


def _render_potential_column(
    value: Union[
        ColumnClause[Any], Column[Any], TextClause, FunctionElement[Any]
    ],
    autogen_context: AutogenContext,
) -> str:
    if isinstance(value, ColumnClause):
        if value.is_literal:
            # like literal_column("int8range(from, to)") in ExcludeConstraint
            template = "%(prefix)sliteral_column(%(name)r)"
        else:
            template = "%(prefix)scolumn(%(name)r)"

        return template % {
            "prefix": render._sqlalchemy_autogenerate_prefix(autogen_context),
            "name": value.name,
        }
    else:
        return render._render_potential_expr(
            value,
            autogen_context,
            wrap_in_element=isinstance(value, (TextClause, FunctionElement)),
        )
Name	Size	Permission
__pycache__	---	0755
__init__.py	152 bytes	0644
_autogen.py	9275 bytes	0644
base.py	9772 bytes	0644
impl.py	30127 bytes	0644
mssql.py	14219 bytes	0644
mysql.py	17301 bytes	0644
oracle.py	6243 bytes	0644
postgresql.py	29931 bytes	0644
sqlite.py	7995 bytes	0644
File Content: postgresql.py

File Content: `postgresql.py`
