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diff --git a/lib/sqlalchemy/dialects/postgresql/dml.py b/lib/sqlalchemy/dialects/postgresql/dml.py
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+# postgresql/on_conflict.py
+# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
+# <see AUTHORS file>
+#
+# This module is part of SQLAlchemy and is released under
+# the MIT License: https://www.opensource.org/licenses/mit-license.php
+
+from . import ext
+from ... import util
+from ...sql import coercions
+from ...sql import roles
+from ...sql import schema
+from ...sql.base import _exclusive_against
+from ...sql.base import _generative
+from ...sql.base import ColumnCollection
+from ...sql.dml import Insert as StandardInsert
+from ...sql.elements import ClauseElement
+from ...sql.expression import alias
+from ...util.langhelpers import public_factory
+
+
+__all__ = ("Insert", "insert")
+
+
+class Insert(StandardInsert):
+    """PostgreSQL-specific implementation of INSERT.
+
+    Adds methods for PG-specific syntaxes such as ON CONFLICT.
+
+    The :class:`_postgresql.Insert` object is created using the
+    :func:`sqlalchemy.dialects.postgresql.insert` function.
+
+    .. versionadded:: 1.1
+
+    """
+
+    stringify_dialect = "postgresql"
+    inherit_cache = False
+
+    @util.memoized_property
+    def excluded(self):
+        """Provide the ``excluded`` namespace for an ON CONFLICT statement
+
+        PG's ON CONFLICT clause allows reference to the row that would
+        be inserted, known as ``excluded``.  This attribute provides
+        all columns in this row to be referenceable.
+
+        .. tip::  The :attr:`_postgresql.Insert.excluded` attribute is an
+            instance of :class:`_expression.ColumnCollection`, which provides
+            an interface the same as that of the :attr:`_schema.Table.c`
+            collection described at :ref:`metadata_tables_and_columns`.
+            With this collection, ordinary names are accessible like attributes
+            (e.g. ``stmt.excluded.some_column``), but special names and
+            dictionary method names should be accessed using indexed access,
+            such as ``stmt.excluded["column name"]`` or
+            ``stmt.excluded["values"]``.   See the docstring for
+            :class:`_expression.ColumnCollection` for further examples.
+
+        .. seealso::
+
+            :ref:`postgresql_insert_on_conflict` - example of how
+            to use :attr:`_expression.Insert.excluded`
+
+        """
+        return alias(self.table, name="excluded").columns
+
+    _on_conflict_exclusive = _exclusive_against(
+        "_post_values_clause",
+        msgs={
+            "_post_values_clause": "This Insert construct already has "
+            "an ON CONFLICT clause established"
+        },
+    )
+
+    @_generative
+    @_on_conflict_exclusive
+    def on_conflict_do_update(
+        self,
+        constraint=None,
+        index_elements=None,
+        index_where=None,
+        set_=None,
+        where=None,
+    ):
+        r"""
+        Specifies a DO UPDATE SET action for ON CONFLICT clause.
+
+        Either the ``constraint`` or ``index_elements`` argument is
+        required, but only one of these can be specified.
+
+        :param constraint:
+         The name of a unique or exclusion constraint on the table,
+         or the constraint object itself if it has a .name attribute.
+
+        :param index_elements:
+         A sequence consisting of string column names, :class:`_schema.Column`
+         objects, or other column expression objects that will be used
+         to infer a target index.
+
+        :param index_where:
+         Additional WHERE criterion that can be used to infer a
+         conditional target index.
+
+        :param set\_:
+         A dictionary or other mapping object
+         where the keys are either names of columns in the target table,
+         or :class:`_schema.Column` objects or other ORM-mapped columns
+         matching that of the target table, and expressions or literals
+         as values, specifying the ``SET`` actions to take.
+
+         .. versionadded:: 1.4 The
+            :paramref:`_postgresql.Insert.on_conflict_do_update.set_`
+            parameter supports :class:`_schema.Column` objects from the target
+            :class:`_schema.Table` as keys.
+
+         .. warning:: This dictionary does **not** take into account
+            Python-specified default UPDATE values or generation functions,
+            e.g. those specified using :paramref:`_schema.Column.onupdate`.
+            These values will not be exercised for an ON CONFLICT style of
+            UPDATE, unless they are manually specified in the
+            :paramref:`.Insert.on_conflict_do_update.set_` dictionary.
+
+        :param where:
+         Optional argument. If present, can be a literal SQL
+         string or an acceptable expression for a ``WHERE`` clause
+         that restricts the rows affected by ``DO UPDATE SET``. Rows
+         not meeting the ``WHERE`` condition will not be updated
+         (effectively a ``DO NOTHING`` for those rows).
+
+         .. versionadded:: 1.1
+
+
+        .. seealso::
+
+            :ref:`postgresql_insert_on_conflict`
+
+        """
+        self._post_values_clause = OnConflictDoUpdate(
+            constraint, index_elements, index_where, set_, where
+        )
+
+    @_generative
+    @_on_conflict_exclusive
+    def on_conflict_do_nothing(
+        self, constraint=None, index_elements=None, index_where=None
+    ):
+        """
+        Specifies a DO NOTHING action for ON CONFLICT clause.
+
+        The ``constraint`` and ``index_elements`` arguments
+        are optional, but only one of these can be specified.
+
+        :param constraint:
+         The name of a unique or exclusion constraint on the table,
+         or the constraint object itself if it has a .name attribute.
+
+        :param index_elements:
+         A sequence consisting of string column names, :class:`_schema.Column`
+         objects, or other column expression objects that will be used
+         to infer a target index.
+
+        :param index_where:
+         Additional WHERE criterion that can be used to infer a
+         conditional target index.
+
+         .. versionadded:: 1.1
+
+        .. seealso::
+
+            :ref:`postgresql_insert_on_conflict`
+
+        """
+        self._post_values_clause = OnConflictDoNothing(
+            constraint, index_elements, index_where
+        )
+
+
+insert = public_factory(
+    Insert, ".dialects.postgresql.insert", ".dialects.postgresql.Insert"
+)
+
+
+class OnConflictClause(ClauseElement):
+    stringify_dialect = "postgresql"
+
+    def __init__(self, constraint=None, index_elements=None, index_where=None):
+
+        if constraint is not None:
+            if not isinstance(constraint, util.string_types) and isinstance(
+                constraint,
+                (schema.Index, schema.Constraint, ext.ExcludeConstraint),
+            ):
+                constraint = getattr(constraint, "name") or constraint
+
+        if constraint is not None:
+            if index_elements is not None:
+                raise ValueError(
+                    "'constraint' and 'index_elements' are mutually exclusive"
+                )
+
+            if isinstance(constraint, util.string_types):
+                self.constraint_target = constraint
+                self.inferred_target_elements = None
+                self.inferred_target_whereclause = None
+            elif isinstance(constraint, schema.Index):
+                index_elements = constraint.expressions
+                index_where = constraint.dialect_options["postgresql"].get(
+                    "where"
+                )
+            elif isinstance(constraint, ext.ExcludeConstraint):
+                index_elements = constraint.columns
+                index_where = constraint.where
+            else:
+                index_elements = constraint.columns
+                index_where = constraint.dialect_options["postgresql"].get(
+                    "where"
+                )
+
+        if index_elements is not None:
+            self.constraint_target = None
+            self.inferred_target_elements = index_elements
+            self.inferred_target_whereclause = index_where
+        elif constraint is None:
+            self.constraint_target = (
+                self.inferred_target_elements
+            ) = self.inferred_target_whereclause = None
+
+
+class OnConflictDoNothing(OnConflictClause):
+    __visit_name__ = "on_conflict_do_nothing"
+
+
+class OnConflictDoUpdate(OnConflictClause):
+    __visit_name__ = "on_conflict_do_update"
+
+    def __init__(
+        self,
+        constraint=None,
+        index_elements=None,
+        index_where=None,
+        set_=None,
+        where=None,
+    ):
+        super(OnConflictDoUpdate, self).__init__(
+            constraint=constraint,
+            index_elements=index_elements,
+            index_where=index_where,
+        )
+
+        if (
+            self.inferred_target_elements is None
+            and self.constraint_target is None
+        ):
+            raise ValueError(
+                "Either constraint or index_elements, "
+                "but not both, must be specified unless DO NOTHING"
+            )
+
+        if isinstance(set_, dict):
+            if not set_:
+                raise ValueError("set parameter dictionary must not be empty")
+        elif isinstance(set_, ColumnCollection):
+            set_ = dict(set_)
+        else:
+            raise ValueError(
+                "set parameter must be a non-empty dictionary "
+                "or a ColumnCollection such as the `.c.` collection "
+                "of a Table object"
+            )
+        self.update_values_to_set = [
+            (coercions.expect(roles.DMLColumnRole, key), value)
+            for key, value in set_.items()
+        ]
+        self.update_whereclause = where