pokedex/db/load.py

   1 """CSV to database or vice versa."""
   2 import csv
   3 import pkg_resources
   4 import sys
   5
   6 from sqlalchemy.orm.attributes import instrumentation_registry
   7 import sqlalchemy.types
   8
   9 from pokedex.db import metadata
  10 import pokedex.db.tables as tables
  11
  12
  13 def _get_verbose_prints(verbose):
  14     """If `verbose` is true, returns two functions: one for printing a starting
  15     message, and the other for printing a success or failure message when
  16     finished.
  17
  18     If `verbose` is false, returns two no-op functions.
  19     """
  20
  21     if verbose:
  22         import sys
  23         def print_start(thing):
  24             # Truncate to 66 characters, leaving 10 characters for a success
  25             # or failure message
  26             truncated_thing = thing[0:66]
  27
  28             # Also, space-pad to keep the cursor in a known column
  29             num_spaces = 66 - len(truncated_thing)
  30
  31             print "%s...%s" % (truncated_thing, ' ' * num_spaces),
  32             sys.stdout.flush()
  33
  34         def print_done(msg='ok'):
  35             print msg
  36             sys.stdout.flush()
  37
  38         return print_start, print_done
  39
  40     # Not verbose; return dummies
  41     def dummy(*args, **kwargs):
  42         pass
  43
  44     return dummy, dummy
  45
  46
  47 def load(session, directory=None, drop_tables=False, verbose=False):
  48     """Load data from CSV files into the given database session.
  49
  50     Tables are created automatically.
  51
  52     `session`
  53         SQLAlchemy session to use.
  54
  55     `directory`
  56         Directory the CSV files reside in.  Defaults to the `pokedex` data
  57         directory.
  58
  59     `drop_tables`
  60         If set to True, existing `pokedex`-related tables will be dropped.
  61
  62     `verbose`
  63         If set to True, status messages will be printed to stdout.
  64     """
  65
  66     # First take care of verbosity
  67     print_start, print_done = _get_verbose_prints(verbose)
  68
  69
  70     if not directory:
  71         directory = pkg_resources.resource_filename('pokedex', 'data/csv')
  72
  73     # Drop all tables if requested
  74     if drop_tables:
  75         print_start('Dropping tables')
  76         metadata.drop_all()
  77         print_done()
  78
  79     metadata.create_all()
  80
  81     # SQLAlchemy is retarded and there is no way for me to get a list of ORM
  82     # classes besides to inspect the module they all happen to live in for
  83     # things that look right.
  84     table_base = tables.TableBase
  85     orm_classes = {}  # table object => table class
  86
  87     for name in dir(tables):
  88         # dir() returns strings!  How /convenient/.
  89         thingy = getattr(tables, name)
  90
  91         if not isinstance(thingy, type):
  92             # Not a class; bail
  93             continue
  94         elif not issubclass(thingy, table_base):
  95             # Not a declarative table; bail
  96             continue
  97         elif thingy == table_base:
  98             # Declarative table base, so not a real table; bail
  99             continue
 100
 101         # thingy is definitely a table class!  Hallelujah.
 102         orm_classes[thingy.__table__] = thingy
 103
 104     # Okay, run through the tables and actually load the data now
 105     for table_obj in metadata.sorted_tables:
 106         table_class = orm_classes[table_obj]
 107         table_name = table_obj.name
 108
 109         print_start(table_name)
 110
 111         try:
 112             csvfile = open("%s/%s.csv" % (directory, table_name), 'rb')
 113         except IOError:
 114             # File doesn't exist; don't load anything!
 115             print_done('missing?')
 116             continue
 117
 118         reader = csv.reader(csvfile, lineterminator='\n')
 119         column_names = [unicode(column) for column in reader.next()]
 120
 121         # Self-referential tables may contain rows with foreign keys of other
 122         # rows in the same table that do not yet exist.  Pull these out and add
 123         # them to the session last
 124         # ASSUMPTION: Self-referential tables have a single PK called "id"
 125         deferred_rows = []  # ( row referring to id, [foreign ids we need] )
 126         seen_ids = {}       # primary key we've seen => 1
 127
 128         # Fetch foreign key columns that point at this table, if any
 129         self_ref_columns = []
 130         for column in table_obj.c:
 131             if any(_.references(table_obj) for _ in column.foreign_keys):
 132                 self_ref_columns.append(column)
 133
 134         for csvs in reader:
 135             row = table_class()
 136
 137             for column_name, value in zip(column_names, csvs):
 138                 column = table_obj.c[column_name]
 139                 if column.nullable and value == '':
 140                     # Empty string in a nullable column really means NULL
 141                     value = None
 142                 elif isinstance(column.type, sqlalchemy.types.Boolean):
 143                     # Boolean values are stored as string values 0/1, but both
 144                     # of those evaluate as true; SQLA wants True/False
 145                     if value == '0':
 146                         value = False
 147                     else:
 148                         value = True
 149                 else:
 150                     # Otherwise, unflatten from bytes
 151                     value = value.decode('utf-8')
 152
 153                 setattr(row, column_name, value)
 154
 155             # May need to stash this row and add it later if it refers to a
 156             # later row in this table
 157             if self_ref_columns:
 158                 foreign_ids = [getattr(row, _.name) for _ in self_ref_columns]
 159                 foreign_ids = [_ for _ in foreign_ids if _]  # remove NULL ids
 160
 161                 if not foreign_ids:
 162                     # NULL key.  Remember this row and add as usual.
 163                     seen_ids[row.id] = 1
 164
 165                 elif all(_ in seen_ids for _ in foreign_ids):
 166                     # Non-NULL key we've already seen.  Remember it and commit
 167                     # so we know the old row exists when we add the new one
 168                     session.commit()
 169                     seen_ids[row.id] = 1
 170
 171                 else:
 172                     # Non-NULL future id.  Save this and insert it later!
 173                     deferred_rows.append((row, foreign_ids))
 174                     continue
 175
 176             session.add(row)
 177
 178         session.commit()
 179
 180         # Attempt to add any spare rows we've collected
 181         for row, foreign_ids in deferred_rows:
 182             if not all(_ in seen_ids for _ in foreign_ids):
 183                 # Could happen if row A refers to B which refers to C.
 184                 # This is ridiculous and doesn't happen in my data so far
 185                 raise ValueError("Too many levels of self-reference!  "
 186                                  "Row was: " + str(row.__dict__))
 187
 188             session.add(row)
 189             seen_ids[row.id] = 1
 190             session.commit()
 191
 192         print_done()
 193
 194
 195
 196 def dump(session, directory=None, verbose=False):
 197     """Dumps the contents of a database to a set of CSV files.  Probably not
 198     useful to anyone besides a developer.
 199
 200     `session`
 201         SQLAlchemy session to use.
 202
 203     `directory`
 204         Directory the CSV files should be put in.  Defaults to the `pokedex`
 205         data directory.
 206
 207     `verbose`
 208         If set to True, status messages will be printed to stdout.
 209     """
 210
 211     # First take care of verbosity
 212     print_start, print_done = _get_verbose_prints(verbose)
 213
 214
 215     if not directory:
 216         directory = pkg_resources.resource_filename('pokedex', 'data/csv')
 217
 218     for table_name in sorted(metadata.tables.keys()):
 219         print_start(table_name)
 220         table = metadata.tables[table_name]
 221
 222         writer = csv.writer(open("%s/%s.csv" % (directory, table_name), 'wb'),
 223                             lineterminator='\n')
 224         columns = [col.name for col in table.columns]
 225         writer.writerow(columns)
 226
 227         primary_key = table.primary_key
 228         for row in session.query(table).order_by(*primary_key).all():
 229             csvs = []
 230             for col in columns:
 231                 # Convert Pythony values to something more universal
 232                 val = getattr(row, col)
 233                 if val == None:
 234                     val = ''
 235                 elif val == True:
 236                     val = '1'
 237                 elif val == False:
 238                     val = '0'
 239                 else:
 240                     val = unicode(val).encode('utf-8')
 241
 242                 csvs.append(val)
 243
 244             writer.writerow(csvs)
 245
 246         print_done()