database/db_utils.py

   1 TABLE_TYPE = object()
   2 VIEW_TYPE = object()
   3
   4
   5 class NameMissingException(Exception):
   6     pass
   7
   8
   9 def drop_views(manager, views):
  10     """
  11     Drops the specified views from the database
  12
  13     If a specified view does not exist in the database, this method fails
  14     without modification
  15
  16     @param manager the migration manager
  17     @param views the views to drop
  18     """
  19     check_exists(manager, views, VIEW_TYPE)
  20     for view in views:
  21         manager.execute('DROP VIEW `%s`' % view)
  22
  23
  24 def rename(manager, mapping):
  25     """
  26     Renames specified tables in the database
  27
  28     Use this to rename a specified set of tables in a database. If a source in
  29     the mapping does not exist, this method fails without modification.
  30
  31     @param manager the migration manager
  32     @param mapping a dictionary of orig_name => new_name. Any table not matching
  33                    an entry in this dictionary will not be renamed
  34     """
  35     check_exists(manager, (table for table, _ in mapping.iteritems()),
  36                   TABLE_TYPE)
  37     for orig_name, new_name in mapping.iteritems():
  38         manager.execute('RENAME TABLE `%s` TO `%s`' % (orig_name, new_name))
  39
  40
  41 def move_tables(manager, src_manager, tables):
  42     """
  43     Moves the specified tables from another database
  44
  45     If a table does not exist in the source database, this method fails without
  46     modification
  47
  48     @param manager the migration manager
  49     @param src_manager a migration manager that handles the source database
  50     @param tables a list of tables to move
  51     """
  52     check_exists(src_manager, tables, TABLE_TYPE)
  53     for table in tables:
  54         manager.execute('RENAME TABLE `%(db)s`.`%(table)s` TO `%(table)s`'
  55                         % dict(db=src_manager.get_db_name(), table=table))
  56
  57
  58 def drop_database(manager):
  59     """
  60     Drops the database that the specified manager controls
  61
  62     @param manager the migration manager
  63     """
  64     manager.execute('DROP DATABASE `%s`' % manager.get_db_name())
  65
  66
  67 def check_exists(manager, names, type):
  68     """
  69     Checks if the tables or views exists.
  70
  71     Raise an Exception if any of the names do not exist
  72
  73     @param manager the migration manager
  74     @param names the table/view names
  75     @param type one of 'TABLE' or 'VIEW'
  76     """
  77     if type == TABLE_TYPE:
  78         info_table = 'TABLES'
  79     elif type == VIEW_TYPE:
  80         info_table = 'VIEWS'
  81     else:
  82         raise Exception("type parameter must be either TABLE_TYPE or VIEW_TYPE")
  83
  84     query = ('SELECT table_name FROM information_schema.%s '
  85              'WHERE table_schema = %%s' % info_table)
  86     rows = manager.execute(query, manager.get_db_name())
  87     existing_names = [row[0] for row in rows]
  88
  89     for name in names:
  90         if name not in existing_names:
  91             raise NameMissingException(
  92                     '%s missing from database, stopping' % name)
  93
  94
  95 def check_index_exists(manager, table_name, index_name):
  96     """
  97     Checks if a particular index exists on the table
  98
  99     @param manager the migration manager
 100     @param table_name the table to check
 101     @param index_name the index to check
 102     """
 103     query = ('SELECT 1 FROM information_schema.statistics '
 104              'WHERE table_schema = %s AND table_name = %s AND index_name = %s')
 105     rows = manager.execute(query, manager.get_db_name(), table_name, index_name)
 106     return bool(rows)
 107
 108
 109 DJANGO_AUTH_TABLES = ('auth_group', 'auth_group_permissions', 'auth_permission')
 110
 111 def auth_tables_exist(manager):
 112     try:
 113         check_exists(manager, DJANGO_AUTH_TABLES, TABLE_TYPE)
 114         return True
 115     except NameMissingException:
 116         return False