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- 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
- ]
- )
- )
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