summaryrefslogtreecommitdiffstats
path: root/Bugzilla/DB.pm
blob: 7756ff53b79117657e03f76e5671de236bd5325b (plain)
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
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
#
# This Source Code Form is "Incompatible With Secondary Licenses", as
# defined by the Mozilla Public License, v. 2.0.

package Bugzilla::DB;

use 5.10.1;
use strict;

use DBI;

# Inherit the DB class from DBI::db.
use base qw(DBI::db);

use Bugzilla::Constants;
use Bugzilla::Install::Requirements;
use Bugzilla::Install::Util qw(vers_cmp install_string);
use Bugzilla::Install::Localconfig;
use Bugzilla::Util;
use Bugzilla::Error;
use Bugzilla::DB::Schema;

use List::Util qw(max);
use Storable qw(dclone);

#####################################################################
# Constants
#####################################################################

use constant BLOB_TYPE => DBI::SQL_BLOB;
use constant ISOLATION_LEVEL => 'REPEATABLE READ';

# Set default values for what used to be the enum types.  These values
# are no longer stored in localconfig.  If we are upgrading from a
# Bugzilla with enums to a Bugzilla without enums, we use the
# enum values.
#
# The values that you see here are ONLY DEFAULTS. They are only used
# the FIRST time you run checksetup.pl, IF you are NOT upgrading from a
# Bugzilla with enums. After that, they are either controlled through
# the Bugzilla UI or through the DB.
use constant ENUM_DEFAULTS => {
    bug_severity  => ['blocker', 'critical', 'major', 'normal',
                      'minor', 'trivial', 'enhancement'],
    priority     => ["Highest", "High", "Normal", "Low", "Lowest", "---"],
    op_sys       => ["All","Windows","Mac OS","Linux","Other"],
    rep_platform => ["All","PC","Macintosh","Other"],
    bug_status   => ["UNCONFIRMED","CONFIRMED","IN_PROGRESS","RESOLVED",
                     "VERIFIED"],
    resolution   => ["","FIXED","INVALID","WONTFIX", "DUPLICATE","WORKSFORME"],
};

# The character that means "OR" in a boolean fulltext search. If empty,
# the database doesn't support OR searches in fulltext searches.
# Used by Bugzilla::Bug::possible_duplicates.
use constant FULLTEXT_OR => '';

# These are used in regular expressions to mean "the start or end of a word".
#
# We don't use [[:<:]] and [[:>:]], even though they mean
# "start and end of a word" and are supported by both MySQL and PostgreSQL,
# because they don't work if your search starts or ends with a non-alphanumeric
# character, and there's a fair chance somebody will want to use the "word"
# search to search flags for something like "review+".
#
# We do use [:almum:] because it is supported by at least MySQL and
# PostgreSQL, and hopefully will get us as much Unicode support as possible,
# depending on how well the regexp engines of the various databases support
# Unicode.
use constant WORD_START => '(^|[^[:alnum:]])';
use constant WORD_END   => '($|[^[:alnum:]])';

# On most databases, in order to drop an index, you have to first drop
# the foreign keys that use that index. However, on some databases,
# dropping the FK immediately before dropping the index causes problems
# and doesn't need to be done anyway, so those DBs set this to 0.
use constant INDEX_DROPS_REQUIRE_FK_DROPS => 1;

#####################################################################
# Overridden Superclass Methods 
#####################################################################

sub quote {
    my $self = shift;
    my $retval = $self->SUPER::quote(@_);
    trick_taint($retval) if defined $retval;
    return $retval;
}

#####################################################################
# Connection Methods
#####################################################################

sub connect_shadow {
    my $params = Bugzilla->params;
    die "Tried to connect to non-existent shadowdb" 
        unless $params->{'shadowdb'};

    # Instead of just passing in a new hashref, we locally modify the
    # values of "localconfig", because some drivers access it while
    # connecting.
    my %connect_params = %{ Bugzilla->localconfig };
    $connect_params{db_host} = $params->{'shadowdbhost'};
    $connect_params{db_name} = $params->{'shadowdb'};
    $connect_params{db_port} = $params->{'shadowdbport'};
    $connect_params{db_sock} = $params->{'shadowdbsock'};

    return _connect(\%connect_params);
}

sub connect_main {
    my $lc = Bugzilla->localconfig;
    return _connect(Bugzilla->localconfig); 
}

sub _connect {
    my ($params) = @_;

    my $driver = $params->{db_driver};
    my $pkg_module = DB_MODULE->{lc($driver)}->{db};

    # do the actual import
    eval ("require $pkg_module")
        || die ("'$driver' is not a valid choice for \$db_driver in "
                . " localconfig: " . $@);

    # instantiate the correct DB specific module
    my $dbh = $pkg_module->new($params);

    return $dbh;
}

sub _handle_error {
    require Carp;

    # Cut down the error string to a reasonable size
    $_[0] = substr($_[0], 0, 2000) . ' ... ' . substr($_[0], -2000)
        if length($_[0]) > 4000;
    $_[0] = Carp::longmess($_[0]);
    return 0; # Now let DBI handle raising the error
}

sub bz_check_requirements {
    my ($output) = @_;

    my $lc = Bugzilla->localconfig;
    my $db = DB_MODULE->{lc($lc->{db_driver})};

    # Only certain values are allowed for $db_driver.
    if (!defined $db) {
        die "$lc->{db_driver} is not a valid choice for \$db_driver in"
            . bz_locations()->{'localconfig'};
    }

    # Check the existence and version of the DBD that we need.
    my $dbd = $db->{dbd};
    _bz_check_dbd($db, $output);

    # We don't try to connect to the actual database if $db_check is
    # disabled.
    unless ($lc->{db_check}) {
        print "\n" if $output;
        return;
    }

    # And now check the version of the database server itself.
    my $dbh = _get_no_db_connection();
    $dbh->bz_check_server_version($db, $output);

    print "\n" if $output;
}

sub _bz_check_dbd {
    my ($db, $output) = @_;

    my $dbd = $db->{dbd};
    unless (have_vers($dbd, $output)) {
        my $sql_server = $db->{name};
        my $command = install_command($dbd);
        my $root    = ROOT_USER;
        my $dbd_mod = $dbd->{module};
        my $dbd_ver = $dbd->{version};
        die <<EOT;

For $sql_server, Bugzilla requires that perl's $dbd_mod $dbd_ver or later be
installed. To install this module, run the following command (as $root):

    $command

EOT
    }
}

sub bz_check_server_version {
    my ($self, $db, $output) = @_;

    my $sql_vers = $self->bz_server_version;
    $self->disconnect;

    my $sql_want = $db->{db_version};
    my $version_ok = vers_cmp($sql_vers, $sql_want) > -1 ? 1 : 0;

    my $sql_server = $db->{name};
    if ($output) {
        Bugzilla::Install::Requirements::_checking_for({
            package => $sql_server, wanted => $sql_want,
            found   => $sql_vers, ok => $version_ok });
    }

    # Check what version of the database server is installed and let
    # the user know if the version is too old to be used with Bugzilla.
    if (!$version_ok) {
        die <<EOT;

Your $sql_server v$sql_vers is too old. Bugzilla requires version
$sql_want or later of $sql_server. Please download and install a
newer version.

EOT
    }

    # This is used by subclasses.
    return $sql_vers;
}

# Note that this function requires that localconfig exist and
# be valid.
sub bz_create_database {
    my $dbh;
    # See if we can connect to the actual Bugzilla database.
    my $conn_success = eval { $dbh = connect_main() };
    my $db_name = Bugzilla->localconfig->{db_name};

    if (!$conn_success) {
        $dbh = _get_no_db_connection();
        say "Creating database $db_name...";

        # Try to create the DB, and if we fail print a friendly error.
        my $success  = eval {
            my @sql = $dbh->_bz_schema->get_create_database_sql($db_name);
            # This ends with 1 because this particular do doesn't always
            # return something.
            $dbh->do($_) foreach @sql; 1;
        };
        if (!$success) {
            my $error = $dbh->errstr || $@;
            chomp($error);
            die "The '$db_name' database could not be created.",
                " The error returned was:\n\n    $error\n\n",
                _bz_connect_error_reasons();
        }
    }

    $dbh->disconnect;
}

# A helper for bz_create_database and bz_check_requirements.
sub _get_no_db_connection {
    my ($sql_server) = @_;
    my $dbh;
    my %connect_params = %{ Bugzilla->localconfig };
    $connect_params{db_name} = '';
    my $conn_success = eval {
        $dbh = _connect(\%connect_params);
    };
    if (!$conn_success) {
        my $driver = $connect_params{db_driver};
        my $sql_server = DB_MODULE->{lc($driver)}->{name};
        # Can't use $dbh->errstr because $dbh is undef.
        my $error = $DBI::errstr || $@;
        chomp($error);
        die "There was an error connecting to $sql_server:\n\n",
            "    $error\n\n", _bz_connect_error_reasons(), "\n";
    }
    return $dbh;    
}

# Just a helper because we have to re-use this text.
# We don't use this in db_new because it gives away the database
# username, and db_new errors can show up on CGIs.
sub _bz_connect_error_reasons {
    my $lc_file = bz_locations()->{'localconfig'};
    my $lc      = Bugzilla->localconfig;
    my $db      = DB_MODULE->{lc($lc->{db_driver})};
    my $server  = $db->{name};

return <<EOT;
This might have several reasons:

* $server is not running.
* $server is running, but there is a problem either in the
  server configuration or the database access rights. Read the Bugzilla
  Guide in the doc directory. The section about database configuration
  should help.
* Your password for the '$lc->{db_user}' user, specified in \$db_pass, is 
  incorrect, in '$lc_file'.
* There is a subtle problem with Perl, DBI, or $server. Make
  sure all settings in '$lc_file' are correct. If all else fails, set
  '\$db_check' to 0.

EOT
}

# List of abstract methods we are checking the derived class implements
our @_abstract_methods = qw(new sql_regexp sql_not_regexp sql_limit sql_to_days
                            sql_date_format sql_date_math bz_explain
                            sql_group_concat);

# This overridden import method will check implementation of inherited classes
# for missing implementation of abstract methods
# See http://perlmonks.thepen.com/44265.html
sub import {
    my $pkg = shift;

    # do not check this module
    if ($pkg ne __PACKAGE__) {
        # make sure all abstract methods are implemented
        foreach my $meth (@_abstract_methods) {
            $pkg->can($meth)
                or die("Class $pkg does not define method $meth");
        }
    }

    # Now we want to call our superclass implementation.
    # If our superclass is Exporter, which is using caller() to find
    # a namespace to populate, we need to adjust for this extra call.
    # All this can go when we stop using deprecated functions.
    my $is_exporter = $pkg->isa('Exporter');
    $Exporter::ExportLevel++ if $is_exporter;
    $pkg->SUPER::import(@_);
    $Exporter::ExportLevel-- if $is_exporter;
}

sub sql_istrcmp {
    my ($self, $left, $right, $op) = @_;
    $op ||= "=";

    return $self->sql_istring($left) . " $op " . $self->sql_istring($right);
}

sub sql_istring {
    my ($self, $string) = @_;

    return "LOWER($string)";
}

sub sql_iposition {
    my ($self, $fragment, $text) = @_;
    $fragment = $self->sql_istring($fragment);
    $text = $self->sql_istring($text);
    return $self->sql_position($fragment, $text);
}

sub sql_position {
    my ($self, $fragment, $text) = @_;

    return "POSITION($fragment IN $text)";
}

sub sql_group_by {
    my ($self, $needed_columns, $optional_columns) = @_;

    my $expression = "GROUP BY $needed_columns";
    $expression .= ", " . $optional_columns if $optional_columns;
    
    return $expression;
}

sub sql_string_concat {
    my ($self, @params) = @_;
    
    return '(' . join(' || ', @params) . ')';
}

sub sql_string_until {
    my ($self, $string, $substring) = @_;

    my $position = $self->sql_position($substring, $string);
    return "CASE WHEN $position != 0"
             . " THEN SUBSTR($string, 1, $position - 1)"
             . " ELSE $string END";
}

sub sql_in {
    my ($self, $column_name, $in_list_ref) = @_;
    return " $column_name IN (" . join(',', @$in_list_ref) . ") ";
}

sub sql_fulltext_search {
    my ($self, $column, $text) = @_;

    # This is as close as we can get to doing full text search using
    # standard ANSI SQL, without real full text search support. DB specific
    # modules should override this, as this will be always much slower.

    # make the string lowercase to do case insensitive search
    my $lower_text = lc($text);

    # split the text we're searching for into separate words. As a hack
    # to allow quicksearch to work, if the field starts and ends with
    # a double-quote, then we don't split it into words. We can't use
    # Text::ParseWords here because it gets very confused by unbalanced
    # quotes, which breaks searches like "don't try this" (because of the
    # unbalanced single-quote in "don't").
    my @words;
    if ($lower_text =~ /^"/ and $lower_text =~ /"$/) {
        $lower_text =~ s/^"//;
        $lower_text =~ s/"$//;
        @words = ($lower_text);
    }
    else {
        @words = split(/\s+/, $lower_text);
    }

    # surround the words with wildcards and SQL quotes so we can use them
    # in LIKE search clauses
    @words = map($self->quote("\%$_\%"), @words);

    # untaint words, since they are safe to use now that we've quoted them
    trick_taint($_) foreach @words;

    # turn the words into a set of LIKE search clauses
    @words = map("LOWER($column) LIKE $_", @words);

    # search for occurrences of all specified words in the column
    return join (" AND ", @words), "CASE WHEN (" . join(" AND ", @words) . ") THEN 1 ELSE 0 END";
}

#####################################################################
# General Info Methods
#####################################################################

# XXX - Needs to be documented.
sub bz_server_version {
    my ($self) = @_;
    return $self->get_info(18); # SQL_DBMS_VER
}

sub bz_last_key {
    my ($self, $table, $column) = @_;

    return $self->last_insert_id(Bugzilla->localconfig->{db_name}, undef, 
                                 $table, $column);
}

sub bz_check_regexp {
    my ($self, $pattern) = @_;

    eval { $self->do("SELECT " . $self->sql_regexp($self->quote("a"), $pattern, 1)) };

    $@ && ThrowUserError('illegal_regexp', 
        { value => $pattern, dberror => $self->errstr }); 
}

#####################################################################
# Database Setup
#####################################################################

sub bz_setup_database {
    my ($self) = @_;

    # If we haven't ever stored a serialized schema,
    # set up the bz_schema table and store it.
    $self->_bz_init_schema_storage();
   
    # We don't use bz_table_list here, because that uses _bz_real_schema.
    # We actually want the table list from the ABSTRACT_SCHEMA in
    # Bugzilla::DB::Schema.
    my @desired_tables = $self->_bz_schema->get_table_list();
    my $bugs_exists = $self->bz_table_info('bugs');
    if (!$bugs_exists) {
        say install_string('db_table_setup');
    }

    foreach my $table_name (@desired_tables) {
        $self->bz_add_table($table_name, { silently => !$bugs_exists });
    }
}

# This really just exists to get overridden in Bugzilla::DB::Mysql.
sub bz_enum_initial_values {
    return ENUM_DEFAULTS;
}

sub bz_populate_enum_tables {
    my ($self) = @_; 

    my $any_severities = $self->selectrow_array(
        'SELECT 1 FROM bug_severity ' . $self->sql_limit(1));
    print install_string('db_enum_setup'), "\n  " if !$any_severities;

    my $enum_values = $self->bz_enum_initial_values();
    while (my ($table, $values) = each %$enum_values) {
        $self->_bz_populate_enum_table($table, $values);
    }

    print "\n" if !$any_severities;
}

sub bz_setup_foreign_keys {
    my ($self) = @_;

    # profiles_activity was the first table to get foreign keys,
    # so if it doesn't have them, then we're setting up FKs
    # for the first time, and should be quieter about it.
    my $activity_fk = $self->bz_fk_info('profiles_activity', 'userid');
    my $any_fks = $activity_fk && $activity_fk->{created};
    if (!$any_fks) {
        say get_text('install_fk_setup');
    }

    my @tables = $self->bz_table_list();
    foreach my $table (@tables) {
        my @columns = $self->bz_table_columns($table);
        my %add_fks;
        foreach my $column (@columns) {
            # First we check for any FKs that have created => 0,
            # in the _bz_real_schema. This also picks up FKs with
            # created => 1, but bz_add_fks will ignore those.
            my $fk = $self->bz_fk_info($table, $column);
            # Then we check the abstract schema to see if there
            # should be an FK on this column, but one wasn't set in the
            # _bz_real_schema for some reason. We do this to handle
            # various problems caused by upgrading from versions
            # prior to 4.2, and also to handle problems caused
            # by enabling an extension pre-4.2, disabling it for
            # the 4.2 upgrade, and then re-enabling it later.
            unless ($fk && $fk->{created}) {
                my $standard_def = 
                    $self->_bz_schema->get_column_abstract($table, $column);
                if (exists $standard_def->{REFERENCES}) {
                    $fk = dclone($standard_def->{REFERENCES});
                }
            }

            $add_fks{$column} = $fk if $fk;
        }
        $self->bz_add_fks($table, \%add_fks, { silently => !$any_fks });
    }
}

# This is used by contrib/bzdbcopy.pl, mostly.
sub bz_drop_foreign_keys {
    my ($self) = @_;

    my @tables = $self->bz_table_list();
    foreach my $table (@tables) {
        my @columns = $self->bz_table_columns($table);
        foreach my $column (@columns) {
            $self->bz_drop_fk($table, $column);
        }
    }
}

#####################################################################
# Schema Modification Methods
#####################################################################

sub bz_add_column {
    my ($self, $table, $name, $new_def, $init_value) = @_;

    # You can't add a NOT NULL column to a table with
    # no DEFAULT statement, unless you have an init_value.
    # SERIAL types are an exception, though, because they can
    # auto-populate.
    if ( $new_def->{NOTNULL} && !exists $new_def->{DEFAULT} 
         && !defined $init_value && $new_def->{TYPE} !~ /SERIAL/)
    {
        ThrowCodeError('column_not_null_without_default',
                       { name => "$table.$name" });
    }

    my $current_def = $self->bz_column_info($table, $name);

    if (!$current_def) {
        my @statements = $self->_bz_real_schema->get_add_column_ddl(
            $table, $name, $new_def, 
            defined $init_value ? $self->quote($init_value) : undef);
        print get_text('install_column_add',
                       { column => $name, table => $table }) . "\n"
            if Bugzilla->usage_mode == USAGE_MODE_CMDLINE;
        foreach my $sql (@statements) {
            $self->do($sql);
        }

        # To make things easier for callers, if they don't specify
        # a REFERENCES item, we pull it from the _bz_schema if the
        # column exists there and has a REFERENCES item.
        # bz_setup_foreign_keys will then add this FK at the end of
        # Install::DB.
        my $col_abstract = 
            $self->_bz_schema->get_column_abstract($table, $name);
        if (exists $col_abstract->{REFERENCES}) {
            my $new_fk = dclone($col_abstract->{REFERENCES});
            $new_fk->{created} = 0;
            $new_def->{REFERENCES} = $new_fk;
        }
        
        $self->_bz_real_schema->set_column($table, $name, $new_def);
        $self->_bz_store_real_schema;
    }
}

sub bz_add_fk {
    my ($self, $table, $column, $def) = @_;
    $self->bz_add_fks($table, { $column => $def });
}

sub bz_add_fks {
    my ($self, $table, $column_fks, $options) = @_;

    my %add_these;
    foreach my $column (keys %$column_fks) {
        my $current_fk = $self->bz_fk_info($table, $column);
        next if ($current_fk and $current_fk->{created});
        my $new_fk = $column_fks->{$column};
        $self->_check_references($table, $column, $new_fk);
        $add_these{$column} = $new_fk;
        if (Bugzilla->usage_mode == USAGE_MODE_CMDLINE 
            and !$options->{silently}) 
        {
            print get_text('install_fk_add',
                           { table => $table, column => $column, 
                             fk    => $new_fk }), "\n";
        }
    }

    return if !scalar(keys %add_these);

    my @sql = $self->_bz_real_schema->get_add_fks_sql($table, \%add_these);
    $self->do($_) foreach @sql;

    foreach my $column (keys %add_these) {
        my $fk_def = $add_these{$column};
        $fk_def->{created} = 1;
        $self->_bz_real_schema->set_fk($table, $column, $fk_def);
    }

    $self->_bz_store_real_schema();
}

sub bz_alter_column {
    my ($self, $table, $name, $new_def, $set_nulls_to) = @_;

    my $current_def = $self->bz_column_info($table, $name);

    if (!$self->_bz_schema->columns_equal($current_def, $new_def)) {
        # You can't change a column to be NOT NULL if you have no DEFAULT
        # and no value for $set_nulls_to, if there are any NULL values 
        # in that column.
        if ($new_def->{NOTNULL} && 
            !exists $new_def->{DEFAULT} && !defined $set_nulls_to)
        {
            # Check for NULLs
            my $any_nulls = $self->selectrow_array(
                "SELECT 1 FROM $table WHERE $name IS NULL");
            ThrowCodeError('column_not_null_no_default_alter', 
                           { name => "$table.$name" }) if ($any_nulls);
        }
        # Preserve foreign key definitions in the Schema object when altering
        # types.
        if (my $fk = $self->bz_fk_info($table, $name)) {
            $new_def->{REFERENCES} = $fk;
        }
        $self->bz_alter_column_raw($table, $name, $new_def, $current_def,
                                   $set_nulls_to);
        $self->_bz_real_schema->set_column($table, $name, $new_def);
        $self->_bz_store_real_schema;
    }
}


# bz_alter_column_raw($table, $name, $new_def, $current_def)
#
# Description: A helper function for bz_alter_column.
#              Alters a column in the database
#              without updating any Schema object. Generally
#              should only be called by bz_alter_column.
#              Used when either: (1) You don't yet have a Schema
#              object but you need to alter a column, for some reason.
#              (2) You need to alter a column for some database-specific
#              reason.
# Params:      $table   - The name of the table the column is on.
#              $name    - The name of the column you're changing.
#              $new_def - The abstract definition that you are changing
#                         this column to.
#              $current_def - (optional) The current definition of the
#                             column. Will be used in the output message,
#                             if given.
#              $set_nulls_to - The same as the param of the same name
#                              from bz_alter_column.
# Returns:     nothing
#
sub bz_alter_column_raw {
    my ($self, $table, $name, $new_def, $current_def, $set_nulls_to) = @_;
    my @statements = $self->_bz_real_schema->get_alter_column_ddl(
        $table, $name, $new_def,
        defined $set_nulls_to ? $self->quote($set_nulls_to) : undef);
    my $new_ddl = $self->_bz_schema->get_type_ddl($new_def);
    say "Updating column $name in table $table ...";
    if (defined $current_def) {
        my $old_ddl = $self->_bz_schema->get_type_ddl($current_def);
        say "Old: $old_ddl";
    }
    say "New: $new_ddl";
    $self->do($_) foreach (@statements);
}

sub bz_alter_fk {
    my ($self, $table, $column, $fk_def) = @_;
    my $current_fk = $self->bz_fk_info($table, $column);
    ThrowCodeError('column_alter_nonexistent_fk',
                   { table => $table, column => $column }) if !$current_fk;
    $self->bz_drop_fk($table, $column);
    $self->bz_add_fk($table, $column, $fk_def);
}

sub bz_add_index {
    my ($self, $table, $name, $definition) = @_;

    my $index_exists = $self->bz_index_info($table, $name);

    if (!$index_exists) {
        $self->bz_add_index_raw($table, $name, $definition);
        $self->_bz_real_schema->set_index($table, $name, $definition);
        $self->_bz_store_real_schema;
    }
}

# bz_add_index_raw($table, $name, $silent)
#
# Description: A helper function for bz_add_index.
#              Adds an index to the database
#              without updating any Schema object. Generally
#              should only be called by bz_add_index.
#              Used when you don't yet have a Schema
#              object but you need to add an index, for some reason.
# Params:      $table  - The name of the table the index is on.
#              $name   - The name of the index you're adding.
#              $definition - The abstract index definition, in hashref
#                            or arrayref format.
#              $silent - (optional) If specified and true, don't output
#                        any message about this change.
# Returns:     nothing
#
sub bz_add_index_raw {
    my ($self, $table, $name, $definition, $silent) = @_;
    my @statements = $self->_bz_schema->get_add_index_ddl(
        $table, $name, $definition);
    print "Adding new index '$name' to the $table table ...\n" unless $silent;
    $self->do($_) foreach (@statements);
}

sub bz_add_table {
    my ($self, $name, $options) = @_;

    my $table_exists = $self->bz_table_info($name);

    if (!$table_exists) {
        $self->_bz_add_table_raw($name, $options);
        my $table_def = dclone($self->_bz_schema->get_table_abstract($name));

        my %fields = @{$table_def->{FIELDS}};
        foreach my $col (keys %fields) {
            # Foreign Key references have to be added by Install::DB after
            # initial table creation, because column names have changed
            # over history and it's impossible to keep track of that info
            # in ABSTRACT_SCHEMA.
            next unless exists $fields{$col}->{REFERENCES};
            $fields{$col}->{REFERENCES}->{created} =
                $self->_bz_real_schema->FK_ON_CREATE;
        }
        
        $self->_bz_real_schema->add_table($name, $table_def);
        $self->_bz_store_real_schema;
    }
}

# _bz_add_table_raw($name) - Private
#
# Description: A helper function for bz_add_table.
#              Creates a table in the database without
#              updating any Schema object. Generally
#              should only be called by bz_add_table and by
#              _bz_init_schema_storage. Used when you don't
#              yet have a Schema object but you need to
#              add a table, for some reason.
# Params:      $name - The name of the table you're creating. 
#                  The definition for the table is pulled from 
#                  _bz_schema.
# Returns:     nothing
#
sub _bz_add_table_raw {
    my ($self, $name, $options) = @_;
    my @statements = $self->_bz_schema->get_table_ddl($name);
    if (Bugzilla->usage_mode == USAGE_MODE_CMDLINE
        and !$options->{silently})
    {
        say install_string('db_table_new', { table => $name });
    }
    $self->do($_) foreach (@statements);
}

sub _bz_add_field_table {
    my ($self, $name, $schema_ref) = @_;
    # We do nothing if the table already exists.
    return if $self->bz_table_info($name);

    # Copy this so that we're not modifying the passed reference.
    # (This avoids modifying a constant in Bugzilla::DB::Schema.)
    my %table_schema = %$schema_ref;
    my %indexes = @{ $table_schema{INDEXES} };
    my %fixed_indexes;
    foreach my $key (keys %indexes) {
        $fixed_indexes{$name . "_" . $key} = $indexes{$key};
    }
    # INDEXES is supposed to be an arrayref, so we have to convert back.
    my @indexes_array = %fixed_indexes;
    $table_schema{INDEXES} = \@indexes_array;
    # We add this to the abstract schema so that bz_add_table can find it.
    $self->_bz_schema->add_table($name, \%table_schema);
    $self->bz_add_table($name);
}

sub bz_add_field_tables {
    my ($self, $field) = @_;
    
    $self->_bz_add_field_table($field->name,
                               $self->_bz_schema->FIELD_TABLE_SCHEMA, $field->type);
    if ($field->type == FIELD_TYPE_MULTI_SELECT) {
        my $ms_table = "bug_" . $field->name;
        $self->_bz_add_field_table($ms_table,
            $self->_bz_schema->MULTI_SELECT_VALUE_TABLE);

        $self->bz_add_fks($ms_table, 
            { bug_id => {TABLE => 'bugs', COLUMN => 'bug_id',
                         DELETE => 'CASCADE'},

              value  => {TABLE  => $field->name, COLUMN => 'value'} });
    }
}

sub bz_drop_field_tables {
    my ($self, $field) = @_;
    if ($field->type == FIELD_TYPE_MULTI_SELECT) {
        $self->bz_drop_table('bug_' . $field->name);
    }
    $self->bz_drop_table($field->name);
}

sub bz_drop_column {
    my ($self, $table, $column) = @_;

    my $current_def = $self->bz_column_info($table, $column);

    if ($current_def) {
        my @statements = $self->_bz_real_schema->get_drop_column_ddl(
            $table, $column);
        print get_text('install_column_drop', 
                       { table => $table, column => $column }) . "\n"
            if Bugzilla->usage_mode == USAGE_MODE_CMDLINE;
        foreach my $sql (@statements) {
            # Because this is a deletion, we don't want to die hard if
            # we fail because of some local customization. If something
            # is already gone, that's fine with us!
            eval { $self->do($sql); } or warn "Failed SQL: [$sql] Error: $@";
        }
        $self->_bz_real_schema->delete_column($table, $column);
        $self->_bz_store_real_schema;
    }
}

sub bz_drop_fk {
    my ($self, $table, $column) = @_;

    my $fk_def = $self->bz_fk_info($table, $column);
    if ($fk_def and $fk_def->{created}) {
        print get_text('install_fk_drop',
                       { table => $table, column => $column, fk => $fk_def })
            . "\n" if Bugzilla->usage_mode == USAGE_MODE_CMDLINE;
        my @statements = 
            $self->_bz_real_schema->get_drop_fk_sql($table, $column, $fk_def);
        foreach my $sql (@statements) {
            # Because this is a deletion, we don't want to die hard if
            # we fail because of some local customization. If something
            # is already gone, that's fine with us!
            eval { $self->do($sql); } or warn "Failed SQL: [$sql] Error: $@";
        }
        # Under normal circumstances, we don't permanently drop the fk--
        # we want checksetup to re-create it again later. The only
        # time that FKs get permanently dropped is if the column gets
        # dropped.
        $fk_def->{created} = 0;
        $self->_bz_real_schema->set_fk($table, $column, $fk_def);
        $self->_bz_store_real_schema;
    }

}

sub bz_get_related_fks {
    my ($self, $table, $column) = @_;
    my @tables = $self->_bz_real_schema->get_table_list();
    my @related;
    foreach my $check_table (@tables) {
        my @columns = $self->bz_table_columns($check_table);
        foreach my $check_column (@columns) {
            my $fk = $self->bz_fk_info($check_table, $check_column);
            if ($fk 
                and (($fk->{TABLE} eq $table and $fk->{COLUMN} eq $column)
                     or ($check_column eq $column and $check_table eq $table)))
            {
                push(@related, [$check_table, $check_column, $fk]);
            }
        } # foreach $column
    } # foreach $table

    return \@related;
}

sub bz_drop_related_fks {
    my $self = shift;
    my $related = $self->bz_get_related_fks(@_);
    foreach my $item (@$related) {
        my ($table, $column) = @$item;
        $self->bz_drop_fk($table, $column);
    }
    return $related;
}

sub bz_drop_index {
    my ($self, $table, $name) = @_;

    my $index_exists = $self->bz_index_info($table, $name);

    if ($index_exists) {
        if ($self->INDEX_DROPS_REQUIRE_FK_DROPS) {
            # We cannot delete an index used by a FK.
            foreach my $column (@{$index_exists->{FIELDS}}) {
                $self->bz_drop_related_fks($table, $column);
            }
        }
        $self->bz_drop_index_raw($table, $name);
        $self->_bz_real_schema->delete_index($table, $name);
        $self->_bz_store_real_schema;        
    }
}

# bz_drop_index_raw($table, $name, $silent)
#
# Description: A helper function for bz_drop_index.
#              Drops an index from the database
#              without updating any Schema object. Generally
#              should only be called by bz_drop_index.
#              Used when either: (1) You don't yet have a Schema 
#              object but you need to drop an index, for some reason.
#              (2) You need to drop an index that somehow got into the
#              database but doesn't exist in Schema.
# Params:      $table  - The name of the table the index is on.
#              $name   - The name of the index you're dropping.
#              $silent - (optional) If specified and true, don't output
#                        any message about this change.
# Returns:     nothing
#
sub bz_drop_index_raw {
    my ($self, $table, $name, $silent) = @_;
    my @statements = $self->_bz_schema->get_drop_index_ddl(
        $table, $name);
    print "Removing index '$name' from the $table table...\n" unless $silent;
    foreach my $sql (@statements) {
        # Because this is a deletion, we don't want to die hard if
        # we fail because of some local customization. If something
        # is already gone, that's fine with us!
        eval { $self->do($sql) } or warn "Failed SQL: [$sql] Error: $@";
    }
}

sub bz_drop_table {
    my ($self, $name) = @_;

    my $table_exists = $self->bz_table_info($name);

    if ($table_exists) {
        my @statements = $self->_bz_schema->get_drop_table_ddl($name);
        print get_text('install_table_drop', { name => $name }) . "\n"
            if Bugzilla->usage_mode == USAGE_MODE_CMDLINE;
        foreach my $sql (@statements) {
            # Because this is a deletion, we don't want to die hard if
            # we fail because of some local customization. If something
            # is already gone, that's fine with us!
            eval { $self->do($sql); } or warn "Failed SQL: [$sql] Error: $@";
        }
        $self->_bz_real_schema->delete_table($name);
        $self->_bz_store_real_schema;
    }
}

sub bz_fk_info {
    my ($self, $table, $column) = @_;
    my $col_info = $self->bz_column_info($table, $column);
    return undef if !$col_info;
    my $fk = $col_info->{REFERENCES};
    return $fk;
}

sub bz_rename_column {
    my ($self, $table, $old_name, $new_name) = @_;

    my $old_col_exists  = $self->bz_column_info($table, $old_name);

    if ($old_col_exists) {
        my $already_renamed = $self->bz_column_info($table, $new_name);
            ThrowCodeError('db_rename_conflict',
                           { old => "$table.$old_name", 
                             new => "$table.$new_name" }) if $already_renamed;
        my @statements = $self->_bz_real_schema->get_rename_column_ddl(
            $table, $old_name, $new_name);

        print get_text('install_column_rename', 
                       { old => "$table.$old_name", new => "$table.$new_name" })
               . "\n" if Bugzilla->usage_mode == USAGE_MODE_CMDLINE;

        foreach my $sql (@statements) {
            $self->do($sql);
        }
        $self->_bz_real_schema->rename_column($table, $old_name, $new_name);
        $self->_bz_store_real_schema;
    }
}

sub bz_rename_table {
    my ($self, $old_name, $new_name) = @_;
    my $old_table = $self->bz_table_info($old_name);
    return if !$old_table;

    my $new = $self->bz_table_info($new_name);
    ThrowCodeError('db_rename_conflict', { old => $old_name,
                                           new => $new_name }) if $new;

    # FKs will all have the wrong names unless we drop and then let them
    # be re-created later. Under normal circumstances, checksetup.pl will
    # automatically re-create these dropped FKs at the end of its DB upgrade
    # run, so we don't need to re-create them in this method.
    my @columns = $self->bz_table_columns($old_name);
    foreach my $column (@columns) {
        # these just return silently if there's no FK to drop
        $self->bz_drop_fk($old_name, $column);
        $self->bz_drop_related_fks($old_name, $column);
    }

    my @sql = $self->_bz_real_schema->get_rename_table_sql($old_name, $new_name);
    print get_text('install_table_rename', 
                   { old => $old_name, new => $new_name }) . "\n"
        if Bugzilla->usage_mode == USAGE_MODE_CMDLINE;
    $self->do($_) foreach @sql;
    $self->_bz_real_schema->rename_table($old_name, $new_name);
    $self->_bz_store_real_schema;
}

sub bz_set_next_serial_value {
    my ($self, $table, $column, $value) = @_;
    if (!$value) {
        $value = $self->selectrow_array("SELECT MAX($column) FROM $table") || 0;
        $value++;
    }
    my @sql = $self->_bz_real_schema->get_set_serial_sql($table, $column, $value);
    $self->do($_) foreach @sql;
}

#####################################################################
# Schema Information Methods
#####################################################################

sub _bz_schema {
    my ($self) = @_;
    return $self->{private_bz_schema} if exists $self->{private_bz_schema};
    my @module_parts = split('::', ref $self);
    my $module_name  = pop @module_parts;
    $self->{private_bz_schema} = Bugzilla::DB::Schema->new($module_name);
    return $self->{private_bz_schema};
}

# _bz_get_initial_schema()
#
# Description: A protected method, intended for use only by Bugzilla::DB
#              and subclasses. Used to get the initial Schema that will
#              be written to disk for _bz_init_schema_storage. You probably
#              want to use _bz_schema or _bz_real_schema instead of this
#              method.
# Params:      none
# Returns:     A Schema object that can be serialized and written to disk
#              for _bz_init_schema_storage.
sub _bz_get_initial_schema {
    my ($self) = @_;
    return $self->_bz_schema->get_empty_schema();
}

sub bz_column_info {
    my ($self, $table, $column) = @_;
    my $def = $self->_bz_real_schema->get_column_abstract($table, $column);
    # We dclone it so callers can't modify the Schema.
    $def = dclone($def) if defined $def;
    return $def;
}

sub bz_index_info {
    my ($self, $table, $index) = @_;
    my $index_def =
        $self->_bz_real_schema->get_index_abstract($table, $index);
    if (ref($index_def) eq 'ARRAY') {
        $index_def = {FIELDS => $index_def, TYPE => ''};
    }
    return $index_def;
}

sub bz_table_info {
    my ($self, $table) = @_;
    return $self->_bz_real_schema->get_table_abstract($table);
}


sub bz_table_columns {
    my ($self, $table) = @_;
    return $self->_bz_real_schema->get_table_columns($table);
}

sub bz_table_indexes {
    my ($self, $table) = @_;
    my $indexes = $self->_bz_real_schema->get_table_indexes_abstract($table);
    my %return_indexes;
    # We do this so that they're always hashes.
    foreach my $name (keys %$indexes) {
        $return_indexes{$name} = $self->bz_index_info($table, $name);
    }
    return \%return_indexes;
}

sub bz_table_list {
    my ($self) = @_;
    return $self->_bz_real_schema->get_table_list();
}

#####################################################################
# Protected "Real Database" Schema Information Methods
#####################################################################

# Only Bugzilla::DB and subclasses should use these methods.
# If you need a method that does the same thing as one of these
# methods, use the version without _real on the end.

# bz_table_columns_real($table)
#
# Description: Returns a list of columns on a given table
#              as the table actually is, on the disk.
# Params:      $table - Name of the table.
# Returns:     An array of column names.
#
sub bz_table_columns_real {
    my ($self, $table) = @_;
    my $sth = $self->column_info(undef, undef, $table, '%');
    return @{ $self->selectcol_arrayref($sth, {Columns => [4]}) };
}

# bz_table_list_real()
#
# Description: Gets a list of tables in the current
#              database, directly from the disk.
# Params:      none
# Returns:     An array containing table names.
sub bz_table_list_real {
    my ($self) = @_;
    my $table_sth = $self->table_info(undef, undef, undef, "TABLE");
    return @{$self->selectcol_arrayref($table_sth, { Columns => [3] })};
}

#####################################################################
# Transaction Methods
#####################################################################

sub bz_in_transaction {
    return $_[0]->{private_bz_transaction_count} ? 1 : 0;
}

sub bz_start_transaction {
    my ($self) = @_;

    if ($self->bz_in_transaction) {
        $self->{private_bz_transaction_count}++;
    } else {
        # Turn AutoCommit off and start a new transaction
        $self->begin_work();
        # REPEATABLE READ means "We work on a snapshot of the DB that
        # is created when we execute our first SQL statement." It's
        # what we need in Bugzilla to be safe, for what we do.
        # Different DBs have different defaults for their isolation
        # level, so we just set it here manually.
        if ($self->ISOLATION_LEVEL) {
            $self->do('SET TRANSACTION ISOLATION LEVEL ' 
                      . $self->ISOLATION_LEVEL);
        }
        $self->{private_bz_transaction_count} = 1;
    }
}

sub bz_commit_transaction {
    my ($self) = @_;
    
    if ($self->{private_bz_transaction_count} > 1) {
        $self->{private_bz_transaction_count}--;
    } elsif ($self->bz_in_transaction) {
        $self->commit();
        $self->{private_bz_transaction_count} = 0;
    } else {
       ThrowCodeError('not_in_transaction');
    }
}

sub bz_rollback_transaction {
    my ($self) = @_;

    # Unlike start and commit, if we rollback at any point it happens
    # instantly, even if we're in a nested transaction.
    if (!$self->bz_in_transaction) {
        ThrowCodeError("not_in_transaction");
    } else {
        $self->rollback();
        $self->{private_bz_transaction_count} = 0;
    }
}

#####################################################################
# Subclass Helpers
#####################################################################

sub db_new {
    my ($class, $params) = @_;
    my ($dsn, $user, $pass, $override_attrs) = 
        @$params{qw(dsn user pass attrs)};

    # set up default attributes used to connect to the database
    # (may be overridden by DB driver implementations)
    my $attributes = { RaiseError => 0,
                       AutoCommit => 1,
                       PrintError => 0,
                       ShowErrorStatement => 1,
                       HandleError => \&_handle_error,
                       TaintIn => 1,
                       # See https://rt.perl.org/rt3/Public/Bug/Display.html?id=30933
                       # for the reason to use NAME instead of NAME_lc (bug 253696).
                       FetchHashKeyName => 'NAME',
                     };

    if ($override_attrs) {
        foreach my $key (keys %$override_attrs) {
            $attributes->{$key} = $override_attrs->{$key};
        }
    }

    # connect using our known info to the specified db
    my $self = DBI->connect($dsn, $user, $pass, $attributes)
        or die "\nCan't connect to the database.\nError: $DBI::errstr\n"
        . "  Is your database installed and up and running?\n  Do you have"
        . " the correct username and password selected in localconfig?\n\n";

    # RaiseError was only set to 0 so that we could catch the 
    # above "die" condition.
    $self->{RaiseError} = 1;

    bless ($self, $class);

    return $self;
}

#####################################################################
# Private Methods
#####################################################################

=begin private

=head1 PRIVATE METHODS

These methods really are private. Do not override them in subclasses.

=over 4

=item C<_init_bz_schema_storage>

 Description: Initializes the bz_schema table if it contains nothing.
 Params:      none
 Returns:     nothing

=cut

sub _bz_init_schema_storage {
    my ($self) = @_;

    my $table_size;
    eval {
        $table_size = 
            $self->selectrow_array("SELECT COUNT(*) FROM bz_schema");
    };

    if (!$table_size) {
        my $init_schema = $self->_bz_get_initial_schema;
        my $store_me = $init_schema->serialize_abstract();
        my $schema_version = $init_schema->SCHEMA_VERSION;

        # If table_size is not defined, then we hit an error reading the
        # bz_schema table, which means it probably doesn't exist yet. So,
        # we have to create it. If we failed above for some other reason,
        # we'll see the failure here.
        # However, we must create the table after we do get_initial_schema,
        # because some versions of get_initial_schema read that the table
        # exists and then add it to the Schema, where other versions don't.
        if (!defined $table_size) {
            $self->_bz_add_table_raw('bz_schema');
        }

        say install_string('db_schema_init');
        my $sth = $self->prepare("INSERT INTO bz_schema "
                                 ." (schema_data, version) VALUES (?,?)");
        $sth->bind_param(1, $store_me, $self->BLOB_TYPE);
        $sth->bind_param(2, $schema_version);
        $sth->execute();

        # And now we have to update the on-disk schema to hold the bz_schema
        # table, if the bz_schema table didn't exist when we were called.
        if (!defined $table_size) {
            $self->_bz_real_schema->add_table('bz_schema',
                $self->_bz_schema->get_table_abstract('bz_schema'));
            $self->_bz_store_real_schema;
        }
    } 
    # Sanity check
    elsif ($table_size > 1) {
        # We tell them to delete the newer one. Better to have checksetup
        # run migration code too many times than to have it not run the
        # correct migration code at all.
        die "Attempted to initialize the schema but there are already "
            . " $table_size copies of it stored.\nThis should never happen.\n"
            . " Compare the rows of the bz_schema table and delete the "
            . "newer one(s).";
    }
}

=item C<_bz_real_schema()>

 Description: Returns a Schema object representing the database
              that is being used in the current installation.
 Params:      none
 Returns:     A C<Bugzilla::DB::Schema> object representing the database
              as it exists on the disk.

=cut

sub _bz_real_schema {
    my ($self) = @_;
    return $self->{private_real_schema} if exists $self->{private_real_schema};

    my ($data, $version) = $self->selectrow_array(
        "SELECT schema_data, version FROM bz_schema");

    (die "_bz_real_schema tried to read the bz_schema table but it's empty!")
        if !$data;

    $self->{private_real_schema} = 
        $self->_bz_schema->deserialize_abstract($data, $version);

    return $self->{private_real_schema};
}

=item C<_bz_store_real_schema()>

 Description: Stores the _bz_real_schema structures in the database
              for later recovery. Call this function whenever you make
              a change to the _bz_real_schema.
 Params:      none
 Returns:     nothing

 Precondition: $self->{_bz_real_schema} must exist.

=back

=end private

=cut

sub _bz_store_real_schema {
    my ($self) = @_;

    # Make sure that there's a schema to update
    my $table_size = $self->selectrow_array("SELECT COUNT(*) FROM bz_schema");

    die "Attempted to update the bz_schema table but there's nothing "
        . "there to update. Run checksetup." unless $table_size;

    # We want to store the current object, not one
    # that we read from the database. So we use the actual hash
    # member instead of the subroutine call. If the hash
    # member is not defined, we will (and should) fail.
    my $update_schema = $self->{private_real_schema};
    my $store_me = $update_schema->serialize_abstract();
    my $schema_version = $update_schema->SCHEMA_VERSION;
    my $sth = $self->prepare("UPDATE bz_schema 
                                 SET schema_data = ?, version = ?");
    $sth->bind_param(1, $store_me, $self->BLOB_TYPE);
    $sth->bind_param(2, $schema_version);
    $sth->execute();
}

# For bz_populate_enum_tables
sub _bz_populate_enum_table {
    my ($self, $table, $valuelist) = @_;

    my $sql_table = $self->quote_identifier($table);

    # Check if there are any table entries
    my $table_size = $self->selectrow_array("SELECT COUNT(*) FROM $sql_table");

    # If the table is empty...
    if (!$table_size) {
        print " $table";
        my $insert = $self->prepare(
            "INSERT INTO $sql_table (value,sortkey) VALUES (?,?)");
        my $sortorder = 0;
        my $maxlen    = max(map(length($_), @$valuelist)) + 2;
        foreach my $value (@$valuelist) {
            $sortorder += 100;
            $insert->execute($value, $sortorder);
        }
    }
}

# This is used before adding a foreign key to a column, to make sure
# that the database won't fail adding the key.
sub _check_references {
    my ($self, $table, $column, $fk) = @_;
    my $foreign_table = $fk->{TABLE};
    my $foreign_column = $fk->{COLUMN};

    # We use table aliases because sometimes we join a table to itself,
    # and we can't use the same table name on both sides of the join.
    # We also can't use the words "table" or "foreign" because those are
    # reserved words.
    my $bad_values = $self->selectcol_arrayref(
        "SELECT DISTINCT tabl.$column 
           FROM $table AS tabl LEFT JOIN $foreign_table AS forn
                ON tabl.$column = forn.$foreign_column
          WHERE forn.$foreign_column IS NULL
                AND tabl.$column IS NOT NULL");

    if (@$bad_values) {
        my $delete_action = $fk->{DELETE} || '';
        if ($delete_action eq 'CASCADE') {
            $self->do("DELETE FROM $table WHERE $column IN (" 
                      . join(',', ('?') x @$bad_values)  . ")",
                      undef, @$bad_values);
            if (Bugzilla->usage_mode == USAGE_MODE_CMDLINE) {
                print "\n", get_text('install_fk_invalid_fixed',
                    { table => $table, column => $column,
                      foreign_table => $foreign_table,
                      foreign_column => $foreign_column,
                      'values' => $bad_values, action => 'delete' }), "\n";
            }
        }
        elsif ($delete_action eq 'SET NULL') {
            $self->do("UPDATE $table SET $column = NULL
                        WHERE $column IN ("
                      . join(',', ('?') x @$bad_values)  . ")",
                      undef, @$bad_values);
            if (Bugzilla->usage_mode == USAGE_MODE_CMDLINE) {
                print "\n", get_text('install_fk_invalid_fixed',
                    { table => $table, column => $column,
                      foreign_table => $foreign_table, 
                      foreign_column => $foreign_column,
                      'values' => $bad_values, action => 'null' }), "\n";
            }
        }
        else {
            die "\n", get_text('install_fk_invalid',
                { table => $table, column => $column,
                  foreign_table => $foreign_table,
                  foreign_column => $foreign_column,
                 'values' => $bad_values }), "\n";
        }
    }
}

1;

__END__

=head1 NAME

Bugzilla::DB - Database access routines, using L<DBI>

=head1 SYNOPSIS

  # Obtain db handle
  use Bugzilla::DB;
  my $dbh = Bugzilla->dbh;

  # prepare a query using DB methods
  my $sth = $dbh->prepare("SELECT " .
                          $dbh->sql_date_format("creation_ts", "%Y%m%d") .
                          " FROM bugs WHERE bug_status != 'RESOLVED' " .
                          $dbh->sql_limit(1));

  # Execute the query
  $sth->execute;

  # Get the results
  my @result = $sth->fetchrow_array;

  # Schema Modification
  $dbh->bz_add_column($table, $name, \%definition, $init_value);
  $dbh->bz_add_index($table, $name, $definition);
  $dbh->bz_add_table($name);
  $dbh->bz_drop_index($table, $name);
  $dbh->bz_drop_table($name);
  $dbh->bz_alter_column($table, $name, \%new_def, $set_nulls_to);
  $dbh->bz_drop_column($table, $column);
  $dbh->bz_rename_column($table, $old_name, $new_name);

  # Schema Information
  my $column = $dbh->bz_column_info($table, $column);
  my $index  = $dbh->bz_index_info($table, $index);

=head1 DESCRIPTION

Functions in this module allows creation of a database handle to connect
to the Bugzilla database. This should never be done directly; all users
should use the L<Bugzilla> module to access the current C<dbh> instead.

This module also contains methods extending the returned handle with
functionality which is different between databases allowing for easy
customization for particular database via inheritance. These methods
should be always preffered over hard-coding SQL commands.

=head1 CONSTANTS

Subclasses of Bugzilla::DB are required to define certain constants. These
constants are required to be subroutines or "use constant" variables.

=over

=item C<BLOB_TYPE>

The C<\%attr> argument that must be passed to bind_param in order to 
correctly escape a C<LONGBLOB> type.

=item C<ISOLATION_LEVEL>

The argument that this database should send to 
C<SET TRANSACTION ISOLATION LEVEL> when starting a transaction. If you
override this in a subclass, the isolation level you choose should
be as strict as or more strict than the default isolation level defined in
L<Bugzilla::DB>.

=back


=head1 CONNECTION

A new database handle to the required database can be created using this
module. This is normally done by the L<Bugzilla> module, and so these routines
should not be called from anywhere else.

=head2 Functions

=over

=item C<connect_main>

=over

=item B<Description>

Function to connect to the main database, returning a new database handle.

=item B<Params>

=over

=item C<$no_db_name> (optional) - If true, connect to the database
server, but don't connect to a specific database. This is only used 
when creating a database. After you create the database, you should 
re-create a new Bugzilla::DB object without using this parameter. 

=back

=item B<Returns>

New instance of the DB class

=back

=item C<connect_shadow>

=over

=item B<Description>

Function to connect to the shadow database, returning a new database handle.
This routine C<die>s if no shadow database is configured.

=item B<Params> (none)

=item B<Returns>

A new instance of the DB class

=back

=item C<bz_check_requirements>

=over

=item B<Description>

Checks to make sure that you have the correct DBD and database version 
installed for the database that Bugzilla will be using. Prints a message 
and exits if you don't pass the requirements.

If C<$db_check> is false (from F<localconfig>), we won't check the 
database version.

=item B<Params>

=over

=item C<$output> - C<true> if the function should display informational 
output about what it's doing, such as versions found.

=back

=item B<Returns> (nothing)

=back


=item C<bz_create_database>

=over

=item B<Description>

Creates an empty database with the name C<$db_name>, if that database 
doesn't already exist. Prints an error message and exits if we can't 
create the database.

=item B<Params> (none)

=item B<Returns> (nothing)

=back

=item C<_connect>

=over

=item B<Description>

Internal function, creates and returns a new, connected instance of the 
correct DB class.  This routine C<die>s if no driver is specified.

=item B<Params>

=over

=item C<$driver> - name of the database driver to use

=item C<$host> - host running the database we are connecting to

=item C<$dbname> - name of the database to connect to

=item C<$port> - port the database is listening on

=item C<$sock> - socket the database is listening on

=item C<$user> - username used to log in to the database

=item C<$pass> - password used to log in to the database

=back

=item B<Returns>

A new instance of the DB class

=back

=item C<_handle_error>

Function passed to the DBI::connect call for error handling. It shortens the 
error for printing.

=item C<import>

Overrides the standard import method to check that derived class
implements all required abstract methods. Also calls original implementation 
in its super class.

=back

=head1 ABSTRACT METHODS

Note: Methods which can be implemented generically for all DBs are implemented in
this module. If needed, they can be overridden with DB specific code.
Methods which do not have standard implementation are abstract and must
be implemented for all supported databases separately.
To avoid confusion with standard DBI methods, all methods returning string with
formatted SQL command have prefix C<sql_>. All other methods have prefix C<bz_>.

=head2 Constructor

=over

=item C<new>

=over

=item B<Description>

Constructor.  Abstract method, should be overridden by database specific 
code.

=item B<Params>

=over 

=item C<$user> - username used to log in to the database

=item C<$pass> - password used to log in to the database

=item C<$host> - host running the database we are connecting to

=item C<$dbname> - name of the database to connect to

=item C<$port> - port the database is listening on

=item C<$sock> - socket the database is listening on

=back

=item B<Returns>

A new instance of the DB class

=item B<Note>

The constructor should create a DSN from the parameters provided and
then call C<db_new()> method of its super class to create a new
class instance. See L<db_new> description in this module. As per
DBI documentation, all class variables must be prefixed with
"private_". See L<DBI>.

=back

=back

=head2 SQL Generation

=over

=item C<sql_regexp>

=over

=item B<Description>

Outputs SQL regular expression operator for POSIX regex
searches (case insensitive) in format suitable for a given
database.

Abstract method, should be overridden by database specific code.

=item B<Params>

=over

=item C<$expr> - SQL expression for the text to be searched (scalar)

=item C<$pattern> - the regular expression to search for (scalar)

=item C<$nocheck> - true if the pattern should not be tested; false otherwise (boolean)

=item C<$real_pattern> - the real regular expression to search for.
This argument is used when C<$pattern> is a placeholder ('?').

=back

=item B<Returns>

Formatted SQL for regular expression search (e.g. REGEXP) (scalar)

=back

=item C<sql_not_regexp>

=over

=item B<Description>

Outputs SQL regular expression operator for negative POSIX
regex searches (case insensitive) in format suitable for a given
database.

Abstract method, should be overridden by database specific code.

=item B<Params>

Same as L</sql_regexp>.

=item B<Returns>

Formatted SQL for negative regular expression search (e.g. NOT REGEXP) 
(scalar)

=back

=item C<sql_limit>

=over

=item B<Description>

Returns SQL syntax for limiting results to some number of rows
with optional offset if not starting from the begining.

Abstract method, should be overridden by database specific code.

=item B<Params>

=over

=item C<$limit> - number of rows to return from query (scalar)

=item C<$offset> - number of rows to skip before counting (scalar)

=back

=item B<Returns>

Formatted SQL for limiting number of rows returned from query
with optional offset (e.g. LIMIT 1, 1) (scalar)

=back

=item C<sql_from_days>

=over

=item B<Description>

Outputs SQL syntax for converting Julian days to date.

Abstract method, should be overridden by database specific code.

=item B<Params>

=over

=item C<$days> - days to convert to date

=back

=item B<Returns>

Formatted SQL for returning Julian days in dates. (scalar)

=back

=item C<sql_to_days>

=over

=item B<Description>

Outputs SQL syntax for converting date to Julian days.

Abstract method, should be overridden by database specific code.

=item B<Params>

=over

=item C<$date> - date to convert to days

=back

=item B<Returns>

Formatted SQL for returning date fields in Julian days. (scalar)

=back

=item C<sql_date_format>

=over

=item B<Description>

Outputs SQL syntax for formatting dates.

Abstract method, should be overridden by database specific code.

=item B<Params>

=over

=item C<$date> - date or name of date type column (scalar)

=item C<$format> - format string for date output (scalar)
(C<%Y> = year, four digits, C<%y> = year, two digits, C<%m> = month,
C<%d> = day, C<%a> = weekday name, 3 letters, C<%H> = hour 00-23,
C<%i> = minute, C<%s> = second)

=back

=item B<Returns>

Formatted SQL for date formatting (scalar)

=back

=item C<sql_date_math>

=over

=item B<Description>

Outputs proper SQL syntax for adding some amount of time to a date.

Abstract method, should be overridden by database specific code.

=item B<Params>

=over

=item C<$date>

C<string> The date being added to or subtracted from.

=item C<$operator>

C<string> Either C<-> or C<+>, depending on whether you're subtracting
or adding.

=item C<$interval>

C<integer> The time interval you're adding or subtracting (e.g. C<30>)

=item C<$units> 

C<string> the units the interval is in (e.g. 'MINUTE')

=back

=item B<Returns>

Formatted SQL for adding or subtracting a date and some amount of time (scalar)

=back

=item C<sql_position>

=over

=item B<Description>

Outputs proper SQL syntax determining position of a substring
(fragment) withing a string (text). Note: if the substring or
text are string constants, they must be properly quoted (e.g. "'pattern'").

It searches for the string in a case-sensitive manner. If you want to do
a case-insensitive search, use L</sql_iposition>.

=item B<Params>

=over

=item C<$fragment> - the string fragment we are searching for (scalar)

=item C<$text> - the text to search (scalar)

=back

=item B<Returns>

Formatted SQL for substring search (scalar)

=back

=item C<sql_iposition>

Just like L</sql_position>, but case-insensitive.

=item C<sql_group_by>

=over

=item B<Description>

Outputs proper SQL syntax for grouping the result of a query.

For ANSI SQL databases, we need to group by all columns we are
querying for (except for columns used in aggregate functions).
Some databases require (or even allow) to specify only one
or few columns if the result is uniquely defined. For those
databases, the default implementation needs to be overloaded.

=item B<Params>

=over

=item C<$needed_columns> - string with comma separated list of columns
we need to group by to get expected result (scalar)

=item C<$optional_columns> - string with comma separated list of all
other columns we are querying for, but which are not in the required list.

=back

=item B<Returns>

Formatted SQL for row grouping (scalar)

=back

=item C<sql_string_concat>

=over

=item B<Description>

Returns SQL syntax for concatenating multiple strings (constants
or values from table columns) together.

=item B<Params>

=over

=item C<@params> - array of column names or strings to concatenate

=back

=item B<Returns>

Formatted SQL for concatenating specified strings

=back

=item C<sql_string_until>

=over

=item B<Description>

Returns SQL for truncating a string at the first occurrence of a certain
substring.

=item B<Params>

Note that both parameters need to be sql-quoted.

=item C<$string> The string we're truncating

=item C<$substring> The substring we're truncating at.

=back

=item C<sql_fulltext_search>

=over

=item B<Description>

Returns one or two SQL expressions for performing a full text search for
specified text on a given column.

If one value is returned, it is a numeric expression that indicates
a match with a positive value and a non-match with zero. In this case,
the DB must support casting numeric expresions to booleans.

If two values are returned, then the first value is a boolean expression
that indicates the presence of a match, and the second value is a numeric
expression that can be used for ranking.

There is a ANSI SQL version of this method implemented using LIKE operator,
but it's not a real full text search. DB specific modules should override 
this, as this generic implementation will be always much slower. This 
generic implementation returns 'relevance' as 0 for no match, or 1 for a 
match.

=item B<Params>

=over

=item C<$column> - name of column to search (scalar)

=item C<$text> - text to search for (scalar)

=back

=item B<Returns>

Formatted SQL for full text search

=back

=item C<sql_istrcmp>

=over

=item B<Description>

Returns SQL for a case-insensitive string comparison.

=item B<Params>

=over

=item C<$left> - What should be on the left-hand-side of the operation.

=item C<$right> - What should be on the right-hand-side of the operation.

=item C<$op> (optional) - What the operation is. Should be a  valid ANSI 
SQL comparison operator, such as C<=>, C<E<lt>>, C<LIKE>, etc. Defaults 
to C<=> if not specified.

=back

=item B<Returns>

A SQL statement that will run the comparison in a case-insensitive fashion.

=item B<Note>

Uses L</sql_istring>, so it has the same performance concerns.
Try to avoid using this function unless absolutely necessary.

Subclass Implementors: Override sql_istring instead of this
function, most of the time (this function uses sql_istring).

=back

=item C<sql_istring>

=over

=item B<Description>

Returns SQL syntax "preparing" a string or text column for case-insensitive 
comparison.

=item B<Params>

=over

=item C<$string> - string to convert (scalar)

=back

=item B<Returns>

Formatted SQL making the string case insensitive.

=item B<Note>

The default implementation simply calls LOWER on the parameter.
If this is used to search on a text column with index, the index
will not be usually used unless it was created as LOWER(column).

=back

=item C<sql_in>

=over

=item B<Description>

Returns SQL syntax for the C<IN ()> operator. 

Only necessary where an C<IN> clause can have more than 1000 items.

=item B<Params>

=over

=item C<$column_name> - Column name (e.g. C<bug_id>)

=item C<$in_list_ref> - an arrayref containing values for C<IN ()>

=back

=item B<Returns>

Formatted SQL for the C<IN> operator.

=back

=back


=head1 IMPLEMENTED METHODS

These methods are implemented in Bugzilla::DB, and only need
to be implemented in subclasses if you need to override them for 
database-compatibility reasons.

=head2 General Information Methods

These methods return information about data in the database.

=over

=item C<bz_last_key>

=over

=item B<Description>

Returns the last serial number, usually from a previous INSERT.

Must be executed directly following the relevant INSERT.
This base implementation uses L<DBI/last_insert_id>. If the
DBD supports it, it is the preffered way to obtain the last
serial index. If it is not supported, the DB-specific code
needs to override this function.

=item B<Params>

=over

=item C<$table> - name of table containing serial column (scalar)

=item C<$column> - name of column containing serial data type (scalar)

=back

=item B<Returns>

Last inserted ID (scalar)

=back

=back

=head2 Database Setup Methods

These methods are used by the Bugzilla installation programs to set up
the database.

=over

=item C<bz_populate_enum_tables>

=over

=item B<Description>

For an upgrade or an initial installation, populates the tables that hold 
the legal values for the old "enum" fields: C<bug_severity>, 
C<resolution>, etc. Prints out information if it inserts anything into the
DB.

=item B<Params> (none)

=item B<Returns> (nothing)

=back

=back


=head2 Schema Modification Methods

These methods modify the current Bugzilla Schema.

Where a parameter says "Abstract index/column definition", it returns/takes
information in the formats defined for indexes and columns in
C<Bugzilla::DB::Schema::ABSTRACT_SCHEMA>.

=over

=item C<bz_add_column>

=over

=item B<Description>

Adds a new column to a table in the database. Prints out a brief statement 
that it did so, to stdout. Note that you cannot add a NOT NULL column that 
has no default -- the database won't know what to set all the NULL
values to.

=item B<Params>

=over

=item C<$table> - the table where the column is being added

=item C<$name> - the name of the new column

=item C<\%definition> - Abstract column definition for the new column

=item C<$init_value> (optional) - An initial value to set the column
to. Required if your column is NOT NULL and has no DEFAULT set.

=back

=item B<Returns> (nothing)

=back

=item C<bz_add_index>

=over

=item B<Description>

Adds a new index to a table in the database. Prints out a brief statement 
that it did so, to stdout. If the index already exists, we will do nothing.

=item B<Params>

=over

=item C<$table> - The table the new index is on.

=item C<$name>  - A name for the new index.

=item C<$definition> - An abstract index definition. Either a hashref 
or an arrayref.

=back

=item B<Returns> (nothing)

=back

=item C<bz_add_table>

=over

=item B<Description>

Creates a new table in the database, based on the definition for that 
table in the abstract schema.

Note that unlike the other 'add' functions, this does not take a 
definition, but always creates the table as it exists in
L<Bugzilla::DB::Schema/ABSTRACT_SCHEMA>.

If a table with that name already exists, then this function returns 
silently.

=item B<Params>

=over

=item C<$name> - The name of the table you want to create.

=back

=item B<Returns> (nothing)

=back

=item C<bz_drop_index>

=over

=item B<Description>

Removes an index from the database. Prints out a brief statement that it 
did so, to stdout. If the index doesn't exist, we do nothing.

=item B<Params>

=over

=item C<$table> - The table that the index is on.

=item C<$name> - The name of the index that you want to drop.

=back

=item B<Returns> (nothing)

=back

=item C<bz_drop_table>

=over

=item B<Description>

Drops a table from the database. If the table doesn't exist, we just 
return silently.

=item B<Params>

=over

=item C<$name> - The name of the table to drop.

=back

=item B<Returns> (nothing)

=back

=item C<bz_alter_column>

=over

=item B<Description>

Changes the data type of a column in a table. Prints out the changes 
being made to stdout. If the new type is the same as the old type, 
the function returns without changing anything.

=item B<Params>

=over

=item C<$table> - the table where the column is

=item C<$name> - the name of the column you want to change

=item C<\%new_def> - An abstract column definition for the new 
data type of the columm

=item C<$set_nulls_to> (Optional) - If you are changing the column
to be NOT NULL, you probably also want to set any existing NULL columns 
to a particular value. Specify that value here. B<NOTE>: The value should 
not already be SQL-quoted.

=back

=item B<Returns> (nothing)

=back

=item C<bz_drop_column>

=over

=item B<Description>

Removes a column from a database table. If the column doesn't exist, we 
return without doing anything. If we do anything, we print a short 
message to C<stdout> about the change.

=item B<Params>

=over

=item C<$table> - The table where the column is

=item C<$column> - The name of the column you want to drop

=back

=item B<Returns> (nothing)

=back

=item C<bz_rename_column>

=over

=item B<Description>

Renames a column in a database table. If the C<$old_name> column 
doesn't exist, we return without doing anything. If C<$old_name> 
and C<$new_name> both already exist in the table specified, we fail.

=item B<Params>

=over

=item C<$table> - The name of the table containing the column 
that you want to rename

=item C<$old_name> - The current name of the column that you want to rename

=item C<$new_name> - The new name of the column

=back

=item B<Returns> (nothing)

=back

=item C<bz_rename_table>

=over

=item B<Description>

Renames a table in the database. Does nothing if the table doesn't exist.

Throws an error if the old table exists and there is already a table 
with the new name.

=item B<Params>

=over

=item C<$old_name> - The current name of the table.

=item C<$new_name> - What you're renaming the table to.

=back

=item B<Returns> (nothing)

=back

=back

=head2 Schema Information Methods

These methods return information about the current Bugzilla database
schema, as it currently exists on the disk. 

Where a parameter says "Abstract index/column definition", it returns/takes
information in the formats defined for indexes and columns for
L<Bugzilla::DB::Schema/ABSTRACT_SCHEMA>.

=over

=item C<bz_column_info>

=over

=item B<Description>

Get abstract column definition.

=item B<Params>

=over

=item C<$table> - The name of the table the column is in.

=item C<$column> - The name of the column.

=back

=item B<Returns>

An abstract column definition for that column. If the table or column 
does not exist, we return C<undef>.

=back

=item C<bz_index_info>

=over

=item B<Description>

Get abstract index definition.

=item B<Params>

=over

=item C<$table> - The table the index is on.

=item C<$index> - The name of the index.

=back

=item B<Returns>

An abstract index definition for that index, always in hashref format. 
The hashref will always contain the C<TYPE> element, but it will
be an empty string if it's just a normal index.

If the index does not exist, we return C<undef>.

=back

=back


=head2 Transaction Methods

These methods deal with the starting and stopping of transactions 
in the database.

=over

=item C<bz_in_transaction>

Returns C<1> if we are currently in the middle of an uncommitted transaction,
C<0> otherwise.

=item C<bz_start_transaction>

Starts a transaction.

It is OK to call C<bz_start_transaction> when you are already inside of
a transaction. However, you must call L</bz_commit_transaction> as many
times as you called C<bz_start_transaction>, in order for your transaction
to actually commit.

Bugzilla uses C<REPEATABLE READ> transactions.

Returns nothing and takes no parameters.

=item C<bz_commit_transaction>

Ends a transaction, commiting all changes. Returns nothing and takes
no parameters.

=item C<bz_rollback_transaction>

Ends a transaction, rolling back all changes. Returns nothing and takes 
no parameters.

=back


=head1 SUBCLASS HELPERS

Methods in this class are intended to be used by subclasses to help them
with their functions.

=over

=item C<db_new>

=over

=item B<Description>

Constructor

=item B<Params>

=over

=item C<$dsn> - database connection string

=item C<$user> - username used to log in to the database

=item C<$pass> - password used to log in to the database

=item C<\%override_attrs> - set of attributes for DB connection (optional).
You only have to set attributes that you want to be different from
the default attributes set inside of C<db_new>.

=back

=item B<Returns>

A new instance of the DB class

=item B<Note>

The name of this constructor is not C<new>, as that would make
our check for implementation of C<new> by derived class useless.

=back

=back


=head1 SEE ALSO

L<DBI>

L<Bugzilla::Constants/DB_MODULE>