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"""Implementation of the JSON adaptation objects
This module exists to avoid a circular import problem: pyscopg2.extras depends
on psycopg2.extension, so I can't create the default JSON typecasters in
extensions importing register_json from extras.
# psycopg/ - Implementation of the JSON adaptation objects
# Copyright (C) 2012-2019 Daniele Varrazzo <>
# Copyright (C) 2020 The Psycopg Team
# psycopg2 is free software: you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# In addition, as a special exception, the copyright holders give
# permission to link this program with the OpenSSL library (or with
# modified versions of OpenSSL that use the same license as OpenSSL),
# and distribute linked combinations including the two.
# You must obey the GNU Lesser General Public License in all respects for
# all of the code used other than OpenSSL.
# psycopg2 is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# License for more details.
import json
from psycopg2._psycopg import ISQLQuote, QuotedString
from psycopg2._psycopg import new_type, new_array_type, register_type
from psycopg2.compat import PY2
# oids from PostgreSQL 9.2
JSON_OID = 114
# oids from PostgreSQL 9.4
JSONB_OID = 3802
class Json(object):
An `~psycopg2.extensions.ISQLQuote` wrapper to adapt a Python object to
:sql:`json` data type.
`!Json` can be used to wrap any object supported by the provided *dumps*
function. If none is provided, the standard :py:func:`json.dumps()` is
def __init__(self, adapted, dumps=None):
self.adapted = adapted
self._conn = None
self._dumps = dumps or json.dumps
def __conform__(self, proto):
if proto is ISQLQuote:
return self
def dumps(self, obj):
"""Serialize *obj* in JSON format.
The default is to call `!json.dumps()` or the *dumps* function
provided in the constructor. You can override this method to create a
customized JSON wrapper.
return self._dumps(obj)
def prepare(self, conn):
self._conn = conn
def getquoted(self):
s = self.dumps(self.adapted)
qs = QuotedString(s)
if self._conn is not None:
return qs.getquoted()
if PY2:
def __str__(self):
return self.getquoted()
def __str__(self):
# getquoted is binary in Py3
return self.getquoted().decode('ascii', 'replace')
def register_json(conn_or_curs=None, globally=False, loads=None,
oid=None, array_oid=None, name='json'):
"""Create and register typecasters converting :sql:`json` type to Python objects.
:param conn_or_curs: a connection or cursor used to find the :sql:`json`
and :sql:`json[]` oids; the typecasters are registered in a scope
limited to this object, unless *globally* is set to `!True`. It can be
`!None` if the oids are provided
:param globally: if `!False` register the typecasters only on
*conn_or_curs*, otherwise register them globally
:param loads: the function used to parse the data into a Python object. If
`!None` use `!json.loads()`, where `!json` is the module chosen
according to the Python version (see above)
:param oid: the OID of the :sql:`json` type if known; If not, it will be
queried on *conn_or_curs*
:param array_oid: the OID of the :sql:`json[]` array type if known;
if not, it will be queried on *conn_or_curs*
:param name: the name of the data type to look for in *conn_or_curs*
The connection or cursor passed to the function will be used to query the
database and look for the OID of the :sql:`json` type (or an alternative
type if *name* if provided). No query is performed if *oid* and *array_oid*
are provided. Raise `~psycopg2.ProgrammingError` if the type is not found.
if oid is None:
oid, array_oid = _get_json_oids(conn_or_curs, name)
JSON, JSONARRAY = _create_json_typecasters(
oid, array_oid, loads=loads, name=name.upper())
register_type(JSON, not globally and conn_or_curs or None)
if JSONARRAY is not None:
register_type(JSONARRAY, not globally and conn_or_curs or None)
def register_default_json(conn_or_curs=None, globally=False, loads=None):
Create and register :sql:`json` typecasters for PostgreSQL 9.2 and following.
Since PostgreSQL 9.2 :sql:`json` is a builtin type, hence its oid is known
and fixed. This function allows specifying a customized *loads* function
for the default :sql:`json` type without querying the database.
All the parameters have the same meaning of `register_json()`.
return register_json(conn_or_curs=conn_or_curs, globally=globally,
loads=loads, oid=JSON_OID, array_oid=JSONARRAY_OID)
def register_default_jsonb(conn_or_curs=None, globally=False, loads=None):
Create and register :sql:`jsonb` typecasters for PostgreSQL 9.4 and following.
As in `register_default_json()`, the function allows to register a
customized *loads* function for the :sql:`jsonb` type at its known oid for
PostgreSQL 9.4 and following versions. All the parameters have the same
meaning of `register_json()`.
return register_json(conn_or_curs=conn_or_curs, globally=globally,
loads=loads, oid=JSONB_OID, array_oid=JSONBARRAY_OID, name='jsonb')
def _create_json_typecasters(oid, array_oid, loads=None, name='JSON'):
"""Create typecasters for json data type."""
if loads is None:
loads = json.loads
def typecast_json(s, cur):
if s is None:
return None
return loads(s)
JSON = new_type((oid, ), name, typecast_json)
if array_oid is not None:
JSONARRAY = new_array_type((array_oid, ), "%sARRAY" % name, JSON)
def _get_json_oids(conn_or_curs, name='json'):
# lazy imports
from psycopg2.extensions import STATUS_IN_TRANSACTION
from psycopg2.extras import _solve_conn_curs
conn, curs = _solve_conn_curs(conn_or_curs)
# Store the transaction status of the connection to revert it after use
conn_status = conn.status
# column typarray not available before PG 8.3
typarray = >= 80300 and "typarray" or "NULL"
# get the oid for the hstore
"SELECT t.oid, %s FROM pg_type t WHERE t.typname = %%s;"
% typarray, (name,))
r = curs.fetchone()
# revert the status of the connection as before the command
if conn_status != STATUS_IN_TRANSACTION and not conn.autocommit:
if not r:
raise conn.ProgrammingError("%s data type not found" % name)
return r
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