summaryrefslogtreecommitdiffstats
path: root/src/alter.c
blob: ec45e14331e0973e0ec2e738b241ea63a9bcd38a (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
/*
** 2005 February 15
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that used to generate VDBE code
** that implements the ALTER TABLE command.
*/
#include "sqliteInt.h"

/*
** The code in this file only exists if we are not omitting the
** ALTER TABLE logic from the build.
*/
#ifndef SQLITE_OMIT_ALTERTABLE

/*
** Parameter zName is the name of a table that is about to be altered
** (either with ALTER TABLE ... RENAME TO or ALTER TABLE ... ADD COLUMN).
** If the table is a system table, this function leaves an error message
** in pParse->zErr (system tables may not be altered) and returns non-zero.
**
** Or, if zName is not a system table, zero is returned.
*/
static int isAlterableTable(Parse *pParse, Table *pTab){
  if( 0==sqlite3StrNICmp(pTab->zName, "sqlite_", 7)
#ifndef SQLITE_OMIT_VIRTUALTABLE
   || (pTab->tabFlags & TF_Eponymous)!=0
   || ( (pTab->tabFlags & TF_Shadow)!=0
        && sqlite3ReadOnlyShadowTables(pParse->db)
   )
#endif
  ){
    sqlite3ErrorMsg(pParse, "table %s may not be altered", pTab->zName);
    return 1;
  }
  return 0;
}

/*
** Generate code to verify that the schemas of database zDb and, if
** bTemp is not true, database "temp", can still be parsed. This is
** called at the end of the generation of an ALTER TABLE ... RENAME ...
** statement to ensure that the operation has not rendered any schema
** objects unusable.
*/
static void renameTestSchema(
  Parse *pParse,                  /* Parse context */
  const char *zDb,                /* Name of db to verify schema of */
  int bTemp,                      /* True if this is the temp db */
  const char *zWhen,              /* "when" part of error message */
  int bNoDQS                      /* Do not allow DQS in the schema */
){
  pParse->colNamesSet = 1;
  sqlite3NestedParse(pParse,
      "SELECT 1 "
      "FROM \"%w\"." LEGACY_SCHEMA_TABLE " "
      "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
      " AND sql NOT LIKE 'create virtual%%'"
      " AND sqlite_rename_test(%Q, sql, type, name, %d, %Q, %d)=NULL ",
      zDb,
      zDb, bTemp, zWhen, bNoDQS
  );

  if( bTemp==0 ){
    sqlite3NestedParse(pParse,
        "SELECT 1 "
        "FROM temp." LEGACY_SCHEMA_TABLE " "
        "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
        " AND sql NOT LIKE 'create virtual%%'"
        " AND sqlite_rename_test(%Q, sql, type, name, 1, %Q, %d)=NULL ",
        zDb, zWhen, bNoDQS
    );
  }
}

/*
** Generate VM code to replace any double-quoted strings (but not double-quoted
** identifiers) within the "sql" column of the sqlite_schema table in
** database zDb with their single-quoted equivalents. If argument bTemp is
** not true, similarly update all SQL statements in the sqlite_schema table
** of the temp db.
*/
static void renameFixQuotes(Parse *pParse, const char *zDb, int bTemp){
  sqlite3NestedParse(pParse,
      "UPDATE \"%w\"." LEGACY_SCHEMA_TABLE
      " SET sql = sqlite_rename_quotefix(%Q, sql)"
      "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
      " AND sql NOT LIKE 'create virtual%%'" , zDb, zDb
  );
  if( bTemp==0 ){
    sqlite3NestedParse(pParse,
      "UPDATE temp." LEGACY_SCHEMA_TABLE
      " SET sql = sqlite_rename_quotefix('temp', sql)"
      "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
      " AND sql NOT LIKE 'create virtual%%'"
    );
  }
}

/*
** Generate code to reload the schema for database iDb. And, if iDb!=1, for
** the temp database as well.
*/
static void renameReloadSchema(Parse *pParse, int iDb, u16 p5){
  Vdbe *v = pParse->pVdbe;
  if( v ){
    sqlite3ChangeCookie(pParse, iDb);
    sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, iDb, 0, p5);
    if( iDb!=1 ) sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, 1, 0, p5);
  }
}

/*
** Generate code to implement the "ALTER TABLE xxx RENAME TO yyy"
** command.
*/
void sqlite3AlterRenameTable(
  Parse *pParse,            /* Parser context. */
  SrcList *pSrc,            /* The table to rename. */
  Token *pName              /* The new table name. */
){
  int iDb;                  /* Database that contains the table */
  char *zDb;                /* Name of database iDb */
  Table *pTab;              /* Table being renamed */
  char *zName = 0;          /* NULL-terminated version of pName */
  sqlite3 *db = pParse->db; /* Database connection */
  int nTabName;             /* Number of UTF-8 characters in zTabName */
  const char *zTabName;     /* Original name of the table */
  Vdbe *v;
  VTable *pVTab = 0;        /* Non-zero if this is a v-tab with an xRename() */

  if( NEVER(db->mallocFailed) ) goto exit_rename_table;
  assert( pSrc->nSrc==1 );
  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );

  pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
  if( !pTab ) goto exit_rename_table;
  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
  zDb = db->aDb[iDb].zDbSName;

  /* Get a NULL terminated version of the new table name. */
  zName = sqlite3NameFromToken(db, pName);
  if( !zName ) goto exit_rename_table;

  /* Check that a table or index named 'zName' does not already exist
  ** in database iDb. If so, this is an error.
  */
  if( sqlite3FindTable(db, zName, zDb)
   || sqlite3FindIndex(db, zName, zDb)
   || sqlite3IsShadowTableOf(db, pTab, zName)
  ){
    sqlite3ErrorMsg(pParse,
        "there is already another table or index with this name: %s", zName);
    goto exit_rename_table;
  }

  /* Make sure it is not a system table being altered, or a reserved name
  ** that the table is being renamed to.
  */
  if( SQLITE_OK!=isAlterableTable(pParse, pTab) ){
    goto exit_rename_table;
  }
  if( SQLITE_OK!=sqlite3CheckObjectName(pParse,zName,"table",zName) ){
    goto exit_rename_table;
  }

#ifndef SQLITE_OMIT_VIEW
  if( IsView(pTab) ){
    sqlite3ErrorMsg(pParse, "view %s may not be altered", pTab->zName);
    goto exit_rename_table;
  }
#endif

#ifndef SQLITE_OMIT_AUTHORIZATION
  /* Invoke the authorization callback. */
  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){
    goto exit_rename_table;
  }
#endif

#ifndef SQLITE_OMIT_VIRTUALTABLE
  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
    goto exit_rename_table;
  }
  if( IsVirtual(pTab) ){
    pVTab = sqlite3GetVTable(db, pTab);
    if( pVTab->pVtab->pModule->xRename==0 ){
      pVTab = 0;
    }
  }
#endif

  /* Begin a transaction for database iDb. Then modify the schema cookie
  ** (since the ALTER TABLE modifies the schema). Call sqlite3MayAbort(),
  ** as the scalar functions (e.g. sqlite_rename_table()) invoked by the
  ** nested SQL may raise an exception.  */
  v = sqlite3GetVdbe(pParse);
  if( v==0 ){
    goto exit_rename_table;
  }
  sqlite3MayAbort(pParse);

  /* figure out how many UTF-8 characters are in zName */
  zTabName = pTab->zName;
  nTabName = sqlite3Utf8CharLen(zTabName, -1);

  /* Rewrite all CREATE TABLE, INDEX, TRIGGER or VIEW statements in
  ** the schema to use the new table name.  */
  sqlite3NestedParse(pParse,
      "UPDATE \"%w\"." LEGACY_SCHEMA_TABLE " SET "
      "sql = sqlite_rename_table(%Q, type, name, sql, %Q, %Q, %d) "
      "WHERE (type!='index' OR tbl_name=%Q COLLATE nocase)"
      "AND   name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
      , zDb, zDb, zTabName, zName, (iDb==1), zTabName
  );

  /* Update the tbl_name and name columns of the sqlite_schema table
  ** as required.  */
  sqlite3NestedParse(pParse,
      "UPDATE %Q." LEGACY_SCHEMA_TABLE " SET "
          "tbl_name = %Q, "
          "name = CASE "
            "WHEN type='table' THEN %Q "
            "WHEN name LIKE 'sqliteX_autoindex%%' ESCAPE 'X' "
            "     AND type='index' THEN "
             "'sqlite_autoindex_' || %Q || substr(name,%d+18) "
            "ELSE name END "
      "WHERE tbl_name=%Q COLLATE nocase AND "
          "(type='table' OR type='index' OR type='trigger');",
      zDb,
      zName, zName, zName,
      nTabName, zTabName
  );

#ifndef SQLITE_OMIT_AUTOINCREMENT
  /* If the sqlite_sequence table exists in this database, then update
  ** it with the new table name.
  */
  if( sqlite3FindTable(db, "sqlite_sequence", zDb) ){
    sqlite3NestedParse(pParse,
        "UPDATE \"%w\".sqlite_sequence set name = %Q WHERE name = %Q",
        zDb, zName, pTab->zName);
  }
#endif

  /* If the table being renamed is not itself part of the temp database,
  ** edit view and trigger definitions within the temp database
  ** as required.  */
  if( iDb!=1 ){
    sqlite3NestedParse(pParse,
        "UPDATE sqlite_temp_schema SET "
            "sql = sqlite_rename_table(%Q, type, name, sql, %Q, %Q, 1), "
            "tbl_name = "
              "CASE WHEN tbl_name=%Q COLLATE nocase AND "
              "  sqlite_rename_test(%Q, sql, type, name, 1, 'after rename', 0) "
              "THEN %Q ELSE tbl_name END "
            "WHERE type IN ('view', 'trigger')"
        , zDb, zTabName, zName, zTabName, zDb, zName);
  }

  /* If this is a virtual table, invoke the xRename() function if
  ** one is defined. The xRename() callback will modify the names
  ** of any resources used by the v-table implementation (including other
  ** SQLite tables) that are identified by the name of the virtual table.
  */
#ifndef SQLITE_OMIT_VIRTUALTABLE
  if( pVTab ){
    int i = ++pParse->nMem;
    sqlite3VdbeLoadString(v, i, zName);
    sqlite3VdbeAddOp4(v, OP_VRename, i, 0, 0,(const char*)pVTab, P4_VTAB);
  }
#endif

  renameReloadSchema(pParse, iDb, INITFLAG_AlterRename);
  renameTestSchema(pParse, zDb, iDb==1, "after rename", 0);

exit_rename_table:
  sqlite3SrcListDelete(db, pSrc);
  sqlite3DbFree(db, zName);
}

/*
** Write code that will raise an error if the table described by
** zDb and zTab is not empty.
*/
static void sqlite3ErrorIfNotEmpty(
  Parse *pParse,        /* Parsing context */
  const char *zDb,      /* Schema holding the table */
  const char *zTab,     /* Table to check for empty */
  const char *zErr      /* Error message text */
){
  sqlite3NestedParse(pParse,
     "SELECT raise(ABORT,%Q) FROM \"%w\".\"%w\"",
     zErr, zDb, zTab
  );
}

/*
** This function is called after an "ALTER TABLE ... ADD" statement
** has been parsed. Argument pColDef contains the text of the new
** column definition.
**
** The Table structure pParse->pNewTable was extended to include
** the new column during parsing.
*/
void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){
  Table *pNew;              /* Copy of pParse->pNewTable */
  Table *pTab;              /* Table being altered */
  int iDb;                  /* Database number */
  const char *zDb;          /* Database name */
  const char *zTab;         /* Table name */
  char *zCol;               /* Null-terminated column definition */
  Column *pCol;             /* The new column */
  Expr *pDflt;              /* Default value for the new column */
  sqlite3 *db;              /* The database connection; */
  Vdbe *v;                  /* The prepared statement under construction */
  int r1;                   /* Temporary registers */

  db = pParse->db;
  assert( db->pParse==pParse );
  if( pParse->nErr ) return;
  assert( db->mallocFailed==0 );
  pNew = pParse->pNewTable;
  assert( pNew );

  assert( sqlite3BtreeHoldsAllMutexes(db) );
  iDb = sqlite3SchemaToIndex(db, pNew->pSchema);
  zDb = db->aDb[iDb].zDbSName;
  zTab = &pNew->zName[16];  /* Skip the "sqlite_altertab_" prefix on the name */
  pCol = &pNew->aCol[pNew->nCol-1];
  pDflt = sqlite3ColumnExpr(pNew, pCol);
  pTab = sqlite3FindTable(db, zTab, zDb);
  assert( pTab );

#ifndef SQLITE_OMIT_AUTHORIZATION
  /* Invoke the authorization callback. */
  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){
    return;
  }
#endif


  /* Check that the new column is not specified as PRIMARY KEY or UNIQUE.
  ** If there is a NOT NULL constraint, then the default value for the
  ** column must not be NULL.
  */
  if( pCol->colFlags & COLFLAG_PRIMKEY ){
    sqlite3ErrorMsg(pParse, "Cannot add a PRIMARY KEY column");
    return;
  }
  if( pNew->pIndex ){
    sqlite3ErrorMsg(pParse,
         "Cannot add a UNIQUE column");
    return;
  }
  if( (pCol->colFlags & COLFLAG_GENERATED)==0 ){
    /* If the default value for the new column was specified with a
    ** literal NULL, then set pDflt to 0. This simplifies checking
    ** for an SQL NULL default below.
    */
    assert( pDflt==0 || pDflt->op==TK_SPAN );
    if( pDflt && pDflt->pLeft->op==TK_NULL ){
      pDflt = 0;
    }
    assert( IsOrdinaryTable(pNew) );
    if( (db->flags&SQLITE_ForeignKeys) && pNew->u.tab.pFKey && pDflt ){
      sqlite3ErrorIfNotEmpty(pParse, zDb, zTab,
          "Cannot add a REFERENCES column with non-NULL default value");
    }
    if( pCol->notNull && !pDflt ){
      sqlite3ErrorIfNotEmpty(pParse, zDb, zTab,
          "Cannot add a NOT NULL column with default value NULL");
    }


    /* Ensure the default expression is something that sqlite3ValueFromExpr()
    ** can handle (i.e. not CURRENT_TIME etc.)
    */
    if( pDflt ){
      sqlite3_value *pVal = 0;
      int rc;
      rc = sqlite3ValueFromExpr(db, pDflt, SQLITE_UTF8, SQLITE_AFF_BLOB, &pVal);
      assert( rc==SQLITE_OK || rc==SQLITE_NOMEM );
      if( rc!=SQLITE_OK ){
        assert( db->mallocFailed == 1 );
        return;
      }
      if( !pVal ){
        sqlite3ErrorIfNotEmpty(pParse, zDb, zTab,
           "Cannot add a column with non-constant default");
      }
      sqlite3ValueFree(pVal);
    }
  }else if( pCol->colFlags & COLFLAG_STORED ){
    sqlite3ErrorIfNotEmpty(pParse, zDb, zTab, "cannot add a STORED column");
  }


  /* Modify the CREATE TABLE statement. */
  zCol = sqlite3DbStrNDup(db, (char*)pColDef->z, pColDef->n);
  if( zCol ){
    char *zEnd = &zCol[pColDef->n-1];
    while( zEnd>zCol && (*zEnd==';' || sqlite3Isspace(*zEnd)) ){
      *zEnd-- = '\0';
    }
    /* substr() operations on characters, but addColOffset is in bytes. So we
    ** have to use printf() to translate between these units: */
    assert( IsOrdinaryTable(pTab) );
    assert( IsOrdinaryTable(pNew) );
    sqlite3NestedParse(pParse,
        "UPDATE \"%w\"." LEGACY_SCHEMA_TABLE " SET "
          "sql = printf('%%.%ds, ',sql) || %Q"
          " || substr(sql,1+length(printf('%%.%ds',sql))) "
        "WHERE type = 'table' AND name = %Q",
      zDb, pNew->u.tab.addColOffset, zCol, pNew->u.tab.addColOffset,
      zTab
    );
    sqlite3DbFree(db, zCol);
  }

  v = sqlite3GetVdbe(pParse);
  if( v ){
    /* Make sure the schema version is at least 3.  But do not upgrade
    ** from less than 3 to 4, as that will corrupt any preexisting DESC
    ** index.
    */
    r1 = sqlite3GetTempReg(pParse);
    sqlite3VdbeAddOp3(v, OP_ReadCookie, iDb, r1, BTREE_FILE_FORMAT);
    sqlite3VdbeUsesBtree(v, iDb);
    sqlite3VdbeAddOp2(v, OP_AddImm, r1, -2);
    sqlite3VdbeAddOp2(v, OP_IfPos, r1, sqlite3VdbeCurrentAddr(v)+2);
    VdbeCoverage(v);
    sqlite3VdbeAddOp3(v, OP_SetCookie, iDb, BTREE_FILE_FORMAT, 3);
    sqlite3ReleaseTempReg(pParse, r1);

    /* Reload the table definition */
    renameReloadSchema(pParse, iDb, INITFLAG_AlterAdd);

    /* Verify that constraints are still satisfied */
    if( pNew->pCheck!=0
     || (pCol->notNull && (pCol->colFlags & COLFLAG_GENERATED)!=0)
     || (pTab->tabFlags & TF_Strict)!=0
    ){
      sqlite3NestedParse(pParse,
        "SELECT CASE WHEN quick_check GLOB 'CHECK*'"
        " THEN raise(ABORT,'CHECK constraint failed')"
        " WHEN quick_check GLOB 'non-* value in*'"
        " THEN raise(ABORT,'type mismatch on DEFAULT')"
        " ELSE raise(ABORT,'NOT NULL constraint failed')"
        " END"
        "  FROM pragma_quick_check(%Q,%Q)"
        " WHERE quick_check GLOB 'CHECK*'"
        " OR quick_check GLOB 'NULL*'"
        " OR quick_check GLOB 'non-* value in*'",
        zTab, zDb
      );
    }
  }
}

/*
** This function is called by the parser after the table-name in
** an "ALTER TABLE <table-name> ADD" statement is parsed. Argument
** pSrc is the full-name of the table being altered.
**
** This routine makes a (partial) copy of the Table structure
** for the table being altered and sets Parse.pNewTable to point
** to it. Routines called by the parser as the column definition
** is parsed (i.e. sqlite3AddColumn()) add the new Column data to
** the copy. The copy of the Table structure is deleted by tokenize.c
** after parsing is finished.
**
** Routine sqlite3AlterFinishAddColumn() will be called to complete
** coding the "ALTER TABLE ... ADD" statement.
*/
void sqlite3AlterBeginAddColumn(Parse *pParse, SrcList *pSrc){
  Table *pNew;
  Table *pTab;
  int iDb;
  int i;
  int nAlloc;
  sqlite3 *db = pParse->db;

  /* Look up the table being altered. */
  assert( pParse->pNewTable==0 );
  assert( sqlite3BtreeHoldsAllMutexes(db) );
  if( db->mallocFailed ) goto exit_begin_add_column;
  pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
  if( !pTab ) goto exit_begin_add_column;

#ifndef SQLITE_OMIT_VIRTUALTABLE
  if( IsVirtual(pTab) ){
    sqlite3ErrorMsg(pParse, "virtual tables may not be altered");
    goto exit_begin_add_column;
  }
#endif

  /* Make sure this is not an attempt to ALTER a view. */
  if( IsView(pTab) ){
    sqlite3ErrorMsg(pParse, "Cannot add a column to a view");
    goto exit_begin_add_column;
  }
  if( SQLITE_OK!=isAlterableTable(pParse, pTab) ){
    goto exit_begin_add_column;
  }

  sqlite3MayAbort(pParse);
  assert( IsOrdinaryTable(pTab) );
  assert( pTab->u.tab.addColOffset>0 );
  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);

  /* Put a copy of the Table struct in Parse.pNewTable for the
  ** sqlite3AddColumn() function and friends to modify.  But modify
  ** the name by adding an "sqlite_altertab_" prefix.  By adding this
  ** prefix, we insure that the name will not collide with an existing
  ** table because user table are not allowed to have the "sqlite_"
  ** prefix on their name.
  */
  pNew = (Table*)sqlite3DbMallocZero(db, sizeof(Table));
  if( !pNew ) goto exit_begin_add_column;
  pParse->pNewTable = pNew;
  pNew->nTabRef = 1;
  pNew->nCol = pTab->nCol;
  assert( pNew->nCol>0 );
  nAlloc = (((pNew->nCol-1)/8)*8)+8;
  assert( nAlloc>=pNew->nCol && nAlloc%8==0 && nAlloc-pNew->nCol<8 );
  pNew->aCol = (Column*)sqlite3DbMallocZero(db, sizeof(Column)*nAlloc);
  pNew->zName = sqlite3MPrintf(db, "sqlite_altertab_%s", pTab->zName);
  if( !pNew->aCol || !pNew->zName ){
    assert( db->mallocFailed );
    goto exit_begin_add_column;
  }
  memcpy(pNew->aCol, pTab->aCol, sizeof(Column)*pNew->nCol);
  for(i=0; i<pNew->nCol; i++){
    Column *pCol = &pNew->aCol[i];
    pCol->zCnName = sqlite3DbStrDup(db, pCol->zCnName);
    pCol->hName = sqlite3StrIHash(pCol->zCnName);
  }
  assert( IsOrdinaryTable(pNew) );
  pNew->u.tab.pDfltList = sqlite3ExprListDup(db, pTab->u.tab.pDfltList, 0);
  pNew->pSchema = db->aDb[iDb].pSchema;
  pNew->u.tab.addColOffset = pTab->u.tab.addColOffset;
  assert( pNew->nTabRef==1 );

exit_begin_add_column:
  sqlite3SrcListDelete(db, pSrc);
  return;
}

/*
** Parameter pTab is the subject of an ALTER TABLE ... RENAME COLUMN
** command. This function checks if the table is a view or virtual
** table (columns of views or virtual tables may not be renamed). If so,
** it loads an error message into pParse and returns non-zero.
**
** Or, if pTab is not a view or virtual table, zero is returned.
*/
#if !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE)
static int isRealTable(Parse *pParse, Table *pTab, int bDrop){
  const char *zType = 0;
#ifndef SQLITE_OMIT_VIEW
  if( IsView(pTab) ){
    zType = "view";
  }
#endif
#ifndef SQLITE_OMIT_VIRTUALTABLE
  if( IsVirtual(pTab) ){
    zType = "virtual table";
  }
#endif
  if( zType ){
    sqlite3ErrorMsg(pParse, "cannot %s %s \"%s\"",
        (bDrop ? "drop column from" : "rename columns of"),
        zType, pTab->zName
    );
    return 1;
  }
  return 0;
}
#else /* !defined(SQLITE_OMIT_VIEW) || !defined(SQLITE_OMIT_VIRTUALTABLE) */
# define isRealTable(x,y,z) (0)
#endif

/*
** Handles the following parser reduction:
**
**  cmd ::= ALTER TABLE pSrc RENAME COLUMN pOld TO pNew
*/
void sqlite3AlterRenameColumn(
  Parse *pParse,                  /* Parsing context */
  SrcList *pSrc,                  /* Table being altered.  pSrc->nSrc==1 */
  Token *pOld,                    /* Name of column being changed */
  Token *pNew                     /* New column name */
){
  sqlite3 *db = pParse->db;       /* Database connection */
  Table *pTab;                    /* Table being updated */
  int iCol;                       /* Index of column being renamed */
  char *zOld = 0;                 /* Old column name */
  char *zNew = 0;                 /* New column name */
  const char *zDb;                /* Name of schema containing the table */
  int iSchema;                    /* Index of the schema */
  int bQuote;                     /* True to quote the new name */

  /* Locate the table to be altered */
  pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
  if( !pTab ) goto exit_rename_column;

  /* Cannot alter a system table */
  if( SQLITE_OK!=isAlterableTable(pParse, pTab) ) goto exit_rename_column;
  if( SQLITE_OK!=isRealTable(pParse, pTab, 0) ) goto exit_rename_column;

  /* Which schema holds the table to be altered */ 
  iSchema = sqlite3SchemaToIndex(db, pTab->pSchema);
  assert( iSchema>=0 );
  zDb = db->aDb[iSchema].zDbSName;

#ifndef SQLITE_OMIT_AUTHORIZATION
  /* Invoke the authorization callback. */
  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){
    goto exit_rename_column;
  }
#endif

  /* Make sure the old name really is a column name in the table to be
  ** altered.  Set iCol to be the index of the column being renamed */
  zOld = sqlite3NameFromToken(db, pOld);
  if( !zOld ) goto exit_rename_column;
  for(iCol=0; iCol<pTab->nCol; iCol++){
    if( 0==sqlite3StrICmp(pTab->aCol[iCol].zCnName, zOld) ) break;
  }
  if( iCol==pTab->nCol ){
    sqlite3ErrorMsg(pParse, "no such column: \"%T\"", pOld);
    goto exit_rename_column;
  }

  /* Ensure the schema contains no double-quoted strings */
  renameTestSchema(pParse, zDb, iSchema==1, "", 0);
  renameFixQuotes(pParse, zDb, iSchema==1);

  /* Do the rename operation using a recursive UPDATE statement that
  ** uses the sqlite_rename_column() SQL function to compute the new
  ** CREATE statement text for the sqlite_schema table.
  */
  sqlite3MayAbort(pParse);
  zNew = sqlite3NameFromToken(db, pNew);
  if( !zNew ) goto exit_rename_column;
  assert( pNew->n>0 );
  bQuote = sqlite3Isquote(pNew->z[0]);
  sqlite3NestedParse(pParse,
      "UPDATE \"%w\"." LEGACY_SCHEMA_TABLE " SET "
      "sql = sqlite_rename_column(sql, type, name, %Q, %Q, %d, %Q, %d, %d) "
      "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X' "
      " AND (type != 'index' OR tbl_name = %Q)",
      zDb,
      zDb, pTab->zName, iCol, zNew, bQuote, iSchema==1,
      pTab->zName
  );

  sqlite3NestedParse(pParse,
      "UPDATE temp." LEGACY_SCHEMA_TABLE " SET "
      "sql = sqlite_rename_column(sql, type, name, %Q, %Q, %d, %Q, %d, 1) "
      "WHERE type IN ('trigger', 'view')",
      zDb, pTab->zName, iCol, zNew, bQuote
  );

  /* Drop and reload the database schema. */
  renameReloadSchema(pParse, iSchema, INITFLAG_AlterRename);
  renameTestSchema(pParse, zDb, iSchema==1, "after rename", 1);

 exit_rename_column:
  sqlite3SrcListDelete(db, pSrc);
  sqlite3DbFree(db, zOld);
  sqlite3DbFree(db, zNew);
  return;
}

/*
** Each RenameToken object maps an element of the parse tree into
** the token that generated that element.  The parse tree element
** might be one of:
**
**     *  A pointer to an Expr that represents an ID
**     *  The name of a table column in Column.zName
**
** A list of RenameToken objects can be constructed during parsing.
** Each new object is created by sqlite3RenameTokenMap().
** As the parse tree is transformed, the sqlite3RenameTokenRemap()
** routine is used to keep the mapping current.
**
** After the parse finishes, renameTokenFind() routine can be used
** to look up the actual token value that created some element in
** the parse tree.
*/
struct RenameToken {
  const void *p;         /* Parse tree element created by token t */
  Token t;               /* The token that created parse tree element p */
  RenameToken *pNext;    /* Next is a list of all RenameToken objects */
};

/*
** The context of an ALTER TABLE RENAME COLUMN operation that gets passed
** down into the Walker.
*/
typedef struct RenameCtx RenameCtx;
struct RenameCtx {
  RenameToken *pList;             /* List of tokens to overwrite */
  int nList;                      /* Number of tokens in pList */
  int iCol;                       /* Index of column being renamed */
  Table *pTab;                    /* Table being ALTERed */
  const char *zOld;               /* Old column name */
};

#ifdef SQLITE_DEBUG
/*
** This function is only for debugging. It performs two tasks:
**
**   1. Checks that pointer pPtr does not already appear in the
**      rename-token list.
**
**   2. Dereferences each pointer in the rename-token list.
**
** The second is most effective when debugging under valgrind or
** address-sanitizer or similar. If any of these pointers no longer
** point to valid objects, an exception is raised by the memory-checking
** tool.
**
** The point of this is to prevent comparisons of invalid pointer values.
** Even though this always seems to work, it is undefined according to the
** C standard. Example of undefined comparison:
**
**     sqlite3_free(x);
**     if( x==y ) ...
**
** Technically, as x no longer points into a valid object or to the byte
** following a valid object, it may not be used in comparison operations.
*/
static void renameTokenCheckAll(Parse *pParse, const void *pPtr){
  assert( pParse==pParse->db->pParse );
  assert( pParse->db->mallocFailed==0 || pParse->nErr!=0 );
  if( pParse->nErr==0 ){
    const RenameToken *p;
    u32 i = 1;
    for(p=pParse->pRename; p; p=p->pNext){
      if( p->p ){
        assert( p->p!=pPtr );
        i += *(u8*)(p->p) | 1;
      }
    }
    assert( i>0 );
  }
}
#else
# define renameTokenCheckAll(x,y)
#endif

/*
** Remember that the parser tree element pPtr was created using
** the token pToken.
**
** In other words, construct a new RenameToken object and add it
** to the list of RenameToken objects currently being built up
** in pParse->pRename.
**
** The pPtr argument is returned so that this routine can be used
** with tail recursion in tokenExpr() routine, for a small performance
** improvement.
*/
const void *sqlite3RenameTokenMap(
  Parse *pParse,
  const void *pPtr,
  const Token *pToken
){
  RenameToken *pNew;
  assert( pPtr || pParse->db->mallocFailed );
  renameTokenCheckAll(pParse, pPtr);
  if( ALWAYS(pParse->eParseMode!=PARSE_MODE_UNMAP) ){
    pNew = sqlite3DbMallocZero(pParse->db, sizeof(RenameToken));
    if( pNew ){
      pNew->p = pPtr;
      pNew->t = *pToken;
      pNew->pNext = pParse->pRename;
      pParse->pRename = pNew;
    }
  }

  return pPtr;
}

/*
** It is assumed that there is already a RenameToken object associated
** with parse tree element pFrom. This function remaps the associated token
** to parse tree element pTo.
*/
void sqlite3RenameTokenRemap(Parse *pParse, const void *pTo, const void *pFrom){
  RenameToken *p;
  renameTokenCheckAll(pParse, pTo);
  for(p=pParse->pRename; p; p=p->pNext){
    if( p->p==pFrom ){
      p->p = pTo;
      break;
    }
  }
}

/*
** Walker callback used by sqlite3RenameExprUnmap().
*/
static int renameUnmapExprCb(Walker *pWalker, Expr *pExpr){
  Parse *pParse = pWalker->pParse;
  sqlite3RenameTokenRemap(pParse, 0, (const void*)pExpr);
  if( ExprUseYTab(pExpr) ){
    sqlite3RenameTokenRemap(pParse, 0, (const void*)&pExpr->y.pTab);
  }
  return WRC_Continue;
}

/*
** Iterate through the Select objects that are part of WITH clauses attached
** to select statement pSelect.
*/
static void renameWalkWith(Walker *pWalker, Select *pSelect){
  With *pWith = pSelect->pWith;
  if( pWith ){
    Parse *pParse = pWalker->pParse;
    int i;
    With *pCopy = 0;
    assert( pWith->nCte>0 );
    if( (pWith->a[0].pSelect->selFlags & SF_Expanded)==0 ){
      /* Push a copy of the With object onto the with-stack. We use a copy
      ** here as the original will be expanded and resolved (flags SF_Expanded
      ** and SF_Resolved) below. And the parser code that uses the with-stack
      ** fails if the Select objects on it have already been expanded and
      ** resolved.  */
      pCopy = sqlite3WithDup(pParse->db, pWith);
      pCopy = sqlite3WithPush(pParse, pCopy, 1);
    }
    for(i=0; i<pWith->nCte; i++){
      Select *p = pWith->a[i].pSelect;
      NameContext sNC;
      memset(&sNC, 0, sizeof(sNC));
      sNC.pParse = pParse;
      if( pCopy ) sqlite3SelectPrep(sNC.pParse, p, &sNC);
      if( sNC.pParse->db->mallocFailed ) return;
      sqlite3WalkSelect(pWalker, p);
      sqlite3RenameExprlistUnmap(pParse, pWith->a[i].pCols);
    }
    if( pCopy && pParse->pWith==pCopy ){
      pParse->pWith = pCopy->pOuter;
    }
  }
}

/*
** Unmap all tokens in the IdList object passed as the second argument.
*/
static void unmapColumnIdlistNames(
  Parse *pParse,
  const IdList *pIdList
){
  int ii;
  assert( pIdList!=0 );
  for(ii=0; ii<pIdList->nId; ii++){
    sqlite3RenameTokenRemap(pParse, 0, (const void*)pIdList->a[ii].zName);
  }
}

/*
** Walker callback used by sqlite3RenameExprUnmap().
*/
static int renameUnmapSelectCb(Walker *pWalker, Select *p){
  Parse *pParse = pWalker->pParse;
  int i;
  if( pParse->nErr ) return WRC_Abort;
  testcase( p->selFlags & SF_View );
  testcase( p->selFlags & SF_CopyCte );
  if( p->selFlags & (SF_View|SF_CopyCte) ){
    return WRC_Prune;
  }
  if( ALWAYS(p->pEList) ){
    ExprList *pList = p->pEList;
    for(i=0; i<pList->nExpr; i++){
      if( pList->a[i].zEName && pList->a[i].fg.eEName==ENAME_NAME ){
        sqlite3RenameTokenRemap(pParse, 0, (void*)pList->a[i].zEName);
      }
    }
  }
  if( ALWAYS(p->pSrc) ){  /* Every Select as a SrcList, even if it is empty */
    SrcList *pSrc = p->pSrc;
    for(i=0; i<pSrc->nSrc; i++){
      sqlite3RenameTokenRemap(pParse, 0, (void*)pSrc->a[i].zName);
      if( pSrc->a[i].fg.isUsing==0 ){
        sqlite3WalkExpr(pWalker, pSrc->a[i].u3.pOn);
      }else{
        unmapColumnIdlistNames(pParse, pSrc->a[i].u3.pUsing);
      }
    }
  }

  renameWalkWith(pWalker, p);
  return WRC_Continue;
}

/*
** Remove all nodes that are part of expression pExpr from the rename list.
*/
void sqlite3RenameExprUnmap(Parse *pParse, Expr *pExpr){
  u8 eMode = pParse->eParseMode;
  Walker sWalker;
  memset(&sWalker, 0, sizeof(Walker));
  sWalker.pParse = pParse;
  sWalker.xExprCallback = renameUnmapExprCb;
  sWalker.xSelectCallback = renameUnmapSelectCb;
  pParse->eParseMode = PARSE_MODE_UNMAP;
  sqlite3WalkExpr(&sWalker, pExpr);
  pParse->eParseMode = eMode;
}

/*
** Remove all nodes that are part of expression-list pEList from the
** rename list.
*/
void sqlite3RenameExprlistUnmap(Parse *pParse, ExprList *pEList){
  if( pEList ){
    int i;
    Walker sWalker;
    memset(&sWalker, 0, sizeof(Walker));
    sWalker.pParse = pParse;
    sWalker.xExprCallback = renameUnmapExprCb;
    sqlite3WalkExprList(&sWalker, pEList);
    for(i=0; i<pEList->nExpr; i++){
      if( ALWAYS(pEList->a[i].fg.eEName==ENAME_NAME) ){
        sqlite3RenameTokenRemap(pParse, 0, (void*)pEList->a[i].zEName);
      }
    }
  }
}

/*
** Free the list of RenameToken objects given in the second argument
*/
static void renameTokenFree(sqlite3 *db, RenameToken *pToken){
  RenameToken *pNext;
  RenameToken *p;
  for(p=pToken; p; p=pNext){
    pNext = p->pNext;
    sqlite3DbFree(db, p);
  }
}

/*
** Search the Parse object passed as the first argument for a RenameToken
** object associated with parse tree element pPtr. If found, return a pointer
** to it. Otherwise, return NULL.
**
** If the second argument passed to this function is not NULL and a matching
** RenameToken object is found, remove it from the Parse object and add it to
** the list maintained by the RenameCtx object.
*/
static RenameToken *renameTokenFind(
  Parse *pParse,
  struct RenameCtx *pCtx,
  const void *pPtr
){
  RenameToken **pp;
  if( NEVER(pPtr==0) ){
    return 0;
  }
  for(pp=&pParse->pRename; (*pp); pp=&(*pp)->pNext){
    if( (*pp)->p==pPtr ){
      RenameToken *pToken = *pp;
      if( pCtx ){
        *pp = pToken->pNext;
        pToken->pNext = pCtx->pList;
        pCtx->pList = pToken;
        pCtx->nList++;
      }
      return pToken;
    }
  }
  return 0;
}

/*
** This is a Walker select callback. It does nothing. It is only required
** because without a dummy callback, sqlite3WalkExpr() and similar do not
** descend into sub-select statements.
*/
static int renameColumnSelectCb(Walker *pWalker, Select *p){
  if( p->selFlags & (SF_View|SF_CopyCte) ){
    testcase( p->selFlags & SF_View );
    testcase( p->selFlags & SF_CopyCte );
    return WRC_Prune;
  }
  renameWalkWith(pWalker, p);
  return WRC_Continue;
}

/*
** This is a Walker expression callback.
**
** For every TK_COLUMN node in the expression tree, search to see
** if the column being references is the column being renamed by an
** ALTER TABLE statement.  If it is, then attach its associated
** RenameToken object to the list of RenameToken objects being
** constructed in RenameCtx object at pWalker->u.pRename.
*/
static int renameColumnExprCb(Walker *pWalker, Expr *pExpr){
  RenameCtx *p = pWalker->u.pRename;
  if( pExpr->op==TK_TRIGGER
   && pExpr->iColumn==p->iCol
   && pWalker->pParse->pTriggerTab==p->pTab
  ){
    renameTokenFind(pWalker->pParse, p, (void*)pExpr);
  }else if( pExpr->op==TK_COLUMN
   && pExpr->iColumn==p->iCol
   && ALWAYS(ExprUseYTab(pExpr))
   && p->pTab==pExpr->y.pTab
  ){
    renameTokenFind(pWalker->pParse, p, (void*)pExpr);
  }
  return WRC_Continue;
}

/*
** The RenameCtx contains a list of tokens that reference a column that
** is being renamed by an ALTER TABLE statement.  Return the "last"
** RenameToken in the RenameCtx and remove that RenameToken from the
** RenameContext.  "Last" means the last RenameToken encountered when
** the input SQL is parsed from left to right.  Repeated calls to this routine
** return all column name tokens in the order that they are encountered
** in the SQL statement.
*/
static RenameToken *renameColumnTokenNext(RenameCtx *pCtx){
  RenameToken *pBest = pCtx->pList;
  RenameToken *pToken;
  RenameToken **pp;

  for(pToken=pBest->pNext; pToken; pToken=pToken->pNext){
    if( pToken->t.z>pBest->t.z ) pBest = pToken;
  }
  for(pp=&pCtx->pList; *pp!=pBest; pp=&(*pp)->pNext);
  *pp = pBest->pNext;

  return pBest;
}

/*
** An error occurred while parsing or otherwise processing a database
** object (either pParse->pNewTable, pNewIndex or pNewTrigger) as part of an
** ALTER TABLE RENAME COLUMN program. The error message emitted by the
** sub-routine is currently stored in pParse->zErrMsg. This function
** adds context to the error message and then stores it in pCtx.
*/
static void renameColumnParseError(
  sqlite3_context *pCtx,
  const char *zWhen,
  sqlite3_value *pType,
  sqlite3_value *pObject,
  Parse *pParse
){
  const char *zT = (const char*)sqlite3_value_text(pType);
  const char *zN = (const char*)sqlite3_value_text(pObject);
  char *zErr;

  zErr = sqlite3MPrintf(pParse->db, "error in %s %s%s%s: %s",
      zT, zN, (zWhen[0] ? " " : ""), zWhen,
      pParse->zErrMsg
  );
  sqlite3_result_error(pCtx, zErr, -1);
  sqlite3DbFree(pParse->db, zErr);
}

/*
** For each name in the the expression-list pEList (i.e. each
** pEList->a[i].zName) that matches the string in zOld, extract the
** corresponding rename-token from Parse object pParse and add it
** to the RenameCtx pCtx.
*/
static void renameColumnElistNames(
  Parse *pParse,
  RenameCtx *pCtx,
  const ExprList *pEList,
  const char *zOld
){
  if( pEList ){
    int i;
    for(i=0; i<pEList->nExpr; i++){
      const char *zName = pEList->a[i].zEName;
      if( ALWAYS(pEList->a[i].fg.eEName==ENAME_NAME)
       && ALWAYS(zName!=0)
       && 0==sqlite3_stricmp(zName, zOld)
      ){
        renameTokenFind(pParse, pCtx, (const void*)zName);
      }
    }
  }
}

/*
** For each name in the the id-list pIdList (i.e. each pIdList->a[i].zName)
** that matches the string in zOld, extract the corresponding rename-token
** from Parse object pParse and add it to the RenameCtx pCtx.
*/
static void renameColumnIdlistNames(
  Parse *pParse,
  RenameCtx *pCtx,
  const IdList *pIdList,
  const char *zOld
){
  if( pIdList ){
    int i;
    for(i=0; i<pIdList->nId; i++){
      const char *zName = pIdList->a[i].zName;
      if( 0==sqlite3_stricmp(zName, zOld) ){
        renameTokenFind(pParse, pCtx, (const void*)zName);
      }
    }
  }
}


/*
** Parse the SQL statement zSql using Parse object (*p). The Parse object
** is initialized by this function before it is used.
*/
static int renameParseSql(
  Parse *p,                       /* Memory to use for Parse object */
  const char *zDb,                /* Name of schema SQL belongs to */
  sqlite3 *db,                    /* Database handle */
  const char *zSql,               /* SQL to parse */
  int bTemp                       /* True if SQL is from temp schema */
){
  int rc;

  sqlite3ParseObjectInit(p, db);
  if( zSql==0 ){
    return SQLITE_NOMEM;
  }
  if( sqlite3StrNICmp(zSql,"CREATE ",7)!=0 ){
    return SQLITE_CORRUPT_BKPT;
  }
  db->init.iDb = bTemp ? 1 : sqlite3FindDbName(db, zDb);
  p->eParseMode = PARSE_MODE_RENAME;
  p->db = db;
  p->nQueryLoop = 1;
  rc = sqlite3RunParser(p, zSql);
  if( db->mallocFailed ) rc = SQLITE_NOMEM;
  if( rc==SQLITE_OK
   && NEVER(p->pNewTable==0 && p->pNewIndex==0 && p->pNewTrigger==0)
  ){
    rc = SQLITE_CORRUPT_BKPT;
  }

#ifdef SQLITE_DEBUG
  /* Ensure that all mappings in the Parse.pRename list really do map to
  ** a part of the input string.  */
  if( rc==SQLITE_OK ){
    int nSql = sqlite3Strlen30(zSql);
    RenameToken *pToken;
    for(pToken=p->pRename; pToken; pToken=pToken->pNext){
      assert( pToken->t.z>=zSql && &pToken->t.z[pToken->t.n]<=&zSql[nSql] );
    }
  }
#endif

  db->init.iDb = 0;
  return rc;
}

/*
** This function edits SQL statement zSql, replacing each token identified
** by the linked list pRename with the text of zNew. If argument bQuote is
** true, then zNew is always quoted first. If no error occurs, the result
** is loaded into context object pCtx as the result.
**
** Or, if an error occurs (i.e. an OOM condition), an error is left in
** pCtx and an SQLite error code returned.
*/
static int renameEditSql(
  sqlite3_context *pCtx,          /* Return result here */
  RenameCtx *pRename,             /* Rename context */
  const char *zSql,               /* SQL statement to edit */
  const char *zNew,               /* New token text */
  int bQuote                      /* True to always quote token */
){
  i64 nNew = sqlite3Strlen30(zNew);
  i64 nSql = sqlite3Strlen30(zSql);
  sqlite3 *db = sqlite3_context_db_handle(pCtx);
  int rc = SQLITE_OK;
  char *zQuot = 0;
  char *zOut;
  i64 nQuot = 0;
  char *zBuf1 = 0;
  char *zBuf2 = 0;

  if( zNew ){
    /* Set zQuot to point to a buffer containing a quoted copy of the
    ** identifier zNew. If the corresponding identifier in the original
    ** ALTER TABLE statement was quoted (bQuote==1), then set zNew to
    ** point to zQuot so that all substitutions are made using the
    ** quoted version of the new column name.  */
    zQuot = sqlite3MPrintf(db, "\"%w\" ", zNew);
    if( zQuot==0 ){
      return SQLITE_NOMEM;
    }else{
      nQuot = sqlite3Strlen30(zQuot)-1;
    }

    assert( nQuot>=nNew );
    zOut = sqlite3DbMallocZero(db, nSql + pRename->nList*nQuot + 1);
  }else{
    zOut = (char*)sqlite3DbMallocZero(db, (nSql*2+1) * 3);
    if( zOut ){
      zBuf1 = &zOut[nSql*2+1];
      zBuf2 = &zOut[nSql*4+2];
    }
  }

  /* At this point pRename->pList contains a list of RenameToken objects
  ** corresponding to all tokens in the input SQL that must be replaced
  ** with the new column name, or with single-quoted versions of themselves.
  ** All that remains is to construct and return the edited SQL string. */
  if( zOut ){
    int nOut = nSql;
    memcpy(zOut, zSql, nSql);
    while( pRename->pList ){
      int iOff;                   /* Offset of token to replace in zOut */
      u32 nReplace;
      const char *zReplace;
      RenameToken *pBest = renameColumnTokenNext(pRename);

      if( zNew ){
        if( bQuote==0 && sqlite3IsIdChar(*pBest->t.z) ){
          nReplace = nNew;
          zReplace = zNew;
        }else{
          nReplace = nQuot;
          zReplace = zQuot;
          if( pBest->t.z[pBest->t.n]=='"' ) nReplace++;
        }
      }else{
        /* Dequote the double-quoted token. Then requote it again, this time
        ** using single quotes. If the character immediately following the
        ** original token within the input SQL was a single quote ('), then
        ** add another space after the new, single-quoted version of the
        ** token. This is so that (SELECT "string"'alias') maps to
        ** (SELECT 'string' 'alias'), and not (SELECT 'string''alias').  */
        memcpy(zBuf1, pBest->t.z, pBest->t.n);
        zBuf1[pBest->t.n] = 0;
        sqlite3Dequote(zBuf1);
        sqlite3_snprintf(nSql*2, zBuf2, "%Q%s", zBuf1,
            pBest->t.z[pBest->t.n]=='\'' ? " " : ""
        );
        zReplace = zBuf2;
        nReplace = sqlite3Strlen30(zReplace);
      }

      iOff = pBest->t.z - zSql;
      if( pBest->t.n!=nReplace ){
        memmove(&zOut[iOff + nReplace], &zOut[iOff + pBest->t.n],
            nOut - (iOff + pBest->t.n)
        );
        nOut += nReplace - pBest->t.n;
        zOut[nOut] = '\0';
      }
      memcpy(&zOut[iOff], zReplace, nReplace);
      sqlite3DbFree(db, pBest);
    }

    sqlite3_result_text(pCtx, zOut, -1, SQLITE_TRANSIENT);
    sqlite3DbFree(db, zOut);
  }else{
    rc = SQLITE_NOMEM;
  }

  sqlite3_free(zQuot);
  return rc;
}

/*
** Set all pEList->a[].fg.eEName fields in the expression-list to val.
*/
static void renameSetENames(ExprList *pEList, int val){
  if( pEList ){
    int i;
    for(i=0; i<pEList->nExpr; i++){
      assert( val==ENAME_NAME || pEList->a[i].fg.eEName==ENAME_NAME );
      pEList->a[i].fg.eEName = val;
    }
  }
}

/*
** Resolve all symbols in the trigger at pParse->pNewTrigger, assuming
** it was read from the schema of database zDb. Return SQLITE_OK if
** successful. Otherwise, return an SQLite error code and leave an error
** message in the Parse object.
*/
static int renameResolveTrigger(Parse *pParse){
  sqlite3 *db = pParse->db;
  Trigger *pNew = pParse->pNewTrigger;
  TriggerStep *pStep;
  NameContext sNC;
  int rc = SQLITE_OK;

  memset(&sNC, 0, sizeof(sNC));
  sNC.pParse = pParse;
  assert( pNew->pTabSchema );
  pParse->pTriggerTab = sqlite3FindTable(db, pNew->table,
      db->aDb[sqlite3SchemaToIndex(db, pNew->pTabSchema)].zDbSName
  );
  pParse->eTriggerOp = pNew->op;
  /* ALWAYS() because if the table of the trigger does not exist, the
  ** error would have been hit before this point */
  if( ALWAYS(pParse->pTriggerTab) ){
    rc = sqlite3ViewGetColumnNames(pParse, pParse->pTriggerTab);
  }

  /* Resolve symbols in WHEN clause */
  if( rc==SQLITE_OK && pNew->pWhen ){
    rc = sqlite3ResolveExprNames(&sNC, pNew->pWhen);
  }

  for(pStep=pNew->step_list; rc==SQLITE_OK && pStep; pStep=pStep->pNext){
    if( pStep->pSelect ){
      sqlite3SelectPrep(pParse, pStep->pSelect, &sNC);
      if( pParse->nErr ) rc = pParse->rc;
    }
    if( rc==SQLITE_OK && pStep->zTarget ){
      SrcList *pSrc = sqlite3TriggerStepSrc(pParse, pStep);
      if( pSrc ){
        Select *pSel = sqlite3SelectNew(
            pParse, pStep->pExprList, pSrc, 0, 0, 0, 0, 0, 0
        );
        if( pSel==0 ){
          pStep->pExprList = 0;
          pSrc = 0;
          rc = SQLITE_NOMEM;
        }else{
          /* pStep->pExprList contains an expression-list used for an UPDATE
          ** statement. So the a[].zEName values are the RHS of the
          ** "<col> = <expr>" clauses of the UPDATE statement. So, before
          ** running SelectPrep(), change all the eEName values in
          ** pStep->pExprList to ENAME_SPAN (from their current value of
          ** ENAME_NAME). This is to prevent any ids in ON() clauses that are
          ** part of pSrc from being incorrectly resolved against the
          ** a[].zEName values as if they were column aliases.  */
          renameSetENames(pStep->pExprList, ENAME_SPAN);
          sqlite3SelectPrep(pParse, pSel, 0);
          renameSetENames(pStep->pExprList, ENAME_NAME);
          rc = pParse->nErr ? SQLITE_ERROR : SQLITE_OK;
          assert( pStep->pExprList==0 || pStep->pExprList==pSel->pEList );
          assert( pSrc==pSel->pSrc );
          if( pStep->pExprList ) pSel->pEList = 0;
          pSel->pSrc = 0;
          sqlite3SelectDelete(db, pSel);
        }
        if( pStep->pFrom ){
          int i;
          for(i=0; i<pStep->pFrom->nSrc && rc==SQLITE_OK; i++){
            SrcItem *p = &pStep->pFrom->a[i];
            if( p->pSelect ){
              sqlite3SelectPrep(pParse, p->pSelect, 0);
            }
          }
        }

        if(  db->mallocFailed ){
          rc = SQLITE_NOMEM;
        }
        sNC.pSrcList = pSrc;
        if( rc==SQLITE_OK && pStep->pWhere ){
          rc = sqlite3ResolveExprNames(&sNC, pStep->pWhere);
        }
        if( rc==SQLITE_OK ){
          rc = sqlite3ResolveExprListNames(&sNC, pStep->pExprList);
        }
        assert( !pStep->pUpsert || (!pStep->pWhere && !pStep->pExprList) );
        if( pStep->pUpsert && rc==SQLITE_OK ){
          Upsert *pUpsert = pStep->pUpsert;
          pUpsert->pUpsertSrc = pSrc;
          sNC.uNC.pUpsert = pUpsert;
          sNC.ncFlags = NC_UUpsert;
          rc = sqlite3ResolveExprListNames(&sNC, pUpsert->pUpsertTarget);
          if( rc==SQLITE_OK ){
            ExprList *pUpsertSet = pUpsert->pUpsertSet;
            rc = sqlite3ResolveExprListNames(&sNC, pUpsertSet);
          }
          if( rc==SQLITE_OK ){
            rc = sqlite3ResolveExprNames(&sNC, pUpsert->pUpsertWhere);
          }
          if( rc==SQLITE_OK ){
            rc = sqlite3ResolveExprNames(&sNC, pUpsert->pUpsertTargetWhere);
          }
          sNC.ncFlags = 0;
        }
        sNC.pSrcList = 0;
        sqlite3SrcListDelete(db, pSrc);
      }else{
        rc = SQLITE_NOMEM;
      }
    }
  }
  return rc;
}

/*
** Invoke sqlite3WalkExpr() or sqlite3WalkSelect() on all Select or Expr
** objects that are part of the trigger passed as the second argument.
*/
static void renameWalkTrigger(Walker *pWalker, Trigger *pTrigger){
  TriggerStep *pStep;

  /* Find tokens to edit in WHEN clause */
  sqlite3WalkExpr(pWalker, pTrigger->pWhen);

  /* Find tokens to edit in trigger steps */
  for(pStep=pTrigger->step_list; pStep; pStep=pStep->pNext){
    sqlite3WalkSelect(pWalker, pStep->pSelect);
    sqlite3WalkExpr(pWalker, pStep->pWhere);
    sqlite3WalkExprList(pWalker, pStep->pExprList);
    if( pStep->pUpsert ){
      Upsert *pUpsert = pStep->pUpsert;
      sqlite3WalkExprList(pWalker, pUpsert->pUpsertTarget);
      sqlite3WalkExprList(pWalker, pUpsert->pUpsertSet);
      sqlite3WalkExpr(pWalker, pUpsert->pUpsertWhere);
      sqlite3WalkExpr(pWalker, pUpsert->pUpsertTargetWhere);
    }
    if( pStep->pFrom ){
      int i;
      for(i=0; i<pStep->pFrom->nSrc; i++){
        sqlite3WalkSelect(pWalker, pStep->pFrom->a[i].pSelect);
      }
    }
  }
}

/*
** Free the contents of Parse object (*pParse). Do not free the memory
** occupied by the Parse object itself.
*/
static void renameParseCleanup(Parse *pParse){
  sqlite3 *db = pParse->db;
  Index *pIdx;
  if( pParse->pVdbe ){
    sqlite3VdbeFinalize(pParse->pVdbe);
  }
  sqlite3DeleteTable(db, pParse->pNewTable);
  while( (pIdx = pParse->pNewIndex)!=0 ){
    pParse->pNewIndex = pIdx->pNext;
    sqlite3FreeIndex(db, pIdx);
  }
  sqlite3DeleteTrigger(db, pParse->pNewTrigger);
  sqlite3DbFree(db, pParse->zErrMsg);
  renameTokenFree(db, pParse->pRename);
  sqlite3ParseObjectReset(pParse);
}

/*
** SQL function:
**
**     sqlite_rename_column(SQL,TYPE,OBJ,DB,TABLE,COL,NEWNAME,QUOTE,TEMP)
**
**   0. zSql:     SQL statement to rewrite
**   1. type:     Type of object ("table", "view" etc.)
**   2. object:   Name of object
**   3. Database: Database name (e.g. "main")
**   4. Table:    Table name
**   5. iCol:     Index of column to rename
**   6. zNew:     New column name
**   7. bQuote:   Non-zero if the new column name should be quoted.
**   8. bTemp:    True if zSql comes from temp schema
**
** Do a column rename operation on the CREATE statement given in zSql.
** The iCol-th column (left-most is 0) of table zTable is renamed from zCol
** into zNew.  The name should be quoted if bQuote is true.
**
** This function is used internally by the ALTER TABLE RENAME COLUMN command.
** It is only accessible to SQL created using sqlite3NestedParse().  It is
** not reachable from ordinary SQL passed into sqlite3_prepare() unless the
** SQLITE_TESTCTRL_INTERNAL_FUNCTIONS test setting is enabled.
*/
static void renameColumnFunc(
  sqlite3_context *context,
  int NotUsed,
  sqlite3_value **argv
){
  sqlite3 *db = sqlite3_context_db_handle(context);
  RenameCtx sCtx;
  const char *zSql = (const char*)sqlite3_value_text(argv[0]);
  const char *zDb = (const char*)sqlite3_value_text(argv[3]);
  const char *zTable = (const char*)sqlite3_value_text(argv[4]);
  int iCol = sqlite3_value_int(argv[5]);
  const char *zNew = (const char*)sqlite3_value_text(argv[6]);
  int bQuote = sqlite3_value_int(argv[7]);
  int bTemp = sqlite3_value_int(argv[8]);
  const char *zOld;
  int rc;
  Parse sParse;
  Walker sWalker;
  Index *pIdx;
  int i;
  Table *pTab;
#ifndef SQLITE_OMIT_AUTHORIZATION
  sqlite3_xauth xAuth = db->xAuth;
#endif

  UNUSED_PARAMETER(NotUsed);
  if( zSql==0 ) return;
  if( zTable==0 ) return;
  if( zNew==0 ) return;
  if( iCol<0 ) return;
  sqlite3BtreeEnterAll(db);
  pTab = sqlite3FindTable(db, zTable, zDb);
  if( pTab==0 || iCol>=pTab->nCol ){
    sqlite3BtreeLeaveAll(db);
    return;
  }
  zOld = pTab->aCol[iCol].zCnName;
  memset(&sCtx, 0, sizeof(sCtx));
  sCtx.iCol = ((iCol==pTab->iPKey) ? -1 : iCol);

#ifndef SQLITE_OMIT_AUTHORIZATION
  db->xAuth = 0;
#endif
  rc = renameParseSql(&sParse, zDb, db, zSql, bTemp);

  /* Find tokens that need to be replaced. */
  memset(&sWalker, 0, sizeof(Walker));
  sWalker.pParse = &sParse;
  sWalker.xExprCallback = renameColumnExprCb;
  sWalker.xSelectCallback = renameColumnSelectCb;
  sWalker.u.pRename = &sCtx;

  sCtx.pTab = pTab;
  if( rc!=SQLITE_OK ) goto renameColumnFunc_done;
  if( sParse.pNewTable ){
    if( IsView(sParse.pNewTable) ){
      Select *pSelect = sParse.pNewTable->u.view.pSelect;
      pSelect->selFlags &= ~SF_View;
      sParse.rc = SQLITE_OK;
      sqlite3SelectPrep(&sParse, pSelect, 0);
      rc = (db->mallocFailed ? SQLITE_NOMEM : sParse.rc);
      if( rc==SQLITE_OK ){
        sqlite3WalkSelect(&sWalker, pSelect);
      }
      if( rc!=SQLITE_OK ) goto renameColumnFunc_done;
    }else if( IsOrdinaryTable(sParse.pNewTable) ){
      /* A regular table */
      int bFKOnly = sqlite3_stricmp(zTable, sParse.pNewTable->zName);
      FKey *pFKey;
      sCtx.pTab = sParse.pNewTable;
      if( bFKOnly==0 ){
        if( iCol<sParse.pNewTable->nCol ){
          renameTokenFind(
              &sParse, &sCtx, (void*)sParse.pNewTable->aCol[iCol].zCnName
          );
        }
        if( sCtx.iCol<0 ){
          renameTokenFind(&sParse, &sCtx, (void*)&sParse.pNewTable->iPKey);
        }
        sqlite3WalkExprList(&sWalker, sParse.pNewTable->pCheck);
        for(pIdx=sParse.pNewTable->pIndex; pIdx; pIdx=pIdx->pNext){
          sqlite3WalkExprList(&sWalker, pIdx->aColExpr);
        }
        for(pIdx=sParse.pNewIndex; pIdx; pIdx=pIdx->pNext){
          sqlite3WalkExprList(&sWalker, pIdx->aColExpr);
        }
#ifndef SQLITE_OMIT_GENERATED_COLUMNS
        for(i=0; i<sParse.pNewTable->nCol; i++){
          Expr *pExpr = sqlite3ColumnExpr(sParse.pNewTable,
                                                  &sParse.pNewTable->aCol[i]);
          sqlite3WalkExpr(&sWalker, pExpr);
        }
#endif
      }

      assert( IsOrdinaryTable(sParse.pNewTable) );
      for(pFKey=sParse.pNewTable->u.tab.pFKey; pFKey; pFKey=pFKey->pNextFrom){
        for(i=0; i<pFKey->nCol; i++){
          if( bFKOnly==0 && pFKey->aCol[i].iFrom==iCol ){
            renameTokenFind(&sParse, &sCtx, (void*)&pFKey->aCol[i]);
          }
          if( 0==sqlite3_stricmp(pFKey->zTo, zTable)
           && 0==sqlite3_stricmp(pFKey->aCol[i].zCol, zOld)
          ){
            renameTokenFind(&sParse, &sCtx, (void*)pFKey->aCol[i].zCol);
          }
        }
      }
    }
  }else if( sParse.pNewIndex ){
    sqlite3WalkExprList(&sWalker, sParse.pNewIndex->aColExpr);
    sqlite3WalkExpr(&sWalker, sParse.pNewIndex->pPartIdxWhere);
  }else{
    /* A trigger */
    TriggerStep *pStep;
    rc = renameResolveTrigger(&sParse);
    if( rc!=SQLITE_OK ) goto renameColumnFunc_done;

    for(pStep=sParse.pNewTrigger->step_list; pStep; pStep=pStep->pNext){
      if( pStep->zTarget ){
        Table *pTarget = sqlite3LocateTable(&sParse, 0, pStep->zTarget, zDb);
        if( pTarget==pTab ){
          if( pStep->pUpsert ){
            ExprList *pUpsertSet = pStep->pUpsert->pUpsertSet;
            renameColumnElistNames(&sParse, &sCtx, pUpsertSet, zOld);
          }
          renameColumnIdlistNames(&sParse, &sCtx, pStep->pIdList, zOld);
          renameColumnElistNames(&sParse, &sCtx, pStep->pExprList, zOld);
        }
      }
    }


    /* Find tokens to edit in UPDATE OF clause */
    if( sParse.pTriggerTab==pTab ){
      renameColumnIdlistNames(&sParse, &sCtx,sParse.pNewTrigger->pColumns,zOld);
    }

    /* Find tokens to edit in various expressions and selects */
    renameWalkTrigger(&sWalker, sParse.pNewTrigger);
  }

  assert( rc==SQLITE_OK );
  rc = renameEditSql(context, &sCtx, zSql, zNew, bQuote);

renameColumnFunc_done:
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_ERROR && sqlite3WritableSchema(db) ){
      sqlite3_result_value(context, argv[0]);
    }else if( sParse.zErrMsg ){
      renameColumnParseError(context, "", argv[1], argv[2], &sParse);
    }else{
      sqlite3_result_error_code(context, rc);
    }
  }

  renameParseCleanup(&sParse);
  renameTokenFree(db, sCtx.pList);
#ifndef SQLITE_OMIT_AUTHORIZATION
  db->xAuth = xAuth;
#endif
  sqlite3BtreeLeaveAll(db);
}

/*
** Walker expression callback used by "RENAME TABLE".
*/
static int renameTableExprCb(Walker *pWalker, Expr *pExpr){
  RenameCtx *p = pWalker->u.pRename;
  if( pExpr->op==TK_COLUMN
   && ALWAYS(ExprUseYTab(pExpr))
   && p->pTab==pExpr->y.pTab
  ){
    renameTokenFind(pWalker->pParse, p, (void*)&pExpr->y.pTab);
  }
  return WRC_Continue;
}

/*
** Walker select callback used by "RENAME TABLE".
*/
static int renameTableSelectCb(Walker *pWalker, Select *pSelect){
  int i;
  RenameCtx *p = pWalker->u.pRename;
  SrcList *pSrc = pSelect->pSrc;
  if( pSelect->selFlags & (SF_View|SF_CopyCte) ){
    testcase( pSelect->selFlags & SF_View );
    testcase( pSelect->selFlags & SF_CopyCte );
    return WRC_Prune;
  }
  if( NEVER(pSrc==0) ){
    assert( pWalker->pParse->db->mallocFailed );
    return WRC_Abort;
  }
  for(i=0; i<pSrc->nSrc; i++){
    SrcItem *pItem = &pSrc->a[i];
    if( pItem->pTab==p->pTab ){
      renameTokenFind(pWalker->pParse, p, pItem->zName);
    }
  }
  renameWalkWith(pWalker, pSelect);

  return WRC_Continue;
}


/*
** This C function implements an SQL user function that is used by SQL code
** generated by the ALTER TABLE ... RENAME command to modify the definition
** of any foreign key constraints that use the table being renamed as the
** parent table. It is passed three arguments:
**
**   0: The database containing the table being renamed.
**   1. type:     Type of object ("table", "view" etc.)
**   2. object:   Name of object
**   3: The complete text of the schema statement being modified,
**   4: The old name of the table being renamed, and
**   5: The new name of the table being renamed.
**   6: True if the schema statement comes from the temp db.
**
** It returns the new schema statement. For example:
**
** sqlite_rename_table('main', 'CREATE TABLE t1(a REFERENCES t2)','t2','t3',0)
**       -> 'CREATE TABLE t1(a REFERENCES t3)'
*/
static void renameTableFunc(
  sqlite3_context *context,
  int NotUsed,
  sqlite3_value **argv
){
  sqlite3 *db = sqlite3_context_db_handle(context);
  const char *zDb = (const char*)sqlite3_value_text(argv[0]);
  const char *zInput = (const char*)sqlite3_value_text(argv[3]);
  const char *zOld = (const char*)sqlite3_value_text(argv[4]);
  const char *zNew = (const char*)sqlite3_value_text(argv[5]);
  int bTemp = sqlite3_value_int(argv[6]);
  UNUSED_PARAMETER(NotUsed);

  if( zInput && zOld && zNew ){
    Parse sParse;
    int rc;
    int bQuote = 1;
    RenameCtx sCtx;
    Walker sWalker;

#ifndef SQLITE_OMIT_AUTHORIZATION
    sqlite3_xauth xAuth = db->xAuth;
    db->xAuth = 0;
#endif

    sqlite3BtreeEnterAll(db);

    memset(&sCtx, 0, sizeof(RenameCtx));
    sCtx.pTab = sqlite3FindTable(db, zOld, zDb);
    memset(&sWalker, 0, sizeof(Walker));
    sWalker.pParse = &sParse;
    sWalker.xExprCallback = renameTableExprCb;
    sWalker.xSelectCallback = renameTableSelectCb;
    sWalker.u.pRename = &sCtx;

    rc = renameParseSql(&sParse, zDb, db, zInput, bTemp);

    if( rc==SQLITE_OK ){
      int isLegacy = (db->flags & SQLITE_LegacyAlter);
      if( sParse.pNewTable ){
        Table *pTab = sParse.pNewTable;

        if( IsView(pTab) ){
          if( isLegacy==0 ){
            Select *pSelect = pTab->u.view.pSelect;
            NameContext sNC;
            memset(&sNC, 0, sizeof(sNC));
            sNC.pParse = &sParse;

            assert( pSelect->selFlags & SF_View );
            pSelect->selFlags &= ~SF_View;
            sqlite3SelectPrep(&sParse, pTab->u.view.pSelect, &sNC);
            if( sParse.nErr ){
              rc = sParse.rc;
            }else{
              sqlite3WalkSelect(&sWalker, pTab->u.view.pSelect);
            }
          }
        }else{
          /* Modify any FK definitions to point to the new table. */
#ifndef SQLITE_OMIT_FOREIGN_KEY
          if( (isLegacy==0 || (db->flags & SQLITE_ForeignKeys))
           && !IsVirtual(pTab)
          ){
            FKey *pFKey;
            assert( IsOrdinaryTable(pTab) );
            for(pFKey=pTab->u.tab.pFKey; pFKey; pFKey=pFKey->pNextFrom){
              if( sqlite3_stricmp(pFKey->zTo, zOld)==0 ){
                renameTokenFind(&sParse, &sCtx, (void*)pFKey->zTo);
              }
            }
          }
#endif

          /* If this is the table being altered, fix any table refs in CHECK
          ** expressions. Also update the name that appears right after the
          ** "CREATE [VIRTUAL] TABLE" bit. */
          if( sqlite3_stricmp(zOld, pTab->zName)==0 ){
            sCtx.pTab = pTab;
            if( isLegacy==0 ){
              sqlite3WalkExprList(&sWalker, pTab->pCheck);
            }
            renameTokenFind(&sParse, &sCtx, pTab->zName);
          }
        }
      }

      else if( sParse.pNewIndex ){
        renameTokenFind(&sParse, &sCtx, sParse.pNewIndex->zName);
        if( isLegacy==0 ){
          sqlite3WalkExpr(&sWalker, sParse.pNewIndex->pPartIdxWhere);
        }
      }

#ifndef SQLITE_OMIT_TRIGGER
      else{
        Trigger *pTrigger = sParse.pNewTrigger;
        TriggerStep *pStep;
        if( 0==sqlite3_stricmp(sParse.pNewTrigger->table, zOld)
            && sCtx.pTab->pSchema==pTrigger->pTabSchema
          ){
          renameTokenFind(&sParse, &sCtx, sParse.pNewTrigger->table);
        }

        if( isLegacy==0 ){
          rc = renameResolveTrigger(&sParse);
          if( rc==SQLITE_OK ){
            renameWalkTrigger(&sWalker, pTrigger);
            for(pStep=pTrigger->step_list; pStep; pStep=pStep->pNext){
              if( pStep->zTarget && 0==sqlite3_stricmp(pStep->zTarget, zOld) ){
                renameTokenFind(&sParse, &sCtx, pStep->zTarget);
              }
              if( pStep->pFrom ){
                int i;
                for(i=0; i<pStep->pFrom->nSrc; i++){
                  SrcItem *pItem = &pStep->pFrom->a[i];
                  if( 0==sqlite3_stricmp(pItem->zName, zOld) ){
                    renameTokenFind(&sParse, &sCtx, pItem->zName);
                  }
                }
              }
            }
          }
        }
      }
#endif
    }

    if( rc==SQLITE_OK ){
      rc = renameEditSql(context, &sCtx, zInput, zNew, bQuote);
    }
    if( rc!=SQLITE_OK ){
      if( rc==SQLITE_ERROR && sqlite3WritableSchema(db) ){
        sqlite3_result_value(context, argv[3]);
      }else if( sParse.zErrMsg ){
        renameColumnParseError(context, "", argv[1], argv[2], &sParse);
      }else{
        sqlite3_result_error_code(context, rc);
      }
    }

    renameParseCleanup(&sParse);
    renameTokenFree(db, sCtx.pList);
    sqlite3BtreeLeaveAll(db);
#ifndef SQLITE_OMIT_AUTHORIZATION
    db->xAuth = xAuth;
#endif
  }

  return;
}

static int renameQuotefixExprCb(Walker *pWalker, Expr *pExpr){
  if( pExpr->op==TK_STRING && (pExpr->flags & EP_DblQuoted) ){
    renameTokenFind(pWalker->pParse, pWalker->u.pRename, (const void*)pExpr);
  }
  return WRC_Continue;
}

/* SQL function: sqlite_rename_quotefix(DB,SQL)
**
** Rewrite the DDL statement "SQL" so that any string literals that use
** double-quotes use single quotes instead.
**
** Two arguments must be passed:
**
**   0: Database name ("main", "temp" etc.).
**   1: SQL statement to edit.
**
** The returned value is the modified SQL statement. For example, given
** the database schema:
**
**   CREATE TABLE t1(a, b, c);
**
**   SELECT sqlite_rename_quotefix('main',
**       'CREATE VIEW v1 AS SELECT "a", "string" FROM t1'
**   );
**
** returns the string:
**
**   CREATE VIEW v1 AS SELECT "a", 'string' FROM t1
**
** If there is a error in the input SQL, then raise an error, except
** if PRAGMA writable_schema=ON, then just return the input string
** unmodified following an error.
*/
static void renameQuotefixFunc(
  sqlite3_context *context,
  int NotUsed,
  sqlite3_value **argv
){
  sqlite3 *db = sqlite3_context_db_handle(context);
  char const *zDb = (const char*)sqlite3_value_text(argv[0]);
  char const *zInput = (const char*)sqlite3_value_text(argv[1]);

#ifndef SQLITE_OMIT_AUTHORIZATION
  sqlite3_xauth xAuth = db->xAuth;
  db->xAuth = 0;
#endif

  sqlite3BtreeEnterAll(db);

  UNUSED_PARAMETER(NotUsed);
  if( zDb && zInput ){
    int rc;
    Parse sParse;
    rc = renameParseSql(&sParse, zDb, db, zInput, 0);

    if( rc==SQLITE_OK ){
      RenameCtx sCtx;
      Walker sWalker;

      /* Walker to find tokens that need to be replaced. */
      memset(&sCtx, 0, sizeof(RenameCtx));
      memset(&sWalker, 0, sizeof(Walker));
      sWalker.pParse = &sParse;
      sWalker.xExprCallback = renameQuotefixExprCb;
      sWalker.xSelectCallback = renameColumnSelectCb;
      sWalker.u.pRename = &sCtx;

      if( sParse.pNewTable ){
        if( IsView(sParse.pNewTable) ){
          Select *pSelect = sParse.pNewTable->u.view.pSelect;
          pSelect->selFlags &= ~SF_View;
          sParse.rc = SQLITE_OK;
          sqlite3SelectPrep(&sParse, pSelect, 0);
          rc = (db->mallocFailed ? SQLITE_NOMEM : sParse.rc);
          if( rc==SQLITE_OK ){
            sqlite3WalkSelect(&sWalker, pSelect);
          }
        }else{
          int i;
          sqlite3WalkExprList(&sWalker, sParse.pNewTable->pCheck);
#ifndef SQLITE_OMIT_GENERATED_COLUMNS
          for(i=0; i<sParse.pNewTable->nCol; i++){
            sqlite3WalkExpr(&sWalker,
               sqlite3ColumnExpr(sParse.pNewTable,
                                         &sParse.pNewTable->aCol[i]));
          }
#endif /* SQLITE_OMIT_GENERATED_COLUMNS */
        }
      }else if( sParse.pNewIndex ){
        sqlite3WalkExprList(&sWalker, sParse.pNewIndex->aColExpr);
        sqlite3WalkExpr(&sWalker, sParse.pNewIndex->pPartIdxWhere);
      }else{
#ifndef SQLITE_OMIT_TRIGGER
        rc = renameResolveTrigger(&sParse);
        if( rc==SQLITE_OK ){
          renameWalkTrigger(&sWalker, sParse.pNewTrigger);
        }
#endif /* SQLITE_OMIT_TRIGGER */
      }

      if( rc==SQLITE_OK ){
        rc = renameEditSql(context, &sCtx, zInput, 0, 0);
      }
      renameTokenFree(db, sCtx.pList);
    }
    if( rc!=SQLITE_OK ){
      if( sqlite3WritableSchema(db) && rc==SQLITE_ERROR ){
        sqlite3_result_value(context, argv[1]);
      }else{
        sqlite3_result_error_code(context, rc);
      }
    }
    renameParseCleanup(&sParse);
  }

#ifndef SQLITE_OMIT_AUTHORIZATION
  db->xAuth = xAuth;
#endif

  sqlite3BtreeLeaveAll(db);
}

/* Function:  sqlite_rename_test(DB,SQL,TYPE,NAME,ISTEMP,WHEN,DQS)
**
** An SQL user function that checks that there are no parse or symbol
** resolution problems in a CREATE TRIGGER|TABLE|VIEW|INDEX statement.
** After an ALTER TABLE .. RENAME operation is performed and the schema
** reloaded, this function is called on each SQL statement in the schema
** to ensure that it is still usable.
**
**   0: Database name ("main", "temp" etc.).
**   1: SQL statement.
**   2: Object type ("view", "table", "trigger" or "index").
**   3: Object name.
**   4: True if object is from temp schema.
**   5: "when" part of error message.
**   6: True to disable the DQS quirk when parsing SQL.
**
** The return value is computed as follows:
**
**   A. If an error is seen and not in PRAGMA writable_schema=ON mode,
**      then raise the error.
**   B. Else if a trigger is created and the the table that the trigger is
**      attached to is in database zDb, then return 1.
**   C. Otherwise return NULL.
*/
static void renameTableTest(
  sqlite3_context *context,
  int NotUsed,
  sqlite3_value **argv
){
  sqlite3 *db = sqlite3_context_db_handle(context);
  char const *zDb = (const char*)sqlite3_value_text(argv[0]);
  char const *zInput = (const char*)sqlite3_value_text(argv[1]);
  int bTemp = sqlite3_value_int(argv[4]);
  int isLegacy = (db->flags & SQLITE_LegacyAlter);
  char const *zWhen = (const char*)sqlite3_value_text(argv[5]);
  int bNoDQS = sqlite3_value_int(argv[6]);

#ifndef SQLITE_OMIT_AUTHORIZATION
  sqlite3_xauth xAuth = db->xAuth;
  db->xAuth = 0;
#endif

  UNUSED_PARAMETER(NotUsed);

  if( zDb && zInput ){
    int rc;
    Parse sParse;
    int flags = db->flags;
    if( bNoDQS ) db->flags &= ~(SQLITE_DqsDML|SQLITE_DqsDDL);
    rc = renameParseSql(&sParse, zDb, db, zInput, bTemp);
    db->flags |= (flags & (SQLITE_DqsDML|SQLITE_DqsDDL));
    if( rc==SQLITE_OK ){
      if( isLegacy==0 && sParse.pNewTable && IsView(sParse.pNewTable) ){
        NameContext sNC;
        memset(&sNC, 0, sizeof(sNC));
        sNC.pParse = &sParse;
        sqlite3SelectPrep(&sParse, sParse.pNewTable->u.view.pSelect, &sNC);
        if( sParse.nErr ) rc = sParse.rc;
      }

      else if( sParse.pNewTrigger ){
        if( isLegacy==0 ){
          rc = renameResolveTrigger(&sParse);
        }
        if( rc==SQLITE_OK ){
          int i1 = sqlite3SchemaToIndex(db, sParse.pNewTrigger->pTabSchema);
          int i2 = sqlite3FindDbName(db, zDb);
          if( i1==i2 ){
            /* Handle output case B */
            sqlite3_result_int(context, 1);
          }
        }
      }
    }

    if( rc!=SQLITE_OK && zWhen && !sqlite3WritableSchema(db) ){
      /* Output case A */
      renameColumnParseError(context, zWhen, argv[2], argv[3],&sParse);
    }
    renameParseCleanup(&sParse);
  }

#ifndef SQLITE_OMIT_AUTHORIZATION
  db->xAuth = xAuth;
#endif
}

/*
** The implementation of internal UDF sqlite_drop_column().
**
** Arguments:
**
**  argv[0]: An integer - the index of the schema containing the table
**  argv[1]: CREATE TABLE statement to modify.
**  argv[2]: An integer - the index of the column to remove.
**
** The value returned is a string containing the CREATE TABLE statement
** with column argv[2] removed.
*/
static void dropColumnFunc(
  sqlite3_context *context,
  int NotUsed,
  sqlite3_value **argv
){
  sqlite3 *db = sqlite3_context_db_handle(context);
  int iSchema = sqlite3_value_int(argv[0]);
  const char *zSql = (const char*)sqlite3_value_text(argv[1]);
  int iCol = sqlite3_value_int(argv[2]);
  const char *zDb = db->aDb[iSchema].zDbSName;
  int rc;
  Parse sParse;
  RenameToken *pCol;
  Table *pTab;
  const char *zEnd;
  char *zNew = 0;

#ifndef SQLITE_OMIT_AUTHORIZATION
  sqlite3_xauth xAuth = db->xAuth;
  db->xAuth = 0;
#endif

  UNUSED_PARAMETER(NotUsed);
  rc = renameParseSql(&sParse, zDb, db, zSql, iSchema==1);
  if( rc!=SQLITE_OK ) goto drop_column_done;
  pTab = sParse.pNewTable;
  if( pTab==0 || pTab->nCol==1 || iCol>=pTab->nCol ){
    /* This can happen if the sqlite_schema table is corrupt */
    rc = SQLITE_CORRUPT_BKPT;
    goto drop_column_done;
  }

  pCol = renameTokenFind(&sParse, 0, (void*)pTab->aCol[iCol].zCnName);
  if( iCol<pTab->nCol-1 ){
    RenameToken *pEnd;
    pEnd = renameTokenFind(&sParse, 0, (void*)pTab->aCol[iCol+1].zCnName);
    zEnd = (const char*)pEnd->t.z;
  }else{
    assert( IsOrdinaryTable(pTab) );
    zEnd = (const char*)&zSql[pTab->u.tab.addColOffset];
    while( ALWAYS(pCol->t.z[0]!=0) && pCol->t.z[0]!=',' ) pCol->t.z--;
  }

  zNew = sqlite3MPrintf(db, "%.*s%s", pCol->t.z-zSql, zSql, zEnd);
  sqlite3_result_text(context, zNew, -1, SQLITE_TRANSIENT);
  sqlite3_free(zNew);

drop_column_done:
  renameParseCleanup(&sParse);
#ifndef SQLITE_OMIT_AUTHORIZATION
  db->xAuth = xAuth;
#endif
  if( rc!=SQLITE_OK ){
    sqlite3_result_error_code(context, rc);
  }
}

/*
** This function is called by the parser upon parsing an
**
**     ALTER TABLE pSrc DROP COLUMN pName
**
** statement. Argument pSrc contains the possibly qualified name of the
** table being edited, and token pName the name of the column to drop.
*/
void sqlite3AlterDropColumn(Parse *pParse, SrcList *pSrc, const Token *pName){
  sqlite3 *db = pParse->db;       /* Database handle */
  Table *pTab;                    /* Table to modify */
  int iDb;                        /* Index of db containing pTab in aDb[] */
  const char *zDb;                /* Database containing pTab ("main" etc.) */
  char *zCol = 0;                 /* Name of column to drop */
  int iCol;                       /* Index of column zCol in pTab->aCol[] */

  /* Look up the table being altered. */
  assert( pParse->pNewTable==0 );
  assert( sqlite3BtreeHoldsAllMutexes(db) );
  if( NEVER(db->mallocFailed) ) goto exit_drop_column;
  pTab = sqlite3LocateTableItem(pParse, 0, &pSrc->a[0]);
  if( !pTab ) goto exit_drop_column;

  /* Make sure this is not an attempt to ALTER a view, virtual table or
  ** system table. */
  if( SQLITE_OK!=isAlterableTable(pParse, pTab) ) goto exit_drop_column;
  if( SQLITE_OK!=isRealTable(pParse, pTab, 1) ) goto exit_drop_column;

  /* Find the index of the column being dropped. */
  zCol = sqlite3NameFromToken(db, pName);
  if( zCol==0 ){
    assert( db->mallocFailed );
    goto exit_drop_column;
  }
  iCol = sqlite3ColumnIndex(pTab, zCol);
  if( iCol<0 ){
    sqlite3ErrorMsg(pParse, "no such column: \"%T\"", pName);
    goto exit_drop_column;
  }

  /* Do not allow the user to drop a PRIMARY KEY column or a column
  ** constrained by a UNIQUE constraint.  */
  if( pTab->aCol[iCol].colFlags & (COLFLAG_PRIMKEY|COLFLAG_UNIQUE) ){
    sqlite3ErrorMsg(pParse, "cannot drop %s column: \"%s\"",
        (pTab->aCol[iCol].colFlags&COLFLAG_PRIMKEY) ? "PRIMARY KEY" : "UNIQUE",
        zCol
    );
    goto exit_drop_column;
  }

  /* Do not allow the number of columns to go to zero */
  if( pTab->nCol<=1 ){
    sqlite3ErrorMsg(pParse, "cannot drop column \"%s\": no other columns exist",zCol);
    goto exit_drop_column;
  }

  /* Edit the sqlite_schema table */
  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
  assert( iDb>=0 );
  zDb = db->aDb[iDb].zDbSName;
#ifndef SQLITE_OMIT_AUTHORIZATION
  /* Invoke the authorization callback. */
  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, zCol) ){
    goto exit_drop_column;
  }
#endif
  renameTestSchema(pParse, zDb, iDb==1, "", 0);
  renameFixQuotes(pParse, zDb, iDb==1);
  sqlite3NestedParse(pParse,
      "UPDATE \"%w\"." LEGACY_SCHEMA_TABLE " SET "
      "sql = sqlite_drop_column(%d, sql, %d) "
      "WHERE (type=='table' AND tbl_name=%Q COLLATE nocase)"
      , zDb, iDb, iCol, pTab->zName
  );

  /* Drop and reload the database schema. */
  renameReloadSchema(pParse, iDb, INITFLAG_AlterDrop);
  renameTestSchema(pParse, zDb, iDb==1, "after drop column", 1);

  /* Edit rows of table on disk */
  if( pParse->nErr==0 && (pTab->aCol[iCol].colFlags & COLFLAG_VIRTUAL)==0 ){
    int i;
    int addr;
    int reg;
    int regRec;
    Index *pPk = 0;
    int nField = 0;               /* Number of non-virtual columns after drop */
    int iCur;
    Vdbe *v = sqlite3GetVdbe(pParse);
    iCur = pParse->nTab++;
    sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenWrite);
    addr = sqlite3VdbeAddOp1(v, OP_Rewind, iCur); VdbeCoverage(v);
    reg = ++pParse->nMem;
    if( HasRowid(pTab) ){
      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, reg);
      pParse->nMem += pTab->nCol;
    }else{
      pPk = sqlite3PrimaryKeyIndex(pTab);
      pParse->nMem += pPk->nColumn;
      for(i=0; i<pPk->nKeyCol; i++){
        sqlite3VdbeAddOp3(v, OP_Column, iCur, i, reg+i+1);
      }
      nField = pPk->nKeyCol;
    }
    regRec = ++pParse->nMem;
    for(i=0; i<pTab->nCol; i++){
      if( i!=iCol && (pTab->aCol[i].colFlags & COLFLAG_VIRTUAL)==0 ){
        int regOut;
        if( pPk ){
          int iPos = sqlite3TableColumnToIndex(pPk, i);
          int iColPos = sqlite3TableColumnToIndex(pPk, iCol);
          if( iPos<pPk->nKeyCol ) continue;
          regOut = reg+1+iPos-(iPos>iColPos);
        }else{
          regOut = reg+1+nField;
        }
        if( i==pTab->iPKey ){
          sqlite3VdbeAddOp2(v, OP_Null, 0, regOut);
        }else{
          sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, i, regOut);
        }
        nField++;
      }
    }
    if( nField==0 ){
      /* dbsqlfuzz 5f09e7bcc78b4954d06bf9f2400d7715f48d1fef */
      pParse->nMem++;
      sqlite3VdbeAddOp2(v, OP_Null, 0, reg+1);
      nField = 1;
    }
    sqlite3VdbeAddOp3(v, OP_MakeRecord, reg+1, nField, regRec);
    if( pPk ){
      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iCur, regRec, reg+1, pPk->nKeyCol);
    }else{
      sqlite3VdbeAddOp3(v, OP_Insert, iCur, regRec, reg);
    }
    sqlite3VdbeChangeP5(v, OPFLAG_SAVEPOSITION);

    sqlite3VdbeAddOp2(v, OP_Next, iCur, addr+1); VdbeCoverage(v);
    sqlite3VdbeJumpHere(v, addr);
  }

exit_drop_column:
  sqlite3DbFree(db, zCol);
  sqlite3SrcListDelete(db, pSrc);
}

/*
** Register built-in functions used to help implement ALTER TABLE
*/
void sqlite3AlterFunctions(void){
  static FuncDef aAlterTableFuncs[] = {
    INTERNAL_FUNCTION(sqlite_rename_column,  9, renameColumnFunc),
    INTERNAL_FUNCTION(sqlite_rename_table,   7, renameTableFunc),
    INTERNAL_FUNCTION(sqlite_rename_test,    7, renameTableTest),
    INTERNAL_FUNCTION(sqlite_drop_column,    3, dropColumnFunc),
    INTERNAL_FUNCTION(sqlite_rename_quotefix,2, renameQuotefixFunc),
  };
  sqlite3InsertBuiltinFuncs(aAlterTableFuncs, ArraySize(aAlterTableFuncs));
}
#endif  /* SQLITE_ALTER_TABLE */