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# postgresql/on_conflict.py
# Copyright (C) 2005-2017 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
from ...sql.elements import ClauseElement, _literal_as_binds
from ...sql.dml import Insert as StandardInsert
from ...sql.expression import alias
from ...sql import schema
from ...util.langhelpers import public_factory
from ...sql.base import _generative
from ... import util
from . import ext
__all__ = ('Insert', 'insert')
class Insert(StandardInsert):
"""PostgreSQL-specific implementation of INSERT.
Adds methods for PG-specific syntaxes such as ON CONFLICT.
.. versionadded:: 1.1
"""
@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 referenaceable.
.. seealso::
:ref:`postgresql_insert_on_conflict` - example of how
to use :attr:`.Insert.excluded`
"""
return alias(self.table, name='excluded').columns
@_generative
def on_conflict_do_update(
self,
constraint=None, index_elements=None,
index_where=None, set_=None, where=None):
"""
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:`.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_:
Required argument. A dictionary or other mapping object
with column names as keys and expressions or literals as values,
specifying the ``SET`` actions to take.
If the target :class:`.Column` specifies a ".key" attribute distinct
from the column name, that key should be used.
.. warning:: This dictionary does **not** take into account
Python-specified default UPDATE values or generation functions,
e.g. those specified using :paramref:`.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)
return self
@_generative
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:`.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)
return self
insert = public_factory(Insert, '.dialects.postgresql.insert')
class OnConflictClause(ClauseElement):
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 (not isinstance(set_, dict) or not set_):
raise ValueError("set parameter must be a non-empty dictionary")
self.update_values_to_set = [
(key, value)
for key, value in set_.items()
]
self.update_whereclause = where
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