Source

sqlalchemy-2179 / lib / sqlalchemy / orm / strategies.py

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
# orm/strategies.py
# Copyright (C) 2005-2012 the SQLAlchemy authors and contributors <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

"""sqlalchemy.orm.interfaces.LoaderStrategy 
   implementations, and related MapperOptions."""

from sqlalchemy import exc as sa_exc
from sqlalchemy import sql, util, log, event
from sqlalchemy.sql import util as sql_util
from sqlalchemy.sql import visitors
from sqlalchemy.orm import attributes, interfaces, exc as orm_exc
from sqlalchemy.orm.mapper import _none_set
from sqlalchemy.orm.interfaces import (
    LoaderStrategy, StrategizedOption, MapperOption, PropertyOption,
    StrategizedProperty
    )
from sqlalchemy.orm import session as sessionlib, unitofwork
from sqlalchemy.orm import util as mapperutil
from sqlalchemy.orm.query import Query
import itertools

def _register_attribute(strategy, mapper, useobject,
        compare_function=None, 
        typecallable=None,
        copy_function=None, 
        mutable_scalars=False, 
        uselist=False,
        callable_=None, 
        proxy_property=None, 
        active_history=False,
        impl_class=None, 
        **kw
):

    prop = strategy.parent_property

    attribute_ext = list(util.to_list(prop.extension, default=[]))

    listen_hooks = []

    if useobject and prop.single_parent:
        listen_hooks.append(single_parent_validator)

    if prop.key in prop.parent.validators:
        listen_hooks.append(
            lambda desc, prop: mapperutil._validator_events(desc, 
                                prop.key, 
                                prop.parent.validators[prop.key])
        )

    if useobject:
        listen_hooks.append(unitofwork.track_cascade_events)

    # need to assemble backref listeners
    # after the singleparentvalidator, mapper validator
    backref = kw.pop('backref', None)
    if backref:
        listen_hooks.append(
            lambda desc, prop: attributes.backref_listeners(desc, 
                                backref, 
                                uselist)
        )

    for m in mapper.self_and_descendants:
        if prop is m._props.get(prop.key):

            desc = attributes.register_attribute_impl(
                m.class_, 
                prop.key, 
                parent_token=prop,
                mutable_scalars=mutable_scalars,
                uselist=uselist, 
                copy_function=copy_function, 
                compare_function=compare_function, 
                useobject=useobject,
                extension=attribute_ext, 
                trackparent=useobject and (prop.single_parent or prop.direction is interfaces.ONETOMANY), 
                typecallable=typecallable,
                callable_=callable_, 
                active_history=active_history,
                impl_class=impl_class,
                doc=prop.doc,
                **kw
                )

            for hook in listen_hooks:
                hook(desc, prop)

class UninstrumentedColumnLoader(LoaderStrategy):
    """Represent the a non-instrumented MapperProperty.

    The polymorphic_on argument of mapper() often results in this,
    if the argument is against the with_polymorphic selectable.

    """
    def init(self):
        self.columns = self.parent_property.columns

    def setup_query(self, context, entity, path, reduced_path, adapter, 
                            column_collection=None, **kwargs):
        for c in self.columns:
            if adapter:
                c = adapter.columns[c]
            column_collection.append(c)

    def create_row_processor(self, context, path, reduced_path, mapper, row, adapter):
        return None, None, None

class ColumnLoader(LoaderStrategy):
    """Provide loading behavior for a :class:`.ColumnProperty`."""

    def init(self):
        self.columns = self.parent_property.columns
        self.is_composite = hasattr(self.parent_property, 'composite_class')

    def setup_query(self, context, entity, path, reduced_path, 
                            adapter, column_collection, **kwargs):
        for c in self.columns:
            if adapter:
                c = adapter.columns[c]
            column_collection.append(c)

    def init_class_attribute(self, mapper):
        self.is_class_level = True
        coltype = self.columns[0].type
        # TODO: check all columns ?  check for foreign key as well?
        active_history = self.parent_property.active_history or \
                            self.columns[0].primary_key

        _register_attribute(self, mapper, useobject=False,
            compare_function=coltype.compare_values,
            copy_function=coltype.copy_value,
            mutable_scalars=self.columns[0].type.is_mutable(),
            active_history = active_history
       )

    def create_row_processor(self, context, path, reduced_path, 
                                            mapper, row, adapter):
        key = self.key
        # look through list of columns represented here
        # to see which, if any, is present in the row.
        for col in self.columns:
            if adapter:
                col = adapter.columns[col]
            if col is not None and col in row:
                def fetch_col(state, dict_, row):
                    dict_[key] = row[col]
                return fetch_col, None, None
        else:
            def expire_for_non_present_col(state, dict_, row):
                state.expire_attribute_pre_commit(dict_, key)
            return expire_for_non_present_col, None, None

log.class_logger(ColumnLoader)

class DeferredColumnLoader(LoaderStrategy):
    """Provide loading behavior for a deferred :class:`.ColumnProperty`."""

    def create_row_processor(self, context, path, reduced_path, mapper, row, adapter):
        col = self.columns[0]
        if adapter:
            col = adapter.columns[col]

        key = self.key
        if col in row:
            return self.parent_property._get_strategy(ColumnLoader).\
                        create_row_processor(
                                context, path, reduced_path, mapper, row, adapter)

        elif not self.is_class_level:
            def set_deferred_for_local_state(state, dict_, row):
                state.set_callable(dict_, key, LoadDeferredColumns(state, key))
            return set_deferred_for_local_state, None, None
        else:
            def reset_col_for_deferred(state, dict_, row):
                # reset state on the key so that deferred callables
                # fire off on next access.
                state.reset(dict_, key)
            return reset_col_for_deferred, None, None

    def init(self):
        if hasattr(self.parent_property, 'composite_class'):
            raise NotImplementedError("Deferred loading for composite "
                                    "types not implemented yet")
        self.columns = self.parent_property.columns
        self.group = self.parent_property.group

    def init_class_attribute(self, mapper):
        self.is_class_level = True

        _register_attribute(self, mapper, useobject=False,
             compare_function=self.columns[0].type.compare_values,
             copy_function=self.columns[0].type.copy_value,
             mutable_scalars=self.columns[0].type.is_mutable(),
             callable_=self._load_for_state,
             expire_missing=False
        )

    def setup_query(self, context, entity, path, reduced_path, adapter, 
                                only_load_props=None, **kwargs):
        if (
                self.group is not None and 
                context.attributes.get(('undefer', self.group), False)
            ) or (only_load_props and self.key in only_load_props):
            self.parent_property._get_strategy(ColumnLoader).\
                            setup_query(context, entity,
                                        path, reduced_path, adapter, **kwargs)

    def _load_for_state(self, state, passive):
        if not state.key:
            return attributes.ATTR_EMPTY

        if passive is attributes.PASSIVE_NO_FETCH:
            return attributes.PASSIVE_NO_RESULT

        localparent = state.manager.mapper

        if self.group:
            toload = [
                    p.key for p in 
                    localparent.iterate_properties 
                    if isinstance(p, StrategizedProperty) and 
                      isinstance(p.strategy, DeferredColumnLoader) and 
                      p.group==self.group
                    ]
        else:
            toload = [self.key]

        # narrow the keys down to just those which have no history
        group = [k for k in toload if k in state.unmodified]

        session = sessionlib._state_session(state)
        if session is None:
            raise orm_exc.DetachedInstanceError(
                "Parent instance %s is not bound to a Session; "
                "deferred load operation of attribute '%s' cannot proceed" % 
                (mapperutil.state_str(state), self.key)
                )

        query = session.query(localparent)
        if query._load_on_ident(state.key, 
                    only_load_props=group, refresh_state=state) is None:
            raise orm_exc.ObjectDeletedError(state)

        return attributes.ATTR_WAS_SET

log.class_logger(DeferredColumnLoader)

class LoadDeferredColumns(object):
    """serializable loader object used by DeferredColumnLoader"""

    def __init__(self, state, key):
        self.state = state
        self.key = key

    def __call__(self, passive=attributes.PASSIVE_OFF):
        state, key = self.state, self.key

        localparent = state.manager.mapper
        prop = localparent._props[key]
        strategy = prop._strategies[DeferredColumnLoader]
        return strategy._load_for_state(state, passive)

class DeferredOption(StrategizedOption):
    propagate_to_loaders = True

    def __init__(self, key, defer=False):
        super(DeferredOption, self).__init__(key)
        self.defer = defer

    def get_strategy_class(self):
        if self.defer:
            return DeferredColumnLoader
        else:
            return ColumnLoader

class UndeferGroupOption(MapperOption):
    propagate_to_loaders = True

    def __init__(self, group):
        self.group = group

    def process_query(self, query):
        query._attributes[('undefer', self.group)] = True

class AbstractRelationshipLoader(LoaderStrategy):
    """LoaderStratgies which deal with related objects."""

    def init(self):
        self.mapper = self.parent_property.mapper
        self.target = self.parent_property.target
        self.uselist = self.parent_property.uselist

class NoLoader(AbstractRelationshipLoader):
    """Provide loading behavior for a :class:`.RelationshipProperty`
    with "lazy=None".
    
    """

    def init_class_attribute(self, mapper):
        self.is_class_level = True

        _register_attribute(self, mapper,
            useobject=True, 
            uselist=self.parent_property.uselist,
            typecallable = self.parent_property.collection_class,
        )

    def create_row_processor(self, context, path, reduced_path, mapper, row, adapter):
        def invoke_no_load(state, dict_, row):
            state.initialize(self.key)
        return invoke_no_load, None, None

log.class_logger(NoLoader)

class LazyLoader(AbstractRelationshipLoader):
    """Provide loading behavior for a :class:`.RelationshipProperty`
    with "lazy=True", that is loads when first accessed.
    
    """

    def init(self):
        super(LazyLoader, self).init()
        self._lazywhere, \
        self._bind_to_col, \
        self._equated_columns = self._create_lazy_clause(self.parent_property)

        self._rev_lazywhere, \
        self._rev_bind_to_col, \
        self._rev_equated_columns = self._create_lazy_clause(
                                                self.parent_property, 
                                                reverse_direction=True)

        self.logger.info("%s lazy loading clause %s", self, self._lazywhere)

        # determine if our "lazywhere" clause is the same as the mapper's
        # get() clause.  then we can just use mapper.get()
        #from sqlalchemy.orm import query
        self.use_get = not self.uselist and \
                        self.mapper._get_clause[0].compare(
                            self._lazywhere, 
                            use_proxies=True, 
                            equivalents=self.mapper._equivalent_columns
                        )

        if self.use_get:
            for col in self._equated_columns.keys():
                if col in self.mapper._equivalent_columns:
                    for c in self.mapper._equivalent_columns[col]:
                        self._equated_columns[c] = self._equated_columns[col]

            self.logger.info("%s will use query.get() to "
                                    "optimize instance loads" % self)

    def init_class_attribute(self, mapper):
        self.is_class_level = True

        # MANYTOONE currently only needs the 
        # "old" value for delete-orphan
        # cascades.  the required _SingleParentValidator 
        # will enable active_history
        # in that case.  otherwise we don't need the 
        # "old" value during backref operations.
        _register_attribute(self, 
                mapper,
                useobject=True,
                callable_=self._load_for_state,
                uselist = self.parent_property.uselist,
                backref = self.parent_property.back_populates,
                typecallable = self.parent_property.collection_class,
                active_history = \
                    self.parent_property.active_history or \
                    self.parent_property.direction is not \
                        interfaces.MANYTOONE or \
                    not self.use_get,
                )

    def lazy_clause(self, state, reverse_direction=False, 
                                alias_secondary=False, 
                                adapt_source=None):
        if state is None:
            return self._lazy_none_clause(
                                        reverse_direction, 
                                        adapt_source=adapt_source)

        if not reverse_direction:
            criterion, bind_to_col, rev = \
                                            self._lazywhere, \
                                            self._bind_to_col, \
                                            self._equated_columns
        else:
            criterion, bind_to_col, rev = \
                                            self._rev_lazywhere, \
                                            self._rev_bind_to_col, \
                                            self._rev_equated_columns

        if reverse_direction:
            mapper = self.parent_property.mapper
        else:
            mapper = self.parent_property.parent

        o = state.obj() # strong ref
        dict_ = attributes.instance_dict(o)

        # use the "committed state" only if we're in a flush
        # for this state.

        sess = sessionlib._state_session(state)
        if sess is not None and sess._flushing:
            def visit_bindparam(bindparam):
                if bindparam._identifying_key in bind_to_col:
                    bindparam.callable = \
                        lambda: mapper._get_committed_state_attr_by_column(
                            state, dict_, 
                            bind_to_col[bindparam._identifying_key])
        else:
            def visit_bindparam(bindparam):
                if bindparam._identifying_key in bind_to_col:
                    bindparam.callable = \
                            lambda: mapper._get_state_attr_by_column(
                                    state, dict_, 
                                    bind_to_col[bindparam._identifying_key])


        if self.parent_property.secondary is not None and alias_secondary:
            criterion = sql_util.ClauseAdapter(
                                self.parent_property.secondary.alias()).\
                                traverse(criterion)

        criterion = visitors.cloned_traverse(
                                criterion, {}, {'bindparam':visit_bindparam})

        if adapt_source:
            criterion = adapt_source(criterion)
        return criterion

    def _lazy_none_clause(self, reverse_direction=False, adapt_source=None):
        if not reverse_direction:
            criterion, bind_to_col, rev = \
                                        self._lazywhere, \
                                        self._bind_to_col,\
                                        self._equated_columns
        else:
            criterion, bind_to_col, rev = \
                                            self._rev_lazywhere, \
                                            self._rev_bind_to_col, \
                                            self._rev_equated_columns

        criterion = sql_util.adapt_criterion_to_null(criterion, bind_to_col)

        if adapt_source:
            criterion = adapt_source(criterion)
        return criterion

    def _load_for_state(self, state, passive):
        if not state.key and \
            (not self.parent_property.load_on_pending or not state.session_id):
            return attributes.ATTR_EMPTY

        pending = not state.key
        ident_key = None

        if (
                (passive is attributes.PASSIVE_NO_FETCH or \
                    passive is attributes.PASSIVE_NO_FETCH_RELATED) and 
                not self.use_get
            ) or (
                passive is attributes.PASSIVE_ONLY_PERSISTENT and 
                pending
            ):
            return attributes.PASSIVE_NO_RESULT

        session = sessionlib._state_session(state)
        if not session:
            raise orm_exc.DetachedInstanceError(
                "Parent instance %s is not bound to a Session; "
                "lazy load operation of attribute '%s' cannot proceed" % 
                (mapperutil.state_str(state), self.key)
            )

        # if we have a simple primary key load, check the 
        # identity map without generating a Query at all
        if self.use_get:
            ident = self._get_ident_for_use_get(
                session,
                state,
                passive
            )
            if attributes.PASSIVE_NO_RESULT in ident:
                return attributes.PASSIVE_NO_RESULT
            elif attributes.NEVER_SET in ident:
                return attributes.NEVER_SET

            if _none_set.issuperset(ident):
                return None

            ident_key = self.mapper.identity_key_from_primary_key(ident)
            instance = Query._get_from_identity(session, ident_key, passive)
            if instance is not None:
                return instance
            elif passive is attributes.PASSIVE_NO_FETCH or \
                passive is attributes.PASSIVE_NO_FETCH_RELATED:
                return attributes.PASSIVE_NO_RESULT

        return self._emit_lazyload(session, state, ident_key)

    def _get_ident_for_use_get(self, session, state, passive):
        instance_mapper = state.manager.mapper

        if session._flushing:
            get_attr = instance_mapper._get_committed_state_attr_by_column
        else:
            get_attr = instance_mapper._get_state_attr_by_column

        dict_ = state.dict

        if passive is attributes.PASSIVE_NO_FETCH_RELATED:
            attr_passive = attributes.PASSIVE_OFF
        else:
            attr_passive = passive

        return [
            get_attr(
                    state,
                    dict_,
                    self._equated_columns[pk],
                    passive=attr_passive)
            for pk in self.mapper.primary_key
        ]

    def _emit_lazyload(self, session, state, ident_key):
        q = session.query(self.mapper)._adapt_all_clauses()

        q = q._with_invoke_all_eagers(False)

        pending = not state.key

        # don't autoflush on pending
        if pending:
            q = q.autoflush(False)

        if state.load_path:
            q = q._with_current_path(state.load_path + (self.key,))

        if state.load_options:
            q = q._conditional_options(*state.load_options)

        if self.use_get:
            return q._load_on_ident(ident_key)

        if self.parent_property.order_by:
            q = q.order_by(*util.to_list(self.parent_property.order_by))

        for rev in self.parent_property._reverse_property:
            # reverse props that are MANYTOONE are loading *this* 
            # object from get(), so don't need to eager out to those.
            if rev.direction is interfaces.MANYTOONE and \
                        rev._use_get and \
                        not isinstance(rev.strategy, LazyLoader):
                q = q.options(EagerLazyOption((rev.key,), lazy='select'))

        lazy_clause = self.lazy_clause(state)

        if pending:
            bind_values = sql_util.bind_values(lazy_clause)
            if None in bind_values:
                return None

        q = q.filter(lazy_clause)

        result = q.all()
        if self.uselist:
            return result
        else:
            l = len(result)
            if l:
                if l > 1:
                    util.warn(
                        "Multiple rows returned with "
                        "uselist=False for lazily-loaded attribute '%s' " 
                        % self.parent_property)

                return result[0]
            else:
                return None


    def create_row_processor(self, context, path, reduced_path, 
                                    mapper, row, adapter):
        key = self.key
        if not self.is_class_level:
            def set_lazy_callable(state, dict_, row):
                # we are not the primary manager for this attribute 
                # on this class - set up a
                # per-instance lazyloader, which will override the 
                # class-level behavior.
                # this currently only happens when using a 
                # "lazyload" option on a "no load"
                # attribute - "eager" attributes always have a 
                # class-level lazyloader installed.
                state.set_callable(dict_, key, LoadLazyAttribute(state, key))
            return set_lazy_callable, None, None
        else:
            def reset_for_lazy_callable(state, dict_, row):
                # we are the primary manager for this attribute on 
                # this class - reset its
                # per-instance attribute state, so that the class-level 
                # lazy loader is
                # executed when next referenced on this instance.
                # this is needed in
                # populate_existing() types of scenarios to reset 
                # any existing state.
                state.reset(dict_, key)

            return reset_for_lazy_callable, None, None

    @classmethod
    def _create_lazy_clause(cls, prop, reverse_direction=False):
        binds = util.column_dict()
        lookup = util.column_dict()
        equated_columns = util.column_dict()

        if reverse_direction and prop.secondaryjoin is None:
            for l, r in prop.local_remote_pairs:
                _list = lookup.setdefault(r, [])
                _list.append((r, l))
                equated_columns[l] = r
        else:
            for l, r in prop.local_remote_pairs:
                _list = lookup.setdefault(l, [])
                _list.append((l, r))
                equated_columns[r] = l

        def col_to_bind(col):
            if col in lookup:
                for tobind, equated in lookup[col]:
                    if equated in binds:
                        return None
                if col not in binds:
                    binds[col] = sql.bindparam(None, None, type_=col.type, unique=True)
                return binds[col]
            return None

        lazywhere = prop.primaryjoin

        if prop.secondaryjoin is None or not reverse_direction:
            lazywhere = visitors.replacement_traverse(
                                            lazywhere, {}, col_to_bind) 

        if prop.secondaryjoin is not None:
            secondaryjoin = prop.secondaryjoin
            if reverse_direction:
                secondaryjoin = visitors.replacement_traverse(
                                            secondaryjoin, {}, col_to_bind)
            lazywhere = sql.and_(lazywhere, secondaryjoin)

        bind_to_col = dict((binds[col].key, col) for col in binds)

        return lazywhere, bind_to_col, equated_columns

log.class_logger(LazyLoader)

class LoadLazyAttribute(object):
    """serializable loader object used by LazyLoader"""

    def __init__(self, state, key):
        self.state = state
        self.key = key

    def __call__(self, passive=attributes.PASSIVE_OFF):
        state, key = self.state, self.key
        instance_mapper = state.manager.mapper
        prop = instance_mapper._props[key]
        strategy = prop._strategies[LazyLoader]

        return strategy._load_for_state(state, passive)


class ImmediateLoader(AbstractRelationshipLoader):
    def init_class_attribute(self, mapper):
        self.parent_property.\
                _get_strategy(LazyLoader).\
                init_class_attribute(mapper)

    def setup_query(self, context, entity, 
                        path, reduced_path, adapter, column_collection=None,
                        parentmapper=None, **kwargs):
        pass

    def create_row_processor(self, context, path, reduced_path, 
                                mapper, row, adapter):
        def load_immediate(state, dict_, row):
            state.get_impl(self.key).get(state, dict_)

        return None, None, load_immediate

class SubqueryLoader(AbstractRelationshipLoader):
    def init(self):
        super(SubqueryLoader, self).init()
        self.join_depth = self.parent_property.join_depth

    def init_class_attribute(self, mapper):
        self.parent_property.\
                _get_strategy(LazyLoader).\
                init_class_attribute(mapper)

    def setup_query(self, context, entity, 
                        path, reduced_path, adapter, 
                        column_collection=None,
                        parentmapper=None, **kwargs):

        if not context.query._enable_eagerloads:
            return

        path = path + (self.key, )
        reduced_path = reduced_path + (self.key, )

        # build up a path indicating the path from the leftmost
        # entity to the thing we're subquery loading.
        subq_path = context.attributes.get(('subquery_path', None), ())

        subq_path = subq_path + path

        # join-depth / recursion check
        if ("loaderstrategy", reduced_path) not in context.attributes:
            if self.join_depth:
                if len(path) / 2 > self.join_depth:
                    return
            else:
                if self.mapper.base_mapper in \
                    interfaces._reduce_path(subq_path):
                    return

        subq_mapper, leftmost_mapper, leftmost_attr = \
                self._get_leftmost(subq_path)

        orig_query = context.attributes.get(
                                ("orig_query", SubqueryLoader), 
                                context.query)

        # generate a new Query from the original, then
        # produce a subquery from it.
        left_alias = self._generate_from_original_query(
                            orig_query, leftmost_mapper,
                            leftmost_attr, subq_path
        )

        # generate another Query that will join the 
        # left alias to the target relationships.
        # basically doing a longhand
        # "from_self()".  (from_self() itself not quite industrial
        # strength enough for all contingencies...but very close)
        q = orig_query.session.query(self.mapper)
        q._attributes = {
            ("orig_query", SubqueryLoader): orig_query,
            ('subquery_path', None) : subq_path
        }
        q = q._enable_single_crit(False)

        to_join, local_attr, parent_alias = \
                    self._prep_for_joins(left_alias, subq_path)
        q = q.order_by(*local_attr)
        q = q.add_columns(*local_attr)

        q = self._apply_joins(q, to_join, left_alias, parent_alias)

        q = self._setup_options(q, subq_path, orig_query)
        q = self._setup_outermost_orderby(q)

        # add new query to attributes to be picked up 
        # by create_row_processor
        context.attributes[('subquery', reduced_path)] = q

    def _get_leftmost(self, subq_path):
        subq_mapper = mapperutil._class_to_mapper(subq_path[0])

        # determine attributes of the leftmost mapper
        if self.parent.isa(subq_mapper) and self.key==subq_path[1]:
            leftmost_mapper, leftmost_prop = \
                                    self.parent, self.parent_property
        else:
            leftmost_mapper, leftmost_prop = \
                                    subq_mapper, \
                                    subq_mapper._props[subq_path[1]]
        leftmost_cols, remote_cols = self._local_remote_columns(leftmost_prop)

        leftmost_attr = [
            leftmost_mapper._columntoproperty[c].class_attribute
            for c in leftmost_cols
        ]
        return subq_mapper, leftmost_mapper, leftmost_attr

    def _generate_from_original_query(self,
            orig_query, leftmost_mapper,
            leftmost_attr, subq_path
    ):
        # reformat the original query
        # to look only for significant columns
        q = orig_query._clone().correlate(None)

        # TODO: why does polymporphic etc. require hardcoding 
        # into _adapt_col_list ?  Does query.add_columns(...) work
        # with polymorphic loading ?
        q._set_entities(q._adapt_col_list(leftmost_attr))

        if q._order_by is False:
            q._order_by = leftmost_mapper.order_by

        # don't need ORDER BY if no limit/offset
        if q._limit is None and q._offset is None:
            q._order_by = None

        # the original query now becomes a subquery
        # which we'll join onto.
        embed_q = q.with_labels().subquery()
        left_alias = mapperutil.AliasedClass(leftmost_mapper, embed_q)
        return left_alias


    def _prep_for_joins(self, left_alias, subq_path):
        # figure out what's being joined.  a.k.a. the fun part
        to_join = [
                    (subq_path[i], subq_path[i+1]) 
                    for i in xrange(0, len(subq_path), 2)
                ]

        # determine the immediate parent class we are joining from,
        # which needs to be aliased.

        if len(to_join) < 2:
            # in the case of a one level eager load, this is the
            # leftmost "left_alias".
            parent_alias = left_alias
        elif subq_path[-2].isa(self.parent):
            # In the case of multiple levels, retrieve
            # it from subq_path[-2]. This is the same as self.parent 
            # in the vast majority of cases, and [ticket:2014] 
            # illustrates a case where sub_path[-2] is a subclass
            # of self.parent
            parent_alias = mapperutil.AliasedClass(subq_path[-2])
        else:
            # if of_type() were used leading to this relationship, 
            # self.parent is more specific than subq_path[-2]
            parent_alias = mapperutil.AliasedClass(self.parent)

        local_cols, remote_cols = \
                        self._local_remote_columns(self.parent_property)

        local_attr = [
            getattr(parent_alias, self.parent._columntoproperty[c].key)
            for c in local_cols
        ]

        return to_join, local_attr, parent_alias

    def _apply_joins(self, q, to_join, left_alias, parent_alias):
        for i, (mapper, key) in enumerate(to_join):

            # we need to use query.join() as opposed to
            # orm.join() here because of the 
            # rich behavior it brings when dealing with 
            # "with_polymorphic" mappers.  "aliased"
            # and "from_joinpoint" take care of most of 
            # the chaining and aliasing for us.

            first = i == 0
            middle = i < len(to_join) - 1
            second_to_last = i == len(to_join) - 2

            if first:
                attr = getattr(left_alias, key)
            else:
                attr = key

            if second_to_last:
                q = q.join(parent_alias, attr, from_joinpoint=True)
            else:
                q = q.join(attr, aliased=middle, from_joinpoint=True)
        return q

    def _local_remote_columns(self, prop):
        if prop.secondary is None:
            return zip(*prop.local_remote_pairs)
        else:
            return \
                [p[0] for p in prop.synchronize_pairs],\
                [
                    p[0] for p in prop.
                                        secondary_synchronize_pairs
                ]

    def _setup_options(self, q, subq_path, orig_query):
        # propagate loader options etc. to the new query.
        # these will fire relative to subq_path.
        q = q._with_current_path(subq_path)
        q = q._conditional_options(*orig_query._with_options)
        return q

    def _setup_outermost_orderby(self, q):
        if self.parent_property.order_by:
            # if there's an ORDER BY, alias it the same
            # way joinedloader does, but we have to pull out 
            # the "eagerjoin" from the query.
            # this really only picks up the "secondary" table
            # right now.
            eagerjoin = q._from_obj[0]
            eager_order_by = \
                            eagerjoin._target_adapter.\
                                copy_and_process(
                                    util.to_list(
                                        self.parent_property.order_by
                                    )
                                )
            q = q.order_by(*eager_order_by)
        return q

    def create_row_processor(self, context, path, reduced_path, 
                                    mapper, row, adapter):
        if not self.parent.class_manager[self.key].impl.supports_population:
            raise sa_exc.InvalidRequestError(
                        "'%s' does not support object "
                        "population - eager loading cannot be applied." % 
                        self)

        reduced_path = reduced_path + (self.key,)

        if ('subquery', reduced_path) not in context.attributes:
            return None, None, None

        local_cols, remote_cols = self._local_remote_columns(self.parent_property)

        q = context.attributes[('subquery', reduced_path)]

        collections = dict(
                    (k, [v[0] for v in v]) 
                    for k, v in itertools.groupby(
                        q, 
                        lambda x:x[1:]
                    ))

        if adapter:
            local_cols = [adapter.columns[c] for c in local_cols]

        if self.uselist:
            return self._create_collection_loader(collections, local_cols)
        else:
            return self._create_scalar_loader(collections, local_cols)

    def _create_collection_loader(self, collections, local_cols):
        def load_collection_from_subq(state, dict_, row):
            collection = collections.get(
                tuple([row[col] for col in local_cols]), 
                ()
            )
            state.get_impl(self.key).\
                    set_committed_value(state, dict_, collection)

        return load_collection_from_subq, None, None

    def _create_scalar_loader(self, collections, local_cols):
        def load_scalar_from_subq(state, dict_, row):
            collection = collections.get(
                tuple([row[col] for col in local_cols]), 
                (None,)
            )
            if len(collection) > 1:
                util.warn(
                    "Multiple rows returned with "
                    "uselist=False for eagerly-loaded attribute '%s' "
                    % self)

            scalar = collection[0]
            state.get_impl(self.key).\
                    set_committed_value(state, dict_, scalar)

        return load_scalar_from_subq, None, None

log.class_logger(SubqueryLoader)

class JoinedLoader(AbstractRelationshipLoader):
    """Provide loading behavior for a :class:`.RelationshipProperty`
    using joined eager loading.
    
    """
    def init(self):
        super(JoinedLoader, self).init()
        self.join_depth = self.parent_property.join_depth

    def init_class_attribute(self, mapper):
        self.parent_property.\
            _get_strategy(LazyLoader).init_class_attribute(mapper)

    def setup_query(self, context, entity, path, reduced_path, adapter, \
                                column_collection=None, parentmapper=None,
                                allow_innerjoin=True,
                                **kwargs):
        """Add a left outer join to the statement thats being constructed."""


        if not context.query._enable_eagerloads:
            return

        path = path + (self.key,)
        reduced_path = reduced_path + (self.key,)

        if ("user_defined_eager_row_processor", reduced_path) in\
                context.attributes:
            clauses, adapter, add_to_collection = \
                self._get_user_defined_adapter(
                    context, entity, reduced_path, adapter
                )
        else:
            # check for join_depth or basic recursion,
            # if the current path was not explicitly stated as 
            # a desired "loaderstrategy" (i.e. via query.options())
            if ("loaderstrategy", reduced_path) not in context.attributes:
                if self.join_depth:
                    if len(path) / 2 > self.join_depth:
                        return
                else:
                    if self.mapper.base_mapper in reduced_path:
                        return

            clauses, adapter, add_to_collection, \
                allow_innerjoin = self._generate_row_adapter(
                    context, entity, path, reduced_path, adapter,
                    column_collection, parentmapper, allow_innerjoin
                )

        path += (self.mapper,)
        reduced_path += (self.mapper.base_mapper,)

        for value in self.mapper._polymorphic_properties:
            value.setup(
                context, 
                entity, 
                path, 
                reduced_path,
                clauses, 
                parentmapper=self.mapper, 
                column_collection=add_to_collection,
                allow_innerjoin=allow_innerjoin)

    def _get_user_defined_adapter(self, context, entity, 
                                reduced_path, adapter):
            clauses = context.attributes[
                                ("user_defined_eager_row_processor",
                                reduced_path)]

            adapter = entity._get_entity_clauses(context.query, context)
            if adapter and clauses:
                context.attributes[
                            ("user_defined_eager_row_processor",
                            reduced_path)] = clauses = clauses.wrap(adapter)
            elif adapter:
                context.attributes[
                            ("user_defined_eager_row_processor",
                            reduced_path)] = clauses = adapter

            add_to_collection = context.primary_columns
            return clauses, adapter, add_to_collection

    def _generate_row_adapter(self, 
        context, entity, path, reduced_path, adapter,
        column_collection, parentmapper, allow_innerjoin
    ):
        clauses = mapperutil.ORMAdapter(
                    mapperutil.AliasedClass(self.mapper), 
                    equivalents=self.mapper._equivalent_columns,
                    adapt_required=True)

        if self.parent_property.direction != interfaces.MANYTOONE:
            context.multi_row_eager_loaders = True

        innerjoin = allow_innerjoin and context.attributes.get(
                            ("eager_join_type", path), 
                            self.parent_property.innerjoin)
        if not innerjoin:
            # if this is an outer join, all eager joins from
            # here must also be outer joins
            allow_innerjoin = False

        context.create_eager_joins.append(
            (self._create_eager_join, context, 
            entity, path, adapter, 
            parentmapper, clauses, innerjoin)
        )

        add_to_collection = context.secondary_columns
        context.attributes[
                            ("eager_row_processor", reduced_path)
                          ] = clauses
        return clauses, adapter, add_to_collection, allow_innerjoin

    def _create_eager_join(self, context, entity, 
                            path, adapter, parentmapper, 
                            clauses, innerjoin):

        if parentmapper is None:
            localparent = entity.mapper
        else:
            localparent = parentmapper

        # whether or not the Query will wrap the selectable in a subquery,
        # and then attach eager load joins to that (i.e., in the case of 
        # LIMIT/OFFSET etc.)
        should_nest_selectable = context.multi_row_eager_loaders and \
            context.query._should_nest_selectable

        entity_key = None
        if entity not in context.eager_joins and \
            not should_nest_selectable and \
            context.from_clause:
            index, clause = \
                sql_util.find_join_source(
                                context.from_clause, entity.selectable)
            if clause is not None:
                # join to an existing FROM clause on the query.
                # key it to its list index in the eager_joins dict.
                # Query._compile_context will adapt as needed and 
                # append to the FROM clause of the select().
                entity_key, default_towrap = index, clause

        if entity_key is None:
            entity_key, default_towrap = entity, entity.selectable

        towrap = context.eager_joins.setdefault(entity_key, default_towrap)

        join_to_left = False
        if adapter:
            if getattr(adapter, 'aliased_class', None):
                onclause = getattr(
                                adapter.aliased_class, self.key,
                                self.parent_property)
            else:
                onclause = getattr(
                                mapperutil.AliasedClass(
                                        self.parent, 
                                        adapter.selectable
                                ), 
                                self.key, self.parent_property
                            )

            if onclause is self.parent_property:
                # TODO: this is a temporary hack to 
                # account for polymorphic eager loads where
                # the eagerload is referencing via of_type().
                join_to_left = True
        else:
            onclause = self.parent_property

        context.eager_joins[entity_key] = eagerjoin = \
                                mapperutil.join(
                                            towrap, 
                                            clauses.aliased_class, 
                                            onclause, 
                                            join_to_left=join_to_left, 
                                            isouter=not innerjoin
                                            )

        # send a hint to the Query as to where it may "splice" this join
        eagerjoin.stop_on = entity.selectable

        if self.parent_property.secondary is None and \
                not parentmapper:
            # for parentclause that is the non-eager end of the join,
            # ensure all the parent cols in the primaryjoin are actually 
            # in the
            # columns clause (i.e. are not deferred), so that aliasing applied 
            # by the Query propagates those columns outward.
            # This has the effect 
            # of "undefering" those columns.
            for col in sql_util.find_columns(
                                self.parent_property.primaryjoin):
                if localparent.mapped_table.c.contains_column(col):
                    if adapter:
                        col = adapter.columns[col]
                    context.primary_columns.append(col)

        if self.parent_property.order_by:
            context.eager_order_by += \
                            eagerjoin._target_adapter.\
                                copy_and_process(
                                    util.to_list(
                                        self.parent_property.order_by
                                    )
                                )


    def _create_eager_adapter(self, context, row, adapter, path, reduced_path):
        if ("user_defined_eager_row_processor", reduced_path) in \
                                                    context.attributes:
            decorator = context.attributes[
                            ("user_defined_eager_row_processor",
                            reduced_path)]
            # user defined eagerloads are part of the "primary" 
            # portion of the load.
            # the adapters applied to the Query should be honored.
            if context.adapter and decorator:
                decorator = decorator.wrap(context.adapter)
            elif context.adapter:
                decorator = context.adapter
        elif ("eager_row_processor", reduced_path) in context.attributes:
            decorator = context.attributes[
                            ("eager_row_processor", reduced_path)]
        else:
            return False

        try:
            self.mapper.identity_key_from_row(row, decorator)
            return decorator
        except KeyError:
            # no identity key - dont return a row 
            # processor, will cause a degrade to lazy
            return False

    def create_row_processor(self, context, path, reduced_path, mapper, row, adapter):
        if not self.parent.class_manager[self.key].impl.supports_population:
            raise sa_exc.InvalidRequestError(
                        "'%s' does not support object "
                        "population - eager loading cannot be applied." % 
                        self)

        our_path = path + (self.key,)
        our_reduced_path = reduced_path + (self.key,)

        eager_adapter = self._create_eager_adapter(
                                                context, 
                                                row, 
                                                adapter, our_path,
                                                our_reduced_path)

        if eager_adapter is not False:
            key = self.key
            _instance = self.mapper._instance_processor(
                                context, 
                                our_path + (self.mapper,), 
                                our_reduced_path + (self.mapper.base_mapper,),
                                eager_adapter)

            if not self.uselist:
                return self._create_scalar_loader(context, key, _instance)
            else:
                return self._create_collection_loader(context, key, _instance)
        else:
            return self.parent_property.\
                            _get_strategy(LazyLoader).\
                            create_row_processor(
                                            context, path, 
                                            reduced_path,
                                            mapper, row, adapter)

    def _create_collection_loader(self, context, key, _instance):
        def load_collection_from_joined_new_row(state, dict_, row):
            collection = attributes.init_state_collection(
                                            state, dict_, key)
            result_list = util.UniqueAppender(collection,
                                              'append_without_event')
            context.attributes[(state, key)] = result_list
            _instance(row, result_list)

        def load_collection_from_joined_existing_row(state, dict_, row):
            if (state, key) in context.attributes:
                result_list = context.attributes[(state, key)]
            else:
                # appender_key can be absent from context.attributes
                # with isnew=False when self-referential eager loading
                # is used; the same instance may be present in two
                # distinct sets of result columns
                collection = attributes.init_state_collection(state,
                                dict_, key)
                result_list = util.UniqueAppender(
                                        collection,
                                        'append_without_event')
                context.attributes[(state, key)] = result_list
            _instance(row, result_list)

        def load_collection_from_joined_exec(state, dict_, row):
            _instance(row, None)

        return load_collection_from_joined_new_row, \
                load_collection_from_joined_existing_row, \
                None, load_collection_from_joined_exec

    def _create_scalar_loader(self, context, key, _instance):
        def load_scalar_from_joined_new_row(state, dict_, row):
            # set a scalar object instance directly on the parent
            # object, bypassing InstrumentedAttribute event handlers.
            dict_[key] = _instance(row, None)

        def load_scalar_from_joined_existing_row(state, dict_, row):
            # call _instance on the row, even though the object has
            # been created, so that we further descend into properties
            existing = _instance(row, None)
            if existing is not None \
                and key in dict_ \
                and existing is not dict_[key]:
                util.warn(
                    "Multiple rows returned with "
                    "uselist=False for eagerly-loaded attribute '%s' "
                    % self)

        def load_scalar_from_joined_exec(state, dict_, row):
            _instance(row, None)

        return load_scalar_from_joined_new_row, \
                load_scalar_from_joined_existing_row, \
                None, load_scalar_from_joined_exec

EagerLoader = JoinedLoader
"""Deprecated, use JoinedLoader"""

log.class_logger(JoinedLoader)

class EagerLazyOption(StrategizedOption):
    def __init__(self, key, lazy=True, chained=False,
                    propagate_to_loaders=True
                    ):
        if isinstance(key[0], basestring) and key[0] == '*':
            if len(key) != 1:
                raise sa_exc.ArgumentError(
                        "Wildcard identifier '*' must "
                        "be specified alone.")
            key = ("relationship:*",)
            propagate_to_loaders = False
        super(EagerLazyOption, self).__init__(key)
        self.lazy = lazy
        self.chained = self.lazy in (False, 'joined', 'subquery') and chained
        self.propagate_to_loaders = propagate_to_loaders
        self.strategy_cls = factory(lazy)

    def get_strategy_class(self):
        return self.strategy_cls

def factory(identifier):
    if identifier is False or identifier == 'joined':
        return JoinedLoader
    elif identifier is None or identifier == 'noload':
        return NoLoader
    elif identifier is False or identifier == 'select':
        return LazyLoader
    elif identifier == 'subquery':
        return SubqueryLoader
    elif identifier == 'immediate':
        return ImmediateLoader
    else:
        return LazyLoader

class EagerJoinOption(PropertyOption):

    def __init__(self, key, innerjoin, chained=False):
        super(EagerJoinOption, self).__init__(key)
        self.innerjoin = innerjoin
        self.chained = chained

    def process_query_property(self, query, paths, mappers):
        if self.chained:
            for path in paths:
                query._attributes[("eager_join_type", path)] = self.innerjoin
        else:
            query._attributes[("eager_join_type", paths[-1])] = self.innerjoin

class LoadEagerFromAliasOption(PropertyOption):

    def __init__(self, key, alias=None, chained=False):
        super(LoadEagerFromAliasOption, self).__init__(key)
        if alias is not None:
            if not isinstance(alias, basestring):
                m, alias, is_aliased_class = mapperutil._entity_info(alias)
        self.alias = alias
        self.chained = chained

    def process_query_property(self, query, paths, mappers):
        if self.chained:
            for path in paths[0:-1]:
                (root_mapper, propname) = path[-2:]
                prop = root_mapper._props[propname]
                adapter = query._polymorphic_adapters.get(prop.mapper, None)
                query._attributes.setdefault(
                            ("user_defined_eager_row_processor", 
                            interfaces._reduce_path(path)), adapter)

        if self.alias is not None:
            if isinstance(self.alias, basestring):
                (root_mapper, propname) = paths[-1][-2:]
                prop = root_mapper._props[propname]
                self.alias = prop.target.alias(self.alias)
            query._attributes[
                        ("user_defined_eager_row_processor", 
                        interfaces._reduce_path(paths[-1]))
                        ] = sql_util.ColumnAdapter(self.alias)
        else:
            (root_mapper, propname) = paths[-1][-2:]
            prop = root_mapper._props[propname]
            adapter = query._polymorphic_adapters.get(prop.mapper, None)
            query._attributes[
                        ("user_defined_eager_row_processor", 
                        interfaces._reduce_path(paths[-1]))] = adapter

def single_parent_validator(desc, prop):
    def _do_check(state, value, oldvalue, initiator):
        if value is not None and initiator.key == prop.key:
            hasparent = initiator.hasparent(attributes.instance_state(value))
            if hasparent and oldvalue is not value: 
                raise sa_exc.InvalidRequestError(
                    "Instance %s is already associated with an instance "
                    "of %s via its %s attribute, and is only allowed a "
                    "single parent." % 
                    (mapperutil.instance_str(value), state.class_, prop)
                )
        return value

    def append(state, value, initiator):
        return _do_check(state, value, None, initiator)

    def set_(state, value, oldvalue, initiator):
        return _do_check(state, value, oldvalue, initiator)

    event.listen(desc, 'append', append, raw=True, retval=True, active_history=True)
    event.listen(desc, 'set', set_, raw=True, retval=True, active_history=True)
Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for ProjectModifiedEvent.java.
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
Tip: Use ↑ and ↓ arrow keys to navigate and return to view the file.
Tip: You can also navigate files with Ctrl+j (next) and Ctrl+k (previous) and view the file with Ctrl+o.
Tip: You can also navigate files with Alt+j (next) and Alt+k (previous) and view the file with Alt+o.