summaryrefslogtreecommitdiff
path: root/includes/db/DatabaseIbm_db2.php
blob: fcd0bc2d82332129649fdb3154f6b9f0241c7e37 (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
<?php
/**
 * This script is the IBM DB2 database abstraction layer
 *
 * See maintenance/ibm_db2/README for development notes and other specific information
 * @ingroup Database
 * @file
 * @author leo.petr+mediawiki@gmail.com
 */

/**
 * Utility class for generating blank objects
 * Intended as an equivalent to {} in Javascript
 * @ingroup Database
 */
class BlankObject {
}

/**
 * This represents a column in a DB2 database
 * @ingroup Database
 */
class IBM_DB2Field {
	private $name, $tablename, $type, $nullable, $max_length;

	/**
	 * Builder method for the class 
	 * @param Object $db Database interface
	 * @param string $table table name
	 * @param string $field column name
	 * @return IBM_DB2Field
	 */
	static function fromText($db, $table, $field) {
		global $wgDBmwschema;

		$q = <<<END
SELECT
lcase(coltype) AS typname,
nulls AS attnotnull, length AS attlen
FROM sysibm.syscolumns
WHERE tbcreator=%s AND tbname=%s AND name=%s;
END;
		$res = $db->query(sprintf($q,
				$db->addQuotes($wgDBmwschema),
				$db->addQuotes($table),
				$db->addQuotes($field)));
		$row = $db->fetchObject($res);
		if (!$row)
			return null;
		$n = new IBM_DB2Field;
		$n->type = $row->typname;
		$n->nullable = ($row->attnotnull == 'N');
		$n->name = $field;
		$n->tablename = $table;
		$n->max_length = $row->attlen;
		return $n;
	}
	/**
	 * Get column name
	 * @return string column name
	 */
	function name() { return $this->name; }
	/**
	 * Get table name
	 * @return string table name
	 */
	function tableName() { return $this->tablename; }
	/**
	 * Get column type
	 * @return string column type
	 */
	function type() { return $this->type; }
	/**
	 * Can column be null?
	 * @return bool true or false
	 */
	function nullable() { return $this->nullable; }
	/**
	 * How much can you fit in the column per row?
	 * @return int length
	 */
	function maxLength() { return $this->max_length; }
}

/**
 * Wrapper around binary large objects
 * @ingroup Database
 */
class IBM_DB2Blob {
	private $mData;

	function __construct($data) {
		$this->mData = $data;
	}

	function getData() {
		return $this->mData;
	}
}

/**
 * Primary database interface
 * @ingroup Database
 */
class DatabaseIbm_db2 extends Database {
	/*
	 * Inherited members
	protected $mLastQuery = '';
	protected $mPHPError = false;

	protected $mServer, $mUser, $mPassword, $mConn = null, $mDBname;
	protected $mOut, $mOpened = false;

	protected $mFailFunction;
	protected $mTablePrefix;
	protected $mFlags;
	protected $mTrxLevel = 0;
	protected $mErrorCount = 0;
	protected $mLBInfo = array();
	protected $mFakeSlaveLag = null, $mFakeMaster = false;
	 *
	 */
	
	/// Server port for uncataloged connections
	protected $mPort = NULL;
	/// Whether connection is cataloged
	protected $mCataloged = NULL;
	/// Schema for tables, stored procedures, triggers
	protected $mSchema = NULL;
	/// Whether the schema has been applied in this session
	protected $mSchemaSet = false;
	/// Result of last query
	protected $mLastResult = NULL;
	/// Number of rows affected by last INSERT/UPDATE/DELETE
	protected $mAffectedRows = NULL;
	/// Number of rows returned by last SELECT
	protected $mNumRows = NULL;
	
	
	const CATALOGED = "cataloged";
	const UNCATALOGED = "uncataloged";
	const USE_GLOBAL = "get from global";
	
	/// Last sequence value used for a primary key
	protected $mInsertId = NULL;
	
	/*
	 * These can be safely inherited
	 * 
	 * Getter/Setter: (18)
	 * failFunction
	 * setOutputPage
	 * bufferResults
	 * ignoreErrors
	 * trxLevel
	 * errorCount
	 * getLBInfo
	 * setLBInfo
	 * lastQuery
	 * isOpen
	 * setFlag
	 * clearFlag
	 * getFlag
	 * getProperty
	 * getDBname
	 * getServer
	 * tableNameCallback
	 * tablePrefix
	 * 
	 * Administrative: (8)
	 * debug
	 * installErrorHandler
	 * restoreErrorHandler
	 * connectionErrorHandler
	 * reportConnectionError
	 * sourceFile
	 * sourceStream
	 * replaceVars
	 * 
	 * Database: (5)
	 * query
	 * set
	 * selectField
	 * generalizeSQL
	 * update
	 * strreplace
	 * deadlockLoop
	 * 
	 * Prepared Statement: 6
	 * prepare
	 * freePrepared
	 * execute
	 * safeQuery
	 * fillPrepared
	 * fillPreparedArg
	 * 
	 * Slave/Master: (4) 
	 * masterPosWait
	 * getSlavePos
	 * getMasterPos
	 * getLag
	 * 
	 * Generation: (9)
	 * tableNames
	 * tableNamesN
	 * tableNamesWithUseIndexOrJOIN
	 * escapeLike
	 * delete
	 * insertSelect
	 * timestampOrNull
	 * resultObject
	 * aggregateValue
	 * selectSQLText
	 * selectRow
	 * makeUpdateOptions
	 * 
	 * Reflection: (1)
	 * indexExists
	 */
	
	/*
	 * These need to be implemented TODO
	 * 
	 * Administrative: 7 / 7
	 * constructor [Done]
	 * open [Done]
	 * openCataloged [Done]
	 * close [Done]
	 * newFromParams [Done]
	 * openUncataloged [Done]
	 * setup_database [Done]
	 * 
	 * Getter/Setter: 13 / 13
	 * cascadingDeletes [Done]
	 * cleanupTriggers  [Done]
	 * strictIPs  [Done]
	 * realTimestamps  [Done]
	 * impliciGroupby  [Done]
	 * implicitOrderby  [Done]
	 * searchableIPs  [Done]
	 * functionalIndexes  [Done]
	 * getWikiID  [Done]
	 * isOpen [Done]
	 * getServerVersion [Done]
	 * getSoftwareLink [Done]
	 * getSearchEngine [Done]
	 * 
	 * Database driver wrapper: 23 / 23
	 * lastError [Done]
	 * lastErrno [Done]
	 * doQuery [Done]
	 * tableExists [Done]
	 * fetchObject [Done]
	 * fetchRow [Done]
	 * freeResult [Done]
	 * numRows [Done]
	 * numFields [Done]
	 * fieldName [Done]
	 * insertId [Done]
	 * dataSeek [Done]
	 * affectedRows [Done]
	 * selectDB [Done]
	 * strencode [Done]
	 * conditional [Done]
	 * wasDeadlock [Done]
	 * ping [Done]
	 * getStatus [Done]
	 * setTimeout [Done]
	 * lock [Done]
	 * unlock [Done]
	 * insert [Done]
	 * select [Done]
	 * 
	 * Slave/master: 2 / 2
	 * setFakeSlaveLag [Done]
	 * setFakeMaster [Done]
	 * 
	 * Reflection: 6 / 6
	 * fieldExists [Done]
	 * indexInfo [Done]
	 * fieldInfo [Done]
	 * fieldType [Done]
	 * indexUnique [Done]
	 * textFieldSize [Done]
	 * 
	 * Generation: 16 / 16
	 * tableName [Done]
	 * addQuotes [Done]
	 * makeList [Done]
	 * makeSelectOptions [Done]
	 * estimateRowCount [Done]
	 * nextSequenceValue [Done]
	 * useIndexClause [Done]
	 * replace [Done]
	 * deleteJoin [Done]
	 * lowPriorityOption [Done]
	 * limitResult [Done]
	 * limitResultForUpdate [Done]
	 * timestamp [Done]
	 * encodeBlob [Done]
	 * decodeBlob [Done]
	 * buildConcat [Done]
	 */
	
	######################################
	# Getters and Setters
	######################################
	
	/**
	 * Returns true if this database supports (and uses) cascading deletes
	 */
	function cascadingDeletes() {
		return true;
	}

	/**
	 * Returns true if this database supports (and uses) triggers (e.g. on the page table)
	 */
	function cleanupTriggers() {
		return true;
	}

	/**
	 * Returns true if this database is strict about what can be put into an IP field.
	 * Specifically, it uses a NULL value instead of an empty string.
	 */
	function strictIPs() {
		return true;
	}
	
	/**
	 * Returns true if this database uses timestamps rather than integers
	*/
	function realTimestamps() {
		return true;
	}

	/**
	 * Returns true if this database does an implicit sort when doing GROUP BY
	 */
	function implicitGroupby() {
		return false;
	}

	/**
	 * Returns true if this database does an implicit order by when the column has an index
	 * For example: SELECT page_title FROM page LIMIT 1
	 */
	function implicitOrderby() {
		return false;
	}

	/**
	 * Returns true if this database can do a native search on IP columns
	 * e.g. this works as expected: .. WHERE rc_ip = '127.42.12.102/32';
	 */
	function searchableIPs() {
		return true;
	}

	/**
	 * Returns true if this database can use functional indexes
	 */
	function functionalIndexes() {
		return true;
	}
	
	/**
	 * Returns a unique string representing the wiki on the server
	 */
	function getWikiID() {
		if( $this->mSchema ) {
			return "{$this->mDBname}-{$this->mSchema}";
		} else {
			return $this->mDBname;
		}
	}
	
	
	######################################
	# Setup
	######################################
	
	
	/**
	 * 
	 * @param string $server hostname of database server
	 * @param string $user username
	 * @param string $password
	 * @param string $dbName database name on the server
	 * @param function $failFunction (optional)
	 * @param integer $flags database behaviour flags (optional, unused)
	 */
	public function DatabaseIbm_db2($server = false, $user = false, $password = false,
							$dbName = false, $failFunction = false, $flags = 0,
							$schema = self::USE_GLOBAL )
	{

		global $wgOut, $wgDBmwschema;
		# Can't get a reference if it hasn't been set yet
		if ( !isset( $wgOut ) ) {
			$wgOut = NULL;
		}
		$this->mOut =& $wgOut;
		$this->mFailFunction = $failFunction;
		$this->mFlags = DBO_TRX | $flags;
		
		if ( $schema == self::USE_GLOBAL ) {
			$this->mSchema = $wgDBmwschema;
		}
		else {
			$this->mSchema = $schema;
		}
		
		$this->open( $server, $user, $password, $dbName);
	}
	
	/**
	 * Opens a database connection and returns it
	 * Closes any existing connection
	 * @return a fresh connection
	 * @param string $server hostname
	 * @param string $user
	 * @param string $password
	 * @param string $dbName database name
	 */
	public function open( $server, $user, $password, $dbName )
	{
		// Load the port number
		global $wgDBport_db2, $wgDBcataloged;
		wfProfileIn( __METHOD__ );
		
		// Load IBM DB2 driver if missing
		if (!@extension_loaded('ibm_db2')) {
			@dl('ibm_db2.so');
		}
		// Test for IBM DB2 support, to avoid suppressed fatal error
		if ( !function_exists( 'db2_connect' ) ) {
			$error = "DB2 functions missing, have you enabled the ibm_db2 extension for PHP?\n";
			wfDebug($error);
			$this->reportConnectionError($error);
		}

		if (!strlen($user)) { // Copied from Postgres
			return null;
		}
		
		// Close existing connection
		$this->close();
		// Cache conn info
		$this->mServer = $server;
		$this->mPort = $port = $wgDBport_db2;
		$this->mUser = $user;
		$this->mPassword = $password;
		$this->mDBname = $dbName;
		$this->mCataloged = $cataloged = $wgDBcataloged;
		
		if ( $cataloged == self::CATALOGED ) {
			$this->openCataloged($dbName, $user, $password);
		}
		elseif ( $cataloged == self::UNCATALOGED ) {
			$this->openUncataloged($dbName, $user, $password, $server, $port);
		}
		// Don't do this
		// Not all MediaWiki code is transactional
		// Rather, turn it off in the begin function and turn on after a commit
		// db2_autocommit($this->mConn, DB2_AUTOCOMMIT_OFF);
		db2_autocommit($this->mConn, DB2_AUTOCOMMIT_ON);

		if ( $this->mConn == false ) {
			wfDebug( "DB connection error\n" );
			wfDebug( "Server: $server, Database: $dbName, User: $user, Password: " . substr( $password, 0, 3 ) . "...\n" );
			wfDebug( $this->lastError()."\n" );
			return null;
		}

		$this->mOpened = true;
		$this->applySchema();
		
		wfProfileOut( __METHOD__ );
		return $this->mConn;
	}
	
	/**
	 * Opens a cataloged database connection, sets mConn
	 */
	protected function openCataloged( $dbName, $user, $password )
	{
		@$this->mConn = db2_connect($dbName, $user, $password);
	}
	
	/**
	 * Opens an uncataloged database connection, sets mConn
	 */
	protected function openUncataloged( $dbName, $user, $password, $server, $port )
	{
		$str = "DRIVER={IBM DB2 ODBC DRIVER};";
		$str .= "DATABASE=$dbName;";
		$str .= "HOSTNAME=$server;";
		if ($port) $str .= "PORT=$port;";
		$str .= "PROTOCOL=TCPIP;";
		$str .= "UID=$user;";
		$str .= "PWD=$password;";
		
		@$this->mConn = db2_connect($str, $user, $password);
	}
	
	/**
	 * Closes a database connection, if it is open
	 * Returns success, true if already closed
	 */
	public function close() {
		$this->mOpened = false;
		if ( $this->mConn ) {
			if ($this->trxLevel() > 0) {
				$this->commit();
			}
			return db2_close( $this->mConn );
		}
		else {
			return true;
		}
	}
	
	/**
	 * Returns a fresh instance of this class
	 * @static
	 * @return 
	 * @param string $server hostname of database server
	 * @param string $user username
	 * @param string $password
	 * @param string $dbName database name on the server
	 * @param function $failFunction (optional)
	 * @param integer $flags database behaviour flags (optional, unused)
	 */
	static function newFromParams( $server, $user, $password, $dbName, $failFunction = false, $flags = 0)
	{
		return new DatabaseIbm_db2( $server, $user, $password, $dbName, $failFunction, $flags );
	}
	
	/**
	 * Retrieves the most current database error
	 * Forces a database rollback
	 */
	public function lastError() {
		if ($this->lastError2()) {
			$this->rollback();
			return true;
		}
		return false;
	}
	
	private function lastError2() {
		$connerr = db2_conn_errormsg();
		if ($connerr) return $connerr;
		$stmterr = db2_stmt_errormsg();
		if ($stmterr) return $stmterr;
		if ($this->mConn) return "No open connection.";
		if ($this->mOpened) return "No open connection allegedly.";
		
		return false;
	}
	
	/**
	 * Get the last error number
	 * Return 0 if no error
	 * @return integer
	 */
	public function lastErrno() {
		$connerr = db2_conn_error();
		if ($connerr) return $connerr;
		$stmterr = db2_stmt_error();
		if ($stmterr) return $stmterr;
		return 0;
	}
	
	/**
	 * Is a database connection open?
	 * @return 
	 */
	public function isOpen() { return $this->mOpened; }
	
	/**
	 * The DBMS-dependent part of query()
	 * @param  $sql String: SQL query.
	 * @return object Result object to feed to fetchObject, fetchRow, ...; or false on failure
	 * @access private
	 */
	/*private*/
	public function doQuery( $sql ) {
		//print "<li><pre>$sql</pre></li>";
		// Switch into the correct namespace
		$this->applySchema();
		
		$ret = db2_exec( $this->mConn, $sql );
		if( !$ret ) {
			print "<br><pre>";
			print $sql;
			print "</pre><br>";
			$error = db2_stmt_errormsg();
			throw new DBUnexpectedError($this,  'SQL error: ' . htmlspecialchars( $error ) );
		}
		$this->mLastResult = $ret;
		$this->mAffectedRows = NULL;	// Not calculated until asked for
		return $ret;
	}
	
	/**
	 * @return string Version information from the database
	 */
	public function getServerVersion() {
		$info = db2_server_info( $this->mConn );
		return $info->DBMS_VER;
	}
	
	/**
	 * Queries whether a given table exists
	 * @return boolean
	 */
	public function tableExists( $table ) {
		$schema = $this->mSchema;
		$sql = <<< EOF
SELECT COUNT(*) FROM SYSIBM.SYSTABLES ST
WHERE ST.NAME = '$table' AND ST.CREATOR = '$schema'
EOF;
		$res = $this->query( $sql );
		if (!$res) return false;
		
		// If the table exists, there should be one of it
		@$row = $this->fetchRow($res);
		$count = $row[0];
		if ($count == '1' or $count == 1) {
			return true;
		}
		
		return false;
	}
	
	/**
	 * Fetch the next row from the given result object, in object form.
	 * Fields can be retrieved with $row->fieldname, with fields acting like
	 * member variables.
	 *
	 * @param $res SQL result object as returned from Database::query(), etc.
	 * @return DB2 row object
	 * @throws DBUnexpectedError Thrown if the database returns an error
	 */
	public function fetchObject( $res ) {
		if ( $res instanceof ResultWrapper ) {
			$res = $res->result;
		}
		@$row = db2_fetch_object( $res );
		if( $this->lastErrno() ) {
			throw new DBUnexpectedError( $this, 'Error in fetchObject(): ' . htmlspecialchars( $this->lastError() ) );
		}
		// Make field names lowercase for compatibility with MySQL
		if ($row)
		{
			$row2 = new BlankObject();
			foreach ($row as $key => $value)
			{
				$keyu = strtolower($key);
				$row2->$keyu = $value;
			}
			$row = $row2;
		}
		return $row;
	}

	/**
	 * Fetch the next row from the given result object, in associative array
	 * form.  Fields are retrieved with $row['fieldname'].
	 *
	 * @param $res SQL result object as returned from Database::query(), etc.
	 * @return DB2 row object
	 * @throws DBUnexpectedError Thrown if the database returns an error
	 */
	public function fetchRow( $res ) {
		if ( $res instanceof ResultWrapper ) {
			$res = $res->result;
		}
		@$row = db2_fetch_array( $res );
		if ( $this->lastErrno() ) {
			throw new DBUnexpectedError( $this, 'Error in fetchRow(): ' . htmlspecialchars( $this->lastError() ) );
		}
		return $row;
	}
	
	/**
	 * Override if introduced to base Database class
	 */
	public function initial_setup() {
		// do nothing
	}
	
	/**
	 * Create tables, stored procedures, and so on
	 */
	public function setup_database() {
		// Timeout was being changed earlier due to mysterious crashes
		// Changing it now may cause more problems than not changing it
		//set_time_limit(240);
		try {
			// TODO: switch to root login if available
			
			// Switch into the correct namespace
			$this->applySchema();
			$this->begin();
			
			$res = dbsource( "../maintenance/ibm_db2/tables.sql", $this);
			$res = null;
	
			// TODO: update mediawiki_version table
			
			// TODO: populate interwiki links
			
			$this->commit();
		}
		catch (MWException $mwe)
		{
			print "<br><pre>$mwe</pre><br>";
		}
	}

	/**
	 * Escapes strings
	 * Doesn't escape numbers
	 * @param string s string to escape
	 * @return escaped string
	 */
	public function addQuotes( $s ) {
		//wfDebug("DB2::addQuotes($s)\n");
		if ( is_null( $s ) ) {
			return "NULL";
		} else if ($s instanceof Blob) {
			return "'".$s->fetch($s)."'";
		}
		$s = $this->strencode($s);
		if ( is_numeric($s) ) {
			return $s;
		}
		else {
			return "'$s'";
		}
	}
	
	/**
	 * Escapes strings
	 * Only escapes numbers going into non-numeric fields
	 * @param string s string to escape
	 * @return escaped string
	 */
	public function addQuotesSmart( $table, $field, $s ) {
		if ( is_null( $s ) ) {
			return "NULL";
		} else if ($s instanceof Blob) {
			return "'".$s->fetch($s)."'";
		}
		$s = $this->strencode($s);
		if ( is_numeric($s) ) {
			// Check with the database if the column is actually numeric
			// This allows for numbers in titles, etc
			$res = $this->doQuery("SELECT $field FROM $table FETCH FIRST 1 ROWS ONLY");
			$type = db2_field_type($res, strtoupper($field));
			if ( $this->is_numeric_type( $type ) ) {
				//wfDebug("DB2: Numeric value going in a numeric column: $s in $type $field in $table\n");
				return $s;
			}
			else {
				wfDebug("DB2: Numeric in non-numeric: '$s' in $type $field in $table\n");
				return "'$s'";
			}
		}
		else {
			return "'$s'";
		}
	}
	
	/**
	 * Verifies that a DB2 column/field type is numeric
	 * @return bool true if numeric
	 * @param string $type DB2 column type
	 */
	public function is_numeric_type( $type ) {
		switch (strtoupper($type)) {
		case 'SMALLINT':
		case 'INTEGER':
		case 'INT':
		case 'BIGINT':
		case 'DECIMAL':
		case 'REAL':
		case 'DOUBLE':
		case 'DECFLOAT':
			return true;
		}
		return false;
	}
	
	/**
	 * Alias for addQuotes()
	 * @param string s string to escape
	 * @return escaped string
	 */
	public function strencode( $s ) {
		// Bloody useless function
		//  Prepends backslashes to \x00, \n, \r, \, ', " and \x1a. 
		//  But also necessary
		$s = db2_escape_string($s);
		// Wide characters are evil -- some of them look like '
		$s = utf8_encode($s);
		// Fix its stupidity
		$from =	array("\\\\",	"\\'",	'\\n',	'\\t',	'\\"',	'\\r');
		$to =	array("\\",		"''",	"\n",	"\t",	'"',	"\r");
		$s = str_replace($from, $to, $s); // DB2 expects '', not \' escaping
		return $s;
	}
	
	/**
	 * Switch into the database schema
	 */
	protected function applySchema() {
		if ( !($this->mSchemaSet) ) {
			$this->mSchemaSet = true;
			$this->begin();
			$this->doQuery("SET SCHEMA = $this->mSchema");
			$this->commit();
		}	
	}
	
	/**
	 * Start a transaction (mandatory)
	 */
	public function begin() {
		// turn off auto-commit
		db2_autocommit($this->mConn, DB2_AUTOCOMMIT_OFF);
		$this->mTrxLevel = 1;
	}
	
	/**
	 * End a transaction
	 * Must have a preceding begin()
	 */
	public function commit() {
		db2_commit($this->mConn);
		// turn auto-commit back on
		db2_autocommit($this->mConn, DB2_AUTOCOMMIT_ON);
		$this->mTrxLevel = 0;
	}
	
	/**
	 * Cancel a transaction
	 */
	public function rollback() {
		db2_rollback($this->mConn);
		// turn auto-commit back on
		// not sure if this is appropriate
		db2_autocommit($this->mConn, DB2_AUTOCOMMIT_ON);
		$this->mTrxLevel = 0;
	}
	
	/**
	 * Makes an encoded list of strings from an array
	 * $mode:
	 *        LIST_COMMA         - comma separated, no field names
	 *        LIST_AND           - ANDed WHERE clause (without the WHERE)
	 *        LIST_OR            - ORed WHERE clause (without the WHERE)
	 *        LIST_SET           - comma separated with field names, like a SET clause
	 *        LIST_NAMES         - comma separated field names
	 */
	public function makeList( $a, $mode = LIST_COMMA ) {
		wfDebug("DB2::makeList()\n");
		if ( !is_array( $a ) ) {
			throw new DBUnexpectedError( $this, 'Database::makeList called with incorrect parameters' );
		}

		$first = true;
		$list = '';
		foreach ( $a as $field => $value ) {
			if ( !$first ) {
				if ( $mode == LIST_AND ) {
					$list .= ' AND ';
				} elseif($mode == LIST_OR) {
					$list .= ' OR ';
				} else {
					$list .= ',';
				}
			} else {
				$first = false;
			}
			if ( ($mode == LIST_AND || $mode == LIST_OR) && is_numeric( $field ) ) {
				$list .= "($value)";
			} elseif ( ($mode == LIST_SET) && is_numeric( $field ) ) {
				$list .= "$value";
			} elseif ( ($mode == LIST_AND || $mode == LIST_OR) && is_array($value) ) {
				if( count( $value ) == 0 ) {
					throw new MWException( __METHOD__.': empty input' );
				} elseif( count( $value ) == 1 ) {
					// Special-case single values, as IN isn't terribly efficient
					// Don't necessarily assume the single key is 0; we don't
					// enforce linear numeric ordering on other arrays here.
					$value = array_values( $value );
					$list .= $field." = ".$this->addQuotes( $value[0] );
				} else {
					$list .= $field." IN (".$this->makeList($value).") ";
				}
			} elseif( is_null($value) ) {
				if ( $mode == LIST_AND || $mode == LIST_OR ) {
					$list .= "$field IS ";
				} elseif ( $mode == LIST_SET ) {
					$list .= "$field = ";
				}
				$list .= 'NULL';
			} else {
				if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
					$list .= "$field = ";
				}
				if ( $mode == LIST_NAMES ) {
					$list .= $value;
				}
				// Leo: Can't insert quoted numbers into numeric columns
				// (?) Might cause other problems. May have to check column type before insertion.
				else if ( is_numeric($value) ) {
					$list .= $value;
				}
				else {
					$list .= $this->addQuotes( $value );
				}
			}
		}
		return $list;
	}
	
	/**
	 * Makes an encoded list of strings from an array
	 * Quotes numeric values being inserted into non-numeric fields
	 * @return string
	 * @param string $table name of the table
	 * @param array $a list of values
	 * @param $mode:
	 *        LIST_COMMA         - comma separated, no field names
	 *        LIST_AND           - ANDed WHERE clause (without the WHERE)
	 *        LIST_OR            - ORed WHERE clause (without the WHERE)
	 *        LIST_SET           - comma separated with field names, like a SET clause
	 *        LIST_NAMES         - comma separated field names
	 */
	public function makeListSmart( $table, $a, $mode = LIST_COMMA ) {
		if ( !is_array( $a ) ) {
			throw new DBUnexpectedError( $this, 'Database::makeList called with incorrect parameters' );
		}

		$first = true;
		$list = '';
		foreach ( $a as $field => $value ) {
			if ( !$first ) {
				if ( $mode == LIST_AND ) {
					$list .= ' AND ';
				} elseif($mode == LIST_OR) {
					$list .= ' OR ';
				} else {
					$list .= ',';
				}
			} else {
				$first = false;
			}
			if ( ($mode == LIST_AND || $mode == LIST_OR) && is_numeric( $field ) ) {
				$list .= "($value)";
			} elseif ( ($mode == LIST_SET) && is_numeric( $field ) ) {
				$list .= "$value";
			} elseif ( ($mode == LIST_AND || $mode == LIST_OR) && is_array($value) ) {
				if( count( $value ) == 0 ) {
					throw new MWException( __METHOD__.': empty input' );
				} elseif( count( $value ) == 1 ) {
					// Special-case single values, as IN isn't terribly efficient
					// Don't necessarily assume the single key is 0; we don't
					// enforce linear numeric ordering on other arrays here.
					$value = array_values( $value );
					$list .= $field." = ".$this->addQuotes( $value[0] );
				} else {
					$list .= $field." IN (".$this->makeList($value).") ";
				}
			} elseif( is_null($value) ) {
				if ( $mode == LIST_AND || $mode == LIST_OR ) {
					$list .= "$field IS ";
				} elseif ( $mode == LIST_SET ) {
					$list .= "$field = ";
				}
				$list .= 'NULL';
			} else {
				if ( $mode == LIST_AND || $mode == LIST_OR || $mode == LIST_SET ) {
					$list .= "$field = ";
				}
				if ( $mode == LIST_NAMES ) {
					$list .= $value;
				}
				else {
					$list .= $this->addQuotesSmart( $table, $field, $value );
				}
			}
		}
		return $list;
	}
	
	/**
	 * Construct a LIMIT query with optional offset
	 * This is used for query pages
	 * $sql string SQL query we will append the limit too
	 * $limit integer the SQL limit
	 * $offset integer the SQL offset (default false)
	 */
	public function limitResult($sql, $limit, $offset=false) {
		if( !is_numeric($limit) ) {
			throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
		}
		if( $offset ) {
			wfDebug("Offset parameter not supported in limitResult()\n");
		}
		// TODO implement proper offset handling
		// idea: get all the rows between 0 and offset, advance cursor to offset
		return "$sql FETCH FIRST $limit ROWS ONLY ";
	}
	
	/**
	 * Handle reserved keyword replacement in table names
	 * @return 
	 * @param $name Object
	 */
	public function tableName( $name ) {
		# Replace reserved words with better ones
		switch( $name ) {
			case 'user':
				return 'mwuser';
			case 'text':
				return 'pagecontent';
			default:
				return $name;
		}
	}
	
	/**
	 * Generates a timestamp in an insertable format
	 * @return string timestamp value
	 * @param timestamp $ts
	 */
	public function timestamp( $ts=0 ) {
		// TS_MW cannot be easily distinguished from an integer
		return wfTimestamp(TS_DB2,$ts);
	}

	/**
	 * Return the next in a sequence, save the value for retrieval via insertId()
	 * @param string seqName Name of a defined sequence in the database
	 * @return next value in that sequence
	 */
	public function nextSequenceValue( $seqName ) {
		$safeseq = preg_replace( "/'/", "''", $seqName );
		$res = $this->query( "VALUES NEXTVAL FOR $safeseq" );
		$row = $this->fetchRow( $res );
		$this->mInsertId = $row[0];
		$this->freeResult( $res );
		return $this->mInsertId;
	}
	
	/**
	 * This must be called after nextSequenceVal
	 * @return Last sequence value used as a primary key
	 */
	public function insertId() {
		return $this->mInsertId;
	}
	
	/**
	 * INSERT wrapper, inserts an array into a table
	 *
	 * $args may be a single associative array, or an array of these with numeric keys,
	 * for multi-row insert
	 *
	 * @param array $table   String: Name of the table to insert to.
	 * @param array $args    Array: Items to insert into the table.
	 * @param array $fname   String: Name of the function, for profiling
	 * @param mixed $options String or Array. Valid options: IGNORE
	 *
	 * @return bool Success of insert operation. IGNORE always returns true.
	 */
	public function insert( $table, $args, $fname = 'DatabaseIbm_db2::insert', $options = array() ) {
		wfDebug("DB2::insert($table)\n");
		if ( !count( $args ) ) {
			return true;
		}

		$table = $this->tableName( $table );

		if ( !is_array( $options ) )
			$options = array( $options );

		if ( isset( $args[0] ) && is_array( $args[0] ) ) {
		}
		else {
			$args = array($args);
		}
		$keys = array_keys( $args[0] );

		// If IGNORE is set, we use savepoints to emulate mysql's behavior
		$ignore = in_array( 'IGNORE', $options ) ? 'mw' : '';
		
		// Cache autocommit value at the start
		$oldautocommit = db2_autocommit($this->mConn);

		// If we are not in a transaction, we need to be for savepoint trickery
		$didbegin = 0;
		if (! $this->mTrxLevel) {
			$this->begin();
			$didbegin = 1;
		}
		if ( $ignore ) {
			$olde = error_reporting( 0 );
			// For future use, we may want to track the number of actual inserts
			// Right now, insert (all writes) simply return true/false
			$numrowsinserted = 0;
		}

		$sql = "INSERT INTO $table (" . implode( ',', $keys ) . ') VALUES ';

		if ( !$ignore ) {
			$first = true;
			foreach ( $args as $row ) {
				if ( $first ) {
					$first = false;
				} else {
					$sql .= ',';
				}
				$sql .= '(' . $this->makeListSmart( $table, $row ) . ')';
			}
			$res = (bool)$this->query( $sql, $fname, $ignore );
		}
		else {
			$res = true;
			$origsql = $sql;
			foreach ( $args as $row ) {
				$tempsql = $origsql;
				$tempsql .= '(' . $this->makeListSmart( $table, $row ) . ')';

				if ( $ignore ) {
					db2_exec($this->mConn, "SAVEPOINT $ignore");
				}

				$tempres = (bool)$this->query( $tempsql, $fname, $ignore );

				if ( $ignore ) {
					$bar = db2_stmt_error();
					if ($bar != false) {
						db2_exec( $this->mConn, "ROLLBACK TO SAVEPOINT $ignore" );
					}
					else {
						db2_exec( $this->mConn, "RELEASE SAVEPOINT $ignore" );
						$numrowsinserted++;
					}
				}

				// If any of them fail, we fail overall for this function call
				// Note that this will be ignored if IGNORE is set
				if (! $tempres)
					$res = false;
			}
		}

		if ($didbegin) {
			$this->commit();
		}
		// if autocommit used to be on, it's ok to commit everything
		else if ($oldautocommit)
		{
			$this->commit();
		}
		
		if ( $ignore ) {
			$olde = error_reporting( $olde );
			// Set the affected row count for the whole operation
			$this->mAffectedRows = $numrowsinserted;

			// IGNORE always returns true
			return true;
		}
		
		return $res;
	}
	
	/**
	 * UPDATE wrapper, takes a condition array and a SET array
	 *
	 * @param string $table  The table to UPDATE
	 * @param array  $values An array of values to SET
	 * @param array  $conds  An array of conditions (WHERE). Use '*' to update all rows.
	 * @param string $fname  The Class::Function calling this function
	 *                       (for the log)
	 * @param array  $options An array of UPDATE options, can be one or
	 *                        more of IGNORE, LOW_PRIORITY
	 * @return bool
	 */
	function update( $table, $values, $conds, $fname = 'Database::update', $options = array() ) {
		$table = $this->tableName( $table );
		$opts = $this->makeUpdateOptions( $options );
		$sql = "UPDATE $opts $table SET " . $this->makeListSmart( $table, $values, LIST_SET );
		if ( $conds != '*' ) {
			$sql .= " WHERE " . $this->makeListSmart( $table, $conds, LIST_AND );
		}
		return $this->query( $sql, $fname );
	}
	
	/**
	 * DELETE query wrapper
	 *
	 * Use $conds == "*" to delete all rows
	 */
	function delete( $table, $conds, $fname = 'Database::delete' ) {
		if ( !$conds ) {
			throw new DBUnexpectedError( $this, 'Database::delete() called with no conditions' );
		}
		$table = $this->tableName( $table );
		$sql = "DELETE FROM $table";
		if ( $conds != '*' ) {
			$sql .= ' WHERE ' . $this->makeListSmart( $table, $conds, LIST_AND );
		}
		return $this->query( $sql, $fname );
	}
	
	/**
	 * Returns the number of rows affected by the last query or 0
	 * @return int the number of rows affected by the last query
	 */
	public function affectedRows() {
		if ( !is_null( $this->mAffectedRows ) ) {
			// Forced result for simulated queries
			return $this->mAffectedRows;
		}
		if( empty( $this->mLastResult ) )
			return 0;
		return db2_num_rows( $this->mLastResult );
	}
	
	/**
	 * USE INDEX clause
	 * DB2 doesn't have them and returns ""
	 * @param sting $index
	 */
	public function useIndexClause( $index ) {
		return "";
	}
	
	/**
	 * Simulates REPLACE with a DELETE followed by INSERT
	 * @param $table Object
	 * @param array $uniqueIndexes array consisting of indexes and arrays of indexes
	 * @param array $rows Rows to insert
	 * @param string $fname Name of the function for profiling
	 * @return nothing
	 */
	function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseIbm_db2::replace' ) {
		$table = $this->tableName( $table );

		if (count($rows)==0) {
			return;
		}

		# Single row case
		if ( !is_array( reset( $rows ) ) ) {
			$rows = array( $rows );
		}

		foreach( $rows as $row ) {
			# Delete rows which collide
			if ( $uniqueIndexes ) {
				$sql = "DELETE FROM $table WHERE ";
				$first = true;
				foreach ( $uniqueIndexes as $index ) {
					if ( $first ) {
						$first = false;
						$sql .= "(";
					} else {
						$sql .= ') OR (';
					}
					if ( is_array( $index ) ) {
						$first2 = true;
						foreach ( $index as $col ) {
							if ( $first2 ) {
								$first2 = false;
							} else {
								$sql .= ' AND ';
							}
							$sql .= $col.'=' . $this->addQuotes( $row[$col] );
						}
					} else {
						$sql .= $index.'=' . $this->addQuotes( $row[$index] );
					}
				}
				$sql .= ')';
				$this->query( $sql, $fname );
			}

			# Now insert the row
			$sql = "INSERT INTO $table (" . $this->makeList( array_keys( $row ), LIST_NAMES ) .') VALUES (' .
				$this->makeList( $row, LIST_COMMA ) . ')';
			$this->query( $sql, $fname );
		}
	}
	
	/**
	 * Returns the number of rows in the result set
	 * Has to be called right after the corresponding select query
	 * @param Object $res result set
	 * @return int number of rows
	 */
	public function numRows( $res ) {
		if ( $res instanceof ResultWrapper ) {
			$res = $res->result;
		}
		if ( $this->mNumRows ) {
			return $this->mNumRows;
		}
		else {
			return 0;
		}
	}
	
	/**
	 * Moves the row pointer of the result set
	 * @param Object $res result set
	 * @param int $row row number
	 * @return success or failure
	 */
	public function dataSeek( $res, $row ) {
		if ( $res instanceof ResultWrapper ) {
			$res = $res->result;
		}
		return db2_fetch_row( $res, $row );
	}
	
	###
	# Fix notices in Block.php 
	###
	
	/**
	 * Frees memory associated with a statement resource
	 * @param Object $res Statement resource to free
	 * @return bool success or failure
	 */
	public function freeResult( $res ) {
		if ( $res instanceof ResultWrapper ) {
			$res = $res->result;
		}
		if ( !@db2_free_result( $res ) ) {
			throw new DBUnexpectedError($this,  "Unable to free DB2 result\n" );
		}
	}
	
	/**
	 * Returns the number of columns in a resource
	 * @param Object $res Statement resource
	 * @return Number of fields/columns in resource
	 */
	public function numFields( $res ) {
		if ( $res instanceof ResultWrapper ) {
			$res = $res->result;
		}
		return db2_num_fields( $res );
	}
	
	/**
	 * Returns the nth column name
	 * @param Object $res Statement resource
	 * @param int $n Index of field or column
	 * @return string name of nth column
	 */
	public function fieldName( $res, $n ) {
		if ( $res instanceof ResultWrapper ) {
			$res = $res->result;
		}
		return db2_field_name( $res, $n );
	}
	
	/**
	 * SELECT wrapper
	 *
	 * @param mixed  $table   Array or string, table name(s) (prefix auto-added)
	 * @param mixed  $vars    Array or string, field name(s) to be retrieved
	 * @param mixed  $conds   Array or string, condition(s) for WHERE
	 * @param string $fname   Calling function name (use __METHOD__) for logs/profiling
	 * @param array  $options Associative array of options (e.g. array('GROUP BY' => 'page_title')),
	 *                        see Database::makeSelectOptions code for list of supported stuff
	 * @param array $join_conds Associative array of table join conditions (optional)
	 *                        (e.g. array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
	 * @return mixed Database result resource (feed to Database::fetchObject or whatever), or false on failure
	 */
	public function select( $table, $vars, $conds='', $fname = 'DatabaseIbm_db2::select', $options = array(), $join_conds = array() )
	{
		$res = parent::select( $table, $vars, $conds, $fname, $options, $join_conds );
		
		// We must adjust for offset
		if ( isset( $options['LIMIT'] ) ) {
			if ( isset ($options['OFFSET'] ) ) {
				$limit = $options['LIMIT'];
				$offset = $options['OFFSET'];
			}
		}
		
		
		// DB2 does not have a proper num_rows() function yet, so we must emulate it
		// DB2 9.5.3/9.5.4 and the corresponding ibm_db2 driver will introduce a working one
		// Yay!
		
		// we want the count
		$vars2 = array('count(*) as num_rows');
		// respecting just the limit option
		$options2 = array();
		if ( isset( $options['LIMIT'] ) ) $options2['LIMIT'] = $options['LIMIT'];
		// but don't try to emulate for GROUP BY
		if ( isset( $options['GROUP BY'] ) ) return $res;
		
		$res2 = parent::select( $table, $vars2, $conds, $fname, $options2, $join_conds );
		$obj = $this->fetchObject($res2);
		$this->mNumRows = $obj->num_rows;
		
		wfDebug("DatabaseIbm_db2::select: There are $this->mNumRows rows.\n");
		
		return $res;
	}
	
	/**
	 * Handles ordering, grouping, and having options ('GROUP BY' => colname)
	 * Has limited support for per-column options (colnum => 'DISTINCT')
	 * 
	 * @private
	 *
	 * @param array $options an associative array of options to be turned into
	 *              an SQL query, valid keys are listed in the function.
	 * @return array
	 */
	function makeSelectOptions( $options ) {
		$preLimitTail = $postLimitTail = '';
		$startOpts = '';

		$noKeyOptions = array();
		foreach ( $options as $key => $option ) {
			if ( is_numeric( $key ) ) {
				$noKeyOptions[$option] = true;
			}
		}

		if ( isset( $options['GROUP BY'] ) ) $preLimitTail .= " GROUP BY {$options['GROUP BY']}";
		if ( isset( $options['HAVING'] ) ) $preLimitTail .= " HAVING {$options['HAVING']}";
		if ( isset( $options['ORDER BY'] ) ) $preLimitTail .= " ORDER BY {$options['ORDER BY']}";
		
		if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) $startOpts .= 'DISTINCT';
		
		return array( $startOpts, '', $preLimitTail, $postLimitTail );
	}
	
	/**
	 * Returns link to IBM DB2 free download
	 * @return string wikitext of a link to the server software's web site
	 */
	public function getSoftwareLink() {
		return "[http://www.ibm.com/software/data/db2/express/?s_cmp=ECDDWW01&s_tact=MediaWiki IBM DB2]";
	}
	
	/**
	 * Does nothing
	 * @param object $db
	 * @return bool true
	 */
	public function selectDB( $db ) {
		return true;
	}
	
	/**
	 * Returns an SQL expression for a simple conditional.
	 * Uses CASE on DB2
	 *
	 * @param string $cond SQL expression which will result in a boolean value
	 * @param string $trueVal SQL expression to return if true
	 * @param string $falseVal SQL expression to return if false
	 * @return string SQL fragment
	 */
	public function conditional( $cond, $trueVal, $falseVal ) {
		return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
	}
	
	###
	# Fix search crash
	###
	/**
	 * Get search engine class. All subclasses of this
	 * need to implement this if they wish to use searching.
	 * 
	 * @return string
	 */
	public function getSearchEngine() {
		return "SearchIBM_DB2";
	}
	
	###
	# Tuesday the 14th of October, 2008
	###
	/**
	 * Did the last database access fail because of deadlock?
	 * @return bool
	 */
	public function wasDeadlock() {
		// get SQLSTATE
		$err = $this->lastErrno();
		switch($err) {
			case '40001':	// sql0911n, Deadlock or timeout, rollback
			case '57011':	// sql0904n, Resource unavailable, no rollback
			case '57033':	// sql0913n, Deadlock or timeout, no rollback
			wfDebug("In a deadlock because of SQLSTATE $err");
			return true;
		}
		return false;
	}
	
	/**
	 * Ping the server and try to reconnect if it there is no connection
	 * The connection may be closed and reopened while this happens
	 * @return bool whether the connection exists
	 */
	public function ping() {
		// db2_ping() doesn't exist
		// Emulate
		$this->close();
		if ($this->mCataloged == NULL) {
			return false;
		}
		else if ($this->mCataloged) {
			$this->mConn = $this->openCataloged($this->mDBName, $this->mUser, $this->mPassword);
		}
		else if (!$this->mCataloged) {
			$this->mConn = $this->openUncataloged($this->mDBName, $this->mUser, $this->mPassword, $this->mServer, $this->mPort);
		}
		return false;
	}
	######################################
	# Unimplemented and not applicable
	######################################
	/**
	 * Not implemented
	 * @return string ''
	 * @deprecated
	 */
	public function getStatus( $which ) { wfDebug('Not implemented for DB2: getStatus()'); return ''; }
	/**
	 * Not implemented
	 * @deprecated
	 */
	public function setTimeout( $timeout ) { wfDebug('Not implemented for DB2: setTimeout()'); }
	/**
	 * Not implemented
	 * TODO
	 * @return bool true
	 */
	public function lock( $lockName, $method ) { wfDebug('Not implemented for DB2: lock()'); return true; }
	/**
	 * Not implemented
	 * TODO
	 * @return bool true
	 */
	public function unlock( $lockName, $method ) { wfDebug('Not implemented for DB2: unlock()'); return true; }
	/**
	 * Not implemented
	 * @deprecated
	 */
	public function setFakeSlaveLag( $lag ) { wfDebug('Not implemented for DB2: setFakeSlaveLag()'); }
	/**
	 * Not implemented
	 * @deprecated
	 */
	public function setFakeMaster( $enabled ) { wfDebug('Not implemented for DB2: setFakeMaster()'); }
	/**
	 * Not implemented
	 * @return string $sql
	 * @deprecated
	 */ 
	public function limitResultForUpdate($sql, $num) { return $sql; }
	/**
	 * No such option
	 * @return string ''
	 * @deprecated
	 */
	public function lowPriorityOption() { return ''; }
	
	######################################
	# Reflection
	######################################
	
	/**
	 * Query whether a given column exists in the mediawiki schema
	 * @param string $table name of the table
	 * @param string $field name of the column
	 * @param string $fname function name for logging and profiling
	 */
	public function fieldExists( $table, $field, $fname = 'DatabaseIbm_db2::fieldExists' ) {
		$table = $this->tableName( $table );
		$schema = $this->mSchema;
		$etable = preg_replace("/'/", "''", $table);
		$eschema = preg_replace("/'/", "''", $schema);
		$ecol = preg_replace("/'/", "''", $field);
		$sql = <<<SQL
SELECT 1 as fieldexists
FROM sysibm.syscolumns sc
WHERE sc.name='$ecol' AND sc.tbname='$etable' AND sc.tbcreator='$eschema'
SQL;
		$res = $this->query( $sql, $fname );
		$count = $res ? $this->numRows($res) : 0;
		if ($res)
			$this->freeResult( $res );
		return $count;
	}
	
	/**
	 * Returns information about an index
	 * If errors are explicitly ignored, returns NULL on failure
	 * @param string $table table name
	 * @param string $index index name
	 * @param string
	 * @return object query row in object form
	 */
	public function indexInfo( $table, $index, $fname = 'DatabaseIbm_db2::indexExists' ) {
		$table = $this->tableName( $table );
		$sql = <<<SQL
SELECT name as indexname
FROM sysibm.sysindexes si
WHERE si.name='$index' AND si.tbname='$table' AND sc.tbcreator='$this->mSchema'
SQL;
		$res = $this->query( $sql, $fname );
		if ( !$res ) {
			return NULL;
		}
		$row = $this->fetchObject( $res );
		if ($row != NULL) return $row;
		else return false;
	}
	
	/**
	 * Returns an information object on a table column
	 * @param string $table table name
	 * @param string $field column name
	 * @return IBM_DB2Field
	 */
	public function fieldInfo( $table, $field ) {
		return IBM_DB2Field::fromText($this, $table, $field);
	}
	
	/**
	 * db2_field_type() wrapper
	 * @param Object $res Result of executed statement
	 * @param mixed $index number or name of the column
	 * @return string column type
	 */
	public function fieldType( $res, $index ) {
		if ( $res instanceof ResultWrapper ) {
			$res = $res->result;
		}
		return db2_field_type( $res, $index );
	}
	
	/**
	 * Verifies that an index was created as unique
	 * @param string $table table name
	 * @param string $index index name
	 * @param string $fnam function name for profiling
	 * @return bool
	 */
	public function indexUnique ($table, $index, $fname = 'Database::indexUnique' ) {
		$table = $this->tableName( $table );
		$sql = <<<SQL
SELECT si.name as indexname
FROM sysibm.sysindexes si
WHERE si.name='$index' AND si.tbname='$table' AND sc.tbcreator='$this->mSchema'
AND si.uniquerule IN ('U', 'P')
SQL;
		$res = $this->query( $sql, $fname );
		if ( !$res ) {
			return null;
		}
		if ($this->fetchObject( $res )) {
			return true;
		}
		return false;

	}
	
	/**
	 * Returns the size of a text field, or -1 for "unlimited"
	 * @param string $table table name
	 * @param string $field column name
	 * @return int length or -1 for unlimited
	 */
	public function textFieldSize( $table, $field ) {
		$table = $this->tableName( $table );
		$sql = <<<SQL
SELECT length as size
FROM sysibm.syscolumns sc
WHERE sc.name='$field' AND sc.tbname='$table' AND sc.tbcreator='$this->mSchema'
SQL;
		$res = $this->query($sql);
		$row = $this->fetchObject($res);
		$size = $row->size;
		$this->freeResult( $res );
		return $size;
	}
	
	/**
	 * DELETE where the condition is a join
	 * @param string $delTable deleting from this table
	 * @param string $joinTable using data from this table
	 * @param string $delVar variable in deleteable table
	 * @param string $joinVar variable in data table
	 * @param array $conds conditionals for join table
	 * @param string $fname function name for profiling
	 */
	public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds, $fname = "DatabaseIbm_db2::deleteJoin" ) {
		if ( !$conds ) {
			throw new DBUnexpectedError($this,  'Database::deleteJoin() called with empty $conds' );
		}

		$delTable = $this->tableName( $delTable );
		$joinTable = $this->tableName( $joinTable );
		$sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
		if ( $conds != '*' ) {
			$sql .= 'WHERE ' . $this->makeList( $conds, LIST_AND );
		}
		$sql .= ')';

		$this->query( $sql, $fname );
	}
	
	/**
	 * Estimate rows in dataset
	 * Returns estimated count, based on COUNT(*) output
	 * Takes same arguments as Database::select()
	 * @param string $table table name
	 * @param array $vars unused
	 * @param array $conds filters on the table
	 * @param string $fname function name for profiling
	 * @param array $options options for select
	 * @return int row count
	 */
	public function estimateRowCount( $table, $vars='*', $conds='', $fname = 'Database::estimateRowCount', $options = array() ) {
		$rows = 0;
		$res = $this->select ($table, 'COUNT(*) as mwrowcount', $conds, $fname, $options );
		if ($res) {
			$row = $this->fetchRow($res);
			$rows = (isset($row['mwrowcount'])) ? $row['mwrowcount'] : 0;
		}
		$this->freeResult($res);
		return $rows;
	}
	
	/**
	 * Description is left as an exercise for the reader
	 * @param mixed $b data to be encoded
	 * @return IBM_DB2Blob
	 */
	public function encodeBlob($b) {
		return new IBM_DB2Blob($b);
	}
	
	/**
	 * Description is left as an exercise for the reader
	 * @param IBM_DB2Blob $b data to be decoded
	 * @return mixed
	 */
	public function decodeBlob($b) {
		return $b->getData();
	}
	
	/**
	 * Convert into a list of string being concatenated
	 * @param array $stringList strings that need to be joined together by the SQL engine
	 * @return string joined by the concatenation operator
	 */
	public function buildConcat( $stringList ) {
		// || is equivalent to CONCAT
		// Sample query: VALUES 'foo' CONCAT 'bar' CONCAT 'baz'
		return implode( ' || ', $stringList );
	}
	
	/**
	 * Generates the SQL required to convert a DB2 timestamp into a Unix epoch
	 * @param string $column name of timestamp column
	 * @return string SQL code
	 */
	public function extractUnixEpoch( $column ) {
		// TODO
		// see SpecialAncientpages
	}
}
?>