ndk/prebuilt/linux-x86_64/lib/python2.7/bsddb/dbtables.py

   1 #-----------------------------------------------------------------------
   2 #
   3 # Copyright (C) 2000, 2001 by Autonomous Zone Industries
   4 # Copyright (C) 2002 Gregory P. Smith
   5 #
   6 # License:      This is free software.  You may use this software for any
   7 #               purpose including modification/redistribution, so long as
   8 #               this header remains intact and that you do not claim any
   9 #               rights of ownership or authorship of this software.  This
  10 #               software has been tested, but no warranty is expressed or
  11 #               implied.
  12 #
  13 #   --  Gregory P. Smith <greg@krypto.org>
  14
  15 # This provides a simple database table interface built on top of
  16 # the Python Berkeley DB 3 interface.
  17 #
  18 _cvsid = '$Id$'
  19
  20 import re
  21 import sys
  22 import copy
  23 import random
  24 import struct
  25
  26
  27 if sys.version_info[0] >= 3 :
  28     import pickle
  29 else :
  30     if sys.version_info < (2, 6) :
  31         import cPickle as pickle
  32     else :
  33         # When we drop support for python 2.4
  34         # we could use: (in 2.5 we need a __future__ statement)
  35         #
  36         #    with warnings.catch_warnings():
  37         #        warnings.filterwarnings(...)
  38         #        ...
  39         #
  40         # We can not use "with" as is, because it would be invalid syntax
  41         # in python 2.4 and (with no __future__) 2.5.
  42         # Here we simulate "with" following PEP 343 :
  43         import warnings
  44         w = warnings.catch_warnings()
  45         w.__enter__()
  46         try :
  47             warnings.filterwarnings('ignore',
  48                 message='the cPickle module has been removed in Python 3.0',
  49                 category=DeprecationWarning)
  50             import cPickle as pickle
  51         finally :
  52             w.__exit__()
  53         del w
  54
  55 try:
  56     # For Pythons w/distutils pybsddb
  57     from bsddb3 import db
  58 except ImportError:
  59     # For Python 2.3
  60     from bsddb import db
  61
  62 class TableDBError(StandardError):
  63     pass
  64 class TableAlreadyExists(TableDBError):
  65     pass
  66
  67
  68 class Cond:
  69     """This condition matches everything"""
  70     def __call__(self, s):
  71         return 1
  72
  73 class ExactCond(Cond):
  74     """Acts as an exact match condition function"""
  75     def __init__(self, strtomatch):
  76         self.strtomatch = strtomatch
  77     def __call__(self, s):
  78         return s == self.strtomatch
  79
  80 class PrefixCond(Cond):
  81     """Acts as a condition function for matching a string prefix"""
  82     def __init__(self, prefix):
  83         self.prefix = prefix
  84     def __call__(self, s):
  85         return s[:len(self.prefix)] == self.prefix
  86
  87 class PostfixCond(Cond):
  88     """Acts as a condition function for matching a string postfix"""
  89     def __init__(self, postfix):
  90         self.postfix = postfix
  91     def __call__(self, s):
  92         return s[-len(self.postfix):] == self.postfix
  93
  94 class LikeCond(Cond):
  95     """
  96     Acts as a function that will match using an SQL 'LIKE' style
  97     string.  Case insensitive and % signs are wild cards.
  98     This isn't perfect but it should work for the simple common cases.
  99     """
 100     def __init__(self, likestr, re_flags=re.IGNORECASE):
 101         # escape python re characters
 102         chars_to_escape = '.*+()[]?'
 103         for char in chars_to_escape :
 104             likestr = likestr.replace(char, '\\'+char)
 105         # convert %s to wildcards
 106         self.likestr = likestr.replace('%', '.*')
 107         self.re = re.compile('^'+self.likestr+'$', re_flags)
 108     def __call__(self, s):
 109         return self.re.match(s)
 110
 111 #
 112 # keys used to store database metadata
 113 #
 114 _table_names_key = '__TABLE_NAMES__'  # list of the tables in this db
 115 _columns = '._COLUMNS__'  # table_name+this key contains a list of columns
 116
 117 def _columns_key(table):
 118     return table + _columns
 119
 120 #
 121 # these keys are found within table sub databases
 122 #
 123 _data =  '._DATA_.'  # this+column+this+rowid key contains table data
 124 _rowid = '._ROWID_.' # this+rowid+this key contains a unique entry for each
 125                      # row in the table.  (no data is stored)
 126 _rowid_str_len = 8   # length in bytes of the unique rowid strings
 127
 128
 129 def _data_key(table, col, rowid):
 130     return table + _data + col + _data + rowid
 131
 132 def _search_col_data_key(table, col):
 133     return table + _data + col + _data
 134
 135 def _search_all_data_key(table):
 136     return table + _data
 137
 138 def _rowid_key(table, rowid):
 139     return table + _rowid + rowid + _rowid
 140
 141 def _search_rowid_key(table):
 142     return table + _rowid
 143
 144 def contains_metastrings(s) :
 145     """Verify that the given string does not contain any
 146     metadata strings that might interfere with dbtables database operation.
 147     """
 148     if (s.find(_table_names_key) >= 0 or
 149         s.find(_columns) >= 0 or
 150         s.find(_data) >= 0 or
 151         s.find(_rowid) >= 0):
 152         # Then
 153         return 1
 154     else:
 155         return 0
 156
 157
 158 class bsdTableDB :
 159     def __init__(self, filename, dbhome, create=0, truncate=0, mode=0600,
 160                  recover=0, dbflags=0):
 161         """bsdTableDB(filename, dbhome, create=0, truncate=0, mode=0600)
 162
 163         Open database name in the dbhome Berkeley DB directory.
 164         Use keyword arguments when calling this constructor.
 165         """
 166         self.db = None
 167         myflags = db.DB_THREAD
 168         if create:
 169             myflags |= db.DB_CREATE
 170         flagsforenv = (db.DB_INIT_MPOOL | db.DB_INIT_LOCK | db.DB_INIT_LOG |
 171                        db.DB_INIT_TXN | dbflags)
 172         # DB_AUTO_COMMIT isn't a valid flag for env.open()
 173         try:
 174             dbflags |= db.DB_AUTO_COMMIT
 175         except AttributeError:
 176             pass
 177         if recover:
 178             flagsforenv = flagsforenv | db.DB_RECOVER
 179         self.env = db.DBEnv()
 180         # enable auto deadlock avoidance
 181         self.env.set_lk_detect(db.DB_LOCK_DEFAULT)
 182         self.env.open(dbhome, myflags | flagsforenv)
 183         if truncate:
 184             myflags |= db.DB_TRUNCATE
 185         self.db = db.DB(self.env)
 186         # this code relies on DBCursor.set* methods to raise exceptions
 187         # rather than returning None
 188         self.db.set_get_returns_none(1)
 189         # allow duplicate entries [warning: be careful w/ metadata]
 190         self.db.set_flags(db.DB_DUP)
 191         self.db.open(filename, db.DB_BTREE, dbflags | myflags, mode)
 192         self.dbfilename = filename
 193
 194         if sys.version_info[0] >= 3 :
 195             class cursor_py3k(object) :
 196                 def __init__(self, dbcursor) :
 197                     self._dbcursor = dbcursor
 198
 199                 def close(self) :
 200                     return self._dbcursor.close()
 201
 202                 def set_range(self, search) :
 203                     v = self._dbcursor.set_range(bytes(search, "iso8859-1"))
 204                     if v is not None :
 205                         v = (v[0].decode("iso8859-1"),
 206                                 v[1].decode("iso8859-1"))
 207                     return v
 208
 209                 def __next__(self) :
 210                     v = getattr(self._dbcursor, "next")()
 211                     if v is not None :
 212                         v = (v[0].decode("iso8859-1"),
 213                                 v[1].decode("iso8859-1"))
 214                     return v
 215
 216             class db_py3k(object) :
 217                 def __init__(self, db) :
 218                     self._db = db
 219
 220                 def cursor(self, txn=None) :
 221                     return cursor_py3k(self._db.cursor(txn=txn))
 222
 223                 def has_key(self, key, txn=None) :
 224                     return getattr(self._db,"has_key")(bytes(key, "iso8859-1"),
 225                             txn=txn)
 226
 227                 def put(self, key, value, flags=0, txn=None) :
 228                     key = bytes(key, "iso8859-1")
 229                     if value is not None :
 230                         value = bytes(value, "iso8859-1")
 231                     return self._db.put(key, value, flags=flags, txn=txn)
 232
 233                 def put_bytes(self, key, value, txn=None) :
 234                     key = bytes(key, "iso8859-1")
 235                     return self._db.put(key, value, txn=txn)
 236
 237                 def get(self, key, txn=None, flags=0) :
 238                     key = bytes(key, "iso8859-1")
 239                     v = self._db.get(key, txn=txn, flags=flags)
 240                     if v is not None :
 241                         v = v.decode("iso8859-1")
 242                     return v
 243
 244                 def get_bytes(self, key, txn=None, flags=0) :
 245                     key = bytes(key, "iso8859-1")
 246                     return self._db.get(key, txn=txn, flags=flags)
 247
 248                 def delete(self, key, txn=None) :
 249                     key = bytes(key, "iso8859-1")
 250                     return self._db.delete(key, txn=txn)
 251
 252                 def close (self) :
 253                     return self._db.close()
 254
 255             self.db = db_py3k(self.db)
 256         else :  # Python 2.x
 257             pass
 258
 259         # Initialize the table names list if this is a new database
 260         txn = self.env.txn_begin()
 261         try:
 262             if not getattr(self.db, "has_key")(_table_names_key, txn):
 263                 getattr(self.db, "put_bytes", self.db.put) \
 264                         (_table_names_key, pickle.dumps([], 1), txn=txn)
 265         # Yes, bare except
 266         except:
 267             txn.abort()
 268             raise
 269         else:
 270             txn.commit()
 271         # TODO verify more of the database's metadata?
 272         self.__tablecolumns = {}
 273
 274     def __del__(self):
 275         self.close()
 276
 277     def close(self):
 278         if self.db is not None:
 279             self.db.close()
 280             self.db = None
 281         if self.env is not None:
 282             self.env.close()
 283             self.env = None
 284
 285     def checkpoint(self, mins=0):
 286         self.env.txn_checkpoint(mins)
 287
 288     def sync(self):
 289         self.db.sync()
 290
 291     def _db_print(self) :
 292         """Print the database to stdout for debugging"""
 293         print "******** Printing raw database for debugging ********"
 294         cur = self.db.cursor()
 295         try:
 296             key, data = cur.first()
 297             while 1:
 298                 print repr({key: data})
 299                 next = cur.next()
 300                 if next:
 301                     key, data = next
 302                 else:
 303                     cur.close()
 304                     return
 305         except db.DBNotFoundError:
 306             cur.close()
 307
 308
 309     def CreateTable(self, table, columns):
 310         """CreateTable(table, columns) - Create a new table in the database.
 311
 312         raises TableDBError if it already exists or for other DB errors.
 313         """
 314         assert isinstance(columns, list)
 315
 316         txn = None
 317         try:
 318             # checking sanity of the table and column names here on
 319             # table creation will prevent problems elsewhere.
 320             if contains_metastrings(table):
 321                 raise ValueError(
 322                     "bad table name: contains reserved metastrings")
 323             for column in columns :
 324                 if contains_metastrings(column):
 325                     raise ValueError(
 326                         "bad column name: contains reserved metastrings")
 327
 328             columnlist_key = _columns_key(table)
 329             if getattr(self.db, "has_key")(columnlist_key):
 330                 raise TableAlreadyExists, "table already exists"
 331
 332             txn = self.env.txn_begin()
 333             # store the table's column info
 334             getattr(self.db, "put_bytes", self.db.put)(columnlist_key,
 335                     pickle.dumps(columns, 1), txn=txn)
 336
 337             # add the table name to the tablelist
 338             tablelist = pickle.loads(getattr(self.db, "get_bytes",
 339                 self.db.get) (_table_names_key, txn=txn, flags=db.DB_RMW))
 340             tablelist.append(table)
 341             # delete 1st, in case we opened with DB_DUP
 342             self.db.delete(_table_names_key, txn=txn)
 343             getattr(self.db, "put_bytes", self.db.put)(_table_names_key,
 344                     pickle.dumps(tablelist, 1), txn=txn)
 345
 346             txn.commit()
 347             txn = None
 348         except db.DBError, dberror:
 349             if txn:
 350                 txn.abort()
 351             if sys.version_info < (2, 6) :
 352                 raise TableDBError, dberror[1]
 353             else :
 354                 raise TableDBError, dberror.args[1]
 355
 356
 357     def ListTableColumns(self, table):
 358         """Return a list of columns in the given table.
 359         [] if the table doesn't exist.
 360         """
 361         assert isinstance(table, str)
 362         if contains_metastrings(table):
 363             raise ValueError, "bad table name: contains reserved metastrings"
 364
 365         columnlist_key = _columns_key(table)
 366         if not getattr(self.db, "has_key")(columnlist_key):
 367             return []
 368         pickledcolumnlist = getattr(self.db, "get_bytes",
 369                 self.db.get)(columnlist_key)
 370         if pickledcolumnlist:
 371             return pickle.loads(pickledcolumnlist)
 372         else:
 373             return []
 374
 375     def ListTables(self):
 376         """Return a list of tables in this database."""
 377         pickledtablelist = self.db.get_get(_table_names_key)
 378         if pickledtablelist:
 379             return pickle.loads(pickledtablelist)
 380         else:
 381             return []
 382
 383     def CreateOrExtendTable(self, table, columns):
 384         """CreateOrExtendTable(table, columns)
 385
 386         Create a new table in the database.
 387
 388         If a table of this name already exists, extend it to have any
 389         additional columns present in the given list as well as
 390         all of its current columns.
 391         """
 392         assert isinstance(columns, list)
 393
 394         try:
 395             self.CreateTable(table, columns)
 396         except TableAlreadyExists:
 397             # the table already existed, add any new columns
 398             txn = None
 399             try:
 400                 columnlist_key = _columns_key(table)
 401                 txn = self.env.txn_begin()
 402
 403                 # load the current column list
 404                 oldcolumnlist = pickle.loads(
 405                     getattr(self.db, "get_bytes",
 406                         self.db.get)(columnlist_key, txn=txn, flags=db.DB_RMW))
 407                 # create a hash table for fast lookups of column names in the
 408                 # loop below
 409                 oldcolumnhash = {}
 410                 for c in oldcolumnlist:
 411                     oldcolumnhash[c] = c
 412
 413                 # create a new column list containing both the old and new
 414                 # column names
 415                 newcolumnlist = copy.copy(oldcolumnlist)
 416                 for c in columns:
 417                     if not c in oldcolumnhash:
 418                         newcolumnlist.append(c)
 419
 420                 # store the table's new extended column list
 421                 if newcolumnlist != oldcolumnlist :
 422                     # delete the old one first since we opened with DB_DUP
 423                     self.db.delete(columnlist_key, txn=txn)
 424                     getattr(self.db, "put_bytes", self.db.put)(columnlist_key,
 425                                 pickle.dumps(newcolumnlist, 1),
 426                                 txn=txn)
 427
 428                 txn.commit()
 429                 txn = None
 430
 431                 self.__load_column_info(table)
 432             except db.DBError, dberror:
 433                 if txn:
 434                     txn.abort()
 435                 if sys.version_info < (2, 6) :
 436                     raise TableDBError, dberror[1]
 437                 else :
 438                     raise TableDBError, dberror.args[1]
 439
 440
 441     def __load_column_info(self, table) :
 442         """initialize the self.__tablecolumns dict"""
 443         # check the column names
 444         try:
 445             tcolpickles = getattr(self.db, "get_bytes",
 446                     self.db.get)(_columns_key(table))
 447         except db.DBNotFoundError:
 448             raise TableDBError, "unknown table: %r" % (table,)
 449         if not tcolpickles:
 450             raise TableDBError, "unknown table: %r" % (table,)
 451         self.__tablecolumns[table] = pickle.loads(tcolpickles)
 452
 453     def __new_rowid(self, table, txn) :
 454         """Create a new unique row identifier"""
 455         unique = 0
 456         while not unique:
 457             # Generate a random 64-bit row ID string
 458             # (note: might have <64 bits of true randomness
 459             # but it's plenty for our database id needs!)
 460             blist = []
 461             for x in xrange(_rowid_str_len):
 462                 blist.append(random.randint(0,255))
 463             newid = struct.pack('B'*_rowid_str_len, *blist)
 464
 465             if sys.version_info[0] >= 3 :
 466                 newid = newid.decode("iso8859-1")  # 8 bits
 467
 468             # Guarantee uniqueness by adding this key to the database
 469             try:
 470                 self.db.put(_rowid_key(table, newid), None, txn=txn,
 471                             flags=db.DB_NOOVERWRITE)
 472             except db.DBKeyExistError:
 473                 pass
 474             else:
 475                 unique = 1
 476
 477         return newid
 478
 479
 480     def Insert(self, table, rowdict) :
 481         """Insert(table, datadict) - Insert a new row into the table
 482         using the keys+values from rowdict as the column values.
 483         """
 484
 485         txn = None
 486         try:
 487             if not getattr(self.db, "has_key")(_columns_key(table)):
 488                 raise TableDBError, "unknown table"
 489
 490             # check the validity of each column name
 491             if not table in self.__tablecolumns:
 492                 self.__load_column_info(table)
 493             for column in rowdict.keys() :
 494                 if not self.__tablecolumns[table].count(column):
 495                     raise TableDBError, "unknown column: %r" % (column,)
 496
 497             # get a unique row identifier for this row
 498             txn = self.env.txn_begin()
 499             rowid = self.__new_rowid(table, txn=txn)
 500
 501             # insert the row values into the table database
 502             for column, dataitem in rowdict.items():
 503                 # store the value
 504                 self.db.put(_data_key(table, column, rowid), dataitem, txn=txn)
 505
 506             txn.commit()
 507             txn = None
 508
 509         except db.DBError, dberror:
 510             # WIBNI we could just abort the txn and re-raise the exception?
 511             # But no, because TableDBError is not related to DBError via
 512             # inheritance, so it would be backwards incompatible.  Do the next
 513             # best thing.
 514             info = sys.exc_info()
 515             if txn:
 516                 txn.abort()
 517                 self.db.delete(_rowid_key(table, rowid))
 518             if sys.version_info < (2, 6) :
 519                 raise TableDBError, dberror[1], info[2]
 520             else :
 521                 raise TableDBError, dberror.args[1], info[2]
 522
 523
 524     def Modify(self, table, conditions={}, mappings={}):
 525         """Modify(table, conditions={}, mappings={}) - Modify items in rows matching 'conditions' using mapping functions in 'mappings'
 526
 527         * table - the table name
 528         * conditions - a dictionary keyed on column names containing
 529           a condition callable expecting the data string as an
 530           argument and returning a boolean.
 531         * mappings - a dictionary keyed on column names containing a
 532           condition callable expecting the data string as an argument and
 533           returning the new string for that column.
 534         """
 535
 536         try:
 537             matching_rowids = self.__Select(table, [], conditions)
 538
 539             # modify only requested columns
 540             columns = mappings.keys()
 541             for rowid in matching_rowids.keys():
 542                 txn = None
 543                 try:
 544                     for column in columns:
 545                         txn = self.env.txn_begin()
 546                         # modify the requested column
 547                         try:
 548                             dataitem = self.db.get(
 549                                 _data_key(table, column, rowid),
 550                                 txn=txn)
 551                             self.db.delete(
 552                                 _data_key(table, column, rowid),
 553                                 txn=txn)
 554                         except db.DBNotFoundError:
 555                              # XXXXXXX row key somehow didn't exist, assume no
 556                              # error
 557                             dataitem = None
 558                         dataitem = mappings[column](dataitem)
 559                         if dataitem is not None:
 560                             self.db.put(
 561                                 _data_key(table, column, rowid),
 562                                 dataitem, txn=txn)
 563                         txn.commit()
 564                         txn = None
 565
 566                 # catch all exceptions here since we call unknown callables
 567                 except:
 568                     if txn:
 569                         txn.abort()
 570                     raise
 571
 572         except db.DBError, dberror:
 573             if sys.version_info < (2, 6) :
 574                 raise TableDBError, dberror[1]
 575             else :
 576                 raise TableDBError, dberror.args[1]
 577
 578     def Delete(self, table, conditions={}):
 579         """Delete(table, conditions) - Delete items matching the given
 580         conditions from the table.
 581
 582         * conditions - a dictionary keyed on column names containing
 583           condition functions expecting the data string as an
 584           argument and returning a boolean.
 585         """
 586
 587         try:
 588             matching_rowids = self.__Select(table, [], conditions)
 589
 590             # delete row data from all columns
 591             columns = self.__tablecolumns[table]
 592             for rowid in matching_rowids.keys():
 593                 txn = None
 594                 try:
 595                     txn = self.env.txn_begin()
 596                     for column in columns:
 597                         # delete the data key
 598                         try:
 599                             self.db.delete(_data_key(table, column, rowid),
 600                                            txn=txn)
 601                         except db.DBNotFoundError:
 602                             # XXXXXXX column may not exist, assume no error
 603                             pass
 604
 605                     try:
 606                         self.db.delete(_rowid_key(table, rowid), txn=txn)
 607                     except db.DBNotFoundError:
 608                         # XXXXXXX row key somehow didn't exist, assume no error
 609                         pass
 610                     txn.commit()
 611                     txn = None
 612                 except db.DBError, dberror:
 613                     if txn:
 614                         txn.abort()
 615                     raise
 616         except db.DBError, dberror:
 617             if sys.version_info < (2, 6) :
 618                 raise TableDBError, dberror[1]
 619             else :
 620                 raise TableDBError, dberror.args[1]
 621
 622
 623     def Select(self, table, columns, conditions={}):
 624         """Select(table, columns, conditions) - retrieve specific row data
 625         Returns a list of row column->value mapping dictionaries.
 626
 627         * columns - a list of which column data to return.  If
 628           columns is None, all columns will be returned.
 629         * conditions - a dictionary keyed on column names
 630           containing callable conditions expecting the data string as an
 631           argument and returning a boolean.
 632         """
 633         try:
 634             if not table in self.__tablecolumns:
 635                 self.__load_column_info(table)
 636             if columns is None:
 637                 columns = self.__tablecolumns[table]
 638             matching_rowids = self.__Select(table, columns, conditions)
 639         except db.DBError, dberror:
 640             if sys.version_info < (2, 6) :
 641                 raise TableDBError, dberror[1]
 642             else :
 643                 raise TableDBError, dberror.args[1]
 644         # return the matches as a list of dictionaries
 645         return matching_rowids.values()
 646
 647
 648     def __Select(self, table, columns, conditions):
 649         """__Select() - Used to implement Select and Delete (above)
 650         Returns a dictionary keyed on rowids containing dicts
 651         holding the row data for columns listed in the columns param
 652         that match the given conditions.
 653         * conditions is a dictionary keyed on column names
 654         containing callable conditions expecting the data string as an
 655         argument and returning a boolean.
 656         """
 657         # check the validity of each column name
 658         if not table in self.__tablecolumns:
 659             self.__load_column_info(table)
 660         if columns is None:
 661             columns = self.tablecolumns[table]
 662         for column in (columns + conditions.keys()):
 663             if not self.__tablecolumns[table].count(column):
 664                 raise TableDBError, "unknown column: %r" % (column,)
 665
 666         # keyed on rows that match so far, containings dicts keyed on
 667         # column names containing the data for that row and column.
 668         matching_rowids = {}
 669         # keys are rowids that do not match
 670         rejected_rowids = {}
 671
 672         # attempt to sort the conditions in such a way as to minimize full
 673         # column lookups
 674         def cmp_conditions(atuple, btuple):
 675             a = atuple[1]
 676             b = btuple[1]
 677             if type(a) is type(b):
 678
 679                 # Needed for python 3. "cmp" vanished in 3.0.1
 680                 def cmp(a, b) :
 681                     if a==b : return 0
 682                     if a<b : return -1
 683                     return 1
 684
 685                 if isinstance(a, PrefixCond) and isinstance(b, PrefixCond):
 686                     # longest prefix first
 687                     return cmp(len(b.prefix), len(a.prefix))
 688                 if isinstance(a, LikeCond) and isinstance(b, LikeCond):
 689                     # longest likestr first
 690                     return cmp(len(b.likestr), len(a.likestr))
 691                 return 0
 692             if isinstance(a, ExactCond):
 693                 return -1
 694             if isinstance(b, ExactCond):
 695                 return 1
 696             if isinstance(a, PrefixCond):
 697                 return -1
 698             if isinstance(b, PrefixCond):
 699                 return 1
 700             # leave all unknown condition callables alone as equals
 701             return 0
 702
 703         if sys.version_info < (2, 6) :
 704             conditionlist = conditions.items()
 705             conditionlist.sort(cmp_conditions)
 706         else :  # Insertion Sort. Please, improve
 707             conditionlist = []
 708             for i in conditions.items() :
 709                 for j, k in enumerate(conditionlist) :
 710                     r = cmp_conditions(k, i)
 711                     if r == 1 :
 712                         conditionlist.insert(j, i)
 713                         break
 714                 else :
 715                     conditionlist.append(i)
 716
 717         # Apply conditions to column data to find what we want
 718         cur = self.db.cursor()
 719         column_num = -1
 720         for column, condition in conditionlist:
 721             column_num = column_num + 1
 722             searchkey = _search_col_data_key(table, column)
 723             # speedup: don't linear search columns within loop
 724             if column in columns:
 725                 savethiscolumndata = 1  # save the data for return
 726             else:
 727                 savethiscolumndata = 0  # data only used for selection
 728
 729             try:
 730                 key, data = cur.set_range(searchkey)
 731                 while key[:len(searchkey)] == searchkey:
 732                     # extract the rowid from the key
 733                     rowid = key[-_rowid_str_len:]
 734
 735                     if not rowid in rejected_rowids:
 736                         # if no condition was specified or the condition
 737                         # succeeds, add row to our match list.
 738                         if not condition or condition(data):
 739                             if not rowid in matching_rowids:
 740                                 matching_rowids[rowid] = {}
 741                             if savethiscolumndata:
 742                                 matching_rowids[rowid][column] = data
 743                         else:
 744                             if rowid in matching_rowids:
 745                                 del matching_rowids[rowid]
 746                             rejected_rowids[rowid] = rowid
 747
 748                     key, data = cur.next()
 749
 750             except db.DBError, dberror:
 751                 if dberror.args[0] != db.DB_NOTFOUND:
 752                     raise
 753                 continue
 754
 755         cur.close()
 756
 757         # we're done selecting rows, garbage collect the reject list
 758         del rejected_rowids
 759
 760         # extract any remaining desired column data from the
 761         # database for the matching rows.
 762         if len(columns) > 0:
 763             for rowid, rowdata in matching_rowids.items():
 764                 for column in columns:
 765                     if column in rowdata:
 766                         continue
 767                     try:
 768                         rowdata[column] = self.db.get(
 769                             _data_key(table, column, rowid))
 770                     except db.DBError, dberror:
 771                         if sys.version_info < (2, 6) :
 772                             if dberror[0] != db.DB_NOTFOUND:
 773                                 raise
 774                         else :
 775                             if dberror.args[0] != db.DB_NOTFOUND:
 776                                 raise
 777                         rowdata[column] = None
 778
 779         # return the matches
 780         return matching_rowids
 781
 782
 783     def Drop(self, table):
 784         """Remove an entire table from the database"""
 785         txn = None
 786         try:
 787             txn = self.env.txn_begin()
 788
 789             # delete the column list
 790             self.db.delete(_columns_key(table), txn=txn)
 791
 792             cur = self.db.cursor(txn)
 793
 794             # delete all keys containing this tables column and row info
 795             table_key = _search_all_data_key(table)
 796             while 1:
 797                 try:
 798                     key, data = cur.set_range(table_key)
 799                 except db.DBNotFoundError:
 800                     break
 801                 # only delete items in this table
 802                 if key[:len(table_key)] != table_key:
 803                     break
 804                 cur.delete()
 805
 806             # delete all rowids used by this table
 807             table_key = _search_rowid_key(table)
 808             while 1:
 809                 try:
 810                     key, data = cur.set_range(table_key)
 811                 except db.DBNotFoundError:
 812                     break
 813                 # only delete items in this table
 814                 if key[:len(table_key)] != table_key:
 815                     break
 816                 cur.delete()
 817
 818             cur.close()
 819
 820             # delete the tablename from the table name list
 821             tablelist = pickle.loads(
 822                 getattr(self.db, "get_bytes", self.db.get)(_table_names_key,
 823                     txn=txn, flags=db.DB_RMW))
 824             try:
 825                 tablelist.remove(table)
 826             except ValueError:
 827                 # hmm, it wasn't there, oh well, that's what we want.
 828                 pass
 829             # delete 1st, incase we opened with DB_DUP
 830             self.db.delete(_table_names_key, txn=txn)
 831             getattr(self.db, "put_bytes", self.db.put)(_table_names_key,
 832                     pickle.dumps(tablelist, 1), txn=txn)
 833
 834             txn.commit()
 835             txn = None
 836
 837             if table in self.__tablecolumns:
 838                 del self.__tablecolumns[table]
 839
 840         except db.DBError, dberror:
 841             if txn:
 842                 txn.abort()
 843             raise TableDBError(dberror.args[1])