pgadmin4/web/pgadmin/utils/driver/psycopg2/cursor.py

##########################################################################
#
# pgAdmin 4 - PostgreSQL Tools
#
# Copyright (C) 2013 - 2016, The pgAdmin Development Team
# This software is released under the PostgreSQL Licence
#
##########################################################################

"""
Implementation of an extended cursor, which returns ordered dictionary when
fetching results from it, and also takes care of the duplicate column name in
result.
"""

try:
    from collections import OrderedDict
except ImportError:
    from ordereddict import OrderedDict

from psycopg2.extensions import cursor as _cursor


class _WrapperColumn(object):
    """
    class _WrapperColumn(object)

    A wrapper class, which wraps the individual description column object,
    to allow identify the duplicate column name, created by PostgreSQL database
    server implicitly during query execution.

    Methods:
    -------
    * __init__(_col, _name)
    - Initialize the wrapper around the description column object, which will
      present the dummy name when available instead of the duplicate name.

    * __getattribute__(name)
    - Get attributes from the original column description (which is a named
      tuple) except for few of the attributes of this object (i.e. orig_col,
      dummy_name, __class__, to_dict) are part of this object.

    * __getitem__(idx)
    - Get the item from the original object except for the 0th index item,
      which is for 'name'.

    * __setitem__(idx, value)
    * __delitem__(idx)
    - Override them to make the operations on original object.

    * to_dict()
    - Converts original objects data as OrderedDict (except the name will same
      as dummy name (if available), and one more parameter as 'display_name'.
    """

    def __init__(self, _col, _name):
        """Initializer for _WrapperColumn"""
        self.orig_col = _col
        self.dummy_name = _name

    def __getattribute__(self, name):
        """Getting the attributes from the original object. (except few)"""
        if (name == 'orig_col' or name == 'dummy_name' or
                name == '__class__' or name == 'to_dict'):
            return object.__getattribute__(self, name)
        elif name == 'name':
            res = object.__getattribute__(self, 'dummy_name')
            if res is not None:
                return res
        return self.orig_col.__getattribute__(name)

    def __getitem__(self, idx):
        """Overrides __getitem__ to fetch item from original object"""
        if idx == 0 and self.dummy_name is not None:
            return self.name
        return self.orig_col.__getitem__(idx)

    def __setitem__(self, *args, **kwargs):
        """Orverrides __setitem__ to do the operations on original object."""
        return self.orig_col.__setitem__(*args, **kwargs)

    def __delitem__(self, *args, **kwargs):
        """Orverrides __delitem__ to do the operations on original object."""
        return self.orig_col.__delitem__(*args, **kwargs)

    def to_dict(self):
        """
        Generates an OrderedDict from the fields of the original objects
        with avoiding the duplicate name.
        """
        ores = OrderedDict(self.orig_col._asdict())
        name = ores['name']
        if self.dummy_name:
            ores['name'] = self.dummy_name
        ores['display_name'] = name
        return ores


class DictCursor(_cursor):
    """
    DictCursor

    A class to generate the dictionary from the tuple, and also takes care of
    the duplicate column name in result description.

    Methods:
    -------
    * __init__()
    - Initialize the cursor object

    * _dict_tuple(tuple)
    - Generate a dictionary object from a tuple, based on the column
      description.

    * _ordered_description()
    - Generates the _WrapperColumn object from the description column, and
      identifies duplicate column name
    """

    def __init__(self, *args, **kwargs):
        """
        Initialize the cursor object.
        """
        self._odt_desc = None
        _cursor.__init__(self, *args, **kwargs)

    def _dict_tuple(self, tup):
        """
        Transform the tuple into a dictionary object.
        """
        if self._odt_desc is None:
            self._ordered_description()
        return dict((k[0], v) for k, v in zip(self._odt_desc, tup))

    def _ordered_description(self):
        """
        Transform the regular description to wrapper object, which handles
        duplicate column name.
        """
        self._odt_desc = _cursor.__getattribute__(self, 'description')
        desc = self._odt_desc

        if desc is None or len(desc) == 0:
            return

        res = list()
        od = dict((d[0], 0) for d in desc)
        for d in desc:
            dummy = None
            idx = od[d.name]
            if idx == 0:
                od[d.name] = 1
            else:
                name = d.name
                while name in od:
                    idx += 1
                    name = ("%s-%s" % (d.name, idx))
                    od[d.name] = idx
                dummy = name
            res.append(_WrapperColumn(d, dummy))
        self._odt_desc = tuple(res)

    def ordered_description(self):
        """
        Use this to fetch the description
        """
        if self._odt_desc is None:
            self._ordered_description()
        return self._odt_desc

    def execute(self, query, params=None):
        """
        Execute function
        """
        self._odt_desc = None
        return _cursor.execute(self, query, params)

    def executemany(self, query, params=None):
        """
        Execute many function of regular cursor.
        """
        self._odt_desc = None
        return _cursor.executemany(self, query, params)

    def callproc(self, proname, params=None):
        """
        Call a procedure by a name.
        """
        self._odt_desc = None
        return _cursor.callproc(self, proname, params)

    def fetchmany(self, size=None):
        """
        Fetch many tuples as ordered dictionary list.
        """
        tuples = _cursor.fetchmany(self, size)
        if tuples is not None:
            return [self._dict_tuple(t) for t in tuples]
        return None

    def fetchall(self):
        """
        Fetch all tuples as orderd dictionary list.
        """
        tuples = _cursor.fetchall(self)
        if tuples is not None:
            return [self._dict_tuple(t) for t in tuples]

    def __iter__(self):
        it = _cursor.__iter__(self)
        yield self._dict_tuple(next(it))
        while 1:
            yield self._dict_tuple(next(it))