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
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
//! Traits that construct SELECT statements
//!
//! Traits in this module have methods that generally map to the keyword for the corresponding clause in SQL,
//! unless it conflicts with a Rust keyword (such as `WHERE`/`where`).
//!
//! Methods for constructing queries lives on the [`QueryDsl`] trait.
//! Methods for executing queries live on [`RunQueryDsl`].
//!
//! See also [`expression_methods`][expression_methods] and [`dsl`][dsl].
//!
//! [expression_methods]: super::expression_methods
//! [dsl]: super::dsl

use crate::backend::Backend;
use crate::connection::Connection;
use crate::expression::count::CountStar;
use crate::expression::Expression;
use crate::helper_types::*;
use crate::query_builder::locking_clause as lock;
use crate::query_source::{joins, Table};
use crate::result::QueryResult;

mod belonging_to_dsl;
#[doc(hidden)]
pub mod boxed_dsl;
mod combine_dsl;
mod distinct_dsl;
#[doc(hidden)]
pub mod filter_dsl;
mod group_by_dsl;
mod having_dsl;
mod join_dsl;
#[doc(hidden)]
pub mod limit_dsl;
#[doc(hidden)]
pub mod load_dsl;
mod locking_dsl;
mod nullable_select_dsl;
mod offset_dsl;
pub(crate) mod order_dsl;
#[doc(hidden)]
pub mod positional_order_dsl;
mod save_changes_dsl;
#[doc(hidden)]
pub mod select_dsl;
mod single_value_dsl;

pub use self::belonging_to_dsl::BelongingToDsl;
pub use self::combine_dsl::CombineDsl;
pub use self::join_dsl::{InternalJoinDsl, JoinOnDsl, JoinWithImplicitOnClause};
#[cfg(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes")]
pub use self::load_dsl::CompatibleType;
#[doc(hidden)]
pub use self::load_dsl::LoadQuery;
pub use self::save_changes_dsl::{SaveChangesDsl, UpdateAndFetchResults};

/// The traits used by `QueryDsl`.
///
/// Each trait in this module represents exactly one method from `QueryDsl`.
/// Apps should general rely on `QueryDsl` directly, rather than these traits.
/// However, generic code may need to include a where clause that references
/// these traits.
pub mod methods {
    pub use super::boxed_dsl::BoxedDsl;
    pub use super::distinct_dsl::*;
    #[doc(inline)]
    pub use super::filter_dsl::*;
    pub use super::group_by_dsl::GroupByDsl;
    pub use super::having_dsl::HavingDsl;
    pub use super::limit_dsl::LimitDsl;
    pub use super::load_dsl::{ExecuteDsl, LoadQuery};
    pub use super::locking_dsl::{LockingDsl, ModifyLockDsl};
    pub use super::nullable_select_dsl::SelectNullableDsl;
    pub use super::offset_dsl::OffsetDsl;
    pub use super::order_dsl::{OrderDsl, ThenOrderDsl};
    pub use super::select_dsl::SelectDsl;
    pub use super::single_value_dsl::SingleValueDsl;

    #[cfg(all(feature = "with-deprecated", not(feature = "without-deprecated")))]
    #[doc(hidden)]
    #[allow(deprecated)]
    #[deprecated(note = "Use `LoadQuery::RowIter` directly")]
    pub use super::load_dsl::LoadRet;
}

/// Methods used to construct select statements.
pub trait QueryDsl: Sized {
    /// Adds the `DISTINCT` keyword to a query.
    ///
    /// This method will override any previous distinct clause that was present.
    /// For example, on PostgreSQL, `foo.distinct_on(bar).distinct()` will
    /// create the same query as `foo.distinct()`.
    ///
    /// # Example
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test().unwrap();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// #     diesel::sql_query("DELETE FROM users").execute(connection).unwrap();
    /// diesel::insert_into(users)
    ///     .values(&vec![name.eq("Sean"); 3])
    ///     .execute(connection)?;
    /// let names = users.select(name).load::<String>(connection)?;
    /// let distinct_names = users.select(name).distinct().load::<String>(connection)?;
    ///
    /// assert_eq!(vec!["Sean"; 3], names);
    /// assert_eq!(vec!["Sean"; 1], distinct_names);
    /// #     Ok(())
    /// # }
    /// ```
    fn distinct(self) -> Distinct<Self>
    where
        Self: methods::DistinctDsl,
    {
        methods::DistinctDsl::distinct(self)
    }

    /// Adds the `DISTINCT ON` clause to a query.
    ///
    /// # Example
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # use schema::animals;
    /// #
    /// # #[derive(Queryable, Debug, PartialEq)]
    /// # struct Animal {
    /// #     species: String,
    /// #     name: Option<String>,
    /// #     legs: i32,
    /// # }
    /// #
    /// # impl Animal {
    /// #     fn new<S: Into<String>>(species: S, name: Option<&str>, legs: i32) -> Self {
    /// #         Animal {
    /// #             species: species.into(),
    /// #             name: name.map(Into::into),
    /// #             legs
    /// #         }
    /// #     }
    /// # }
    /// #
    /// # fn main() {
    /// #     use self::animals::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// #     diesel::sql_query("DELETE FROM animals").execute(connection).unwrap();
    /// diesel::insert_into(animals)
    ///     .values(&vec![
    ///         (species.eq("dog"), name.eq(Some("Jack")), legs.eq(4)),
    ///         (species.eq("dog"), name.eq(None), legs.eq(4)),
    ///         (species.eq("spider"), name.eq(None), legs.eq(8)),
    ///     ])
    ///     .execute(connection)
    ///     .unwrap();
    /// let all_animals = animals.select((species, name, legs)).load(connection);
    /// let distinct_animals = animals
    ///     .select((species, name, legs))
    ///     .order_by((species, legs))
    ///     .distinct_on(species)
    ///     .load(connection);
    ///
    /// assert_eq!(Ok(vec![Animal::new("dog", Some("Jack"), 4),
    ///                    Animal::new("dog", None, 4),
    ///                    Animal::new("spider", None, 8)]), all_animals);
    /// assert_eq!(Ok(vec![Animal::new("dog", Some("Jack"), 4),
    ///                    Animal::new("spider", None, 8)]), distinct_animals);
    /// # }
    /// ```
    #[cfg(feature = "postgres_backend")]
    fn distinct_on<Expr>(self, expr: Expr) -> DistinctOn<Self, Expr>
    where
        Self: methods::DistinctOnDsl<Expr>,
    {
        methods::DistinctOnDsl::distinct_on(self, expr)
    }

    // FIXME: Needs usage example and doc rewrite
    /// Adds a `SELECT` clause to the query.
    ///
    /// If there was already a select clause present, it will be overridden.
    /// For example, `foo.select(bar).select(baz)` will produce the same
    /// query as `foo.select(baz)`.
    ///
    /// By default, the select clause will be roughly equivalent to `SELECT *`
    /// (however, Diesel will list all columns to ensure that they are in the
    /// order we expect).
    ///
    /// `select` has slightly stricter bounds on its arguments than other
    /// methods. In particular, when used with a left outer join, `.nullable`
    /// must be called on columns that come from the right side of a join. It
    /// can be called on the column itself, or on an expression containing that
    /// column. `title.nullable()`, `lower(title).nullable()`, and `(id,
    /// title).nullable()` would all be valid.
    ///
    /// In order to use this method with columns from different tables
    /// a method like [`.inner_join`] or [`.left_join`] needs to be called before
    /// calling [`.select`] (See examples below).
    /// This is because you can only access columns from tables
    /// that appear in your query before that function call.
    ///
    /// [`.inner_join`]: QueryDsl::inner_join()
    /// [`.left_join`]: QueryDsl::left_join()
    /// [`.select`]: QueryDsl::select()
    ///
    /// # Examples
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # use schema::users;
    /// #
    /// # fn main() {
    /// #     run_test().unwrap();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use self::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// // By default, all columns will be selected
    /// let all_users = users.load::<(i32, String)>(connection)?;
    /// assert_eq!(vec![(1, String::from("Sean")), (2, String::from("Tess"))], all_users);
    ///
    /// let all_names = users.select(name).load::<String>(connection)?;
    /// assert_eq!(vec!["Sean", "Tess"], all_names);
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// ### When used with a left join
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # use schema::{users, posts};
    /// #
    /// # #[derive(Queryable, PartialEq, Eq, Debug)]
    /// # struct User {
    /// #     id: i32,
    /// #     name: String,
    /// # }
    /// #
    /// # impl User {
    /// #     fn new(id: i32, name: &str) -> Self {
    /// #         User {
    /// #             id,
    /// #             name: name.into(),
    /// #         }
    /// #     }
    /// # }
    /// #
    /// # #[derive(Queryable, PartialEq, Eq, Debug)]
    /// # struct Post {
    /// #     id: i32,
    /// #     user_id: i32,
    /// #     title: String,
    /// # }
    /// #
    /// # impl Post {
    /// #     fn new(id: i32, user_id: i32, title: &str) -> Self {
    /// #         Post {
    /// #             id,
    /// #             user_id,
    /// #             title: title.into(),
    /// #         }
    /// #     }
    /// # }
    /// #
    /// # fn main() {
    /// #     run_test().unwrap();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     let connection = &mut establish_connection();
    /// #     diesel::sql_query("DELETE FROM posts").execute(connection)?;
    /// #     diesel::insert_into(posts::table)
    /// #         .values((posts::user_id.eq(1), posts::title.eq("Sean's Post")))
    /// #         .execute(connection)?;
    /// #     let post_id = posts::table.select(posts::id)
    /// #         .first::<i32>(connection)?;
    /// let join = users::table.left_join(posts::table);
    ///
    /// // By default, all columns from both tables are selected.
    /// // If no explicit select clause is used this means that the result
    /// // type of this query must contain all fields from the original schema in order.
    /// let all_data = join.load::<(User, Option<Post>)>(connection)?;
    /// let expected_data = vec![
    ///     (User::new(1, "Sean"), Some(Post::new(post_id, 1, "Sean's Post"))),
    ///     (User::new(2, "Tess"), None),
    /// ];
    /// assert_eq!(expected_data, all_data);
    ///
    /// // Since `posts` is on the right side of a left join, `.nullable` is
    /// // needed.
    /// let names_and_titles = join.select((users::name, posts::title.nullable()))
    ///     .load::<(String, Option<String>)>(connection)?;
    /// let expected_data = vec![
    ///     (String::from("Sean"), Some(String::from("Sean's Post"))),
    ///     (String::from("Tess"), None),
    /// ];
    /// assert_eq!(expected_data, names_and_titles);
    /// #     Ok(())
    /// # }
    /// ```
    fn select<Selection>(self, selection: Selection) -> Select<Self, Selection>
    where
        Selection: Expression,
        Self: methods::SelectDsl<Selection>,
    {
        methods::SelectDsl::select(self, selection)
    }

    /// Get the count of a query. This is equivalent to `.select(count_star())`
    ///
    /// # Example
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// let count = users.count().get_result(connection);
    /// assert_eq!(Ok(2), count);
    /// # }
    /// ```
    fn count(self) -> Select<Self, CountStar>
    where
        Self: methods::SelectDsl<CountStar>,
    {
        use crate::dsl::count_star;

        QueryDsl::select(self, count_star())
    }

    /// Join two tables using a SQL `INNER JOIN`.
    ///
    /// If you have invoked [`joinable!`] for the two tables, you can pass that
    /// table directly.  Otherwise you will need to use [`.on`] to specify the `ON`
    /// clause.
    ///
    /// [`joinable!`]: crate::joinable!
    /// [`.on`]: JoinOnDsl::on()
    ///
    /// You can join to as many tables as you'd like in a query, with the
    /// restriction that no table can appear in the query more than once. For
    /// tables that appear more than once in a single query the usage of [`alias!`](crate::alias!)
    /// is required.
    ///
    /// You will also need to call [`allow_tables_to_appear_in_same_query!`].
    /// If you are using `diesel print-schema`, this will
    /// have been generated for you.
    /// See the documentation for [`allow_tables_to_appear_in_same_query!`] for
    /// details.
    ///
    /// Diesel expects multi-table joins to be semantically grouped based on the
    /// relationships. For example, `users.inner_join(posts.inner_join(comments))`
    /// is not the same as `users.inner_join(posts).inner_join(comments)`. The first
    /// would deserialize into `(User, (Post, Comment))` and generate the following
    /// SQL:
    ///
    /// ```sql
    /// SELECT * FROM users
    ///     INNER JOIN (
    ///         posts
    ///         INNER JOIN comments ON comments.post_id = posts.id
    ///     ) ON posts.user_id = users.id
    ///
    /// ```
    ///
    /// While the second query would deserialize into `(User, Post, Comment)` and
    /// generate the following SQL:
    ///
    /// ```sql
    /// SELECT * FROM users
    ///     INNER JOIN posts ON posts.user_id = users.id
    ///     INNER JOIN comments ON comments.user_id = users.id
    /// ```
    ///
    /// The exact generated SQL may change in future diesel version as long as the
    /// generated query continues to produce same results. The currently generated
    /// SQL is referred as ["explicit join"](https://www.postgresql.org/docs/current/explicit-joins.html)
    /// by the PostgreSQL documentation and may have implications on the chosen query plan
    /// for large numbers of joins in the same query. Checkout the documentation of the
    /// [`join_collapse_limit` parameter](https://www.postgresql.org/docs/current/runtime-config-query.html#GUC-JOIN-COLLAPSE-LIMIT)
    /// to control this behaviour.
    ///
    /// [associations]: crate::associations
    /// [`allow_tables_to_appear_in_same_query!`]: crate::allow_tables_to_appear_in_same_query!
    ///
    /// Note that in order to use this method with [`.select`], you will need to use it before calling
    /// [`.select`] (See examples below). This is because you can only access columns from tables
    /// that appear in your query before the call to [`.select`].
    ///
    /// [`.select`]: QueryDsl::select()
    ///
    /// # Examples
    ///
    /// ### With implicit `ON` clause
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # use schema::{users, posts};
    /// # /*
    /// joinable!(posts -> users (user_id));
    /// allow_tables_to_appear_in_same_query!(users, posts);
    /// # */
    ///
    /// # fn main() {
    /// #     use self::users::dsl::{users, name};
    /// #     use self::posts::dsl::{posts, user_id, title};
    /// #     let connection = &mut establish_connection();
    /// let data = users.inner_join(posts)
    ///     .select((name, title))
    ///     .load(connection);
    ///
    /// let expected_data = vec![
    ///     (String::from("Sean"), String::from("My first post")),
    ///     (String::from("Sean"), String::from("About Rust")),
    ///     (String::from("Tess"), String::from("My first post too")),
    /// ];
    /// assert_eq!(Ok(expected_data), data);
    /// # }
    /// ```
    ///
    /// ### With explicit `ON` clause
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # use schema::{users, posts};
    /// #
    /// # /*
    /// allow_tables_to_appear_in_same_query!(users, posts);
    /// # */
    ///
    /// # fn main() {
    /// #     use self::users::dsl::{users, name};
    /// #     use self::posts::dsl::{posts, user_id, title};
    /// #     let connection = &mut establish_connection();
    /// diesel::insert_into(posts)
    ///     .values(&vec![
    ///         (user_id.eq(1), title.eq("Sean's post")),
    ///         (user_id.eq(2), title.eq("Sean is a jerk")),
    ///     ])
    ///     .execute(connection)
    ///     .unwrap();
    ///
    /// let data = users
    ///     .inner_join(posts.on(title.like(name.concat("%"))))
    ///     .select((name, title))
    ///     .load(connection);
    /// let expected_data = vec![
    ///     (String::from("Sean"), String::from("Sean's post")),
    ///     (String::from("Sean"), String::from("Sean is a jerk")),
    /// ];
    /// assert_eq!(Ok(expected_data), data);
    /// # }
    /// ```
    ///
    /// ### With explicit `ON` clause (struct)
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # use schema::{users, posts};
    /// #
    /// # /*
    /// allow_tables_to_appear_in_same_query!(users, posts);
    /// # */
    ///
    /// # fn main() {
    /// #     use self::users::dsl::{users, name};
    /// #     use self::posts::dsl::{posts, user_id, title};
    /// #     let connection = &mut establish_connection();
    /// #[derive(Debug, PartialEq, Queryable)]
    /// struct User {
    ///     id: i32,
    ///     name: String,
    /// }
    ///
    /// #[derive(Debug, PartialEq, Queryable)]
    /// struct Post {
    ///     id: i32,
    ///     user_id: i32,
    ///     title: String,
    /// }
    ///
    /// diesel::insert_into(posts)
    ///     .values(&vec![
    ///         (user_id.eq(1), title.eq("Sean's post")),
    ///         (user_id.eq(2), title.eq("Sean is a jerk")),
    ///     ])
    ///     .execute(connection)
    ///     .unwrap();
    ///
    /// // By default, all columns from both tables are selected.
    /// // If no explicit select clause is used this means that the
    /// // result type of this query must contain all fields from the
    /// // original schema in order.
    /// let data = users
    ///     .inner_join(posts.on(title.like(name.concat("%"))))
    ///     .load::<(User, Post)>(connection); // type could be elided
    /// let expected_data = vec![
    ///     (
    ///         User { id: 1, name: String::from("Sean") },
    ///         Post { id: 4, user_id: 1, title: String::from("Sean's post") },
    ///     ),
    ///     (
    ///         User { id: 1, name: String::from("Sean") },
    ///         Post { id: 5, user_id: 2, title: String::from("Sean is a jerk") },
    ///     ),
    /// ];
    /// assert_eq!(Ok(expected_data), data);
    /// # }
    /// ```
    fn inner_join<Rhs>(self, rhs: Rhs) -> InnerJoin<Self, Rhs>
    where
        Self: JoinWithImplicitOnClause<Rhs, joins::Inner>,
    {
        self.join_with_implicit_on_clause(rhs, joins::Inner)
    }

    /// Join two tables using a SQL `LEFT OUTER JOIN`.
    ///
    /// Behaves similarly to [`inner_join`], but will produce a left join
    /// instead. See [`inner_join`] for usage examples.
    ///
    /// [`inner_join`]: QueryDsl::inner_join()
    ///
    /// Columns in the right hand table will become `Nullable` which means
    /// you must call `nullable()` on the corresponding fields in the select
    /// clause:
    ///
    /// ### Selecting after a left join
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # use schema::{users, posts};
    /// #
    /// # #[derive(Queryable, PartialEq, Eq, Debug)]
    /// # struct User {
    /// #     id: i32,
    /// #     name: String,
    /// # }
    /// #
    /// # impl User {
    /// #     fn new(id: i32, name: &str) -> Self {
    /// #         User {
    /// #             id,
    /// #             name: name.into(),
    /// #         }
    /// #     }
    /// # }
    /// #
    /// # #[derive(Queryable, PartialEq, Eq, Debug)]
    /// # struct Post {
    /// #     id: i32,
    /// #     user_id: i32,
    /// #     title: String,
    /// # }
    /// #
    /// # impl Post {
    /// #     fn new(id: i32, user_id: i32, title: &str) -> Self {
    /// #         Post {
    /// #             id,
    /// #             user_id,
    /// #             title: title.into(),
    /// #         }
    /// #     }
    /// # }
    /// #
    /// # fn main() {
    /// #     run_test().unwrap();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     let connection = &mut establish_connection();
    /// #     diesel::sql_query("DELETE FROM posts").execute(connection)?;
    /// #     diesel::insert_into(posts::table)
    /// #         .values((posts::user_id.eq(1), posts::title.eq("Sean's Post")))
    /// #         .execute(connection)?;
    /// #     let post_id = posts::table.select(posts::id)
    /// #         .first::<i32>(connection)?;
    /// let join = users::table.left_join(posts::table);
    ///
    /// // Since `posts` is on the right side of a left join, `.nullable` is
    /// // needed.
    /// let names_and_titles = join.select((users::name, posts::title.nullable()))
    ///     .load::<(String, Option<String>)>(connection)?;
    /// let expected_data = vec![
    ///     (String::from("Sean"), Some(String::from("Sean's Post"))),
    ///     (String::from("Tess"), None),
    /// ];
    /// assert_eq!(expected_data, names_and_titles);
    /// #     Ok(())
    /// # }
    /// ```
    fn left_outer_join<Rhs>(self, rhs: Rhs) -> LeftJoin<Self, Rhs>
    where
        Self: JoinWithImplicitOnClause<Rhs, joins::LeftOuter>,
    {
        self.join_with_implicit_on_clause(rhs, joins::LeftOuter)
    }

    /// Alias for [`left_outer_join`].
    ///
    /// [`left_outer_join`]: QueryDsl::left_outer_join()
    fn left_join<Rhs>(self, rhs: Rhs) -> LeftJoin<Self, Rhs>
    where
        Self: JoinWithImplicitOnClause<Rhs, joins::LeftOuter>,
    {
        self.left_outer_join(rhs)
    }

    /// Adds to the `WHERE` clause of a query.
    ///
    /// If there is already a `WHERE` clause, the result will be `old AND new`.
    ///
    /// Note that in order to use this method with columns from different tables, you need to call
    ///  [`.inner_join`] or [`.left_join`] beforehand.
    /// This is because you can only access columns from tables
    /// that appear in your query before the call to [`.filter`].
    ///
    /// [`.inner_join`]: QueryDsl::inner_join()
    /// [`.left_join`]: QueryDsl::left_join()
    /// [`.filter`]: QueryDsl::filter()
    ///
    /// # Example:
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// let seans_id = users.filter(name.eq("Sean")).select(id)
    ///     .first(connection);
    /// assert_eq!(Ok(1), seans_id);
    /// let tess_id = users.filter(name.eq("Tess")).select(id)
    ///     .first(connection);
    /// assert_eq!(Ok(2), tess_id);
    /// # }
    /// ```
    #[doc(alias = "where")]
    fn filter<Predicate>(self, predicate: Predicate) -> Filter<Self, Predicate>
    where
        Self: methods::FilterDsl<Predicate>,
    {
        methods::FilterDsl::filter(self, predicate)
    }

    /// Adds to the `WHERE` clause of a query using `OR`
    ///
    /// If there is already a `WHERE` clause, the result will be `(old OR new)`.
    /// Calling `foo.filter(bar).or_filter(baz)`
    /// is identical to `foo.filter(bar.or(baz))`.
    /// However, the second form is much harder to do dynamically.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test().unwrap();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use schema::animals::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// #     diesel::delete(animals).execute(connection)?;
    /// diesel::insert_into(animals)
    ///     .values(&vec![
    ///         (species.eq("cat"), legs.eq(4), name.eq("Sinatra")),
    ///         (species.eq("dog"), legs.eq(3), name.eq("Fido")),
    ///         (species.eq("spider"), legs.eq(8), name.eq("Charlotte")),
    ///     ])
    ///     .execute(connection)?;
    ///
    /// let good_animals = animals
    ///     .filter(name.eq("Fido"))
    ///     .or_filter(legs.eq(4))
    ///     .select(name)
    ///     .get_results::<Option<String>>(connection)?;
    /// let expected = vec![
    ///     Some(String::from("Sinatra")),
    ///     Some(String::from("Fido")),
    /// ];
    /// assert_eq!(expected, good_animals);
    /// #     Ok(())
    /// # }
    /// ```
    #[doc(alias = "where")]
    fn or_filter<Predicate>(self, predicate: Predicate) -> OrFilter<Self, Predicate>
    where
        Self: methods::OrFilterDsl<Predicate>,
    {
        methods::OrFilterDsl::or_filter(self, predicate)
    }

    /// Attempts to find a single record from the given table by primary key.
    ///
    /// # Example
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     use schema::users::dsl::*;
    /// #     use diesel::result::Error::NotFound;
    /// #     let connection = &mut establish_connection();
    /// let sean = (1, "Sean".to_string());
    /// let tess = (2, "Tess".to_string());
    /// assert_eq!(Ok(sean), users.find(1).first(connection));
    /// assert_eq!(Ok(tess), users.find(2).first(connection));
    /// assert_eq!(Err::<(i32, String), _>(NotFound), users.find(3).first(connection));
    /// # }
    /// ```
    fn find<PK>(self, id: PK) -> Find<Self, PK>
    where
        Self: methods::FindDsl<PK>,
    {
        methods::FindDsl::find(self, id)
    }

    /// Sets the order clause of a query.
    ///
    /// If there was already an order clause, it will be overridden. See
    /// also:
    /// [`.desc()`](crate::expression_methods::ExpressionMethods::desc())
    /// and
    /// [`.asc()`](crate::expression_methods::ExpressionMethods::asc())
    ///
    /// Ordering by multiple columns can be achieved by passing a tuple of those
    /// columns.
    /// To construct an order clause of an unknown number of columns,
    /// see [`QueryDsl::then_order_by`](QueryDsl::then_order_by())
    ///
    /// # Examples
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// #     diesel::sql_query("DELETE FROM users").execute(connection)?;
    /// diesel::insert_into(users)
    ///     .values(&vec![
    ///         name.eq("Saul"),
    ///         name.eq("Steve"),
    ///         name.eq("Stan"),
    ///     ])
    ///     .execute(connection)?;
    ///
    /// let ordered_names = users.select(name)
    ///     .order(name.desc())
    ///     .load::<String>(connection)?;
    /// assert_eq!(vec!["Steve", "Stan", "Saul"], ordered_names);
    ///
    /// diesel::insert_into(users).values(name.eq("Stan")).execute(connection)?;
    ///
    /// let data = users.select((name, id))
    ///     .order((name.asc(), id.desc()))
    ///     .load(connection)?;
    /// let expected_data = vec![
    ///     (String::from("Saul"), 3),
    ///     (String::from("Stan"), 6),
    ///     (String::from("Stan"), 5),
    ///     (String::from("Steve"), 4),
    /// ];
    /// assert_eq!(expected_data, data);
    /// #    Ok(())
    /// # }
    /// ```
    fn order<Expr>(self, expr: Expr) -> Order<Self, Expr>
    where
        Expr: Expression,
        Self: methods::OrderDsl<Expr>,
    {
        methods::OrderDsl::order(self, expr)
    }

    /// Alias for `order`
    fn order_by<Expr>(self, expr: Expr) -> Order<Self, Expr>
    where
        Expr: Expression,
        Self: methods::OrderDsl<Expr>,
    {
        QueryDsl::order(self, expr)
    }

    /// Appends to the `ORDER BY` clause of this SQL query.
    ///
    /// Unlike `.order`, this method will append rather than replace.
    /// In other words,
    /// `.order_by(foo).order_by(bar)` is equivalent to `.order_by(bar)`.
    /// In contrast,
    /// `.order_by(foo).then_order_by(bar)` is equivalent to `.order((foo, bar))`.
    /// This method is only present on boxed queries.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// #     diesel::sql_query("DELETE FROM users").execute(connection)?;
    /// diesel::insert_into(users)
    ///     .values(&vec![
    ///         name.eq("Saul"),
    ///         name.eq("Steve"),
    ///         name.eq("Stan"),
    ///         name.eq("Stan"),
    ///     ])
    ///     .execute(connection)?;
    ///
    /// let data = users.select((name, id))
    ///     .order_by(name.asc())
    ///     .then_order_by(id.desc())
    ///     .load(connection)?;
    /// let expected_data = vec![
    ///     (String::from("Saul"), 3),
    ///     (String::from("Stan"), 6),
    ///     (String::from("Stan"), 5),
    ///     (String::from("Steve"), 4),
    /// ];
    /// assert_eq!(expected_data, data);
    /// #    Ok(())
    /// # }
    /// ```
    fn then_order_by<Order>(self, order: Order) -> ThenOrderBy<Self, Order>
    where
        Self: methods::ThenOrderDsl<Order>,
    {
        methods::ThenOrderDsl::then_order_by(self, order)
    }

    /// Sets the limit clause of the query.
    ///
    /// If there was already a limit clause, it will be overridden.
    ///
    /// # Example
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # use schema::users;
    /// #
    /// # fn main() {
    /// #     run_test().unwrap();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use self::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// #     diesel::delete(users).execute(connection)?;
    /// #     diesel::insert_into(users)
    /// #        .values(&vec![
    /// #            name.eq("Sean"),
    /// #            name.eq("Bastien"),
    /// #            name.eq("Pascal"),
    /// #        ])
    /// #        .execute(connection)?;
    /// #
    /// // Using a limit
    /// let limited = users.select(name)
    ///     .order(id)
    ///     .limit(1)
    ///     .load::<String>(connection)?;
    ///
    /// // Without a limit
    /// let no_limit = users.select(name)
    ///     .order(id)
    ///     .load::<String>(connection)?;
    ///
    /// assert_eq!(vec!["Sean"], limited);
    /// assert_eq!(vec!["Sean", "Bastien", "Pascal"], no_limit);
    /// #    Ok(())
    /// # }
    /// ```
    fn limit(self, limit: i64) -> Limit<Self>
    where
        Self: methods::LimitDsl,
    {
        methods::LimitDsl::limit(self, limit)
    }

    /// Sets the offset clause of the query.
    ///
    /// If there was already a offset clause, it will be overridden.
    ///
    /// # Example
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # use schema::users;
    /// #
    /// # fn main() {
    /// #     run_test().unwrap();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use self::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// #     diesel::delete(users).execute(connection)?;
    /// #     diesel::insert_into(users)
    /// #        .values(&vec![
    /// #            name.eq("Sean"),
    /// #            name.eq("Bastien"),
    /// #            name.eq("Pascal"),
    /// #        ])
    /// #        .execute(connection)?;
    /// #
    /// // Using an offset
    /// let offset = users.select(name)
    ///     .order(id)
    ///     .limit(2)
    ///     .offset(1)
    ///     .load::<String>(connection)?;
    ///
    /// // No Offset
    /// let no_offset = users.select(name)
    ///     .order(id)
    ///     .limit(2)
    ///     .load::<String>(connection)?;
    ///
    /// assert_eq!(vec!["Bastien", "Pascal"], offset);
    /// assert_eq!(vec!["Sean", "Bastien"], no_offset);
    /// #     Ok(())
    /// # }
    /// ```
    fn offset(self, offset: i64) -> Offset<Self>
    where
        Self: methods::OffsetDsl,
    {
        methods::OffsetDsl::offset(self, offset)
    }

    /// Sets the `group by` clause of a query.
    ///
    /// **Note:** Queries having a `group by` clause require a custom select clause.
    /// Use [`QueryDsl::select()`] to specify one.
    ///
    /// If there was already a group by clause, it will be overridden.
    /// Grouping by multiple columns can be achieved by passing a tuple of those
    /// columns.
    ///
    /// Diesel follows postgresql's group by semantic, this means any column
    /// appearing in a group by clause is considered to be aggregated. If a
    /// primary key is part of the group by clause every column from the
    /// corresponding table is considered to be aggregated. Select clauses
    /// cannot mix aggregated and non aggregated expressions.
    ///
    /// For group by clauses containing columns from more than one table it
    /// is required to call [`allow_columns_to_appear_in_same_group_by_clause!`]
    ///
    /// [`allow_columns_to_appear_in_same_group_by_clause!`]: crate::allow_columns_to_appear_in_same_group_by_clause!
    ///
    /// # Examples
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use crate::schema::{users, posts};
    /// #     use diesel::dsl::count;
    /// #     let connection = &mut establish_connection();
    /// let data = users::table.inner_join(posts::table)
    ///     .group_by(users::id)
    ///     .select((users::name, count(posts::id)))
    /// #   .order_by(users::id.asc())
    ///     .load::<(String, i64)>(connection)?;
    ///
    /// assert_eq!(vec![(String::from("Sean"), 2), (String::from("Tess"), 1)], data);
    /// # Ok(())
    /// # }
    /// ```
    fn group_by<GB>(self, group_by: GB) -> GroupBy<Self, GB>
    where
        GB: Expression,
        Self: methods::GroupByDsl<GB>,
    {
        methods::GroupByDsl::group_by(self, group_by)
    }

    /// Adds to the `HAVING` clause of a query.
    ///
    /// # Examples
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use crate::schema::{users, posts};
    /// #     use diesel::dsl::count;
    /// #     let connection = &mut establish_connection();
    /// let data = users::table.inner_join(posts::table)
    ///     .group_by(users::id)
    ///     .having(count(posts::id).gt(1))
    ///     .select((users::name, count(posts::id)))
    ///     .load::<(String, i64)>(connection)?;
    ///
    /// assert_eq!(vec![(String::from("Sean"), 2)], data);
    /// # Ok(())
    /// # }
    /// ```
    fn having<Predicate>(self, predicate: Predicate) -> Having<Self, Predicate>
    where
        Self: methods::HavingDsl<Predicate>,
    {
        methods::HavingDsl::having(self, predicate)
    }

    /// Adds `FOR UPDATE` to the end of the select statement.
    ///
    /// This method is only available for MySQL and PostgreSQL. SQLite does not
    /// provide any form of row locking.
    ///
    /// Additionally, `.for_update` cannot be used on queries with a distinct
    /// clause, group by clause, having clause, or any unions. Queries with
    /// a `FOR UPDATE` clause cannot be boxed.
    ///
    /// # Example
    ///
    /// ```
    /// # include!("../doctest_setup.rs");
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # #[cfg(any(feature = "mysql", feature = "postgres"))]
    /// # fn run_test() -> QueryResult<()> {
    /// #     use crate::schema::users;
    /// #     let connection = &mut establish_connection();
    /// // Executes `SELECT * FROM users FOR UPDATE`
    /// let users_for_update = users::table.for_update().load(connection)?;
    /// # let u: Vec<(i32, String)> = users_for_update;
    /// # Ok(())
    /// # }
    /// # #[cfg(feature = "sqlite")]
    /// # fn run_test() -> QueryResult<()> { Ok(()) }
    /// ```
    fn for_update(self) -> ForUpdate<Self>
    where
        Self: methods::LockingDsl<lock::ForUpdate>,
    {
        methods::LockingDsl::with_lock(self, lock::ForUpdate)
    }

    /// Adds `FOR NO KEY UPDATE` to the end of the select statement.
    ///
    /// This method is only available for PostgreSQL. SQLite does not
    /// provide any form of row locking, and MySQL does not support anything
    /// finer than row-level locking.
    ///
    /// Additionally, `.for_no_key_update` cannot be used on queries with a distinct
    /// clause, group by clause, having clause, or any unions. Queries with
    /// a `FOR NO KEY UPDATE` clause cannot be boxed.
    ///
    /// # Example
    ///
    /// ```
    /// # include!("../doctest_setup.rs");
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # #[cfg(feature = "postgres")]
    /// # fn run_test() -> QueryResult<()> {
    /// #     use crate::schema::users;
    /// #     let connection = &mut establish_connection();
    /// // Executes `SELECT * FROM users FOR NO KEY UPDATE`
    /// let users_for_no_key_update = users::table.for_no_key_update().load(connection)?;
    /// # let u: Vec<(i32, String)> = users_for_no_key_update;
    /// # Ok(())
    /// # }
    /// # #[cfg(not(feature = "postgres"))]
    /// # fn run_test() -> QueryResult<()> { Ok(()) }
    /// ```
    fn for_no_key_update(self) -> ForNoKeyUpdate<Self>
    where
        Self: methods::LockingDsl<lock::ForNoKeyUpdate>,
    {
        methods::LockingDsl::with_lock(self, lock::ForNoKeyUpdate)
    }

    /// Adds `FOR SHARE` to the end of the select statement.
    ///
    /// This method is only available for MySQL and PostgreSQL. SQLite does not
    /// provide any form of row locking.
    ///
    /// Additionally, `.for_share` cannot be used on queries with a distinct
    /// clause, group by clause, having clause, or any unions. Queries with
    /// a `FOR SHARE` clause cannot be boxed.
    ///
    /// # Example
    ///
    /// ```
    /// # include!("../doctest_setup.rs");
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # #[cfg(any(feature = "mysql", feature = "postgres"))]
    /// # fn run_test() -> QueryResult<()> {
    /// #     use crate::schema::users;
    /// #     let connection = &mut establish_connection();
    /// // Executes `SELECT * FROM users FOR SHARE`
    /// let users_for_share = users::table.for_share().load(connection)?;
    /// # let u: Vec<(i32, String)> = users_for_share;
    /// # Ok(())
    /// # }
    /// # #[cfg(feature = "sqlite")]
    /// # fn run_test() -> QueryResult<()> { Ok(()) }
    /// ```
    fn for_share(self) -> ForShare<Self>
    where
        Self: methods::LockingDsl<lock::ForShare>,
    {
        methods::LockingDsl::with_lock(self, lock::ForShare)
    }

    /// Adds `FOR KEY SHARE` to the end of the select statement.
    ///
    /// This method is only available for PostgreSQL. SQLite does not
    /// provide any form of row locking, and MySQL does not support anything
    /// finer than row-level locking.
    ///
    /// Additionally, `.for_key_share` cannot be used on queries with a distinct
    /// clause, group by clause, having clause, or any unions. Queries with
    /// a `FOR KEY SHARE` clause cannot be boxed.
    ///
    /// # Example
    ///
    /// ```
    /// # include!("../doctest_setup.rs");
    /// # fn main() {
    /// #     run_test();
    /// # }
    ///
    /// # #[cfg(feature = "postgres")]
    /// # fn run_test() -> QueryResult<()> {
    /// #     use crate::schema::users;
    /// #     let connection = &mut establish_connection();
    /// // Executes `SELECT * FROM users FOR KEY SHARE`
    /// let users_for_key_share = users::table.for_key_share().load(connection)?;
    /// # let u: Vec<(i32, String)> = users_for_key_share;
    /// # Ok(())
    /// # }
    /// # #[cfg(not(feature = "postgres"))]
    /// # fn run_test() -> QueryResult<()> { Ok(()) }
    /// ```
    fn for_key_share(self) -> ForKeyShare<Self>
    where
        Self: methods::LockingDsl<lock::ForKeyShare>,
    {
        methods::LockingDsl::with_lock(self, lock::ForKeyShare)
    }

    /// Adds `SKIP LOCKED` to the end of a `FOR UPDATE` clause.
    ///
    /// This modifier is only supported in PostgreSQL 9.5+ and MySQL 8+.
    ///
    /// # Example
    ///
    /// ```
    /// # include!("../doctest_setup.rs");
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # #[cfg(any(feature = "postgres", feature = "mysql"))]
    /// # fn run_test() -> QueryResult<()> {
    /// #     use crate::schema::users;
    /// #     let connection = &mut establish_connection();
    /// // Executes `SELECT * FROM users FOR UPDATE SKIP LOCKED`
    /// let user_skipped_locked = users::table.for_update().skip_locked().load(connection)?;
    /// # let u: Vec<(i32, String)> = user_skipped_locked;
    /// # Ok(())
    /// # }
    /// # #[cfg(feature = "sqlite")]
    /// # fn run_test() -> QueryResult<()> { Ok(()) }
    /// ```
    fn skip_locked(self) -> SkipLocked<Self>
    where
        Self: methods::ModifyLockDsl<lock::SkipLocked>,
    {
        methods::ModifyLockDsl::modify_lock(self, lock::SkipLocked)
    }

    /// Adds `NOWAIT` to the end of a `FOR UPDATE` clause.
    ///
    /// This modifier is only supported in PostgreSQL 9.5+ and MySQL 8+.
    ///
    /// # Example
    ///
    /// ```
    /// # include!("../doctest_setup.rs");
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # #[cfg(any(feature = "mysql", feature = "postgres"))]
    /// # fn run_test() -> QueryResult<()> {
    /// #     use crate::schema::users;
    /// #     let connection = &mut establish_connection();
    /// // Executes `SELECT * FROM users FOR UPDATE NOWAIT`
    /// let users_no_wait = users::table.for_update().no_wait().load(connection)?;
    /// # let u: Vec<(i32, String)> = users_no_wait;
    /// # Ok(())
    /// # }
    /// # #[cfg(feature = "sqlite")]
    /// # fn run_test() -> QueryResult<()> { Ok(()) }
    /// ```
    fn no_wait(self) -> NoWait<Self>
    where
        Self: methods::ModifyLockDsl<lock::NoWait>,
    {
        methods::ModifyLockDsl::modify_lock(self, lock::NoWait)
    }

    /// Boxes the pieces of a query into a single type.
    ///
    /// This is useful for cases where you want to conditionally modify a query,
    /// but need the type to remain the same. The backend must be specified as
    /// part of this. It is not possible to box a query and have it be useable
    /// on multiple backends.
    ///
    /// A boxed query will incur a minor performance penalty, as the query builder
    /// can no longer be inlined by the compiler. For most applications this cost
    /// will be minimal.
    ///
    /// ### Example
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # use schema::users;
    /// #
    /// # fn main() {
    /// #     use std::collections::HashMap;
    /// #     let connection = &mut establish_connection();
    /// #     let mut params = HashMap::new();
    /// #     params.insert("name", "Sean");
    /// let mut query = users::table.into_boxed();
    /// if let Some(name) = params.get("name") {
    ///     query = query.filter(users::name.eq(name));
    /// }
    /// let users = query.load(connection);
    /// #     let expected = vec![(1, String::from("Sean"))];
    /// #     assert_eq!(Ok(expected), users);
    /// # }
    /// ```
    ///
    /// Diesel queries also have a similar problem to [`Iterator`], where
    /// returning them from a function requires exposing the implementation of that
    /// function. The [`helper_types`][helper_types] module exists to help with this,
    /// but you might want to hide the return type or have it conditionally change.
    /// Boxing can achieve both.
    ///
    /// [helper_types]: crate::helper_types
    ///
    /// ### Example
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # use schema::users;
    /// #
    /// # fn main() {
    /// #     let connection = &mut establish_connection();
    /// fn users_by_name(name: &str) -> users::BoxedQuery<DB> {
    ///     users::table.filter(users::name.eq(name)).into_boxed()
    /// }
    ///
    /// assert_eq!(Ok(1), users_by_name("Sean").select(users::id).first(connection));
    /// assert_eq!(Ok(2), users_by_name("Tess").select(users::id).first(connection));
    /// # }
    /// ```
    fn into_boxed<'a, DB>(self) -> IntoBoxed<'a, Self, DB>
    where
        DB: Backend,
        Self: methods::BoxedDsl<'a, DB>,
    {
        methods::BoxedDsl::internal_into_boxed(self)
    }

    /// Wraps this select statement in parenthesis, allowing it to be used
    /// as an expression.
    ///
    /// SQL allows queries such as `foo = (SELECT ...)`, as long as the
    /// subselect returns only a single column, and 0 or 1 rows. This method
    /// indicates that you expect the query to only return a single value (this
    /// will be enforced by adding `LIMIT 1`).
    ///
    /// The SQL type of this will always be `Nullable`, as the query returns
    /// `NULL` if the table is empty or it otherwise returns 0 rows.
    ///
    /// # Example
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use diesel::insert_into;
    /// #     use schema::users::dsl::*;
    /// #     use schema::posts;
    /// #     let connection = &mut establish_connection();
    /// insert_into(posts::table)
    ///     .values(posts::user_id.eq(1))
    ///     .execute(connection)?;
    /// let last_post = posts::table
    ///     .order(posts::id.desc());
    /// let most_recently_active_user = users.select(name)
    ///     .filter(id.nullable().eq(last_post.select(posts::user_id).single_value()))
    ///     .first::<String>(connection)?;
    /// assert_eq!("Sean", most_recently_active_user);
    /// #     Ok(())
    /// # }
    /// ```
    fn single_value(self) -> SingleValue<Self>
    where
        Self: methods::SingleValueDsl,
    {
        methods::SingleValueDsl::single_value(self)
    }

    /// Coerce the SQL type of the select clause to it's nullable equivalent.
    ///
    /// This is useful for writing queries that contain subselects on non null
    /// fields comparing them to nullable fields.
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #    run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     let connection = &mut establish_connection();
    /// table! {
    ///     users {
    ///         id -> Integer,
    ///         name -> Text,
    ///     }
    /// }
    ///
    /// table! {
    ///     posts {
    ///         id -> Integer,
    ///         by_user -> Nullable<Text>,
    ///     }
    /// }
    ///
    /// allow_tables_to_appear_in_same_query!(users, posts);
    ///
    /// # let _: Vec<(i32, Option<String>)> =
    /// posts::table.filter(
    ///    posts::by_user.eq_any(users::table.select(users::name).nullable())
    /// ).load(connection)?;
    /// #     Ok(())
    /// # }
    fn nullable(self) -> NullableSelect<Self>
    where
        Self: methods::SelectNullableDsl,
    {
        methods::SelectNullableDsl::nullable(self)
    }
}

impl<T: Table> QueryDsl for T {}

/// Methods used to execute queries.
pub trait RunQueryDsl<Conn>: Sized {
    /// Executes the given command, returning the number of rows affected.
    ///
    /// `execute` is usually used in conjunction with [`insert_into`](crate::insert_into()),
    /// [`update`](crate::update()) and [`delete`](crate::delete()) where the number of
    /// affected rows is often enough information.
    ///
    /// When asking the database to return data from a query, [`load`](crate::query_dsl::RunQueryDsl::load()) should
    /// probably be used instead.
    ///
    /// # Example
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use diesel::insert_into;
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// let inserted_rows = insert_into(users)
    ///     .values(name.eq("Ruby"))
    ///     .execute(connection)?;
    /// assert_eq!(1, inserted_rows);
    ///
    /// let inserted_rows = insert_into(users)
    ///     .values(&vec![name.eq("Jim"), name.eq("James")])
    ///     .execute(connection)?;
    /// assert_eq!(2, inserted_rows);
    /// #     Ok(())
    /// # }
    /// ```
    fn execute(self, conn: &mut Conn) -> QueryResult<usize>
    where
        Conn: Connection,
        Self: methods::ExecuteDsl<Conn>,
    {
        methods::ExecuteDsl::execute(self, conn)
    }

    /// Executes the given query, returning a [`Vec`] with the returned rows.
    ///
    /// When using the query builder, the return type can be
    /// a tuple of the values, or a struct which implements [`Queryable`].
    ///
    /// When this method is called on [`sql_query`],
    /// the return type can only be a struct which implements [`QueryableByName`]
    ///
    /// For insert, update, and delete operations where only a count of affected is needed,
    /// [`execute`] should be used instead.
    ///
    /// [`Queryable`]: crate::deserialize::Queryable
    /// [`QueryableByName`]: crate::deserialize::QueryableByName
    /// [`execute`]: crate::query_dsl::RunQueryDsl::execute()
    /// [`sql_query`]: crate::sql_query()
    ///
    /// ## How to resolve compiler errors while loading data from the database
    ///
    /// In case you getting uncomprehensable compiler errors while loading data
    /// from the database into a type using [`#[derive(Queryable)]`](derive@crate::prelude::Queryable)
    /// you might want to consider
    /// using  [`#[derive(Selectable)]`](derive@crate::prelude::Selectable) +
    /// `#[diesel(check_for_backend(YourBackendType))]`
    /// to check for mismatching fields at compile time. This drastically improves
    /// the quality of the generated error messages by pointing to concrete type mismatches at
    /// field level.You need to specify the concrete database backend
    /// this specific struct is indented to be used with, as otherwise rustc cannot correctly
    /// identify the required deserialization implementation.
    ///
    /// # Examples
    ///
    /// ## Returning a single field
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use diesel::insert_into;
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// let data = users.select(name)
    ///     .load::<String>(connection)?;
    /// assert_eq!(vec!["Sean", "Tess"], data);
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// ## Returning a tuple
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use diesel::insert_into;
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// let data = users
    ///     .load::<(i32, String)>(connection)?;
    /// let expected_data = vec![
    ///     (1, String::from("Sean")),
    ///     (2, String::from("Tess")),
    /// ];
    /// assert_eq!(expected_data, data);
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// ## Returning a struct
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// #[derive(Queryable, PartialEq, Debug)]
    /// struct User {
    ///     id: i32,
    ///     name: String,
    /// }
    ///
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use diesel::insert_into;
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// let data = users
    ///     .load::<User>(connection)?;
    /// let expected_data = vec![
    ///     User { id: 1, name: String::from("Sean") },
    ///     User { id: 2, name: String::from("Tess") },
    /// ];
    /// assert_eq!(expected_data, data);
    /// #     Ok(())
    /// # }
    /// ```
    fn load<'query, U>(self, conn: &mut Conn) -> QueryResult<Vec<U>>
    where
        Self: LoadQuery<'query, Conn, U>,
    {
        self.internal_load(conn)?.collect()
    }

    /// Executes the given query, returning an [`Iterator`] with the returned rows.
    ///
    /// The iterator's item is [`QueryResult<U>`](crate::result::QueryResult).
    ///
    /// You should normally prefer to use [`RunQueryDsl::load`] instead. This method
    /// is provided for situations where the result needs to be collected into a different
    /// container than a [`Vec`]
    ///
    /// When using the query builder, the return type can be
    /// a tuple of the values, or a struct which implements [`Queryable`].
    /// This type is specified by the first generic type of this function.
    ///
    /// The second generic type parameter specifies the so called loading mode,
    /// which describes how the connection implementation loads data from the database.
    /// All connections should provide a implementation for
    /// [`DefaultLoadingMode`](crate::connection::DefaultLoadingMode).
    ///
    /// They may provide additional modes. Checkout the documentation of the concrete
    /// connection types for details. For connection implementations that provide
    /// more than one loading mode it is **required** to specify this generic paramater.
    /// This is currently true for `PgConnection`.
    ///
    /// When this method is called on [`sql_query`],
    /// the return type can only be a struct which implements [`QueryableByName`]
    ///
    /// For insert, update, and delete operations where only a count of affected is needed,
    /// [`execute`] should be used instead.
    ///
    /// [`Queryable`]: crate::deserialize::Queryable
    /// [`QueryableByName`]: crate::deserialize::QueryableByName
    /// [`execute`]: crate::query_dsl::RunQueryDsl::execute()
    /// [`sql_query`]: crate::sql_query()
    ///
    /// # Examples
    ///
    /// ## Returning a single field
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use diesel::insert_into;
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// use diesel::connection::DefaultLoadingMode;
    ///
    /// let data = users.select(name)
    ///     .load_iter::<String, DefaultLoadingMode>(connection)?
    ///     .collect::<QueryResult<Vec<_>>>()?;
    /// assert_eq!(vec!["Sean", "Tess"], data);
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// ## Returning a tuple
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use diesel::insert_into;
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// use diesel::connection::DefaultLoadingMode;
    ///
    /// let data = users
    ///     .load_iter::<(i32, String), DefaultLoadingMode>(connection)?
    ///     .collect::<QueryResult<Vec<_>>>()?;
    /// let expected_data = vec![
    ///     (1, String::from("Sean")),
    ///     (2, String::from("Tess")),
    /// ];
    /// assert_eq!(expected_data, data);
    /// #     Ok(())
    /// # }
    /// ```
    ///
    /// ## Returning a struct
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// #[derive(Queryable, PartialEq, Debug)]
    /// struct User {
    ///     id: i32,
    ///     name: String,
    /// }
    ///
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use diesel::insert_into;
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// use diesel::connection::DefaultLoadingMode;
    ///
    /// let data = users
    ///     .load_iter::<User, DefaultLoadingMode>(connection)?
    ///     .collect::<QueryResult<Vec<_>>>()?;
    /// let expected_data = vec![
    ///     User { id: 1, name: String::from("Sean") },
    ///     User { id: 2, name: String::from("Tess") },
    /// ];
    /// assert_eq!(expected_data, data);
    /// #     Ok(())
    /// # }
    /// ```
    fn load_iter<'conn, 'query: 'conn, U, B>(
        self,
        conn: &'conn mut Conn,
    ) -> QueryResult<Self::RowIter<'conn>>
    where
        U: 'conn,
        Self: LoadQuery<'query, Conn, U, B> + 'conn,
    {
        self.internal_load(conn)
    }

    /// Runs the command, and returns the affected row.
    ///
    /// `Err(NotFound)` will be returned if the query affected 0 rows. You can
    /// call `.optional()` on the result of this if the command was optional to
    /// get back a `Result<Option<U>>`
    ///
    /// When this method is called on an insert, update, or delete statement,
    /// it will implicitly add a `RETURNING *` to the query,
    /// unless a returning clause was already specified.
    ///
    /// This method only returns the first row that was affected, even if more
    /// rows are affected.
    ///
    /// # Example
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// #
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # #[cfg(feature = "postgres")]
    /// # fn run_test() -> QueryResult<()> {
    /// #     use diesel::{insert_into, update};
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// let inserted_row = insert_into(users)
    ///     .values(name.eq("Ruby"))
    ///     .get_result(connection)?;
    /// assert_eq!((3, String::from("Ruby")), inserted_row);
    ///
    /// // This will return `NotFound`, as there is no user with ID 4
    /// let update_result = update(users.find(4))
    ///     .set(name.eq("Jim"))
    ///     .get_result::<(i32, String)>(connection);
    /// assert_eq!(Err(diesel::NotFound), update_result);
    /// #     Ok(())
    /// # }
    /// #
    /// # #[cfg(not(feature = "postgres"))]
    /// # fn run_test() -> QueryResult<()> {
    /// #     Ok(())
    /// # }
    /// ```
    fn get_result<'query, U>(self, conn: &mut Conn) -> QueryResult<U>
    where
        Self: LoadQuery<'query, Conn, U>,
    {
        match self.internal_load(conn)?.next() {
            Some(v) => v,
            None => Err(crate::result::Error::NotFound),
        }
    }

    /// Runs the command, returning an `Vec` with the affected rows.
    ///
    /// This method is an alias for [`load`], but with a name that makes more
    /// sense for insert, update, and delete statements.
    ///
    /// [`load`]: crate::query_dsl::RunQueryDsl::load()
    fn get_results<'query, U>(self, conn: &mut Conn) -> QueryResult<Vec<U>>
    where
        Self: LoadQuery<'query, Conn, U>,
    {
        self.load(conn)
    }

    /// Attempts to load a single record.
    ///
    /// This method is equivalent to `.limit(1).get_result()`
    ///
    /// Returns `Ok(record)` if found, and `Err(NotFound)` if no results are
    /// returned. If the query truly is optional, you can call `.optional()` on
    /// the result of this to get a `Result<Option<U>>`.
    ///
    /// # Example:
    ///
    /// ```rust
    /// # include!("../doctest_setup.rs");
    /// # fn main() {
    /// #     run_test();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use schema::users::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// diesel::insert_into(users)
    ///     .values(&vec![name.eq("Sean"), name.eq("Pascal")])
    ///     .execute(connection)?;
    ///
    /// let first_name = users.order(id).select(name).first(connection);
    /// assert_eq!(Ok(String::from("Sean")), first_name);
    ///
    /// let not_found = users
    ///     .filter(name.eq("Foo"))
    ///     .first::<(i32, String)>(connection);
    /// assert_eq!(Err(diesel::NotFound), not_found);
    /// #     Ok(())
    /// # }
    /// ```
    fn first<'query, U>(self, conn: &mut Conn) -> QueryResult<U>
    where
        Self: methods::LimitDsl,
        Limit<Self>: LoadQuery<'query, Conn, U>,
    {
        methods::LimitDsl::limit(self, 1).get_result(conn)
    }
}

// Note: We could have a blanket `AsQuery` impl here, which would apply to
// everything we want it to. However, when a query is invalid, we specifically
// want the error to happen on the where clause of the method instead of trait
// resolution. Otherwise our users will get an error saying `<3 page long type>:
// ExecuteDsl is not satisfied` instead of a specific error telling them what
// part of their query is wrong.
impl<T, Conn> RunQueryDsl<Conn> for T where T: Table {}