# Copyright (C) 2005-2018 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

"""

.. dialect:: oracle+cx_oracle
    :name: cx-Oracle
    :dbapi: cx_oracle
    :connectstring: oracle+cx_oracle://user:pass@host:port/dbname\
[?key=value&key=value...]
    :url: http://cx-oracle.sourceforge.net/

Additional Connect Arguments
----------------------------

When connecting with ``dbname`` present, the host, port, and dbname tokens are
converted to a TNS name using
the cx_oracle ``makedsn()`` function.  Otherwise, the host token is taken
directly as a TNS name.

Additional arguments which may be specified either as query string arguments
on the URL, or as keyword arguments to :func:`.create_engine()` are:

* ``arraysize`` - set the cx_oracle.arraysize value on cursors, defaulted
  to 50.  This setting is significant with cx_Oracle as the contents of LOB
  objects are only readable within a "live" row (e.g. within a batch of
  50 rows).

* ``auto_convert_lobs`` - defaults to True; See :ref:`cx_oracle_lob`.

* ``coerce_to_unicode`` - see :ref:`cx_oracle_unicode` for detail.

* ``coerce_to_decimal`` - see :ref:`cx_oracle_numeric` for detail.

* ``mode`` - This is given the string value of SYSDBA or SYSOPER, or
  alternatively an integer value.  This value is only available as a URL query
  string argument.

* ``threaded`` - enable multithreaded access to cx_oracle connections.
  Defaults to ``True``.  Note that this is the opposite default of the
  cx_Oracle DBAPI itself.

* ``service_name`` - An option to use connection string (DSN) with
  ``SERVICE_NAME`` instead of ``SID``. It can't be passed when a ``database``
  part is given.
  E.g. ``oracle+cx_oracle://scott:tiger@host:1521/?service_name=hr``
  is a valid url. This value is only available as a URL query string argument.

  .. versionadded:: 1.0.0

.. _cx_oracle_unicode:

Unicode
-------

The cx_Oracle DBAPI as of version 5 fully supports unicode, and has the
ability to return string results as Python unicode objects natively.

When used in Python 3, cx_Oracle returns all strings as Python unicode objects
(that is, plain ``str`` in Python 3).  In Python 2, it will return as Python
unicode those column values that are of type ``NVARCHAR`` or ``NCLOB``.  For
column values that are of type ``VARCHAR`` or other non-unicode string types,
it will return values as Python strings (e.g. bytestrings).

The cx_Oracle SQLAlchemy dialect presents several different options for the use
case of receiving ``VARCHAR`` column values as Python unicode objects under
Python 2:

* When using Core expression objects as well as the ORM, SQLAlchemy's
  unicode-decoding services are available, which are established by
  using either the :class:`.Unicode` datatype or by using the
  :class:`.String` datatype with :paramref:`.String.convert_unicode` set
  to True.

* When using raw SQL strings, typing behavior can be added for unicode
  conversion using the :func:`.text` construct::

    from sqlalchemy import text, Unicode
    result = conn.execute(
        text("select username from user").columns(username=Unicode))

* Otherwise, when using raw SQL strings sent directly to an ``.execute()``
  method without any Core typing behavior added, the flag
  ``coerce_to_unicode=True`` flag can be passed to :func:`.create_engine`
  which will add an unconditional unicode processor to cx_Oracle for all
  string values::

    engine = create_engine("oracle+cx_oracle://dsn", coerce_to_unicode=True)

  The above approach will add significant latency to result-set fetches
  of plain string values.

Sending String Values as Unicode or Non-Unicode
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

As of SQLAlchemy 1.2.2, the cx_Oracle dialect unconditionally calls
``setinputsizes()`` for bound values that are passed as Python unicode objects.
In Python 3, all string values are Unicode; for cx_Oracle, this corresponds to
``cx_Oracle.NCHAR`` being passed to ``setinputsizes()`` for that parameter.
In some edge cases, such as passing format specifiers for
the ``trunc()`` function, Oracle does not accept these as NCHAR::

    from sqlalchemy import func

    conn.execute(
        func.trunc(func.sysdate(), 'dd')
    )

In these cases, an error as follows may be raised::

    ORA-01899: bad precision specifier

When this error is encountered, it may be necessary to pass the string value
with an explicit non-unicode type::

    from sqlalchemy import func
    from sqlalchemy import literal
    from sqlalchemy import String

    conn.execute(
        func.trunc(func.sysdate(), literal('dd', String))
    )

For full control over this ``setinputsizes()`` behavior, see the section
:ref:`cx_oracle_setinputsizes`

.. _cx_oracle_setinputsizes:

Fine grained control over cx_Oracle data binding and performance with setinputsizes
-----------------------------------------------------------------------------------

The cx_Oracle DBAPI has a deep and fundamental reliance upon the usage of the
DBAPI ``setinputsizes()`` call.   The purpose of this call is to establish the
datatypes that are bound to a SQL statement for Python values being passed as
parameters.  While virtually no other DBAPI assigns any use to the
``setinputsizes()`` call, the cx_Oracle DBAPI relies upon it heavily in its
interactions with the Oracle client interface, and in some scenarios it is  not
possible for SQLAlchemy to know exactly how data should be bound, as some
settings can cause profoundly different performance characteristics, while
altering the type coercion behavior at the same time.

Users of the cx_Oracle dialect are **strongly encouraged** to read through
cx_Oracle's list of built-in datatype symbols at http://cx-oracle.readthedocs.io/en/latest/module.html#types.
Note that in some cases, signficant performance degradation can occur when using
these types vs. not, in particular when specifying ``cx_Oracle.CLOB``.

On the SQLAlchemy side, the :meth:`.DialectEvents.do_setinputsizes` event
can be used both for runtime visibliity (e.g. logging) of the setinputsizes
step as well as to fully control how ``setinputsizes()`` is used on a per-statement
basis.

.. versionadded:: 1.2.9 Added :meth:`.DialectEvents.setinputsizes`


Example 1 - logging all setinputsizes calls
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The following example illustrates how to log the intermediary values from
a SQLAlchemy perspective before they are converted to the raw ``setinputsizes()``
parameter dictionary.  The keys of the dictionary are :class:`.BindParameter`
objects which have a ``.key`` and a ``.type`` attribute::

    from sqlalchemy import create_engine, event

    engine = create_engine("oracle+cx_oracle://scott:tiger@host/xe")

    @event.listens_for(engine, "do_setinputsizes")
    def _log_setinputsizes(inputsizes, cursor, statement, parameters, context):
        for bindparam, dbapitype in inputsizes.items():
                log.info(
                    "Bound parameter name: %s  SQLAlchemy type: %r  "
                    "DBAPI object: %s",
                    bindparam.key, bindparam.type, dbapitype)

Example 2 - remove all bindings to CLOB
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The ``CLOB`` datatype in cx_Oracle incurs a significant performance overhead,
however is set by default for the ``Text`` type within the SQLAlchemy 1.2
series.   This setting can be modified as follows::

    from sqlalchemy import create_engine, event
    from cx_Oracle import CLOB

    engine = create_engine("oracle+cx_oracle://scott:tiger@host/xe")

    @event.listens_for(engine, "do_setinputsizes")
    def _remove_clob(inputsizes, cursor, statement, parameters, context):
        for bindparam, dbapitype in list(inputsizes.items()):
            if dbapitype is CLOB:
                del inputsizes[bindparam]


.. _cx_oracle_returning:

RETURNING Support
-----------------

The cx_Oracle dialect implements RETURNING using OUT parameters.
The dialect supports RETURNING fully, however cx_Oracle 6 is recommended
for complete support.

.. _cx_oracle_lob:

LOB Objects
-----------

cx_oracle returns oracle LOBs using the cx_oracle.LOB object.  SQLAlchemy
converts these to strings so that the interface of the Binary type is
consistent with that of other backends, which takes place within a cx_Oracle
outputtypehandler.

cx_Oracle prior to version 6 would require that LOB objects be read before
a new batch of rows would be read, as determined by the ``cursor.arraysize``.
As of the 6 series, this limitation has been lifted.  Nevertheless, because
SQLAlchemy pre-reads these LOBs up front, this issue is avoided in any case.

To disable the auto "read()" feature of the dialect, the flag
``auto_convert_lobs=False`` may be passed to :func:`.create_engine`.  Under
the cx_Oracle 5 series, having this flag turned off means there is the chance
of reading from a stale LOB object if not read as it is fetched.   With
cx_Oracle 6, this issue is resolved.

.. versionchanged:: 1.2  the LOB handling system has been greatly simplified
   internally to make use of outputtypehandlers, and no longer makes use
   of alternate "buffered" result set objects.

Two Phase Transactions Not Supported
-------------------------------------

Two phase transactions are **not supported** under cx_Oracle due to poor
driver support.   As of cx_Oracle 6.0b1, the interface for
two phase transactions has been changed to be more of a direct pass-through
to the underlying OCI layer with less automation.  The additional logic
to support this system is not implemented in SQLAlchemy.

.. _cx_oracle_numeric:

Precision Numerics
------------------

SQLAlchemy's numeric types can handle receiving and returning values as Python
``Decimal`` objects or float objects.  When a :class:`.Numeric` object, or a
subclass such as :class:`.Float`, :class:`.oracle.DOUBLE_PRECISION` etc. is in
use, the :paramref:`.Numeric.asdecimal` flag determines if values should be
coerced to ``Decimal`` upon return, or returned as float objects.   To make
matters more complicated under Oracle, Oracle's ``NUMBER`` type can also
represent integer values if the "scale" is zero, so the Oracle-specific
:class:`.oracle.NUMBER` type takes this into account as well.

The cx_Oracle dialect makes extensive use of connection- and cursor-level
"outputtypehandler" callables in order to coerce numeric values as requested.
These callables are specific to the specific flavor of :class:`.Numeric` in
use, as well as if no SQLAlchemy typing objects are present.   There are
observed scenarios where Oracle may sends incomplete or ambiguous information
about the numeric types being returned, such as a query where the numeric types
are buried under multiple levels of subquery.  The type handlers do their best
to make the right decision in all cases, deferring to the underlying cx_Oracle
DBAPI for all those cases where the driver can make the best decision.

When no typing objects are present, as when executing plain SQL strings, a
default "outputtypehandler" is present which will generally return numeric
values which specify precision and scale as Python ``Decimal`` objects.  To
disable this coercion to decimal for performance reasons, pass the flag
``coerce_to_decimal=False`` to :func:`.create_engine`::

    engine = create_engine("oracle+cx_oracle://dsn", coerce_to_decimal=False)

The ``coerce_to_decimal`` flag only impacts the results of plain string
SQL staements that are not otherwise associated with a :class:`.Numeric`
SQLAlchemy type (or a subclass of such).

.. versionchanged:: 1.2  The numeric handling system for cx_Oracle has been
   reworked to take advantage of newer cx_Oracle features as well
   as better integration of outputtypehandlers.

"""

from __future__ import absolute_import

from .base import OracleCompiler, OracleDialect, OracleExecutionContext
from . import base as oracle
from ...engine import result as _result
from sqlalchemy import types as sqltypes, util, exc, processors
import random
import collections
import decimal
import re
import time


class _OracleInteger(sqltypes.Integer):
    def _cx_oracle_var(self, dialect, cursor):
        cx_Oracle = dialect.dbapi
        return cursor.var(
            cx_Oracle.STRING,
            255,
            arraysize=cursor.arraysize,
            outconverter=int
        )

    def _cx_oracle_outputtypehandler(self, dialect):
        def handler(cursor, name,
                    default_type, size, precision, scale):
            return self._cx_oracle_var(dialect, cursor)
        return handler


class _OracleNumeric(sqltypes.Numeric):
    is_number = False

    def bind_processor(self, dialect):
        if self.scale == 0:
            return None
        elif self.asdecimal:
            processor = processors.to_decimal_processor_factory(
                decimal.Decimal, self._effective_decimal_return_scale)

            def process(value):
                if isinstance(value, (int, float)):
                    return processor(value)
                elif value is not None and value.is_infinite():
                    return float(value)
                else:
                    return value
            return process
        else:
            return processors.to_float

    def result_processor(self, dialect, coltype):
        return None

    def _cx_oracle_outputtypehandler(self, dialect):
        cx_Oracle = dialect.dbapi

        is_cx_oracle_6 = dialect._is_cx_oracle_6
        has_native_int = dialect._has_native_int

        def handler(cursor, name, default_type, size, precision, scale):
            outconverter = None
            if precision:
                if self.asdecimal: