Added support for ``psycopg`` dialect.

Both sync and async versions are supported.

Fixes: #6842
Change-Id: I57751c5028acebfc6f9c43572562405453a2f2a4

6 files changed, 852 insertions, 157 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/__init__.py b/lib/sqlalchemy/dialects/postgresql/__init__.py
index 08b05dc74..b0af5395e 100644
--- a/lib/sqlalchemy/dialects/postgresql/__init__.py
+++ b/lib/sqlalchemy/dialects/postgresql/__init__.py
@@ -4,9 +4,12 @@
 #
 # This module is part of SQLAlchemy and is released under
 # the MIT License: https://www.opensource.org/licenses/mit-license.php
+from types import ModuleType
+
 from . import asyncpg  # noqa
 from . import base
 from . import pg8000  # noqa
+from . import psycopg  # noqa
 from . import psycopg2  # noqa
 from . import psycopg2cffi  # noqa
 from .array import All
@@ -58,6 +61,11 @@ from .ranges import TSRANGE
 from .ranges import TSTZRANGE
 from ...util import compat
 
+# Alias psycopg also as psycopg_asnyc
+psycopg_async = type(
+    "psycopg_asnyc", (ModuleType,), {"dialect": psycopg.dialect_async}
+)
+
 base.dialect = dialect = psycopg2.dialect
 
 
diff --git a/lib/sqlalchemy/dialects/postgresql/_psycopg_common.py b/lib/sqlalchemy/dialects/postgresql/_psycopg_common.py
new file mode 100644
index 000000000..d82d5f009
--- /dev/null
+++ b/lib/sqlalchemy/dialects/postgresql/_psycopg_common.py
@@ -0,0 +1,188 @@
+import decimal
+
+from .array import ARRAY as PGARRAY
+from .base import _DECIMAL_TYPES
+from .base import _FLOAT_TYPES
+from .base import _INT_TYPES
+from .base import PGDialect
+from .base import PGExecutionContext
+from .base import UUID
+from .hstore import HSTORE
+from ... import exc
+from ... import processors
+from ... import types as sqltypes
+from ... import util
+
+_server_side_id = util.counter()
+
+
+class _PsycopgNumeric(sqltypes.Numeric):
+    def bind_processor(self, dialect):
+        return None
+
+    def result_processor(self, dialect, coltype):
+        if self.asdecimal:
+            if coltype in _FLOAT_TYPES:
+                return processors.to_decimal_processor_factory(
+                    decimal.Decimal, self._effective_decimal_return_scale
+                )
+            elif coltype in _DECIMAL_TYPES or coltype in _INT_TYPES:
+                # psycopg returns Decimal natively for 1700
+                return None
+            else:
+                raise exc.InvalidRequestError(
+                    "Unknown PG numeric type: %d" % coltype
+                )
+        else:
+            if coltype in _FLOAT_TYPES:
+                # psycopg returns float natively for 701
+                return None
+            elif coltype in _DECIMAL_TYPES or coltype in _INT_TYPES:
+                return processors.to_float
+            else:
+                raise exc.InvalidRequestError(
+                    "Unknown PG numeric type: %d" % coltype
+                )
+
+
+class _PsycopgHStore(HSTORE):
+    def bind_processor(self, dialect):
+        if dialect._has_native_hstore:
+            return None
+        else:
+            return super(_PsycopgHStore, self).bind_processor(dialect)
+
+    def result_processor(self, dialect, coltype):
+        if dialect._has_native_hstore:
+            return None
+        else:
+            return super(_PsycopgHStore, self).result_processor(
+                dialect, coltype
+            )
+
+
+class _PsycopgUUID(UUID):
+    def bind_processor(self, dialect):
+        return None
+
+    def result_processor(self, dialect, coltype):
+        if not self.as_uuid and dialect.use_native_uuid:
+
+            def process(value):
+                if value is not None:
+                    value = str(value)
+                return value
+
+            return process
+
+
+class _PsycopgARRAY(PGARRAY):
+    render_bind_cast = True
+
+
+class _PGExecutionContext_common_psycopg(PGExecutionContext):
+    def create_server_side_cursor(self):
+        # use server-side cursors:
+        # psycopg
+        # https://www.psycopg.org/psycopg3/docs/advanced/cursors.html#server-side-cursors
+        # psycopg2
+        # https://www.psycopg.org/docs/usage.html#server-side-cursors
+        ident = "c_%s_%s" % (hex(id(self))[2:], hex(_server_side_id())[2:])
+        return self._dbapi_connection.cursor(ident)
+
+
+class _PGDialect_common_psycopg(PGDialect):
+    supports_statement_cache = True
+    supports_server_side_cursors = True
+
+    default_paramstyle = "pyformat"
+
+    _has_native_hstore = True
+
+    colspecs = util.update_copy(
+        PGDialect.colspecs,
+        {
+            sqltypes.Numeric: _PsycopgNumeric,
+            HSTORE: _PsycopgHStore,
+            UUID: _PsycopgUUID,
+            sqltypes.ARRAY: _PsycopgARRAY,
+        },
+    )
+
+    def __init__(
+        self,
+        client_encoding=None,
+        use_native_hstore=True,
+        use_native_uuid=True,
+        **kwargs
+    ):
+        PGDialect.__init__(self, **kwargs)
+        if not use_native_hstore:
+            self._has_native_hstore = False
+        self.use_native_hstore = use_native_hstore
+        self.use_native_uuid = use_native_uuid
+        self.client_encoding = client_encoding
+
+    def create_connect_args(self, url):
+        opts = url.translate_connect_args(username="user", database="dbname")
+
+        is_multihost = False
+        if "host" in url.query:
+            is_multihost = isinstance(url.query["host"], (list, tuple))
+
+        if opts:
+            if "port" in opts:
+                opts["port"] = int(opts["port"])
+            opts.update(url.query)
+            if is_multihost:
+                opts["host"] = ",".join(url.query["host"])
+            # send individual dbname, user, password, host, port
+            # parameters to psycopg2.connect()
+            return ([], opts)
+        elif url.query:
+            # any other connection arguments, pass directly
+            opts.update(url.query)
+            if is_multihost:
+                opts["host"] = ",".join(url.query["host"])
+            return ([], opts)
+        else:
+            # no connection arguments whatsoever; psycopg2.connect()
+            # requires that "dsn" be present as a blank string.
+            return ([""], opts)
+
+    def get_isolation_level_values(self, dbapi_conn):
+        return (
+            "AUTOCOMMIT",
+            "READ COMMITTED",
+            "READ UNCOMMITTED",
+            "REPEATABLE READ",
+            "SERIALIZABLE",
+        )
+
+    def set_deferrable(self, connection, value):
+        connection.deferrable = value
+
+    def get_deferrable(self, connection):
+        return connection.deferrable
+
+    def _do_autocommit(self, connection, value):
+        connection.autocommit = value
+
+    def do_ping(self, dbapi_connection):
+        cursor = None
+        try:
+            self._do_autocommit(dbapi_connection, True)
+            cursor = dbapi_connection.cursor()
+            try:
+                cursor.execute(self._dialect_specific_select_one)
+            finally:
+                cursor.close()
+                if not dbapi_connection.closed:
+                    self._do_autocommit(dbapi_connection, False)
+        except self.dbapi.Error as err:
+            if self.is_disconnect(err, dbapi_connection, cursor):
+                return False
+            else:
+                raise
+        else:
+            return True
diff --git a/lib/sqlalchemy/dialects/postgresql/asyncpg.py b/lib/sqlalchemy/dialects/postgresql/asyncpg.py
index 5ef9df800..1fdb46b6f 100644
--- a/lib/sqlalchemy/dialects/postgresql/asyncpg.py
+++ b/lib/sqlalchemy/dialects/postgresql/asyncpg.py
@@ -553,7 +553,6 @@ class AsyncAdapt_asyncpg_ss_cursor(AsyncAdapt_asyncpg_cursor):
 class AsyncAdapt_asyncpg_connection(AdaptedConnection):
     __slots__ = (
         "dbapi",
-        "_connection",
         "isolation_level",
         "_isolation_setting",
         "readonly",
diff --git a/lib/sqlalchemy/dialects/postgresql/base.py b/lib/sqlalchemy/dialects/postgresql/base.py
index 008398865..d1d881dc3 100644
--- a/lib/sqlalchemy/dialects/postgresql/base.py
+++ b/lib/sqlalchemy/dialects/postgresql/base.py
@@ -1701,7 +1701,7 @@ class UUID(sqltypes.TypeEngine):
     or as Python uuid objects.
 
     The UUID type is currently known to work within the prominent DBAPI
-    drivers supported by SQLAlchemy including psycopg2, pg8000 and
+    drivers supported by SQLAlchemy including psycopg, psycopg2, pg8000 and
     asyncpg. Support for other DBAPI drivers may be incomplete or non-present.
 
     """
@@ -1992,6 +1992,12 @@ class ENUM(sqltypes.NativeForEmulated, sqltypes.Enum):
 
             self.connection.execute(DropEnumType(enum))
 
+    def get_dbapi_type(self, dbapi):
+        """dont return dbapi.STRING for ENUM in PostgreSQL, since that's
+        a different type"""
+
+        return None
+
     def _check_for_name_in_memos(self, checkfirst, kw):
         """Look in the 'ddl runner' for 'memos', then
         note our name in that collection.
diff --git a/lib/sqlalchemy/dialects/postgresql/psycopg.py b/lib/sqlalchemy/dialects/postgresql/psycopg.py
new file mode 100644
index 000000000..c2017c975
--- /dev/null
+++ b/lib/sqlalchemy/dialects/postgresql/psycopg.py
@@ -0,0 +1,641 @@
+# postgresql/psycopg2.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: https://www.opensource.org/licenses/mit-license.php
+r"""
+.. dialect:: postgresql+psycopg
+    :name: psycopg (a.k.a. psycopg 3)
+    :dbapi: psycopg
+    :connectstring: postgresql+psycopg://user:password@host:port/dbname[?key=value&key=value...]
+    :url: https://pypi.org/project/psycopg/
+
+``psycopg`` is the package and module name for version 3 of the ``psycopg``
+database driver, formerly known as ``psycopg2``.  This driver is different
+enough from its ``psycopg2`` predecessor that SQLAlchemy supports it
+via a totally separate dialect; support for ``psycopg2`` is expected to remain
+for as long as that package continues to function for modern Python versions,
+and also remains the default dialect for the ``postgresql://`` dialect
+series.
+
+The SQLAlchemy ``psycopg`` dialect provides both a sync and an async
+implementation under the same dialect name. The proper version is
+selected depending on how the engine is created:
+
+* calling :func:`_sa.create_engine` with ``postgresql+psycopg://...`` will
+  automatically select the sync version, e.g.::
+
+    from sqlalchemy import create_engine
+    sync_engine = create_engine("postgresql+psycopg://scott:tiger@localhost/test")
+
+* calling :func:`_asyncio.create_async_engine` with
+  ``postgresql+psycopg://...`` will automatically select the async version,
+  e.g.::
+
+    from sqlalchemy.ext.asyncio import create_async_engine
+    asyncio_engine = create_async_engine("postgresql+psycopg://scott:tiger@localhost/test")
+
+The asyncio version of the dialect may also be specified explicitly using the
+``psycopg_async`` suffix, as::
+
+    from sqlalchemy.ext.asyncio import create_async_engine
+    asyncio_engine = create_async_engine("postgresql+psycopg_async://scott:tiger@localhost/test")
+
+The ``psycopg`` dialect has the same API features as that of ``psycopg2``,
+with the exeption of the "fast executemany" helpers.   The "fast executemany"
+helpers are expected to be generalized and ported to ``psycopg`` before the final
+release of SQLAlchemy 2.0, however.
+
+
+.. seealso::
+
+    :ref:`postgresql_psycopg2` - The SQLAlchemy ``psycopg``
+    dialect shares most of its behavior with the ``psycopg2`` dialect.
+    Further documentation is available there.
+
+"""  # noqa
+import logging
+import re
+
+from ._psycopg_common import _PGDialect_common_psycopg
+from ._psycopg_common import _PGExecutionContext_common_psycopg
+from ._psycopg_common import _PsycopgUUID
+from .base import INTERVAL
+from .base import PGCompiler
+from .base import PGIdentifierPreparer
+from .base import UUID
+from .json import JSON
+from .json import JSONB
+from .json import JSONPathType
+from ... import pool
+from ... import types as sqltypes
+from ... import util
+from ...engine import AdaptedConnection
+from ...util.concurrency import await_fallback
+from ...util.concurrency import await_only
+
+logger = logging.getLogger("sqlalchemy.dialects.postgresql")
+
+
+class _PGString(sqltypes.String):
+    render_bind_cast = True
+
+
+class _PGJSON(JSON):
+    render_bind_cast = True
+
+    def bind_processor(self, dialect):
+        return self._make_bind_processor(None, dialect._psycopg_Json)
+
+    def result_processor(self, dialect, coltype):
+        return None
+
+
+class _PGJSONB(JSONB):
+    render_bind_cast = True
+
+    def bind_processor(self, dialect):
+        return self._make_bind_processor(None, dialect._psycopg_Jsonb)
+
+    def result_processor(self, dialect, coltype):
+        return None
+
+
+class _PGJSONIntIndexType(sqltypes.JSON.JSONIntIndexType):
+    __visit_name__ = "json_int_index"
+
+    render_bind_cast = True
+
+
+class _PGJSONStrIndexType(sqltypes.JSON.JSONStrIndexType):
+    __visit_name__ = "json_str_index"
+
+    render_bind_cast = True
+
+
+class _PGJSONPathType(JSONPathType):
+    pass
+
+
+class _PGUUID(_PsycopgUUID):
+    render_bind_cast = True
+
+
+class _PGInterval(INTERVAL):
+    render_bind_cast = True
+
+
+class _PGTimeStamp(sqltypes.DateTime):
+    render_bind_cast = True
+
+
+class _PGDate(sqltypes.Date):
+    render_bind_cast = True
+
+
+class _PGTime(sqltypes.Time):
+    render_bind_cast = True
+
+
+class _PGInteger(sqltypes.Integer):
+    render_bind_cast = True
+
+
+class _PGSmallInteger(sqltypes.SmallInteger):
+    render_bind_cast = True
+
+
+class _PGNullType(sqltypes.NullType):
+    render_bind_cast = True
+
+
+class _PGBigInteger(sqltypes.BigInteger):
+    render_bind_cast = True
+
+
+class _PGBoolean(sqltypes.Boolean):
+    render_bind_cast = True
+
+
+class PGExecutionContext_psycopg(_PGExecutionContext_common_psycopg):
+    pass
+
+
+class PGCompiler_psycopg(PGCompiler):
+    pass
+
+
+class PGIdentifierPreparer_psycopg(PGIdentifierPreparer):
+    pass
+
+
+def _log_notices(diagnostic):
+    logger.info("%s: %s", diagnostic.severity, diagnostic.message_primary)
+
+
+class PGDialect_psycopg(_PGDialect_common_psycopg):
+    driver = "psycopg"
+
+    supports_statement_cache = True
+    supports_server_side_cursors = True
+    default_paramstyle = "pyformat"
+    supports_sane_multi_rowcount = True
+
+    execution_ctx_cls = PGExecutionContext_psycopg
+    statement_compiler = PGCompiler_psycopg
+    preparer = PGIdentifierPreparer_psycopg
+    psycopg_version = (0, 0)
+
+    _has_native_hstore = True
+
+    colspecs = util.update_copy(
+        _PGDialect_common_psycopg.colspecs,
+        {
+            sqltypes.String: _PGString,
+            JSON: _PGJSON,
+            sqltypes.JSON: _PGJSON,
+            JSONB: _PGJSONB,
+            sqltypes.JSON.JSONPathType: _PGJSONPathType,
+            sqltypes.JSON.JSONIntIndexType: _PGJSONIntIndexType,
+            sqltypes.JSON.JSONStrIndexType: _PGJSONStrIndexType,
+            UUID: _PGUUID,
+            sqltypes.Interval: _PGInterval,
+            INTERVAL: _PGInterval,
+            sqltypes.Date: _PGDate,
+            sqltypes.DateTime: _PGTimeStamp,
+            sqltypes.Time: _PGTime,
+            sqltypes.Integer: _PGInteger,
+            sqltypes.SmallInteger: _PGSmallInteger,
+            sqltypes.BigInteger: _PGBigInteger,
+        },
+    )
+
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+
+        if self.dbapi:
+            m = re.match(r"(\d+)\.(\d+)(?:\.(\d+))?", self.dbapi.__version__)
+            if m:
+                self.psycopg_version = tuple(
+                    int(x) for x in m.group(1, 2, 3) if x is not None
+                )
+
+            if self.psycopg_version < (3, 0, 2):
+                raise ImportError(
+                    "psycopg version 3.0.2 or higher is required."
+                )
+
+            from psycopg.adapt import AdaptersMap
+
+            self._psycopg_adapters_map = adapters_map = AdaptersMap(
+                self.dbapi.adapters
+            )
+
+            if self._json_deserializer:
+                from psycopg.types.json import set_json_loads
+
+                set_json_loads(self._json_deserializer, adapters_map)
+
+            if self._json_serializer:
+                from psycopg.types.json import set_json_dumps
+
+                set_json_dumps(self._json_serializer, adapters_map)
+
+    def create_connect_args(self, url):
+        # see https://github.com/psycopg/psycopg/issues/83
+        cargs, cparams = super().create_connect_args(url)
+
+        cparams["context"] = self._psycopg_adapters_map
+        if self.client_encoding is not None:
+            cparams["client_encoding"] = self.client_encoding
+        return cargs, cparams
+
+    def _type_info_fetch(self, connection, name):
+        from psycopg.types import TypeInfo
+
+        return TypeInfo.fetch(connection.connection, name)
+
+    def initialize(self, connection):
+        super().initialize(connection)
+
+        # PGDialect.initialize() checks server version for <= 8.2 and sets
+        # this flag to False if so
+        if not self.full_returning:
+            self.insert_executemany_returning = False
+
+        # HSTORE can't be registered until we have a connection so that
+        # we can look up its OID, so we set up this adapter in
+        # initialize()
+        if self.use_native_hstore:
+            info = self._type_info_fetch(connection, "hstore")
+            self._has_native_hstore = info is not None
+            if self._has_native_hstore:
+                from psycopg.types.hstore import register_hstore
+
+                # register the adapter for connections made subsequent to
+                # this one
+                register_hstore(info, self._psycopg_adapters_map)
+
+                # register the adapter for this connection
+                register_hstore(info, connection.connection)
+
+    @classmethod
+    def dbapi(cls):
+        import psycopg
+
+        return psycopg
+
+    @classmethod
+    def get_async_dialect_cls(cls, url):
+        return PGDialectAsync_psycopg
+
+    @util.memoized_property
+    def _isolation_lookup(self):
+        return {
+            "READ COMMITTED": self.dbapi.IsolationLevel.READ_COMMITTED,
+            "READ UNCOMMITTED": self.dbapi.IsolationLevel.READ_UNCOMMITTED,
+            "REPEATABLE READ": self.dbapi.IsolationLevel.REPEATABLE_READ,
+            "SERIALIZABLE": self.dbapi.IsolationLevel.SERIALIZABLE,
+        }
+
+    @util.memoized_property
+    def _psycopg_Json(self):
+        from psycopg.types import json
+
+        return json.Json
+
+    @util.memoized_property
+    def _psycopg_Jsonb(self):
+        from psycopg.types import json
+
+        return json.Jsonb
+
+    @util.memoized_property
+    def _psycopg_TransactionStatus(self):
+        from psycopg.pq import TransactionStatus
+
+        return TransactionStatus
+
+    def _do_isolation_level(self, connection, autocommit, isolation_level):
+        connection.autocommit = autocommit
+        connection.isolation_level = isolation_level
+
+    def get_isolation_level(self, dbapi_connection):
+        if hasattr(dbapi_connection, "dbapi_connection"):
+            dbapi_connection = dbapi_connection.dbapi_connection
+
+        status_before = dbapi_connection.info.transaction_status
+        value = super().get_isolation_level(dbapi_connection)
+
+        # don't rely on psycopg providing enum symbols, compare with
+        # eq/ne
+        if status_before == self._psycopg_TransactionStatus.IDLE:
+            dbapi_connection.rollback()
+        return value
+
+    def set_isolation_level(self, connection, level):
+        connection = getattr(connection, "dbapi_connection", connection)
+        if level == "AUTOCOMMIT":
+            self._do_isolation_level(
+                connection, autocommit=True, isolation_level=None
+            )
+        else:
+            self._do_isolation_level(
+                connection,
+                autocommit=False,
+                isolation_level=self._isolation_lookup[level],
+            )
+
+    def set_readonly(self, connection, value):
+        connection.read_only = value
+
+    def get_readonly(self, connection):
+        return connection.read_only
+
+    def on_connect(self):
+        def notices(conn):
+            conn.add_notice_handler(_log_notices)
+
+        fns = [notices]
+
+        if self.isolation_level is not None:
+
+            def on_connect(conn):
+                self.set_isolation_level(conn, self.isolation_level)
+
+            fns.append(on_connect)
+
+        # fns always has the notices function
+        def on_connect(conn):
+            for fn in fns:
+                fn(conn)
+
+        return on_connect
+
+    def is_disconnect(self, e, connection, cursor):
+        if isinstance(e, self.dbapi.Error) and connection is not None:
+            if connection.closed or connection.broken:
+                return True
+        return False
+
+    def _do_prepared_twophase(self, connection, command, recover=False):
+        dbapi_conn = connection.connection.dbapi_connection
+        if (
+            recover
+            # don't rely on psycopg providing enum symbols, compare with
+            # eq/ne
+            or dbapi_conn.info.transaction_status
+            != self._psycopg_TransactionStatus.IDLE
+        ):
+            dbapi_conn.rollback()
+        before = dbapi_conn.autocommit
+        try:
+            self._do_autocommit(dbapi_conn, True)
+            dbapi_conn.execute(command)
+        finally:
+            self._do_autocommit(dbapi_conn, before)
+
+    def do_rollback_twophase(
+        self, connection, xid, is_prepared=True, recover=False
+    ):
+        if is_prepared:
+            self._do_prepared_twophase(
+                connection, f"ROLLBACK PREPARED '{xid}'", recover=recover
+            )
+        else:
+            self.do_rollback(connection.connection)
+
+    def do_commit_twophase(
+        self, connection, xid, is_prepared=True, recover=False
+    ):
+        if is_prepared:
+            self._do_prepared_twophase(
+                connection, f"COMMIT PREPARED '{xid}'", recover=recover
+            )
+        else:
+            self.do_commit(connection.connection)
+
+
+class AsyncAdapt_psycopg_cursor:
+    __slots__ = ("_cursor", "await_", "_rows")
+
+    _psycopg_ExecStatus = None
+
+    def __init__(self, cursor, await_) -> None:
+        self._cursor = cursor
+        self.await_ = await_
+        self._rows = []
+
+    def __getattr__(self, name):
+        return getattr(self._cursor, name)
+
+    @property
+    def arraysize(self):
+        return self._cursor.arraysize
+
+    @arraysize.setter
+    def arraysize(self, value):
+        self._cursor.arraysize = value
+
+    def close(self):
+        self._rows.clear()
+        # Normal cursor just call _close() in a non-sync way.
+        self._cursor._close()
+
+    def execute(self, query, params=None, **kw):
+        result = self.await_(self._cursor.execute(query, params, **kw))
+        # sqlalchemy result is not async, so need to pull all rows here
+        res = self._cursor.pgresult
+
+        # don't rely on psycopg providing enum symbols, compare with
+        # eq/ne
+        if res and res.status == self._psycopg_ExecStatus.TUPLES_OK:
+            rows = self.await_(self._cursor.fetchall())
+            if not isinstance(rows, list):
+                self._rows = list(rows)
+            else:
+                self._rows = rows
+        return result
+
+    def executemany(self, query, params_seq):
+        return self.await_(self._cursor.executemany(query, params_seq))
+
+    def __iter__(self):
+        # TODO: try to avoid pop(0) on a list
+        while self._rows:
+            yield self._rows.pop(0)
+
+    def fetchone(self):
+        if self._rows:
+            # TODO: try to avoid pop(0) on a list
+            return self._rows.pop(0)
+        else:
+            return None
+
+    def fetchmany(self, size=None):
+        if size is None:
+            size = self._cursor.arraysize
+
+        retval = self._rows[0:size]
+        self._rows = self._rows[size:]
+        return retval
+
+    def fetchall(self):
+        retval = self._rows
+        self._rows = []
+        return retval
+
+
+class AsyncAdapt_psycopg_ss_cursor(AsyncAdapt_psycopg_cursor):
+    def execute(self, query, params=None, **kw):
+        self.await_(self._cursor.execute(query, params, **kw))
+        return self
+
+    def close(self):
+        self.await_(self._cursor.close())
+
+    def fetchone(self):
+        return self.await_(self._cursor.fetchone())
+
+    def fetchmany(self, size=0):
+        return self.await_(self._cursor.fetchmany(size))
+
+    def fetchall(self):
+        return self.await_(self._cursor.fetchall())
+
+    def __iter__(self):
+        iterator = self._cursor.__aiter__()
+        while True:
+            try:
+                yield self.await_(iterator.__anext__())
+            except StopAsyncIteration:
+                break
+
+
+class AsyncAdapt_psycopg_connection(AdaptedConnection):
+    __slots__ = ()
+    await_ = staticmethod(await_only)
+
+    def __init__(self, connection) -> None:
+        self._connection = connection
+
+    def __getattr__(self, name):
+        return getattr(self._connection, name)
+
+    def execute(self, query, params=None, **kw):
+        cursor = self.await_(self._connection.execute(query, params, **kw))
+        return AsyncAdapt_psycopg_cursor(cursor, self.await_)
+
+    def cursor(self, *args, **kw):
+        cursor = self._connection.cursor(*args, **kw)
+        if hasattr(cursor, "name"):
+            return AsyncAdapt_psycopg_ss_cursor(cursor, self.await_)
+        else:
+            return AsyncAdapt_psycopg_cursor(cursor, self.await_)
+
+    def commit(self):
+        self.await_(self._connection.commit())
+
+    def rollback(self):
+        self.await_(self._connection.rollback())
+
+    def close(self):
+        self.await_(self._connection.close())
+
+    @property
+    def autocommit(self):
+        return self._connection.autocommit
+
+    @autocommit.setter
+    def autocommit(self, value):
+        self.set_autocommit(value)
+
+    def set_autocommit(self, value):
+        self.await_(self._connection.set_autocommit(value))
+
+    def set_isolation_level(self, value):
+        self.await_(self._connection.set_isolation_level(value))
+
+    def set_read_only(self, value):
+        self.await_(self._connection.set_read_only(value))
+
+    def set_deferrable(self, value):
+        self.await_(self._connection.set_deferrable(value))
+
+
+class AsyncAdaptFallback_psycopg_connection(AsyncAdapt_psycopg_connection):
+    __slots__ = ()
+    await_ = staticmethod(await_fallback)
+
+
+class PsycopgAdaptDBAPI:
+    def __init__(self, psycopg) -> None:
+        self.psycopg = psycopg
+
+        for k, v in self.psycopg.__dict__.items():
+            if k != "connect":
+                self.__dict__[k] = v
+
+    def connect(self, *arg, **kw):
+        async_fallback = kw.pop("async_fallback", False)
+        if util.asbool(async_fallback):
+            return AsyncAdaptFallback_psycopg_connection(
+                await_fallback(
+                    self.psycopg.AsyncConnection.connect(*arg, **kw)
+                )
+            )
+        else:
+            return AsyncAdapt_psycopg_connection(
+                await_only(self.psycopg.AsyncConnection.connect(*arg, **kw))
+            )
+
+
+class PGDialectAsync_psycopg(PGDialect_psycopg):
+    is_async = True
+    supports_statement_cache = True
+
+    @classmethod
+    def dbapi(cls):
+        import psycopg
+        from psycopg.pq import ExecStatus
+
+        AsyncAdapt_psycopg_cursor._psycopg_ExecStatus = ExecStatus
+
+        return PsycopgAdaptDBAPI(psycopg)
+
+    @classmethod
+    def get_pool_class(cls, url):
+
+        async_fallback = url.query.get("async_fallback", False)
+
+        if util.asbool(async_fallback):
+            return pool.FallbackAsyncAdaptedQueuePool
+        else:
+            return pool.AsyncAdaptedQueuePool
+
+    def _type_info_fetch(self, connection, name):
+        from psycopg.types import TypeInfo
+
+        adapted = connection.connection
+        return adapted.await_(TypeInfo.fetch(adapted._connection, name))
+
+    def _do_isolation_level(self, connection, autocommit, isolation_level):
+        connection.set_autocommit(autocommit)
+        connection.set_isolation_level(isolation_level)
+
+    def _do_autocommit(self, connection, value):
+        connection.set_autocommit(value)
+
+    def set_readonly(self, connection, value):
+        connection.set_read_only(value)
+
+    def set_deferrable(self, connection, value):
+        connection.set_deferrable(value)
+
+    def get_driver_connection(self, connection):
+        return connection._connection
+
+
+dialect = PGDialect_psycopg
+dialect_async = PGDialectAsync_psycopg
diff --git a/lib/sqlalchemy/dialects/postgresql/psycopg2.py b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
index 39b6e0ed1..3d9f90a29 100644
--- a/lib/sqlalchemy/dialects/postgresql/psycopg2.py
+++ b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
@@ -11,6 +11,8 @@ r"""
     :connectstring: postgresql+psycopg2://user:password@host:port/dbname[?key=value&key=value...]
     :url: https://pypi.org/project/psycopg2/
 
+.. _psycopg2_toplevel:
+
 psycopg2 Connect Arguments
 --------------------------
 
@@ -442,25 +444,15 @@ which may be more performant.
 
 """  # noqa
 import collections.abc as collections_abc
-import decimal
 import logging
 import re
-from uuid import UUID as _python_UUID
 
-from .array import ARRAY as PGARRAY
-from .base import _DECIMAL_TYPES
-from .base import _FLOAT_TYPES
-from .base import _INT_TYPES
+from ._psycopg_common import _PGDialect_common_psycopg
+from ._psycopg_common import _PGExecutionContext_common_psycopg
 from .base import PGCompiler
-from .base import PGDialect
-from .base import PGExecutionContext
 from .base import PGIdentifierPreparer
-from .base import UUID
-from .hstore import HSTORE
 from .json import JSON
 from .json import JSONB
-from ... import exc
-from ... import processors
 from ... import types as sqltypes
 from ... import util
 from ...engine import cursor as _cursor
@@ -469,53 +461,6 @@ from ...engine import cursor as _cursor
 logger = logging.getLogger("sqlalchemy.dialects.postgresql")
 
 
-class _PGNumeric(sqltypes.Numeric):
-    def bind_processor(self, dialect):
-        return None
-
-    def result_processor(self, dialect, coltype):
-        if self.asdecimal:
-            if coltype in _FLOAT_TYPES:
-                return processors.to_decimal_processor_factory(
-                    decimal.Decimal, self._effective_decimal_return_scale
-                )
-            elif coltype in _DECIMAL_TYPES or coltype in _INT_TYPES:
-                # pg8000 returns Decimal natively for 1700
-                return None
-            else:
-                raise exc.InvalidRequestError(
-                    "Unknown PG numeric type: %d" % coltype
-                )
-        else:
-            if coltype in _FLOAT_TYPES:
-                # pg8000 returns float natively for 701
-                return None
-            elif coltype in _DECIMAL_TYPES or coltype in _INT_TYPES:
-                return processors.to_float
-            else:
-                raise exc.InvalidRequestError(
-                    "Unknown PG numeric type: %d" % coltype
-                )
-
-
-class _PGHStore(HSTORE):
-    def bind_processor(self, dialect):
-        if dialect._has_native_hstore:
-            return None
-        else:
-            return super(_PGHStore, self).bind_processor(dialect)
-
-    def result_processor(self, dialect, coltype):
-        if dialect._has_native_hstore:
-            return None
-        else:
-            return super(_PGHStore, self).result_processor(dialect, coltype)
-
-
-class _PGARRAY(PGARRAY):
-    render_bind_cast = True
-
-
 class _PGJSON(JSON):
     def result_processor(self, dialect, coltype):
         return None
@@ -526,40 +471,9 @@ class _PGJSONB(JSONB):
         return None
 
 
-class _PGUUID(UUID):
-    def bind_processor(self, dialect):
-        if not self.as_uuid and dialect.use_native_uuid:
-
-            def process(value):
-                if value is not None:
-                    value = _python_UUID(value)
-                return value
-
-            return process
-
-    def result_processor(self, dialect, coltype):
-        if not self.as_uuid and dialect.use_native_uuid:
-
-            def process(value):
-                if value is not None:
-                    value = str(value)
-                return value
-
-            return process
-
-
-_server_side_id = util.counter()
-
-
-class PGExecutionContext_psycopg2(PGExecutionContext):
+class PGExecutionContext_psycopg2(_PGExecutionContext_common_psycopg):
     _psycopg2_fetched_rows = None
 
-    def create_server_side_cursor(self):
-        # use server-side cursors:
-        # https://lists.initd.org/pipermail/psycopg/2007-January/005251.html
-        ident = "c_%s_%s" % (hex(id(self))[2:], hex(_server_side_id())[2:])
-        return self._dbapi_connection.cursor(ident)
-
     def post_exec(self):
         if (
             self._psycopg2_fetched_rows
@@ -614,7 +528,7 @@ EXECUTEMANY_VALUES_PLUS_BATCH = util.symbol(
 )
 
 
-class PGDialect_psycopg2(PGDialect):
+class PGDialect_psycopg2(_PGDialect_common_psycopg):
     driver = "psycopg2"
 
     supports_statement_cache = True
@@ -631,34 +545,22 @@ class PGDialect_psycopg2(PGDialect):
     _has_native_hstore = True
 
     colspecs = util.update_copy(
-        PGDialect.colspecs,
+        _PGDialect_common_psycopg.colspecs,
         {
-            sqltypes.Numeric: _PGNumeric,
-            HSTORE: _PGHStore,
             JSON: _PGJSON,
             sqltypes.JSON: _PGJSON,
             JSONB: _PGJSONB,
-            UUID: _PGUUID,
-            sqltypes.ARRAY: _PGARRAY,
         },
     )
 
     def __init__(
         self,
-        client_encoding=None,
-        use_native_hstore=True,
-        use_native_uuid=True,
         executemany_mode="values_only",
         executemany_batch_page_size=100,
         executemany_values_page_size=1000,
         **kwargs
     ):
-        PGDialect.__init__(self, **kwargs)
-        if not use_native_hstore:
-            self._has_native_hstore = False
-        self.use_native_hstore = use_native_hstore
-        self.use_native_uuid = use_native_uuid
-        self.client_encoding = client_encoding
+        _PGDialect_common_psycopg.__init__(self, **kwargs)
 
         # Parse executemany_mode argument, allowing it to be only one of the
         # symbol names
@@ -737,9 +639,6 @@ class PGDialect_psycopg2(PGDialect):
             "SERIALIZABLE": extensions.ISOLATION_LEVEL_SERIALIZABLE,
         }
 
-    def get_isolation_level_values(self, dbapi_conn):
-        return list(self._isolation_lookup)
-
     def set_isolation_level(self, connection, level):
         connection.set_isolation_level(self._isolation_lookup[level])
 
@@ -755,25 +654,6 @@ class PGDialect_psycopg2(PGDialect):
     def get_deferrable(self, connection):
         return connection.deferrable
 
-    def do_ping(self, dbapi_connection):
-        cursor = None
-        try:
-            dbapi_connection.autocommit = True
-            cursor = dbapi_connection.cursor()
-            try:
-                cursor.execute(self._dialect_specific_select_one)
-            finally:
-                cursor.close()
-                if not dbapi_connection.closed:
-                    dbapi_connection.autocommit = False
-        except self.dbapi.Error as err:
-            if self.is_disconnect(err, dbapi_connection, cursor):
-                return False
-            else:
-                raise
-        else:
-            return True
-
     def on_connect(self):
         extras = self._psycopg2_extras
 
@@ -911,33 +791,6 @@ class PGDialect_psycopg2(PGDialect):
         else:
             return None
 
-    def create_connect_args(self, url):
-        opts = url.translate_connect_args(username="user")
-
-        is_multihost = False
-        if "host" in url.query:
-            is_multihost = isinstance(url.query["host"], (list, tuple))
-
-        if opts:
-            if "port" in opts:
-                opts["port"] = int(opts["port"])
-            opts.update(url.query)
-            if is_multihost:
-                opts["host"] = ",".join(url.query["host"])
-            # send individual dbname, user, password, host, port
-            # parameters to psycopg2.connect()
-            return ([], opts)
-        elif url.query:
-            # any other connection arguments, pass directly
-            opts.update(url.query)
-            if is_multihost:
-                opts["host"] = ",".join(url.query["host"])
-            return ([], opts)
-        else:
-            # no connection arguments whatsoever; psycopg2.connect()
-            # requires that "dsn" be present as a blank string.
-            return ([""], opts)
-
     def is_disconnect(self, e, connection, cursor):
         if isinstance(e, self.dbapi.Error):
             # check the "closed" flag.  this might not be