##########################
Compliance to PyDB API 2.0
##########################

.. currentmodule:: firebird.driver

Full text of Python Database API 2.0 (PEP 249) is available at
`http://www.python.org/dev/peps/pep-0249/ <http://www.python.org/dev/peps/pep-0249/>`__

Unsupported Optional Features
=============================

`Cursor.nextset`

   This method is not implemented because the database engine does not support
   opening multiple result sets simultaneously with a single cursor.

Supported Optional Features
===========================

  - `Connection.Error`, `Connection.ProgrammingError`, etc.

    All exception classes defined by the DB API standard are exposed on the Connection objects
    as attributes (in addition to being available at module scope).
  - `Cursor.connection`

    This read-only attribute return a reference to the Connection object on which the cursor was created.


Nominally Supported Optional Features
=====================================

`.Cursor`

    `~.Cursor.arraysize`

        As required by the spec, the value of this attribute is observed with
        respect to the `fetchmany` method. However, changing the value of this
        attribute does not make any difference in fetch efficiency because
        the database engine only supports fetching a single row at a time.

    `~.Cursor.setinputsizes`

        Although this method is present, it does nothing, as allowed by the spec.

    `~.Cursor.setoutputsize`

        Although this method is present, it does nothing, as allowed by the spec.


Caveats
=======

Firebird-driver offers a large feature set beyond the minimal requirements
of the Python DB API. This section attempts to document only those
features that overlap with the DB API.


`.Connection`

   `~.Connection.commit(retaining=False)`
   `~.Connection.rollback(retaining=False, savepoint=None)`

      The `commit` and `rollback` methods accept an optional boolean parameter `retaining`
      (default `False`) that indicates whether the transactional context of the transaction
      being resolved should be recycled. For details, see the Advanced
      Transaction Control: Retaining Operations section of this document.
      The `rollback` method accepts an optional string parameter `savepoint`
      that causes the transaction to roll back only as far as the designated
      savepoint, rather than rolling back entirely. For details, see the
      Advanced Transaction Control: Savepoints section of this document.


`.Cursor`

   `~.Cursor.description`

      Firebird-driver makes absolutely no guarantees about `description` except those
      required by the Python Database API Specification 2.0 (that is, `description`
      is either `None` or a sequence of 7-element sequences). Therefore, client
      programmers should *not* rely on `description` being an instance of a particular
      class or type. Firebird-driver provides several named positional constants to be
      used as indices into a given element of `description` . The contents
      of all `description` elements are defined by the DB API spec; these
      constants are provided merely for convenience.

      .. sourcecode:: python

         DESCRIPTION_NAME
         DESCRIPTION_TYPE_CODE
         DESCRIPTION_DISPLAY_SIZE
         DESCRIPTION_INTERNAL_SIZE
         DESCRIPTION_PRECISION
         DESCRIPTION_SCALE
         DESCRIPTION_NULL_OK

      Here is an example of accessing the *name* of the first field in the
      `description` of cursor `cur`:

      .. sourcecode:: python

         nameOfFirstField = cur.description[0][firebird.driver.DESCRIPTION_NAME]

      For more information, see the documentation of Cursor.description in
      the `DB API Specification <Python-DB-API-2.0.html>`__.

   `~.Cursor.rowcount`

      Although `Cursor` in Firebird-driver implement this attribute,
      the database engine's own support for the determination of
      "rows affected"/"rows selected" is quirky. The database engine only
      supports the determination of rowcount for `INSERT`, `UPDATE`,
      `DELETE`, and `SELECT` statements. When stored procedures become
      involved, row count figures are usually not available to the client.
      Determining rowcount for `SELECT` statements is problematic: the
      rowcount is reported as zero until at least one row has been fetched
      from the result set, and the rowcount is misreported if the result set
      is larger than 1302 rows. The server apparently marshals result sets
      internally in batches of 1302, and will misreport the rowcount for
      result sets larger than 1302 rows until the 1303rd row is fetched,
      result sets larger than 2604 rows until the 2605th row is fetched, and
      so on, in increments of 1302. As required by the Python DB API Spec,
      the rowcount attribute "is -1 in case no executeXX() has been
      performed on the cursor or the rowcount of the last operation is not
      determinable by the interface".

      .. note::

         This attribute is just an alias for `.Cursor.affected_rows` property.