126 lines
4.5 KiB
Python
126 lines
4.5 KiB
Python
from ... import types as sqltypes
|
|
|
|
# technically, all the dialect-specific datatypes that don't have any special
|
|
# behaviors would be private with names like _MSJson. However, we haven't been
|
|
# doing this for mysql.JSON or sqlite.JSON which both have JSON / JSONIndexType
|
|
# / JSONPathType in their json.py files, so keep consistent with that
|
|
# sub-convention for now. A future change can update them all to be
|
|
# package-private at once.
|
|
|
|
|
|
class JSON(sqltypes.JSON):
|
|
"""MSSQL JSON type.
|
|
|
|
MSSQL supports JSON-formatted data as of SQL Server 2016.
|
|
|
|
The :class:`_mssql.JSON` datatype at the DDL level will represent the
|
|
datatype as ``NVARCHAR(max)``, but provides for JSON-level comparison
|
|
functions as well as Python coercion behavior.
|
|
|
|
:class:`_mssql.JSON` is used automatically whenever the base
|
|
:class:`_types.JSON` datatype is used against a SQL Server backend.
|
|
|
|
.. seealso::
|
|
|
|
:class:`_types.JSON` - main documentation for the generic
|
|
cross-platform JSON datatype.
|
|
|
|
The :class:`_mssql.JSON` type supports persistence of JSON values
|
|
as well as the core index operations provided by :class:`_types.JSON`
|
|
datatype, by adapting the operations to render the ``JSON_VALUE``
|
|
or ``JSON_QUERY`` functions at the database level.
|
|
|
|
The SQL Server :class:`_mssql.JSON` type necessarily makes use of the
|
|
``JSON_QUERY`` and ``JSON_VALUE`` functions when querying for elements
|
|
of a JSON object. These two functions have a major restriction in that
|
|
they are **mutually exclusive** based on the type of object to be returned.
|
|
The ``JSON_QUERY`` function **only** returns a JSON dictionary or list,
|
|
but not an individual string, numeric, or boolean element; the
|
|
``JSON_VALUE`` function **only** returns an individual string, numeric,
|
|
or boolean element. **both functions either return NULL or raise
|
|
an error if they are not used against the correct expected value**.
|
|
|
|
To handle this awkward requirement, indexed access rules are as follows:
|
|
|
|
1. When extracting a sub element from a JSON that is itself a JSON
|
|
dictionary or list, the :meth:`_types.JSON.Comparator.as_json` accessor
|
|
should be used::
|
|
|
|
stmt = select(
|
|
data_table.c.data["some key"].as_json()
|
|
).where(
|
|
data_table.c.data["some key"].as_json() == {"sub": "structure"}
|
|
)
|
|
|
|
2. When extracting a sub element from a JSON that is a plain boolean,
|
|
string, integer, or float, use the appropriate method among
|
|
:meth:`_types.JSON.Comparator.as_boolean`,
|
|
:meth:`_types.JSON.Comparator.as_string`,
|
|
:meth:`_types.JSON.Comparator.as_integer`,
|
|
:meth:`_types.JSON.Comparator.as_float`::
|
|
|
|
stmt = select(
|
|
data_table.c.data["some key"].as_string()
|
|
).where(
|
|
data_table.c.data["some key"].as_string() == "some string"
|
|
)
|
|
|
|
.. versionadded:: 1.4
|
|
|
|
|
|
"""
|
|
|
|
# note there was a result processor here that was looking for "number",
|
|
# but none of the tests seem to exercise it.
|
|
|
|
|
|
# Note: these objects currently match exactly those of MySQL, however since
|
|
# these are not generalizable to all JSON implementations, remain separately
|
|
# implemented for each dialect.
|
|
class _FormatTypeMixin(object):
|
|
def _format_value(self, value):
|
|
raise NotImplementedError()
|
|
|
|
def bind_processor(self, dialect):
|
|
super_proc = self.string_bind_processor(dialect)
|
|
|
|
def process(value):
|
|
value = self._format_value(value)
|
|
if super_proc:
|
|
value = super_proc(value)
|
|
return value
|
|
|
|
return process
|
|
|
|
def literal_processor(self, dialect):
|
|
super_proc = self.string_literal_processor(dialect)
|
|
|
|
def process(value):
|
|
value = self._format_value(value)
|
|
if super_proc:
|
|
value = super_proc(value)
|
|
return value
|
|
|
|
return process
|
|
|
|
|
|
class JSONIndexType(_FormatTypeMixin, sqltypes.JSON.JSONIndexType):
|
|
def _format_value(self, value):
|
|
if isinstance(value, int):
|
|
value = "$[%s]" % value
|
|
else:
|
|
value = '$."%s"' % value
|
|
return value
|
|
|
|
|
|
class JSONPathType(_FormatTypeMixin, sqltypes.JSON.JSONPathType):
|
|
def _format_value(self, value):
|
|
return "$%s" % (
|
|
"".join(
|
|
[
|
|
"[%s]" % elem if isinstance(elem, int) else '."%s"' % elem
|
|
for elem in value
|
|
]
|
|
)
|
|
)
|