224 lines
6.7 KiB
Python
224 lines
6.7 KiB
Python
# postgresql/ext.py
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# Copyright (C) 2005-2019 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: http://www.opensource.org/licenses/mit-license.php
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from .array import ARRAY
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from ...sql import elements
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from ...sql import expression
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from ...sql import functions
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from ...sql.schema import ColumnCollectionConstraint
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class aggregate_order_by(expression.ColumnElement):
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"""Represent a PostgreSQL aggregate order by expression.
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E.g.::
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from sqlalchemy.dialects.postgresql import aggregate_order_by
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expr = func.array_agg(aggregate_order_by(table.c.a, table.c.b.desc()))
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stmt = select([expr])
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would represent the expression::
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SELECT array_agg(a ORDER BY b DESC) FROM table;
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Similarly::
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expr = func.string_agg(
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table.c.a,
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aggregate_order_by(literal_column("','"), table.c.a)
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)
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stmt = select([expr])
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Would represent::
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SELECT string_agg(a, ',' ORDER BY a) FROM table;
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.. versionadded:: 1.1
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.. versionchanged:: 1.2.13 - the ORDER BY argument may be multiple terms
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.. seealso::
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:class:`.array_agg`
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"""
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__visit_name__ = "aggregate_order_by"
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def __init__(self, target, *order_by):
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self.target = elements._literal_as_binds(target)
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_lob = len(order_by)
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if _lob == 0:
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raise TypeError("at least one ORDER BY element is required")
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elif _lob == 1:
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self.order_by = elements._literal_as_binds(order_by[0])
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else:
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self.order_by = elements.ClauseList(
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*order_by, _literal_as_text=elements._literal_as_binds
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)
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def self_group(self, against=None):
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return self
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def get_children(self, **kwargs):
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return self.target, self.order_by
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def _copy_internals(self, clone=elements._clone, **kw):
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self.target = clone(self.target, **kw)
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self.order_by = clone(self.order_by, **kw)
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@property
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def _from_objects(self):
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return self.target._from_objects + self.order_by._from_objects
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class ExcludeConstraint(ColumnCollectionConstraint):
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"""A table-level EXCLUDE constraint.
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Defines an EXCLUDE constraint as described in the `postgres
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documentation`__.
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__ http://www.postgresql.org/docs/9.0/static/sql-createtable.html#SQL-CREATETABLE-EXCLUDE
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""" # noqa
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__visit_name__ = "exclude_constraint"
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where = None
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@elements._document_text_coercion(
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"where",
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":class:`.ExcludeConstraint`",
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":paramref:`.ExcludeConstraint.where`",
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)
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def __init__(self, *elements, **kw):
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r"""
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Create an :class:`.ExcludeConstraint` object.
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E.g.::
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const = ExcludeConstraint(
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(Column('period'), '&&'),
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(Column('group'), '='),
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where=(Column('group') != 'some group')
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)
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The constraint is normally embedded into the :class:`.Table` construct
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directly, or added later using :meth:`.append_constraint`::
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some_table = Table(
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'some_table', metadata,
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Column('id', Integer, primary_key=True),
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Column('period', TSRANGE()),
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Column('group', String)
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)
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some_table.append_constraint(
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ExcludeConstraint(
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(some_table.c.period, '&&'),
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(some_table.c.group, '='),
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where=some_table.c.group != 'some group',
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name='some_table_excl_const'
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)
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)
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:param \*elements:
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A sequence of two tuples of the form ``(column, operator)`` where
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"column" is a SQL expression element or a raw SQL string, most
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typically a :class:`.Column` object, and "operator" is a string
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containing the operator to use. In order to specify a column name
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when a :class:`.Column` object is not available, while ensuring
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that any necessary quoting rules take effect, an ad-hoc
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:class:`.Column` or :func:`.sql.expression.column` object should be
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used.
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:param name:
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Optional, the in-database name of this constraint.
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:param deferrable:
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Optional bool. If set, emit DEFERRABLE or NOT DEFERRABLE when
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issuing DDL for this constraint.
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:param initially:
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Optional string. If set, emit INITIALLY <value> when issuing DDL
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for this constraint.
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:param using:
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Optional string. If set, emit USING <index_method> when issuing DDL
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for this constraint. Defaults to 'gist'.
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:param where:
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Optional SQL expression construct or literal SQL string.
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If set, emit WHERE <predicate> when issuing DDL
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for this constraint.
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"""
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columns = []
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render_exprs = []
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self.operators = {}
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expressions, operators = zip(*elements)
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for (expr, column, strname, add_element), operator in zip(
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self._extract_col_expression_collection(expressions), operators
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):
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if add_element is not None:
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columns.append(add_element)
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name = column.name if column is not None else strname
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if name is not None:
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# backwards compat
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self.operators[name] = operator
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expr = expression._literal_as_column(expr)
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render_exprs.append((expr, name, operator))
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self._render_exprs = render_exprs
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ColumnCollectionConstraint.__init__(
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self,
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*columns,
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name=kw.get("name"),
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deferrable=kw.get("deferrable"),
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initially=kw.get("initially")
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)
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self.using = kw.get("using", "gist")
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where = kw.get("where")
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if where is not None:
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self.where = expression._literal_as_text(
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where, allow_coercion_to_text=True
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)
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def copy(self, **kw):
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elements = [(col, self.operators[col]) for col in self.columns.keys()]
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c = self.__class__(
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*elements,
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name=self.name,
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deferrable=self.deferrable,
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initially=self.initially,
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where=self.where,
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using=self.using
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)
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c.dispatch._update(self.dispatch)
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return c
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def array_agg(*arg, **kw):
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"""PostgreSQL-specific form of :class:`.array_agg`, ensures
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return type is :class:`.postgresql.ARRAY` and not
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the plain :class:`.types.ARRAY`, unless an explicit ``type_``
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is passed.
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.. versionadded:: 1.1
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"""
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kw["_default_array_type"] = ARRAY
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return functions.func.array_agg(*arg, **kw)
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