Remove Elixir library
Update SQLAlchemy
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Ruud
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# postgresql/json.py
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# Copyright (C) 2005-2014 the SQLAlchemy authors and contributors <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 __future__ import absolute_import
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import json
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from .base import ischema_names
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from ... import types as sqltypes
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from ...sql.operators import custom_op
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from ... import sql
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from ...sql import elements
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from ... import util
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__all__ = ('JSON', 'JSONElement')
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class JSONElement(elements.BinaryExpression):
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"""Represents accessing an element of a :class:`.JSON` value.
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The :class:`.JSONElement` is produced whenever using the Python index
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operator on an expression that has the type :class:`.JSON`::
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expr = mytable.c.json_data['some_key']
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The expression typically compiles to a JSON access such as ``col -> key``.
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Modifiers are then available for typing behavior, including :meth:`.JSONElement.cast`
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and :attr:`.JSONElement.astext`.
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"""
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def __init__(self, left, right, astext=False, opstring=None, result_type=None):
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self._astext = astext
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if opstring is None:
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if hasattr(right, '__iter__') and \
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not isinstance(right, util.string_types):
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opstring = "#>"
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right = "{%s}" % (", ".join(util.text_type(elem) for elem in right))
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else:
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opstring = "->"
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self._json_opstring = opstring
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operator = custom_op(opstring, precedence=5)
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right = left._check_literal(left, operator, right)
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super(JSONElement, self).__init__(left, right, operator, type_=result_type)
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@property
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def astext(self):
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"""Convert this :class:`.JSONElement` to use the 'astext' operator
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when evaluated.
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E.g.::
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select([data_table.c.data['some key'].astext])
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.. seealso::
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:meth:`.JSONElement.cast`
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"""
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if self._astext:
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return self
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else:
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return JSONElement(
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self.left,
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self.right,
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astext=True,
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opstring=self._json_opstring + ">",
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result_type=sqltypes.String(convert_unicode=True)
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)
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def cast(self, type_):
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"""Convert this :class:`.JSONElement` to apply both the 'astext' operator
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as well as an explicit type cast when evaulated.
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E.g.::
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select([data_table.c.data['some key'].cast(Integer)])
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.. seealso::
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:attr:`.JSONElement.astext`
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"""
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if not self._astext:
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return self.astext.cast(type_)
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else:
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return sql.cast(self, type_)
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class JSON(sqltypes.TypeEngine):
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"""Represent the Postgresql JSON type.
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The :class:`.JSON` type stores arbitrary JSON format data, e.g.::
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data_table = Table('data_table', metadata,
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Column('id', Integer, primary_key=True),
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Column('data', JSON)
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)
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with engine.connect() as conn:
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conn.execute(
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data_table.insert(),
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data = {"key1": "value1", "key2": "value2"}
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)
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:class:`.JSON` provides several operations:
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* Index operations::
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data_table.c.data['some key']
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* Index operations returning text (required for text comparison)::
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data_table.c.data['some key'].astext == 'some value'
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* Index operations with a built-in CAST call::
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data_table.c.data['some key'].cast(Integer) == 5
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* Path index operations::
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data_table.c.data[('key_1', 'key_2', ..., 'key_n')]
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* Path index operations returning text (required for text comparison)::
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data_table.c.data[('key_1', 'key_2', ..., 'key_n')].astext == 'some value'
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Index operations return an instance of :class:`.JSONElement`, which represents
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an expression such as ``column -> index``. This element then defines
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methods such as :attr:`.JSONElement.astext` and :meth:`.JSONElement.cast`
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for setting up type behavior.
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The :class:`.JSON` type, when used with the SQLAlchemy ORM, does not detect
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in-place mutations to the structure. In order to detect these, the
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:mod:`sqlalchemy.ext.mutable` extension must be used. This extension will
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allow "in-place" changes to the datastructure to produce events which
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will be detected by the unit of work. See the example at :class:`.HSTORE`
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for a simple example involving a dictionary.
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Custom serializers and deserializers are specified at the dialect level,
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that is using :func:`.create_engine`. The reason for this is that when
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using psycopg2, the DBAPI only allows serializers at the per-cursor
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or per-connection level. E.g.::
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engine = create_engine("postgresql://scott:tiger@localhost/test",
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json_serializer=my_serialize_fn,
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json_deserializer=my_deserialize_fn
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)
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When using the psycopg2 dialect, the json_deserializer is registered
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against the database using ``psycopg2.extras.register_default_json``.
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.. versionadded:: 0.9
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"""
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__visit_name__ = 'JSON'
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class comparator_factory(sqltypes.Concatenable.Comparator):
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"""Define comparison operations for :class:`.JSON`."""
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def __getitem__(self, other):
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"""Get the value at a given key."""
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return JSONElement(self.expr, other)
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def _adapt_expression(self, op, other_comparator):
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if isinstance(op, custom_op):
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if op.opstring == '->':
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return op, sqltypes.Text
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return sqltypes.Concatenable.Comparator.\
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_adapt_expression(self, op, other_comparator)
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def bind_processor(self, dialect):
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json_serializer = dialect._json_serializer or json.dumps
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if util.py2k:
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encoding = dialect.encoding
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def process(value):
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return json_serializer(value).encode(encoding)
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else:
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def process(value):
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return json_serializer(value)
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return process
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def result_processor(self, dialect, coltype):
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json_deserializer = dialect._json_deserializer or json.loads
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if util.py2k:
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encoding = dialect.encoding
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def process(value):
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return json_deserializer(value.decode(encoding))
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else:
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def process(value):
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return json_deserializer(value)
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return process
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ischema_names['json'] = JSON
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