code.grnet.gr Git - pithos/blob - pithos/backends/lib_alchemy/xfeatures.py

   1 # Copyright 2011 GRNET S.A. All rights reserved.
   2 #
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   8 #      copyright notice, this list of conditions and the following
   9 #      disclaimer.
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  12 #      copyright notice, this list of conditions and the following
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  15 #
  16 # THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
  17 # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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  32 # or implied, of GRNET S.A.
  33
  34 from collections import defaultdict
  35 from sqlalchemy import Table, Column, String, Integer, MetaData, ForeignKey
  36 from sqlalchemy.sql import select, and_
  37 from sqlalchemy.schema import Index
  38 from sqlalchemy.sql.expression import desc
  39
  40 from dbworker import DBWorker
  41
  42
  43 class XFeatures(DBWorker):
  44     """XFeatures are path properties that allow non-nested
  45        inheritance patterns. Currently used for storing permissions.
  46     """
  47
  48     def __init__(self, **params):
  49         DBWorker.__init__(self, **params)
  50         metadata = MetaData()
  51         columns=[]
  52         columns.append(Column('feature_id', Integer, primary_key=True))
  53         columns.append(Column('path', String(2048)))
  54         self.xfeatures = Table('xfeatures', metadata, *columns)
  55         # place an index on path
  56         Index('idx_features_path', self.xfeatures.c.path)
  57
  58         columns=[]
  59         columns.append(Column('feature_id', Integer,
  60                               ForeignKey('xfeatures.feature_id',
  61                                          ondelete='CASCADE'),
  62                               primary_key=True))
  63         columns.append(Column('key', Integer, autoincrement=False,
  64                               primary_key=True))
  65         columns.append(Column('value', String(255), primary_key=True))
  66         self.xfeaturevals = Table('xfeaturevals', metadata, *columns)
  67
  68         metadata.create_all(self.engine)
  69         metadata.bind = self.engine
  70
  71     def xfeature_inherit(self, path):
  72         """Return the (path, feature) inherited by the path, or None."""
  73
  74         s = select([self.xfeatures.c.path, self.xfeatures.c.feature_id])
  75         s = s.where(self.xfeatures.c.path <= path)
  76         s = s.order_by(desc(self.xfeatures.c.path)).limit(1)
  77         r = self.conn.execute(s)
  78         row = r.fetchone()
  79         r.close()
  80         if row and path.startswith(row[0]):
  81             return row
  82         else:
  83             return None
  84
  85     def xfeature_list(self, path):
  86         """Return the list of the (prefix, feature) pairs matching path.
  87            A prefix matches path if either the prefix includes the path,
  88            or the path includes the prefix.
  89         """
  90
  91         inherited = self.xfeature_inherit(path)
  92         if inherited:
  93             return [inherited]
  94
  95         s = select([self.xfeatures.c.path, self.xfeatures.c.feature_id])
  96         s = s.where(and_(self.xfeatures.c.path.like(path + '%'),
  97                      self.xfeatures.c.path != path))
  98         s = s.order_by(self.xfeatures.c.path)
  99         r = self.conn.execute(s)
 100         l = r.fetchall()
 101         r.close()
 102         return l
 103
 104     def xfeature_create(self, path):
 105         """Create and return a feature for path.
 106            If the path already inherits a feature or
 107            bestows to paths already inheriting a feature,
 108            create no feature and return None.
 109            If the path has a feature, return it.
 110         """
 111
 112         prefixes = self.xfeature_list(path)
 113         pl = len(prefixes)
 114         if (pl > 1) or (pl == 1 and prefixes[0][0] != path):
 115             return None
 116         if pl == 1 and prefixes[0][0] == path:
 117             return prefixes[0][1]
 118         s = self.xfeatures.insert()
 119         r = self.conn.execute(s, path=path)
 120         inserted_primary_key = r.inserted_primary_key[0]
 121         r.close()
 122         return inserted_primary_key
 123
 124     def xfeature_destroy(self, path):
 125         """Destroy a feature and all its key, value pairs."""
 126
 127         s = self.xfeatures.delete().where(self.xfeatures.c.path == path)
 128         r = self.conn.execute(s)
 129         r.close()
 130
 131     def feature_dict(self, feature):
 132         """Return a dict mapping keys to list of values for feature."""
 133
 134         s = select([self.xfeaturevals.c.key, self.xfeaturevals.c.value])
 135         s = s.where(self.xfeaturevals.c.feature_id == feature)
 136         r = self.conn.execute(s)
 137         d = defaultdict(list)
 138         for key, value in r.fetchall():
 139             d[key].append(value)
 140         r.close()
 141         return d
 142
 143     def feature_set(self, feature, key, value):
 144         """Associate a key, value pair with a feature."""
 145
 146         s = self.xfeaturevals.insert()
 147         r = self.conn.execute(s, feature_id=feature, key=key, value=value)
 148         r.close()
 149
 150     def feature_setmany(self, feature, key, values):
 151         """Associate the given key, and values with a feature."""
 152
 153         s = self.xfeaturevals.insert()
 154         values = [{'feature_id':feature, 'key':key, 'value':v} for v in values]
 155         r = self.conn.execute(s, values)
 156         r.close()
 157
 158     def feature_unset(self, feature, key, value):
 159         """Disassociate a key, value pair from a feature."""
 160
 161         s = self.xfeaturevals.delete()
 162         s = s.where(and_(self.xfeaturevals.c.feature_id == feature,
 163                      self.xfeaturevals.c.key == key,
 164                      self.xfeaturevals.c.value == value))
 165         r = self.conn.execute(s)
 166         r.close()
 167
 168     def feature_unsetmany(self, feature, key, values):
 169         """Disassociate the key for the values given, from a feature."""
 170
 171         for v in values:
 172             conditional = and_(self.xfeaturevals.c.feature_id == feature,
 173                                self.xfeaturevals.c.key == key,
 174                                self.xfeaturevals.c.value == v)
 175             s = self.xfeaturevals.delete().where(conditional)
 176             r = self.conn.execute(s)
 177             r.close()
 178
 179     def feature_get(self, feature, key):
 180         """Return the list of values for a key of a feature."""
 181
 182         s = select([self.xfeaturevals.c.value])
 183         s = s.where(and_(self.xfeaturevals.c.feature_id == feature,
 184                      self.xfeaturevals.c.key == key))
 185         r = self.conn.execute(s)
 186         l = [row[0] for row in r.fetchall()]
 187         r.close()
 188         return l
 189
 190     def feature_clear(self, feature, key):
 191         """Delete all key, value pairs for a key of a feature."""
 192
 193         s = self.xfeaturevals.delete()
 194         s = s.where(and_(self.xfeaturevals.c.feature_id == feature,
 195                      self.xfeaturevals.c.key == key))
 196         r = self.conn.execute(s)
 197         r.close()