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