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     connection = session.connection()
  81
  82     # Okay, run through the tables and actually load the data now
  83     for table_obj in metadata.sorted_tables:
  84         table_name = table_obj.name
  85         insert_stmt = table_obj.insert()
  86
  87         print_start(table_name)
  88
  89         try:
  90             csvfile = open("%s/%s.csv" % (directory, table_name), 'rb')
  91         except IOError:
  92             # File doesn't exist; don't load anything!
  93             print_done('missing?')
  94             continue
  95
  96         reader = csv.reader(csvfile, lineterminator='\n')
  97         column_names = [unicode(column) for column in reader.next()]
  98
  99         # Self-referential tables may contain rows with foreign keys of other
 100         # rows in the same table that do not yet exist.  Pull these out and add
 101         # them to the session last
 102         # ASSUMPTION: Self-referential tables have a single PK called "id"
 103         deferred_rows = []  # ( row referring to id, [foreign ids we need] )
 104         seen_ids = {}       # primary key we've seen => 1
 105
 106         # Fetch foreign key columns that point at this table, if any
 107         self_ref_columns = []
 108         for column in table_obj.c:
 109             if any(_.references(table_obj) for _ in column.foreign_keys):
 110                 self_ref_columns.append(column)
 111
 112         new_rows = []
 113         def insert_and_commit():
 114             session.connection().execute(insert_stmt, new_rows)
 115             session.commit()
 116             new_rows[:] = []
 117
 118         for csvs in reader:
 119             row_data = {}
 120
 121             for column_name, value in zip(column_names, csvs):
 122                 column = table_obj.c[column_name]
 123                 if column.nullable and value == '':
 124                     # Empty string in a nullable column really means NULL
 125                     value = None
 126                 elif isinstance(column.type, sqlalchemy.types.Boolean):
 127                     # Boolean values are stored as string values 0/1, but both
 128                     # of those evaluate as true; SQLA wants True/False
 129                     if value == '0':
 130                         value = False
 131                     else:
 132                         value = True
 133                 else:
 134                     # Otherwise, unflatten from bytes
 135                     value = value.decode('utf-8')
 136
 137                 # nb: Dictionaries flattened with ** have to have string keys
 138                 row_data[ str(column_name) ] = value
 139
 140             # May need to stash this row and add it later if it refers to a
 141             # later row in this table
 142             if self_ref_columns:
 143                 foreign_ids = [row_data[_.name] for _ in self_ref_columns]
 144                 foreign_ids = [_ for _ in foreign_ids if _]  # remove NULL ids
 145
 146                 if not foreign_ids:
 147                     # NULL key.  Remember this row and add as usual.
 148                     seen_ids[row_data['id']] = 1
 149
 150                 elif all(_ in seen_ids for _ in foreign_ids):
 151                     # Non-NULL key we've already seen.  Remember it and commit
 152                     # so we know the old row exists when we add the new one
 153                     insert_and_commit()
 154                     seen_ids[row_data['id']] = 1
 155
 156                 else:
 157                     # Non-NULL future id.  Save this and insert it later!
 158                     deferred_rows.append((row_data, foreign_ids))
 159                     continue
 160
 161             # Insert row!
 162             new_rows.append(row_data)
 163
 164             # Remembering some zillion rows in the session consumes a lot of
 165             # RAM.  Let's not do that.  Commit every 1000 rows
 166             if len(new_rows) > 1000:
 167                 insert_and_commit()
 168
 169         insert_and_commit()
 170
 171         # Attempt to add any spare rows we've collected
 172         for row_data, foreign_ids in deferred_rows:
 173             if not all(_ in seen_ids for _ in foreign_ids):
 174                 # Could happen if row A refers to B which refers to C.
 175                 # This is ridiculous and doesn't happen in my data so far
 176                 raise ValueError("Too many levels of self-reference!  "
 177                                  "Row was: " + str(row))
 178
 179             session.connection().execute(
 180                 insert_stmt.values(**row_data)
 181             )
 182             seen_ids[row_data['id']] = 1
 183         session.commit()
 184
 185         print_done()
 186
 187
 188
 189 def dump(session, directory=None, verbose=False):
 190     """Dumps the contents of a database to a set of CSV files.  Probably not
 191     useful to anyone besides a developer.
 192
 193     `session`
 194         SQLAlchemy session to use.
 195
 196     `directory`
 197         Directory the CSV files should be put in.  Defaults to the `pokedex`
 198         data directory.
 199
 200     `verbose`
 201         If set to True, status messages will be printed to stdout.
 202     """
 203
 204     # First take care of verbosity
 205     print_start, print_done = _get_verbose_prints(verbose)
 206
 207
 208     if not directory:
 209         directory = pkg_resources.resource_filename('pokedex', 'data/csv')
 210
 211     for table_name in sorted(metadata.tables.keys()):
 212         print_start(table_name)
 213         table = metadata.tables[table_name]
 214
 215         writer = csv.writer(open("%s/%s.csv" % (directory, table_name), 'wb'),
 216                             lineterminator='\n')
 217         columns = [col.name for col in table.columns]
 218         writer.writerow(columns)
 219
 220         primary_key = table.primary_key
 221         for row in session.query(table).order_by(*primary_key).all():
 222             csvs = []
 223             for col in columns:
 224                 # Convert Pythony values to something more universal
 225                 val = getattr(row, col)
 226                 if val == None:
 227                     val = ''
 228                 elif val == True:
 229                     val = '1'
 230                 elif val == False:
 231                     val = '0'
 232                 else:
 233                     val = unicode(val).encode('utf-8')
 234
 235                 csvs.append(val)
 236
 237             writer.writerow(csvs)
 238
 239         print_done()