cursor.py

   1 # -*- coding: utf-8 -*-
   2 ##############################################################################
   3 #
   4 #    mojo, a Python library for implementing document based databases
   5 #    Copyright (C) 2013-2014 by Javier Sancho Fernandez <jsf at jsancho dot org>
   6 #
   7 #    This program is free software: you can redistribute it and/or modify
   8 #    it under the terms of the GNU General Public License as published by
   9 #    the Free Software Foundation, either version 3 of the License, or
  10 #    (at your option) any later version.
  11 #
  12 #    This program is distributed in the hope that it will be useful,
  13 #    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 #    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 #    GNU General Public License for more details.
  16 #
  17 #    You should have received a copy of the GNU General Public License
  18 #    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19 #
  20 ##############################################################################
  21
  22 import msgpack
  23
  24 class Cursor(object):
  25     def __init__(self, collection, spec=None, fields=None, **kwargs):
  26         if spec and not type(spec) is dict:
  27             raise Exception("spec must be an instance of dict")
  28
  29         self.Query = collection.database.connection.Query
  30         self.Field = collection.database.connection.Field
  31         self.Table = collection.database.connection.Table
  32         self.Constraint = collection.database.connection.Constraint
  33         self.Literal = collection.database.connection.Literal
  34
  35         self.collection = collection
  36         self.spec = spec
  37         if self.collection.exists():
  38             self.fields = self._get_fields(fields)
  39             self.cursor = self._get_cursor()
  40         else:
  41             self.fields = None
  42             self.cursor = None
  43
  44     def __iter__(self):
  45         return self
  46
  47     def _get_fields(self, fields):
  48         set_all_fields = set(self.collection._get_fields())
  49         if fields is None:
  50             res_fields = list(set_all_fields)
  51         elif type(fields) is dict:
  52             fields_without_id = filter(lambda x: x[0] != '_id', fields.iteritems())
  53             if fields_without_id[0][1]:
  54                 first = True
  55                 res_fields = set()
  56             else:
  57                 first = False
  58                 res_fields = set(set_all_fields)
  59             for f in fields_without_id:
  60                 if f[1] and f[0] in set_all_fields:
  61                     if first:
  62                         res_fields.add(f[0])
  63                     else:
  64                         raise Exception("You cannot currently mix including and excluding fields. Contact us if this is an issue.")
  65                 elif not f[1]:
  66                     if not first:
  67                         res_fields.discard(f[0])
  68                     else:
  69                         raise Exception("You cannot currently mix including and excluding fields. Contact us if this is an issue.")
  70             if '_id' in fields and not fields['_id']:
  71                 res_fields.discard('_id')
  72             else:
  73                 res_fields.add('_id')
  74             res_fields = list(res_fields)
  75         else:
  76             set_fields = set(list(fields))
  77             set_fields.add('_id')
  78             res_fields = list(set_all_fields.intersection(set_fields))
  79
  80         return res_fields
  81
  82     def _get_cursor(self):
  83         table_id = self.Table(self.collection.database.db_name, '%s$_id' % self.collection.table_name)
  84
  85         fields = [self.Field(table_id, 'value')]
  86         for f in filter(lambda x: x != '_id', self.fields):
  87             fields.append(self._get_cursor_field(f))
  88
  89         tables = [table_id]
  90
  91         constraints = [self.Constraint('=', self.Field(table_id, 'name'), self.Literal('_id'))]
  92         if self.spec:
  93             for k, v in self.spec.iteritems():
  94                 constraints.append(self._get_cursor_constraint(k, v))
  95
  96         query = self.Query(fields, tables, constraints)
  97         return self.collection.database.connection._get_cursor(query)
  98
  99     def _get_cursor_field(self, field_name):
 100         table_id = self.Table(self.collection.database.db_name, '%s$_id' % self.collection.table_name)
 101         table_field = self.Table(self.collection.database.db_name, '%s$%s' % (self.collection.table_name, field_name.split(".")[0]))
 102
 103         fields = [self.Field(table_field, 'value')]
 104         tables = [table_field]
 105         constraints = [
 106             self.Constraint('=', self.Field(table_field, 'id'), self.Field(table_id, 'id')),
 107             self.Constraint('=', self.Field(table_field, 'name'), self.Literal(field_name)),
 108             ]
 109         return self.Query(fields, tables, constraints)
 110
 111     def _get_cursor_constraint(self, field_name, field_value):
 112         table_id = self.Table(self.collection.database.db_name, '%s$_id' % self.collection.table_name)
 113         table_field = self.Table(self.collection.database.db_name, '%s$%s' % (self.collection.table_name, field_name.split(".")[0]))
 114
 115         if type(field_value) in (int, float):
 116             field_type = 'number'
 117         else:
 118             field_type = 'value'
 119             field_value = msgpack.dumps(field_value)
 120
 121         fields = [self.Field(table_field, 'id')]
 122         tables = [table_field]
 123         constraints = [
 124             self.Constraint('or', self.Constraint('=', self.Field(table_field, 'name'), self.Literal(field_name)),
 125                                   self.Constraint('starts', self.Field(table_field, 'name'), self.Literal('%s..' % field_name))),
 126             self.Constraint('=', self.Field(table_field, field_type), self.Literal(field_value)),
 127             ]
 128
 129         return self.Constraint('in', self.Field(table_id, 'id'), self.Query(fields, tables, constraints))
 130
 131     def next(self):
 132         if self.cursor is None:
 133             raise StopIteration
 134
 135         if self.cursor:
 136             res = self.collection.database.connection._next(self.cursor)
 137             if res is None:
 138                 raise StopIteration
 139             else:
 140                 document = {}
 141                 if '_id' in self.fields:
 142                     document['_id'] = msgpack.loads(res[0])
 143                 fields_without_id = filter(lambda x: x != '_id', self.fields)
 144                 for i in xrange(len(fields_without_id)):
 145                     if not res[i + 1] is None:
 146                         document[fields_without_id[i]] = msgpack.loads(res[i + 1])
 147                 return document
 148         else:
 149             return None