...

src/calibre/db/cache.py

@@ -7,9 +7,33 @@ __license__   = 'GPL v3'
 __copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
+from functools import wraps
+
 from calibre.db.locking import create_locks
 from calibre.db.fields import create_field
 
+def api(f):
+    f.is_cache_api = True
+    return f
+
+def read_api(f):
+    f = api(f)
+    f.is_read_api = True
+    return f
+
+def write_api(f):
+    f = api(f)
+    f.is_read_api = False
+    return f
+
+def wrap_simple(lock, func):
+    @wraps(func)
+    def ans(*args, **kwargs):
+        with lock:
+            return func(*args, **kwargs)
+    return ans
+
+
 class Cache(object):
 
     def __init__(self, backend):
@@ -17,14 +41,100 @@ class Cache(object):
         self.fields = {}
         self.read_lock, self.write_lock = create_locks()
 
+        # Implement locking for all simple read/write API methods
+        # An unlocked version of the method is stored with the name starting
+        # with a leading underscore. Use the unlocked versions when the lock
+        # has already been acquired.
+        for name in dir(self):
+            func = getattr(self, name)
+            ira = getattr(func, 'is_read_api', None)
+            if ira is not None:
+                # Save original function
+                setattr(self, '_'+name, func)
+                # Wrap it in a lock
+                lock = self.read_lock if ira else self.write_lock
+                setattr(self, name, wrap_simple(lock, func))
+
     # Cache Layer API {{{
 
+    @api
     def init(self):
+        '''
+        Initialize this cache with data from the backend.
+        '''
         with self.write_lock:
             self.backend.read_tables()
 
             for field, table in self.backend.tables.iteritems():
                 self.fields[field] = create_field(field, table)
 
+    @read_api
+    def field_for(self, name, book_id, default_value=None):
+        '''
+        Return the value of the field ``name`` for the book identified by
+        ``book_id``. If no such book exists or it has no defined value for the
+        field ``name`` or no such field exists, then ``default_value`` is returned.
+
+        The returned value for is_multiple fields are always tuples.
+        '''
+        try:
+            return self.fields[name].for_book(book_id, default_value=default_value)
+        except (KeyError, IndexError):
+            return default_value
+
+    @read_api
+    def field_ids_for(self, name, book_id):
+        '''
+        Return the ids (as a tuple) for the values that the field ``name`` has on the book
+        identified by ``book_id``. If there are no values, or no such book, or
+        no such field, an empty tuple is returned.
+        '''
+        try:
+            return self.fields[name].ids_for_book(book_id)
+        except (KeyError, IndexError):
+            return ()
+
+    @read_api
+    def books_for_field(self, name, item_id):
+        '''
+        Return all the books associated with the item identified by
+        ``item_id``, where the item belongs to the field ``name``.
+
+        Returned value is a tuple of book ids, or the empty tuple if the item
+        or the field does not exist.
+        '''
+        try:
+            return self.fields[name].books_for(item_id)
+        except (KeyError, IndexError):
+            return ()
+
+    @read_api
+    def all_book_ids(self):
+        '''
+        Frozen set of all known book ids.
+        '''
+        return frozenset(self.fields['uuid'].iter_book_ids())
+
+    @read_api
+    def all_field_ids(self, name):
+        '''
+        Frozen set of ids for all values in the field ``name``.
+        '''
+        return frozenset(iter(self.fields[name]))
+
     # }}}
 
+# Testing {{{
+
+def test(library_path):
+    from calibre.db.backend import DB
+    backend = DB(library_path)
+    cache = Cache(backend)
+    cache.init()
+    print ('All book ids:', cache.all_book_ids())
+
+if __name__ == '__main__':
+    from calibre.utils.config import prefs
+    test(prefs['library_path'])
+
+# }}}

src/calibre/db/fields.py

@@ -63,6 +63,9 @@ class OneToOneField(Field):
     def __iter__(self):
         return self.table.book_col_map.iterkeys()
 
+    def iter_book_ids(self):
+        return self.table.book_col_map.iterkeys()
+
 class ManyToOneField(Field):
 
     def for_book(self, book_id, default_value=None):

src/calibre/db/tables.py

@@ -110,8 +110,8 @@ class ManyToOneTable(Table):
             self.col_book_map[row[1]].append(row[0])
             self.book_col_map[row[0]] = row[1]
 
-        for key, val in self.col_book_map:
+        for key in tuple(self.col_book_map.iterkeys()):
-            self.col_book_map[key] = tuple(val)
+            self.col_book_map[key] = tuple(self.col_book_map[key])
 
 class ManyToManyTable(ManyToOneTable):
 
@@ -134,20 +134,21 @@ class ManyToManyTable(ManyToOneTable):
                 self.book_col_map[row[0]] = []
             self.book_col_map[row[0]].append(row[1])
 
-        for key, val in self.col_book_map:
+        for key in tuple(self.col_book_map.iterkeys()):
-            self.col_book_map[key] = tuple(val)
+            self.col_book_map[key] = tuple(self.col_book_map[key])
 
-        for key, val in self.book_col_map:
+        for key in tuple(self.book_col_map.iterkeys()):
-            self.book_col_map[key] = tuple(val)
+            self.book_col_map[key] = tuple(self.book_col_map[key])
 
 class AuthorsTable(ManyToManyTable):
 
     def read_id_maps(self, db):
         self.alink_map = {}
+        self.sort_map  = {}
         for row in db.conn.execute(
                 'SELECT id, name, sort, link FROM authors'):
             self.id_map[row[0]] = row[1]
-            self.extra_map[row[0]] = (row[2] if row[2] else
+            self.sort_map[row[0]] = (row[2] if row[2] else
                     author_to_author_sort(row[1]))
             self.alink_map[row[0]] = row[3]
 
@@ -166,11 +167,11 @@ class FormatsTable(ManyToManyTable):
                     self.book_col_map[row[0]] = []
                 self.book_col_map[row[0]].append((row[1], row[2]))
 
-        for key, val in self.col_book_map:
+        for key in tuple(self.col_book_map.iterkeys()):
-            self.col_book_map[key] = tuple(val)
+            self.col_book_map[key] = tuple(self.col_book_map[key])
 
-        for key, val in self.book_col_map:
+        for key in tuple(self.book_col_map.iterkeys()):
-            self.book_col_map[key] = tuple(val)
+            self.book_col_map[key] = tuple(self.book_col_map[key])
 
 class IdentifiersTable(ManyToManyTable):
 
@@ -187,9 +188,9 @@ class IdentifiersTable(ManyToManyTable):
                     self.book_col_map[row[0]] = []
                 self.book_col_map[row[0]].append((row[1], row[2]))
 
-        for key, val in self.col_book_map:
+        for key in tuple(self.col_book_map.iterkeys()):
-            self.col_book_map[key] = tuple(val)
+            self.col_book_map[key] = tuple(self.col_book_map[key])
 
-        for key, val in self.book_col_map:
+        for key in tuple(self.book_col_map.iterkeys()):
-            self.book_col_map[key] = tuple(val)
+            self.book_col_map[key] = tuple(self.book_col_map[key])