two version of R2R are here HEAD master

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diff --git a/.venv/lib/python3.12/site-packages/alembic/autogenerate/compare.py b/.venv/lib/python3.12/site-packages/alembic/autogenerate/compare.py
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+# mypy: allow-untyped-defs, allow-incomplete-defs, allow-untyped-calls
+# mypy: no-warn-return-any, allow-any-generics
+
+from __future__ import annotations
+
+import contextlib
+import logging
+import re
+from typing import Any
+from typing import cast
+from typing import Dict
+from typing import Iterator
+from typing import Mapping
+from typing import Optional
+from typing import Set
+from typing import Tuple
+from typing import TYPE_CHECKING
+from typing import TypeVar
+from typing import Union
+
+from sqlalchemy import event
+from sqlalchemy import inspect
+from sqlalchemy import schema as sa_schema
+from sqlalchemy import text
+from sqlalchemy import types as sqltypes
+from sqlalchemy.sql import expression
+from sqlalchemy.sql.schema import ForeignKeyConstraint
+from sqlalchemy.sql.schema import Index
+from sqlalchemy.sql.schema import UniqueConstraint
+from sqlalchemy.util import OrderedSet
+
+from .. import util
+from ..ddl._autogen import is_index_sig
+from ..ddl._autogen import is_uq_sig
+from ..operations import ops
+from ..util import sqla_compat
+
+if TYPE_CHECKING:
+    from typing import Literal
+
+    from sqlalchemy.engine.reflection import Inspector
+    from sqlalchemy.sql.elements import quoted_name
+    from sqlalchemy.sql.elements import TextClause
+    from sqlalchemy.sql.schema import Column
+    from sqlalchemy.sql.schema import Table
+
+    from alembic.autogenerate.api import AutogenContext
+    from alembic.ddl.impl import DefaultImpl
+    from alembic.operations.ops import AlterColumnOp
+    from alembic.operations.ops import MigrationScript
+    from alembic.operations.ops import ModifyTableOps
+    from alembic.operations.ops import UpgradeOps
+    from ..ddl._autogen import _constraint_sig
+
+
+log = logging.getLogger(__name__)
+
+
+def _populate_migration_script(
+    autogen_context: AutogenContext, migration_script: MigrationScript
+) -> None:
+    upgrade_ops = migration_script.upgrade_ops_list[-1]
+    downgrade_ops = migration_script.downgrade_ops_list[-1]
+
+    _produce_net_changes(autogen_context, upgrade_ops)
+    upgrade_ops.reverse_into(downgrade_ops)
+
+
+comparators = util.Dispatcher(uselist=True)
+
+
+def _produce_net_changes(
+    autogen_context: AutogenContext, upgrade_ops: UpgradeOps
+) -> None:
+    connection = autogen_context.connection
+    assert connection is not None
+    include_schemas = autogen_context.opts.get("include_schemas", False)
+
+    inspector: Inspector = inspect(connection)
+
+    default_schema = connection.dialect.default_schema_name
+    schemas: Set[Optional[str]]
+    if include_schemas:
+        schemas = set(inspector.get_schema_names())
+        # replace default schema name with None
+        schemas.discard("information_schema")
+        # replace the "default" schema with None
+        schemas.discard(default_schema)
+        schemas.add(None)
+    else:
+        schemas = {None}
+
+    schemas = {
+        s for s in schemas if autogen_context.run_name_filters(s, "schema", {})
+    }
+
+    assert autogen_context.dialect is not None
+    comparators.dispatch("schema", autogen_context.dialect.name)(
+        autogen_context, upgrade_ops, schemas
+    )
+
+
+@comparators.dispatch_for("schema")
+def _autogen_for_tables(
+    autogen_context: AutogenContext,
+    upgrade_ops: UpgradeOps,
+    schemas: Union[Set[None], Set[Optional[str]]],
+) -> None:
+    inspector = autogen_context.inspector
+
+    conn_table_names: Set[Tuple[Optional[str], str]] = set()
+
+    version_table_schema = (
+        autogen_context.migration_context.version_table_schema
+    )
+    version_table = autogen_context.migration_context.version_table
+
+    for schema_name in schemas:
+        tables = set(inspector.get_table_names(schema=schema_name))
+        if schema_name == version_table_schema:
+            tables = tables.difference(
+                [autogen_context.migration_context.version_table]
+            )
+
+        conn_table_names.update(
+            (schema_name, tname)
+            for tname in tables
+            if autogen_context.run_name_filters(
+                tname, "table", {"schema_name": schema_name}
+            )
+        )
+
+    metadata_table_names = OrderedSet(
+        [(table.schema, table.name) for table in autogen_context.sorted_tables]
+    ).difference([(version_table_schema, version_table)])
+
+    _compare_tables(
+        conn_table_names,
+        metadata_table_names,
+        inspector,
+        upgrade_ops,
+        autogen_context,
+    )
+
+
+def _compare_tables(
+    conn_table_names: set,
+    metadata_table_names: set,
+    inspector: Inspector,
+    upgrade_ops: UpgradeOps,
+    autogen_context: AutogenContext,
+) -> None:
+    default_schema = inspector.bind.dialect.default_schema_name
+
+    # tables coming from the connection will not have "schema"
+    # set if it matches default_schema_name; so we need a list
+    # of table names from local metadata that also have "None" if schema
+    # == default_schema_name.  Most setups will be like this anyway but
+    # some are not (see #170)
+    metadata_table_names_no_dflt_schema = OrderedSet(
+        [
+            (schema if schema != default_schema else None, tname)
+            for schema, tname in metadata_table_names
+        ]
+    )
+
+    # to adjust for the MetaData collection storing the tables either
+    # as "schemaname.tablename" or just "tablename", create a new lookup
+    # which will match the "non-default-schema" keys to the Table object.
+    tname_to_table = {
+        no_dflt_schema: autogen_context.table_key_to_table[
+            sa_schema._get_table_key(tname, schema)
+        ]
+        for no_dflt_schema, (schema, tname) in zip(
+            metadata_table_names_no_dflt_schema, metadata_table_names
+        )
+    }
+    metadata_table_names = metadata_table_names_no_dflt_schema
+
+    for s, tname in metadata_table_names.difference(conn_table_names):
+        name = "%s.%s" % (s, tname) if s else tname
+        metadata_table = tname_to_table[(s, tname)]
+        if autogen_context.run_object_filters(
+            metadata_table, tname, "table", False, None
+        ):
+            upgrade_ops.ops.append(
+                ops.CreateTableOp.from_table(metadata_table)
+            )
+            log.info("Detected added table %r", name)
+            modify_table_ops = ops.ModifyTableOps(tname, [], schema=s)
+
+            comparators.dispatch("table")(
+                autogen_context,
+                modify_table_ops,
+                s,
+                tname,
+                None,
+                metadata_table,
+            )
+            if not modify_table_ops.is_empty():
+                upgrade_ops.ops.append(modify_table_ops)
+
+    removal_metadata = sa_schema.MetaData()
+    for s, tname in conn_table_names.difference(metadata_table_names):
+        name = sa_schema._get_table_key(tname, s)
+        exists = name in removal_metadata.tables
+        t = sa_schema.Table(tname, removal_metadata, schema=s)
+
+        if not exists:
+            event.listen(
+                t,
+                "column_reflect",
+                # fmt: off
+                autogen_context.migration_context.impl.
+                _compat_autogen_column_reflect
+                (inspector),
+                # fmt: on
+            )
+            inspector.reflect_table(t, include_columns=None)
+        if autogen_context.run_object_filters(t, tname, "table", True, None):
+            modify_table_ops = ops.ModifyTableOps(tname, [], schema=s)
+
+            comparators.dispatch("table")(
+                autogen_context, modify_table_ops, s, tname, t, None
+            )
+            if not modify_table_ops.is_empty():
+                upgrade_ops.ops.append(modify_table_ops)
+
+            upgrade_ops.ops.append(ops.DropTableOp.from_table(t))
+            log.info("Detected removed table %r", name)
+
+    existing_tables = conn_table_names.intersection(metadata_table_names)
+
+    existing_metadata = sa_schema.MetaData()
+    conn_column_info = {}
+    for s, tname in existing_tables:
+        name = sa_schema._get_table_key(tname, s)
+        exists = name in existing_metadata.tables
+        t = sa_schema.Table(tname, existing_metadata, schema=s)
+        if not exists:
+            event.listen(
+                t,
+                "column_reflect",
+                # fmt: off
+                autogen_context.migration_context.impl.
+                _compat_autogen_column_reflect(inspector),
+                # fmt: on
+            )
+            inspector.reflect_table(t, include_columns=None)
+        conn_column_info[(s, tname)] = t
+
+    for s, tname in sorted(existing_tables, key=lambda x: (x[0] or "", x[1])):
+        s = s or None
+        name = "%s.%s" % (s, tname) if s else tname
+        metadata_table = tname_to_table[(s, tname)]
+        conn_table = existing_metadata.tables[name]
+
+        if autogen_context.run_object_filters(
+            metadata_table, tname, "table", False, conn_table
+        ):
+            modify_table_ops = ops.ModifyTableOps(tname, [], schema=s)
+            with _compare_columns(
+                s,
+                tname,
+                conn_table,
+                metadata_table,
+                modify_table_ops,
+                autogen_context,
+                inspector,
+            ):
+                comparators.dispatch("table")(
+                    autogen_context,
+                    modify_table_ops,
+                    s,
+                    tname,
+                    conn_table,
+                    metadata_table,
+                )
+
+            if not modify_table_ops.is_empty():
+                upgrade_ops.ops.append(modify_table_ops)
+
+
+_IndexColumnSortingOps: Mapping[str, Any] = util.immutabledict(
+    {
+        "asc": expression.asc,
+        "desc": expression.desc,
+        "nulls_first": expression.nullsfirst,
+        "nulls_last": expression.nullslast,
+        "nullsfirst": expression.nullsfirst,  # 1_3 name
+        "nullslast": expression.nullslast,  # 1_3 name
+    }
+)
+
+
+def _make_index(
+    impl: DefaultImpl, params: Dict[str, Any], conn_table: Table
+) -> Optional[Index]:
+    exprs: list[Union[Column[Any], TextClause]] = []
+    sorting = params.get("column_sorting")
+
+    for num, col_name in enumerate(params["column_names"]):
+        item: Union[Column[Any], TextClause]
+        if col_name is None:
+            assert "expressions" in params
+            name = params["expressions"][num]
+            item = text(name)
+        else:
+            name = col_name
+            item = conn_table.c[col_name]
+        if sorting and name in sorting:
+            for operator in sorting[name]:
+                if operator in _IndexColumnSortingOps:
+                    item = _IndexColumnSortingOps[operator](item)
+        exprs.append(item)
+    ix = sa_schema.Index(
+        params["name"],
+        *exprs,
+        unique=params["unique"],
+        _table=conn_table,
+        **impl.adjust_reflected_dialect_options(params, "index"),
+    )
+    if "duplicates_constraint" in params:
+        ix.info["duplicates_constraint"] = params["duplicates_constraint"]
+    return ix
+
+
+def _make_unique_constraint(
+    impl: DefaultImpl, params: Dict[str, Any], conn_table: Table
+) -> UniqueConstraint:
+    uq = sa_schema.UniqueConstraint(
+        *[conn_table.c[cname] for cname in params["column_names"]],
+        name=params["name"],
+        **impl.adjust_reflected_dialect_options(params, "unique_constraint"),
+    )
+    if "duplicates_index" in params:
+        uq.info["duplicates_index"] = params["duplicates_index"]
+
+    return uq
+
+
+def _make_foreign_key(
+    params: Dict[str, Any], conn_table: Table
+) -> ForeignKeyConstraint:
+    tname = params["referred_table"]
+    if params["referred_schema"]:
+        tname = "%s.%s" % (params["referred_schema"], tname)
+
+    options = params.get("options", {})
+
+    const = sa_schema.ForeignKeyConstraint(
+        [conn_table.c[cname] for cname in params["constrained_columns"]],
+        ["%s.%s" % (tname, n) for n in params["referred_columns"]],
+        onupdate=options.get("onupdate"),
+        ondelete=options.get("ondelete"),
+        deferrable=options.get("deferrable"),
+        initially=options.get("initially"),
+        name=params["name"],
+    )
+    # needed by 0.7
+    conn_table.append_constraint(const)
+    return const
+
+
+@contextlib.contextmanager
+def _compare_columns(
+    schema: Optional[str],
+    tname: Union[quoted_name, str],
+    conn_table: Table,
+    metadata_table: Table,
+    modify_table_ops: ModifyTableOps,
+    autogen_context: AutogenContext,
+    inspector: Inspector,
+) -> Iterator[None]:
+    name = "%s.%s" % (schema, tname) if schema else tname
+    metadata_col_names = OrderedSet(
+        c.name for c in metadata_table.c if not c.system
+    )
+    metadata_cols_by_name = {
+        c.name: c for c in metadata_table.c if not c.system
+    }
+
+    conn_col_names = {
+        c.name: c
+        for c in conn_table.c
+        if autogen_context.run_name_filters(
+            c.name, "column", {"table_name": tname, "schema_name": schema}
+        )
+    }
+
+    for cname in metadata_col_names.difference(conn_col_names):
+        if autogen_context.run_object_filters(
+            metadata_cols_by_name[cname], cname, "column", False, None
+        ):
+            modify_table_ops.ops.append(
+                ops.AddColumnOp.from_column_and_tablename(
+                    schema, tname, metadata_cols_by_name[cname]
+                )
+            )
+            log.info("Detected added column '%s.%s'", name, cname)
+
+    for colname in metadata_col_names.intersection(conn_col_names):
+        metadata_col = metadata_cols_by_name[colname]
+        conn_col = conn_table.c[colname]
+        if not autogen_context.run_object_filters(
+            metadata_col, colname, "column", False, conn_col
+        ):
+            continue
+        alter_column_op = ops.AlterColumnOp(tname, colname, schema=schema)
+
+        comparators.dispatch("column")(
+            autogen_context,
+            alter_column_op,
+            schema,
+            tname,
+            colname,
+            conn_col,
+            metadata_col,
+        )
+
+        if alter_column_op.has_changes():
+            modify_table_ops.ops.append(alter_column_op)
+
+    yield
+
+    for cname in set(conn_col_names).difference(metadata_col_names):
+        if autogen_context.run_object_filters(
+            conn_table.c[cname], cname, "column", True, None
+        ):
+            modify_table_ops.ops.append(
+                ops.DropColumnOp.from_column_and_tablename(
+                    schema, tname, conn_table.c[cname]
+                )
+            )
+            log.info("Detected removed column '%s.%s'", name, cname)
+
+
+_C = TypeVar("_C", bound=Union[UniqueConstraint, ForeignKeyConstraint, Index])
+
+
+@comparators.dispatch_for("table")
+def _compare_indexes_and_uniques(
+    autogen_context: AutogenContext,
+    modify_ops: ModifyTableOps,
+    schema: Optional[str],
+    tname: Union[quoted_name, str],
+    conn_table: Optional[Table],
+    metadata_table: Optional[Table],
+) -> None:
+    inspector = autogen_context.inspector
+    is_create_table = conn_table is None
+    is_drop_table = metadata_table is None
+    impl = autogen_context.migration_context.impl
+
+    # 1a. get raw indexes and unique constraints from metadata ...
+    if metadata_table is not None:
+        metadata_unique_constraints = {
+            uq
+            for uq in metadata_table.constraints
+            if isinstance(uq, sa_schema.UniqueConstraint)
+        }
+        metadata_indexes = set(metadata_table.indexes)
+    else:
+        metadata_unique_constraints = set()
+        metadata_indexes = set()
+
+    conn_uniques = conn_indexes = frozenset()  # type:ignore[var-annotated]
+
+    supports_unique_constraints = False
+
+    unique_constraints_duplicate_unique_indexes = False
+
+    if conn_table is not None:
+        # 1b. ... and from connection, if the table exists
+        try:
+            conn_uniques = inspector.get_unique_constraints(  # type:ignore[assignment] # noqa
+                tname, schema=schema
+            )
+            supports_unique_constraints = True
+        except NotImplementedError:
+            pass
+        except TypeError:
+            # number of arguments is off for the base
+            # method in SQLAlchemy due to the cache decorator
+            # not being present
+            pass
+        else:
+            conn_uniques = [  # type:ignore[assignment]
+                uq
+                for uq in conn_uniques
+                if autogen_context.run_name_filters(
+                    uq["name"],
+                    "unique_constraint",
+                    {"table_name": tname, "schema_name": schema},
+                )
+            ]
+            for uq in conn_uniques:
+                if uq.get("duplicates_index"):
+                    unique_constraints_duplicate_unique_indexes = True
+        try:
+            conn_indexes = inspector.get_indexes(  # type:ignore[assignment]
+                tname, schema=schema
+            )
+        except NotImplementedError:
+            pass
+        else:
+            conn_indexes = [  # type:ignore[assignment]
+                ix
+                for ix in conn_indexes
+                if autogen_context.run_name_filters(
+                    ix["name"],
+                    "index",
+                    {"table_name": tname, "schema_name": schema},
+                )
+            ]
+
+        # 2. convert conn-level objects from raw inspector records
+        # into schema objects
+        if is_drop_table:
+            # for DROP TABLE uniques are inline, don't need them
+            conn_uniques = set()  # type:ignore[assignment]
+        else:
+            conn_uniques = {  # type:ignore[assignment]
+                _make_unique_constraint(impl, uq_def, conn_table)
+                for uq_def in conn_uniques
+            }
+
+        conn_indexes = {  # type:ignore[assignment]
+            index
+            for index in (
+                _make_index(impl, ix, conn_table) for ix in conn_indexes
+            )
+            if index is not None
+        }
+
+    # 2a. if the dialect dupes unique indexes as unique constraints
+    # (mysql and oracle), correct for that
+
+    if unique_constraints_duplicate_unique_indexes:
+        _correct_for_uq_duplicates_uix(
+            conn_uniques,
+            conn_indexes,
+            metadata_unique_constraints,
+            metadata_indexes,
+            autogen_context.dialect,
+            impl,
+        )
+
+    # 3. give the dialect a chance to omit indexes and constraints that
+    # we know are either added implicitly by the DB or that the DB
+    # can't accurately report on
+    impl.correct_for_autogen_constraints(
+        conn_uniques,  # type: ignore[arg-type]
+        conn_indexes,  # type: ignore[arg-type]
+        metadata_unique_constraints,
+        metadata_indexes,
+    )
+
+    # 4. organize the constraints into "signature" collections, the
+    # _constraint_sig() objects provide a consistent facade over both
+    # Index and UniqueConstraint so we can easily work with them
+    # interchangeably
+    metadata_unique_constraints_sig = {
+        impl._create_metadata_constraint_sig(uq)
+        for uq in metadata_unique_constraints
+    }
+
+    metadata_indexes_sig = {
+        impl._create_metadata_constraint_sig(ix) for ix in metadata_indexes
+    }
+
+    conn_unique_constraints = {
+        impl._create_reflected_constraint_sig(uq) for uq in conn_uniques
+    }
+
+    conn_indexes_sig = {
+        impl._create_reflected_constraint_sig(ix) for ix in conn_indexes
+    }
+
+    # 5. index things by name, for those objects that have names
+    metadata_names = {
+        cast(str, c.md_name_to_sql_name(autogen_context)): c
+        for c in metadata_unique_constraints_sig.union(metadata_indexes_sig)
+        if c.is_named
+    }
+
+    conn_uniques_by_name: Dict[sqla_compat._ConstraintName, _constraint_sig]
+    conn_indexes_by_name: Dict[sqla_compat._ConstraintName, _constraint_sig]
+
+    conn_uniques_by_name = {c.name: c for c in conn_unique_constraints}
+    conn_indexes_by_name = {c.name: c for c in conn_indexes_sig}
+    conn_names = {
+        c.name: c
+        for c in conn_unique_constraints.union(conn_indexes_sig)
+        if sqla_compat.constraint_name_string(c.name)
+    }
+
+    doubled_constraints = {
+        name: (conn_uniques_by_name[name], conn_indexes_by_name[name])
+        for name in set(conn_uniques_by_name).intersection(
+            conn_indexes_by_name
+        )
+    }
+
+    # 6. index things by "column signature", to help with unnamed unique
+    # constraints.
+    conn_uniques_by_sig = {uq.unnamed: uq for uq in conn_unique_constraints}
+    metadata_uniques_by_sig = {
+        uq.unnamed: uq for uq in metadata_unique_constraints_sig
+    }
+    unnamed_metadata_uniques = {
+        uq.unnamed: uq
+        for uq in metadata_unique_constraints_sig
+        if not sqla_compat._constraint_is_named(
+            uq.const, autogen_context.dialect
+        )
+    }
+
+    # assumptions:
+    # 1. a unique constraint or an index from the connection *always*
+    #    has a name.
+    # 2. an index on the metadata side *always* has a name.
+    # 3. a unique constraint on the metadata side *might* have a name.
+    # 4. The backend may double up indexes as unique constraints and
+    #    vice versa (e.g. MySQL, Postgresql)
+
+    def obj_added(obj: _constraint_sig):
+        if is_index_sig(obj):
+            if autogen_context.run_object_filters(
+                obj.const, obj.name, "index", False, None
+            ):
+                modify_ops.ops.append(ops.CreateIndexOp.from_index(obj.const))
+                log.info(
+                    "Detected added index '%r' on '%s'",
+                    obj.name,
+                    obj.column_names,
+                )
+        elif is_uq_sig(obj):
+            if not supports_unique_constraints:
+                # can't report unique indexes as added if we don't
+                # detect them
+                return
+            if is_create_table or is_drop_table:
+                # unique constraints are created inline with table defs
+                return
+            if autogen_context.run_object_filters(
+                obj.const, obj.name, "unique_constraint", False, None
+            ):
+                modify_ops.ops.append(
+                    ops.AddConstraintOp.from_constraint(obj.const)
+                )
+                log.info(
+                    "Detected added unique constraint %r on '%s'",
+                    obj.name,
+                    obj.column_names,
+                )
+        else:
+            assert False
+
+    def obj_removed(obj: _constraint_sig):
+        if is_index_sig(obj):
+            if obj.is_unique and not supports_unique_constraints:
+                # many databases double up unique constraints
+                # as unique indexes.  without that list we can't
+                # be sure what we're doing here
+                return
+
+            if autogen_context.run_object_filters(
+                obj.const, obj.name, "index", True, None
+            ):
+                modify_ops.ops.append(ops.DropIndexOp.from_index(obj.const))
+                log.info("Detected removed index %r on %r", obj.name, tname)
+        elif is_uq_sig(obj):
+            if is_create_table or is_drop_table:
+                # if the whole table is being dropped, we don't need to
+                # consider unique constraint separately
+                return
+            if autogen_context.run_object_filters(
+                obj.const, obj.name, "unique_constraint", True, None
+            ):
+                modify_ops.ops.append(
+                    ops.DropConstraintOp.from_constraint(obj.const)
+                )
+                log.info(
+                    "Detected removed unique constraint %r on %r",
+                    obj.name,
+                    tname,
+                )
+        else:
+            assert False
+
+    def obj_changed(
+        old: _constraint_sig,
+        new: _constraint_sig,
+        msg: str,
+    ):
+        if is_index_sig(old):
+            assert is_index_sig(new)
+
+            if autogen_context.run_object_filters(
+                new.const, new.name, "index", False, old.const
+            ):
+                log.info(
+                    "Detected changed index %r on %r: %s", old.name, tname, msg
+                )
+                modify_ops.ops.append(ops.DropIndexOp.from_index(old.const))
+                modify_ops.ops.append(ops.CreateIndexOp.from_index(new.const))
+        elif is_uq_sig(old):
+            assert is_uq_sig(new)
+
+            if autogen_context.run_object_filters(
+                new.const, new.name, "unique_constraint", False, old.const
+            ):
+                log.info(
+                    "Detected changed unique constraint %r on %r: %s",
+                    old.name,
+                    tname,
+                    msg,
+                )
+                modify_ops.ops.append(
+                    ops.DropConstraintOp.from_constraint(old.const)
+                )
+                modify_ops.ops.append(
+                    ops.AddConstraintOp.from_constraint(new.const)
+                )
+        else:
+            assert False
+
+    for removed_name in sorted(set(conn_names).difference(metadata_names)):
+        conn_obj = conn_names[removed_name]
+        if (
+            is_uq_sig(conn_obj)
+            and conn_obj.unnamed in unnamed_metadata_uniques
+        ):
+            continue
+        elif removed_name in doubled_constraints:
+            conn_uq, conn_idx = doubled_constraints[removed_name]
+            if (
+                all(
+                    conn_idx.unnamed != meta_idx.unnamed
+                    for meta_idx in metadata_indexes_sig
+                )
+                and conn_uq.unnamed not in metadata_uniques_by_sig
+            ):
+                obj_removed(conn_uq)
+                obj_removed(conn_idx)
+        else:
+            obj_removed(conn_obj)
+
+    for existing_name in sorted(set(metadata_names).intersection(conn_names)):
+        metadata_obj = metadata_names[existing_name]
+
+        if existing_name in doubled_constraints:
+            conn_uq, conn_idx = doubled_constraints[existing_name]
+            if is_index_sig(metadata_obj):
+                conn_obj = conn_idx
+            else:
+                conn_obj = conn_uq
+        else:
+            conn_obj = conn_names[existing_name]
+
+        if type(conn_obj) != type(metadata_obj):
+            obj_removed(conn_obj)
+            obj_added(metadata_obj)
+        else:
+            comparison = metadata_obj.compare_to_reflected(conn_obj)
+
+            if comparison.is_different:
+                # constraint are different
+                obj_changed(conn_obj, metadata_obj, comparison.message)
+            elif comparison.is_skip:
+                # constraint cannot be compared, skip them
+                thing = (
+                    "index" if is_index_sig(conn_obj) else "unique constraint"
+                )
+                log.info(
+                    "Cannot compare %s %r, assuming equal and skipping. %s",
+                    thing,
+                    conn_obj.name,
+                    comparison.message,
+                )
+            else:
+                # constraint are equal
+                assert comparison.is_equal
+
+    for added_name in sorted(set(metadata_names).difference(conn_names)):
+        obj = metadata_names[added_name]
+        obj_added(obj)
+
+    for uq_sig in unnamed_metadata_uniques:
+        if uq_sig not in conn_uniques_by_sig:
+            obj_added(unnamed_metadata_uniques[uq_sig])
+
+
+def _correct_for_uq_duplicates_uix(
+    conn_unique_constraints,
+    conn_indexes,
+    metadata_unique_constraints,
+    metadata_indexes,
+    dialect,
+    impl,
+):
+    # dedupe unique indexes vs. constraints, since MySQL / Oracle
+    # doesn't really have unique constraints as a separate construct.
+    # but look in the metadata and try to maintain constructs
+    # that already seem to be defined one way or the other
+    # on that side.  This logic was formerly local to MySQL dialect,
+    # generalized to Oracle and others. See #276
+
+    # resolve final rendered name for unique constraints defined in the
+    # metadata.   this includes truncation of long names.  naming convention
+    # names currently should already be set as cons.name, however leave this
+    # to the sqla_compat to decide.
+    metadata_cons_names = [
+        (sqla_compat._get_constraint_final_name(cons, dialect), cons)
+        for cons in metadata_unique_constraints
+    ]
+
+    metadata_uq_names = {
+        name for name, cons in metadata_cons_names if name is not None
+    }
+
+    unnamed_metadata_uqs = {
+        impl._create_metadata_constraint_sig(cons).unnamed
+        for name, cons in metadata_cons_names
+        if name is None
+    }
+
+    metadata_ix_names = {
+        sqla_compat._get_constraint_final_name(cons, dialect)
+        for cons in metadata_indexes
+        if cons.unique
+    }
+
+    # for reflection side, names are in their final database form
+    # already since they're from the database
+    conn_ix_names = {cons.name: cons for cons in conn_indexes if cons.unique}
+
+    uqs_dupe_indexes = {
+        cons.name: cons
+        for cons in conn_unique_constraints
+        if cons.info["duplicates_index"]
+    }
+
+    for overlap in uqs_dupe_indexes:
+        if overlap not in metadata_uq_names:
+            if (
+                impl._create_reflected_constraint_sig(
+                    uqs_dupe_indexes[overlap]
+                ).unnamed
+                not in unnamed_metadata_uqs
+            ):
+                conn_unique_constraints.discard(uqs_dupe_indexes[overlap])
+        elif overlap not in metadata_ix_names:
+            conn_indexes.discard(conn_ix_names[overlap])
+
+
+@comparators.dispatch_for("column")
+def _compare_nullable(
+    autogen_context: AutogenContext,
+    alter_column_op: AlterColumnOp,
+    schema: Optional[str],
+    tname: Union[quoted_name, str],
+    cname: Union[quoted_name, str],
+    conn_col: Column[Any],
+    metadata_col: Column[Any],
+) -> None:
+    metadata_col_nullable = metadata_col.nullable
+    conn_col_nullable = conn_col.nullable
+    alter_column_op.existing_nullable = conn_col_nullable
+
+    if conn_col_nullable is not metadata_col_nullable:
+        if (
+            sqla_compat._server_default_is_computed(
+                metadata_col.server_default, conn_col.server_default
+            )
+            and sqla_compat._nullability_might_be_unset(metadata_col)
+            or (
+                sqla_compat._server_default_is_identity(
+                    metadata_col.server_default, conn_col.server_default
+                )
+            )
+        ):
+            log.info(
+                "Ignoring nullable change on identity column '%s.%s'",
+                tname,
+                cname,
+            )
+        else:
+            alter_column_op.modify_nullable = metadata_col_nullable
+            log.info(
+                "Detected %s on column '%s.%s'",
+                "NULL" if metadata_col_nullable else "NOT NULL",
+                tname,
+                cname,
+            )
+
+
+@comparators.dispatch_for("column")
+def _setup_autoincrement(
+    autogen_context: AutogenContext,
+    alter_column_op: AlterColumnOp,
+    schema: Optional[str],
+    tname: Union[quoted_name, str],
+    cname: quoted_name,
+    conn_col: Column[Any],
+    metadata_col: Column[Any],
+) -> None:
+    if metadata_col.table._autoincrement_column is metadata_col:
+        alter_column_op.kw["autoincrement"] = True
+    elif metadata_col.autoincrement is True:
+        alter_column_op.kw["autoincrement"] = True
+    elif metadata_col.autoincrement is False:
+        alter_column_op.kw["autoincrement"] = False
+
+
+@comparators.dispatch_for("column")
+def _compare_type(
+    autogen_context: AutogenContext,
+    alter_column_op: AlterColumnOp,
+    schema: Optional[str],
+    tname: Union[quoted_name, str],
+    cname: Union[quoted_name, str],
+    conn_col: Column[Any],
+    metadata_col: Column[Any],
+) -> None:
+    conn_type = conn_col.type
+    alter_column_op.existing_type = conn_type
+    metadata_type = metadata_col.type
+    if conn_type._type_affinity is sqltypes.NullType:
+        log.info(
+            "Couldn't determine database type " "for column '%s.%s'",
+            tname,
+            cname,
+        )
+        return
+    if metadata_type._type_affinity is sqltypes.NullType:
+        log.info(
+            "Column '%s.%s' has no type within " "the model; can't compare",
+            tname,
+            cname,
+        )
+        return
+
+    isdiff = autogen_context.migration_context._compare_type(
+        conn_col, metadata_col
+    )
+
+    if isdiff:
+        alter_column_op.modify_type = metadata_type
+        log.info(
+            "Detected type change from %r to %r on '%s.%s'",
+            conn_type,
+            metadata_type,
+            tname,
+            cname,
+        )
+
+
+def _render_server_default_for_compare(
+    metadata_default: Optional[Any], autogen_context: AutogenContext
+) -> Optional[str]:
+    if isinstance(metadata_default, sa_schema.DefaultClause):
+        if isinstance(metadata_default.arg, str):
+            metadata_default = metadata_default.arg
+        else:
+            metadata_default = str(
+                metadata_default.arg.compile(
+                    dialect=autogen_context.dialect,
+                    compile_kwargs={"literal_binds": True},
+                )
+            )
+    if isinstance(metadata_default, str):
+        return metadata_default
+    else:
+        return None
+
+
+def _normalize_computed_default(sqltext: str) -> str:
+    """we want to warn if a computed sql expression has changed.  however
+    we don't want false positives and the warning is not that critical.
+    so filter out most forms of variability from the SQL text.
+
+    """
+
+    return re.sub(r"[ \(\)'\"`\[\]\t\r\n]", "", sqltext).lower()
+
+
+def _compare_computed_default(
+    autogen_context: AutogenContext,
+    alter_column_op: AlterColumnOp,
+    schema: Optional[str],
+    tname: str,
+    cname: str,
+    conn_col: Column[Any],
+    metadata_col: Column[Any],
+) -> None:
+    rendered_metadata_default = str(
+        cast(sa_schema.Computed, metadata_col.server_default).sqltext.compile(
+            dialect=autogen_context.dialect,
+            compile_kwargs={"literal_binds": True},
+        )
+    )
+
+    # since we cannot change computed columns, we do only a crude comparison
+    # here where we try to eliminate syntactical differences in order to
+    # get a minimal comparison just to emit a warning.
+
+    rendered_metadata_default = _normalize_computed_default(
+        rendered_metadata_default
+    )
+
+    if isinstance(conn_col.server_default, sa_schema.Computed):
+        rendered_conn_default = str(
+            conn_col.server_default.sqltext.compile(
+                dialect=autogen_context.dialect,
+                compile_kwargs={"literal_binds": True},
+            )
+        )
+        if rendered_conn_default is None:
+            rendered_conn_default = ""
+        else:
+            rendered_conn_default = _normalize_computed_default(
+                rendered_conn_default
+            )
+    else:
+        rendered_conn_default = ""
+
+    if rendered_metadata_default != rendered_conn_default:
+        _warn_computed_not_supported(tname, cname)
+
+
+def _warn_computed_not_supported(tname: str, cname: str) -> None:
+    util.warn("Computed default on %s.%s cannot be modified" % (tname, cname))
+
+
+def _compare_identity_default(
+    autogen_context,
+    alter_column_op,
+    schema,
+    tname,
+    cname,
+    conn_col,
+    metadata_col,
+):
+    impl = autogen_context.migration_context.impl
+    diff, ignored_attr, is_alter = impl._compare_identity_default(
+        metadata_col.server_default, conn_col.server_default
+    )
+
+    return diff, is_alter
+
+
+@comparators.dispatch_for("column")
+def _compare_server_default(
+    autogen_context: AutogenContext,
+    alter_column_op: AlterColumnOp,
+    schema: Optional[str],
+    tname: Union[quoted_name, str],
+    cname: Union[quoted_name, str],
+    conn_col: Column[Any],
+    metadata_col: Column[Any],
+) -> Optional[bool]:
+    metadata_default = metadata_col.server_default
+    conn_col_default = conn_col.server_default
+    if conn_col_default is None and metadata_default is None:
+        return False
+
+    if sqla_compat._server_default_is_computed(metadata_default):
+        return _compare_computed_default(  # type:ignore[func-returns-value]
+            autogen_context,
+            alter_column_op,
+            schema,
+            tname,
+            cname,
+            conn_col,
+            metadata_col,
+        )
+    if sqla_compat._server_default_is_computed(conn_col_default):
+        _warn_computed_not_supported(tname, cname)
+        return False
+
+    if sqla_compat._server_default_is_identity(
+        metadata_default, conn_col_default
+    ):
+        alter_column_op.existing_server_default = conn_col_default
+        diff, is_alter = _compare_identity_default(
+            autogen_context,
+            alter_column_op,
+            schema,
+            tname,
+            cname,
+            conn_col,
+            metadata_col,
+        )
+        if is_alter:
+            alter_column_op.modify_server_default = metadata_default
+            if diff:
+                log.info(
+                    "Detected server default on column '%s.%s': "
+                    "identity options attributes %s",
+                    tname,
+                    cname,
+                    sorted(diff),
+                )
+    else:
+        rendered_metadata_default = _render_server_default_for_compare(
+            metadata_default, autogen_context
+        )
+
+        rendered_conn_default = (
+            cast(Any, conn_col_default).arg.text if conn_col_default else None
+        )
+
+        alter_column_op.existing_server_default = conn_col_default
+
+        is_diff = autogen_context.migration_context._compare_server_default(
+            conn_col,
+            metadata_col,
+            rendered_metadata_default,
+            rendered_conn_default,
+        )
+        if is_diff:
+            alter_column_op.modify_server_default = metadata_default
+            log.info("Detected server default on column '%s.%s'", tname, cname)
+
+    return None
+
+
+@comparators.dispatch_for("column")
+def _compare_column_comment(
+    autogen_context: AutogenContext,
+    alter_column_op: AlterColumnOp,
+    schema: Optional[str],
+    tname: Union[quoted_name, str],
+    cname: quoted_name,
+    conn_col: Column[Any],
+    metadata_col: Column[Any],
+) -> Optional[Literal[False]]:
+    assert autogen_context.dialect is not None
+    if not autogen_context.dialect.supports_comments:
+        return None
+
+    metadata_comment = metadata_col.comment
+    conn_col_comment = conn_col.comment
+    if conn_col_comment is None and metadata_comment is None:
+        return False
+
+    alter_column_op.existing_comment = conn_col_comment
+
+    if conn_col_comment != metadata_comment:
+        alter_column_op.modify_comment = metadata_comment
+        log.info("Detected column comment '%s.%s'", tname, cname)
+
+    return None
+
+
+@comparators.dispatch_for("table")
+def _compare_foreign_keys(
+    autogen_context: AutogenContext,
+    modify_table_ops: ModifyTableOps,
+    schema: Optional[str],
+    tname: Union[quoted_name, str],
+    conn_table: Table,
+    metadata_table: Table,
+) -> None:
+    # if we're doing CREATE TABLE, all FKs are created
+    # inline within the table def
+    if conn_table is None or metadata_table is None:
+        return
+
+    inspector = autogen_context.inspector
+    metadata_fks = {
+        fk
+        for fk in metadata_table.constraints
+        if isinstance(fk, sa_schema.ForeignKeyConstraint)
+    }
+
+    conn_fks_list = [
+        fk
+        for fk in inspector.get_foreign_keys(tname, schema=schema)
+        if autogen_context.run_name_filters(
+            fk["name"],
+            "foreign_key_constraint",
+            {"table_name": tname, "schema_name": schema},
+        )
+    ]
+
+    conn_fks = {
+        _make_foreign_key(const, conn_table)  # type: ignore[arg-type]
+        for const in conn_fks_list
+    }
+
+    impl = autogen_context.migration_context.impl
+
+    # give the dialect a chance to correct the FKs to match more
+    # closely
+    autogen_context.migration_context.impl.correct_for_autogen_foreignkeys(
+        conn_fks, metadata_fks
+    )
+
+    metadata_fks_sig = {
+        impl._create_metadata_constraint_sig(fk) for fk in metadata_fks
+    }
+
+    conn_fks_sig = {
+        impl._create_reflected_constraint_sig(fk) for fk in conn_fks
+    }
+
+    # check if reflected FKs include options, indicating the backend
+    # can reflect FK options
+    if conn_fks_list and "options" in conn_fks_list[0]:
+        conn_fks_by_sig = {c.unnamed: c for c in conn_fks_sig}
+        metadata_fks_by_sig = {c.unnamed: c for c in metadata_fks_sig}
+    else:
+        # otherwise compare by sig without options added
+        conn_fks_by_sig = {c.unnamed_no_options: c for c in conn_fks_sig}
+        metadata_fks_by_sig = {
+            c.unnamed_no_options: c for c in metadata_fks_sig
+        }
+
+    metadata_fks_by_name = {
+        c.name: c for c in metadata_fks_sig if c.name is not None
+    }
+    conn_fks_by_name = {c.name: c for c in conn_fks_sig if c.name is not None}
+
+    def _add_fk(obj, compare_to):
+        if autogen_context.run_object_filters(
+            obj.const, obj.name, "foreign_key_constraint", False, compare_to
+        ):
+            modify_table_ops.ops.append(
+                ops.CreateForeignKeyOp.from_constraint(const.const)  # type: ignore[has-type]  # noqa: E501
+            )
+
+            log.info(
+                "Detected added foreign key (%s)(%s) on table %s%s",
+                ", ".join(obj.source_columns),
+                ", ".join(obj.target_columns),
+                "%s." % obj.source_schema if obj.source_schema else "",
+                obj.source_table,
+            )
+
+    def _remove_fk(obj, compare_to):
+        if autogen_context.run_object_filters(
+            obj.const, obj.name, "foreign_key_constraint", True, compare_to
+        ):
+            modify_table_ops.ops.append(
+                ops.DropConstraintOp.from_constraint(obj.const)
+            )
+            log.info(
+                "Detected removed foreign key (%s)(%s) on table %s%s",
+                ", ".join(obj.source_columns),
+                ", ".join(obj.target_columns),
+                "%s." % obj.source_schema if obj.source_schema else "",
+                obj.source_table,
+            )
+
+    # so far it appears we don't need to do this by name at all.
+    # SQLite doesn't preserve constraint names anyway
+
+    for removed_sig in set(conn_fks_by_sig).difference(metadata_fks_by_sig):
+        const = conn_fks_by_sig[removed_sig]
+        if removed_sig not in metadata_fks_by_sig:
+            compare_to = (
+                metadata_fks_by_name[const.name].const
+                if const.name in metadata_fks_by_name
+                else None
+            )
+            _remove_fk(const, compare_to)
+
+    for added_sig in set(metadata_fks_by_sig).difference(conn_fks_by_sig):
+        const = metadata_fks_by_sig[added_sig]
+        if added_sig not in conn_fks_by_sig:
+            compare_to = (
+                conn_fks_by_name[const.name].const
+                if const.name in conn_fks_by_name
+                else None
+            )
+            _add_fk(const, compare_to)
+
+
+@comparators.dispatch_for("table")
+def _compare_table_comment(
+    autogen_context: AutogenContext,
+    modify_table_ops: ModifyTableOps,
+    schema: Optional[str],
+    tname: Union[quoted_name, str],
+    conn_table: Optional[Table],
+    metadata_table: Optional[Table],
+) -> None:
+    assert autogen_context.dialect is not None
+    if not autogen_context.dialect.supports_comments:
+        return
+
+    # if we're doing CREATE TABLE, comments will be created inline
+    # with the create_table op.
+    if conn_table is None or metadata_table is None:
+        return
+
+    if conn_table.comment is None and metadata_table.comment is None:
+        return
+
+    if metadata_table.comment is None and conn_table.comment is not None:
+        modify_table_ops.ops.append(
+            ops.DropTableCommentOp(
+                tname, existing_comment=conn_table.comment, schema=schema
+            )
+        )
+    elif metadata_table.comment != conn_table.comment:
+        modify_table_ops.ops.append(
+            ops.CreateTableCommentOp(
+                tname,
+                metadata_table.comment,
+                existing_comment=conn_table.comment,
+                schema=schema,
+            )
+        )