diff --git a/manifest b/manifest
index a595639ccc..7d02d42122 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Avoid\sinvoking\sthe\supdate\sor\spre-update\shooks\sduring\sVACUUM\soperations.
-D 2021-02-18T15:59:37.490
+C Add\ssupport\sfor\s"ALTER\sTABLE\s...\sDROP\sCOLUMN\s..."\scommands.
+D 2021-02-19T14:32:58.535
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -475,7 +475,7 @@ F spec.template 86a4a43b99ebb3e75e6b9a735d5fd293a24e90ca
 F sqlite.pc.in 42b7bf0d02e08b9e77734a47798d1a55a9e0716b
 F sqlite3.1 fc7ad8990fc8409983309bb80de8c811a7506786
 F sqlite3.pc.in 48fed132e7cb71ab676105d2a4dc77127d8c1f3a
-F src/alter.c c4a973d7fc68f81fbc5d1d028a88ddb2cb212faef8c6f63433175b8d5ecd83dc
+F src/alter.c 1addd06a7aae343497ebede71ec355c2011f175075943007341693ebf7daa47d
 F src/analyze.c 01c6c6765cb4d40b473b71d85535093730770bb186f2f473abac25f07fcdee5c
 F src/attach.c e80162a47411f296bea550ed8fafd730481f4aa71e89ece23ba9c957eed15d4a
 F src/auth.c 08954fdc4cc2da5264ba5b75cfd90b67a6fc7d1710a02ccf917c38eadec77853
@@ -485,7 +485,7 @@ F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
 F src/btree.c 694020ad8a3af3d79b09f74c8f1421272a419cdea42a13401e3b0f7dea6e9c3e
 F src/btree.h 285f8377aa1353185a32bf455faafa9ff9a0d40d074d60509534d14990c7829e
 F src/btreeInt.h 7614cae30f95b6aed0c7cac7718276a55cfe2c77058cbfd8bef5b75329757331
-F src/build.c e50a6d7132b051b7d00c59a896e4889128a55c0f55f81c664da1906fbad51d1c
+F src/build.c 72b868d9c8a0d56aef4237825b0fad38898a2d9310669940383accf20429c5ca
 F src/callback.c d0b853dd413255d2e337b34545e54d888ea02f20da5ad0e63585b389624c4a6c
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/ctime.c 2a322b9a3d75771fb4d99e0702851f4f68dda982507a0f798eefb0712969a410
@@ -530,23 +530,23 @@ F src/os_win.c 77d39873836f1831a9b0b91894fec45ab0e9ca8e067dc8c549e1d1eca1566fe9
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
 F src/pager.c c49952ac5e9cc536778eff528091d79d38b3e45cbeeed4695dc05e207dc6547d
 F src/pager.h 4bf9b3213a4b2bebbced5eaa8b219cf25d4a82f385d093cd64b7e93e5285f66f
-F src/parse.y 67ba503780de64b967ae195b7e14c33531329228e1bc0b83d63324beb733680b
+F src/parse.y cdc4e5efaf1618d82f6b241a30f1a586188bf37e9c55f967258ed15fe24c51a2
 F src/pcache.c 385ff064bca69789d199a98e2169445dc16e4291fa807babd61d4890c3b34177
 F src/pcache.h 4f87acd914cef5016fae3030343540d75f5b85a1877eed1a2a19b9f284248586
 F src/pcache1.c 6596e10baf3d8f84cc1585d226cf1ab26564a5f5caf85a15757a281ff977d51a
 F src/pragma.c 6daaaecc26a4b09481d21722525b079ce756751a43a79cc1d8f122d686806193
 F src/pragma.h 8dc78ab7e9ec6ce3ded8332810a2066f1ef6267e2e03cd7356ee00276125c6cf
-F src/prepare.c a25c7df3a71be19c31231d59d0694e950183837fc54b1828549c5a766538fcf7
+F src/prepare.c 7a534d100c556f45f10aee131f2e4244cb52547b7cf17e1c393f55d8abb62e97
 F src/printf.c 30e92b638fac71dcd85cdea1d12ecfae354c9adee2c71e8e1ae4727cde7c91ed
 F src/random.c 80f5d666f23feb3e6665a6ce04c7197212a88384
 F src/resolve.c 52f81603cc40f78449f5b6aed96dbea9484b194771ecb1937e8c0f6547c186a0
 F src/rowset.c ba9515a922af32abe1f7d39406b9d35730ed65efab9443dc5702693b60854c92
-F src/select.c aa04743edeac1142f0a698ca4a3188795b826bd5ef46ea61f06897a4f71ad6b2
+F src/select.c 371a5c95d47d4e969337548ed9bd344788f15518a1c75921507355bd93815205
 F src/shell.c.in 844417f84df1f6c4fce1c815629a888cfdcf219e86513e9c332bbcc38832f477
 F src/sqlite.h.in 8855a19f37ade8dad189a9e48233a2ebe1b46faf469c7eb0906a654e252dcc57
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h 61b38c073d5e1e96a3d45271b257aef27d0d13da2bea5347692ae579475cd95e
-F src/sqliteInt.h 4d57a17d4697a6e7f992008f36a35852c2a6c3064992fbedf3f56b7bad9df027
+F src/sqliteInt.h 4bd449478df0444ccb9f6a8e6f210b2ceacdd59562f52630edb0bb2d8cc25094
 F src/sqliteLimit.h d7323ffea5208c6af2734574bae933ca8ed2ab728083caa117c9738581a31657
 F src/status.c 4b8bc2a6905163a38b739854a35b826c737333fab5b1f8e03fa7eb9a4799c4c1
 F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
@@ -607,23 +607,23 @@ F src/test_wsd.c 41cadfd9d97fe8e3e4e44f61a4a8ccd6f7ca8fe9
 F src/threads.c 4ae07fa022a3dc7c5beb373cf744a85d3c5c6c3c
 F src/tokenize.c c64c49d7c2ec4490c2fef1f24350167ba16b03b0c6cee58ad1a1d70a4325d4e9
 F src/treeview.c 4b92992176fb2caefbe06ba5bd06e0e0ebcde3d5564758da672631f17aa51cda
-F src/trigger.c 983c7c8464c46840dac1ffe0461a6c447ac12c965746975c108eb5f4283e8801
+F src/trigger.c 861c3ec2c5b0fc830bdf82470454a9324fad70cbaa96d2e208fb54577c9e8d28
 F src/update.c 0f5a61f0787199983530a33f6fffe4f52742f35fcdf6ccfad1078b1a8bc17723
 F src/upsert.c df8f1727d62b5987c4fd302cd4d7c0c84ae57cd65683c5a34a740dfe24039235
 F src/utf.c ee39565f0843775cc2c81135751ddd93eceb91a673ea2c57f61c76f288b041a0
 F src/util.c 41c7a72da1df47864faa378a1c720b38adb288c6838cb6be5594511b6287a048
 F src/vacuum.c 492422c1463c076473bae1858799c7a0a5fe87a133d1223239447c422cd26286
-F src/vdbe.c b3c9a3f9d546d4848a2a8c88a3c40875cd6ba3d248d9b99d01b1eeb38b29c171
-F src/vdbe.h 83603854bfa5851af601fc0947671eb260f4363e62e960e8a994fb9bbcd2aaa1
+F src/vdbe.c 9766281c0febf25f30a043d98b2417011acc7b04f287d3c671c3e59f656fc208
+F src/vdbe.h 25dabb25c7e157b84e59260cfb5b466c3ac103ede9f36f4db371332c47601abe
 F src/vdbeInt.h 3df118924e1711f1bbc8e30c46260d0ab6c3b029b32dd411f789111f76434f3c
 F src/vdbeapi.c 4a43e303ec3354c785f453e881521969378e85628278ab74ba4a9df790c0d93b
-F src/vdbeaux.c c8e96fb57ee6f7150845325ffb8d7fd4e340ff4f73aa527a6f26a485db8b9955
+F src/vdbeaux.c fb51483c2bcaf45c5de63c26cce8649ef37f1332e8e035867033d21ef5e7fc2c
 F src/vdbeblob.c 253ed82894924c362a7fa3079551d3554cd1cdace39aa833da77d3bc67e7c1b1
 F src/vdbemem.c 947f2a65910edb4014dc981d33e414a68c51f169f9df8c4c493a0ba840b6eb1f
 F src/vdbesort.c f5b5e473a7cee44e47a94817b042fd7172cf3aa2c0a7928a8339d612bcfdec5a
 F src/vdbetrace.c 666c6fd9f1b62be6999e072a45b913e3c2c3518bc60dfd4d54fe304130acb724
 F src/vdbevtab.c f99b275366c5fc5e2d99f734729880994ab9500bdafde7fae3b02d562b9d323c
-F src/vtab.c b7773ffbde8d2b134fde8f7349c8d0a0503b308f77561acda7db975d3114d6a1
+F src/vtab.c 032a0165c147fda16927e6a3230e90c068d4af93f887ce94e26f678fe48e5e4c
 F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
 F src/wal.c 69e770e96fd56cc21608992bf2c6f1f3dc5cf2572d0495c6a643b06c3a679f14
 F src/wal.h c3aa7825bfa2fe0d85bef2db94655f99870a285778baa36307c0a16da32b226a
@@ -645,11 +645,14 @@ F test/alter2.test a966ccfcddf9ce0a4e0e6ff1aca9e6e7948e0e242cd7e43fc091948521807
 F test/alter3.test e487958dec7932453e0b83baf21d6b1e71d5e7d9a55bc20eadfa62a51ddffc29
 F test/alter4.test dfd6086faf461b27ca2d2999848dcd207edf23352fc1592d0005c0844f3f08cf
 F test/alterauth.test 63442ba61ceb0c1eeb63aac1f4f5cebfa509d352276059d27106ae256bafc959
-F test/alterauth2.test c0a1ddf5b93d93cb0d15ba7acaf0c5c6fb515bbe861ede75b2d3fabad33b6499
+F test/alterauth2.test 794ac5cef251819fe364b4fe20f12f86e9c5d68070513c7fd26c17cb244c89af
 F test/altercol.test 1d6a6fe698b81e626baea4881f5717f9bc53d7d07f1cd23ee7ad1b931f117ddf
-F test/alterlegacy.test 82022721ce0de29cedc9a7af63bc9fcc078b0ee000f8283b4b6ea9c3eab2f44b
+F test/altercorrupt.test cb17a81f655a0d71bc1e48e44741a5e0905a3b3efbbe485b0b6c7648f2af3eed
+F test/alterdropcol.test baad37ff9b07078ea02dcc33dbfb82bde655f3eee5c453e218f69501c36f02ba
+F test/alterlegacy.test f38c6d06cda39e1f7b955bbce57f2e3ef5b7cb566d3d1234502093e228c15811
 F test/altermalloc.test 167a47de41b5c638f5f5c6efb59784002b196fff70f98d9b4ed3cd74a3fb80c9
 F test/altermalloc2.test fa7b1c1139ea39b8dec407cf1feb032ca8e0076bd429574969b619175ad0174b
+F test/altermalloc3.test 2c7bbd8cf3e9c4a91e28675bb62bcc2ef70f227967fa74349f03d9f4642f0615
 F test/altertab.test 6d7bbac2c4a6ef71b775094a3298fa3a92274d95034ee23157ffba92768e47e6
 F test/altertab2.test b0d62f323ca5dab42b0bc028c52e310ebdd13e655e8fac070fe622bad7852c2b
 F test/altertab3.test 2b82fa2236a3a91553d53ae5555d8e723c7eec174c41f1fa62ff497355398479
@@ -1020,7 +1023,7 @@ F test/fts4noti.test 5553d7bb2e20bf4a06b23e849352efc022ce6309
 F test/fts4onepass.test d69ddc4ee3415e40b0c5d1d0408488a87614d4f63ba9c44f3e52db541d6b7cc7
 F test/fts4opt.test 0fd0cc84000743ff2a883b9b84b4a5be07249f0ba790c8848a757164cdd46b2a
 F test/fts4record.test a48508f69a84c9287c8019d3a1ae712f5730d8335ffaf8e2101e691d078950bb
-F test/fts4rename.test 15fd9985c2bce6dea20da2245b22029ec89bd4710ed317c4c53abbe3cfd0c880
+F test/fts4rename.test 2e0565ffd92b2c51f1a757df0b8f2ca30537197106fec09e943919801d173692
 F test/fts4umlaut.test fcaca4471de7e78c9d1f7e8976e3e8704d7d8ad979d57a739d00f3f757380429
 F test/fts4unicode.test 82a9c16b68ba2f358a856226bb2ee02f81583797bc4744061c54401bf1a0f4c9
 F test/fts4upfrom.test 8df5acb6e10ad73f393d1add082b042ab1db72567888847d098152121e507b34
@@ -1900,7 +1903,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P f985a78ecc0c6d9ff671c730a109d97dc781b06e47a0ab03f441cea5d021a4c3
-R 887c3ab5f5432ba4ea084453147dc94e
+P 3c25cb4ab8885a50e2a485fe76f5ffd5dd8ebe1306aca8c0989e0b7fd7dd18d2 126ee1ec4f3565c0cccca98885fa3665a641ea3df251511de16eed2a1c396124
+R a9f6b9c36a39e6908ea00fd7298f0619
+T +closed 126ee1ec4f3565c0cccca98885fa3665a641ea3df251511de16eed2a1c396124
 U dan
-Z 858d0f25e386aba1accc2e325cd1540d
+Z c1e3973235fcf41f620261cabeb4df13
diff --git a/manifest.uuid b/manifest.uuid
index 81f136ebf3..a03f87c63b 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-3c25cb4ab8885a50e2a485fe76f5ffd5dd8ebe1306aca8c0989e0b7fd7dd18d2
\ No newline at end of file
+c844a331e78949850fde8ed95058cb34f863566944bc9e92e3ae042768f130e1
\ No newline at end of file
diff --git a/src/alter.c b/src/alter.c
index 0f50f195e7..e2af2beb8b 100644
--- a/src/alter.c
+++ b/src/alter.c
@@ -49,16 +49,21 @@ static int isAlterableTable(Parse *pParse, Table *pTab){
 ** statement to ensure that the operation has not rendered any schema
 ** objects unusable.
 */
-static void renameTestSchema(Parse *pParse, const char *zDb, int bTemp){
+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 */
+){
   pParse->colNamesSet = 1;
   sqlite3NestedParse(pParse, 
       "SELECT 1 "
       "FROM \"%w\"." DFLT_SCHEMA_TABLE " "
       "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
       " AND sql NOT LIKE 'create virtual%%'"
-      " AND sqlite_rename_test(%Q, sql, type, name, %d)=NULL ",
+      " AND sqlite_rename_test(%Q, sql, type, name, %d, %Q)=NULL ",
       zDb,
-      zDb, bTemp
+      zDb, bTemp, zWhen
   );
 
   if( bTemp==0 ){
@@ -67,8 +72,8 @@ static void renameTestSchema(Parse *pParse, const char *zDb, int bTemp){
         "FROM temp." DFLT_SCHEMA_TABLE " "
         "WHERE name NOT LIKE 'sqliteX_%%' ESCAPE 'X'"
         " AND sql NOT LIKE 'create virtual%%'"
-        " AND sqlite_rename_test(%Q, sql, type, name, 1)=NULL ",
-        zDb 
+        " AND sqlite_rename_test(%Q, sql, type, name, 1, %Q)=NULL ",
+        zDb, zWhen
     );
   }
 }
@@ -77,12 +82,12 @@ static void renameTestSchema(Parse *pParse, const char *zDb, int bTemp){
 ** 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){
+static void renameReloadSchema(Parse *pParse, int iDb, u16 p5){
   Vdbe *v = pParse->pVdbe;
   if( v ){
     sqlite3ChangeCookie(pParse, iDb);
-    sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, iDb, 0);
-    if( iDb!=1 ) sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, 1, 0);
+    sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, iDb, 0, p5);
+    if( iDb!=1 ) sqlite3VdbeAddParseSchemaOp(pParse->pVdbe, 1, 0, p5);
   }
 }
 
@@ -231,7 +236,7 @@ void sqlite3AlterRenameTable(
             "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) "
+              "    sqlite_rename_test(%Q, sql, type, name, 1, 'after rename') "
               "THEN %Q ELSE tbl_name END "
             "WHERE type IN ('view', 'trigger')"
         , zDb, zTabName, zName, zTabName, zDb, zName);
@@ -250,8 +255,8 @@ void sqlite3AlterRenameTable(
   }
 #endif
 
-  renameReloadSchema(pParse, iDb);
-  renameTestSchema(pParse, zDb, iDb==1);
+  renameReloadSchema(pParse, iDb, INITFLAG_AlterRename);
+  renameTestSchema(pParse, zDb, iDb==1, "after rename");
 
 exit_rename_table:
   sqlite3SrcListDelete(db, pSrc);
@@ -413,7 +418,7 @@ void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){
   }
 
   /* Reload the table definition */
-  renameReloadSchema(pParse, iDb);
+  renameReloadSchema(pParse, iDb, INITFLAG_AlterRename);
 }
 
 /*
@@ -513,7 +518,7 @@ exit_begin_add_column:
 ** 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){
+static int isRealTable(Parse *pParse, Table *pTab, int bDrop){
   const char *zType = 0;
 #ifndef SQLITE_OMIT_VIEW
   if( pTab->pSelect ){
@@ -526,15 +531,16 @@ static int isRealTable(Parse *pParse, Table *pTab){
   }
 #endif
   if( zType ){
-    sqlite3ErrorMsg(
-        pParse, "cannot rename columns of %s \"%s\"", zType, pTab->zName
+    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) (0)
+# define isRealTable(x,y,z) (0)
 #endif
 
 /*
@@ -563,7 +569,7 @@ void sqlite3AlterRenameColumn(
 
   /* Cannot alter a system table */
   if( SQLITE_OK!=isAlterableTable(pParse, pTab) ) goto exit_rename_column;
-  if( SQLITE_OK!=isRealTable(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);
@@ -617,8 +623,8 @@ void sqlite3AlterRenameColumn(
   );
 
   /* Drop and reload the database schema. */
-  renameReloadSchema(pParse, iSchema);
-  renameTestSchema(pParse, zDb, iSchema==1);
+  renameReloadSchema(pParse, iSchema, INITFLAG_AlterRename);
+  renameTestSchema(pParse, zDb, iSchema==1, "after rename");
 
  exit_rename_column:
   sqlite3SrcListDelete(db, pSrc);
@@ -870,23 +876,33 @@ static void renameTokenFree(sqlite3 *db, RenameToken *pToken){
 
 /*
 ** Search the Parse object passed as the first argument for a RenameToken
-** object associated with parse tree element pPtr. If found, remove it
-** from the Parse object and add it to the list maintained by the
-** RenameCtx object passed as the second argument.
+** 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 void renameTokenFind(Parse *pParse, struct RenameCtx *pCtx, void *pPtr){
+static RenameToken *renameTokenFind(
+  Parse *pParse, 
+  struct RenameCtx *pCtx, 
+  void *pPtr
+){
   RenameToken **pp;
   assert( pPtr!=0 );
   for(pp=&pParse->pRename; (*pp); pp=&(*pp)->pNext){
     if( (*pp)->p==pPtr ){
       RenameToken *pToken = *pp;
-      *pp = pToken->pNext;
-      pToken->pNext = pCtx->pList;
-      pCtx->pList = pToken;
-      pCtx->nList++;
-      break;
+      if( pCtx ){
+        *pp = pToken->pNext;
+        pToken->pNext = pCtx->pList;
+        pCtx->pList = pToken;
+        pCtx->nList++;
+      }
+      return pToken;
     }
   }
+  return 0;
 }
 
 /*
@@ -957,7 +973,7 @@ static RenameToken *renameColumnTokenNext(RenameCtx *pCtx){
 */
 static void renameColumnParseError(
   sqlite3_context *pCtx, 
-  int bPost,
+  const char *zWhen,
   sqlite3_value *pType,
   sqlite3_value *pObject,
   Parse *pParse
@@ -966,8 +982,8 @@ static void renameColumnParseError(
   const char *zN = (const char*)sqlite3_value_text(pObject);
   char *zErr;
 
-  zErr = sqlite3_mprintf("error in %s %s%s: %s", 
-      zT, zN, (bPost ? " after rename" : ""),
+  zErr = sqlite3_mprintf("error in %s %s%s%s: %s", 
+      zT, zN, (zWhen[0] ? " " : ""), zWhen,
       pParse->zErrMsg
   );
   sqlite3_result_error(pCtx, zErr, -1);
@@ -1046,7 +1062,7 @@ static int renameParseSql(
   p->eParseMode = PARSE_MODE_RENAME;
   p->db = db;
   p->nQueryLoop = 1;
-  rc = sqlite3RunParser(p, zSql, &zErr);
+  rc = zSql ? sqlite3RunParser(p, zSql, &zErr) : SQLITE_NOMEM;
   assert( p->zErrMsg==0 );
   assert( rc!=SQLITE_OK || zErr==0 );
   p->zErrMsg = zErr;
@@ -1473,7 +1489,7 @@ static void renameColumnFunc(
 renameColumnFunc_done:
   if( rc!=SQLITE_OK ){
     if( sParse.zErrMsg ){
-      renameColumnParseError(context, 0, argv[1], argv[2], &sParse);
+      renameColumnParseError(context, "", argv[1], argv[2], &sParse);
     }else{
       sqlite3_result_error_code(context, rc);
     }
@@ -1662,7 +1678,7 @@ static void renameTableFunc(
     }
     if( rc!=SQLITE_OK ){
       if( sParse.zErrMsg ){
-        renameColumnParseError(context, 0, argv[1], argv[2], &sParse);
+        renameColumnParseError(context, "", argv[1], argv[2], &sParse);
       }else{
         sqlite3_result_error_code(context, rc);
       }
@@ -1691,6 +1707,7 @@ static void renameTableFunc(
 **   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.
 **
 ** Unless it finds an error, this function normally returns NULL. However, it
 ** returns integer value 1 if:
@@ -1708,6 +1725,7 @@ static void renameTableTest(
   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]);
 
 #ifndef SQLITE_OMIT_AUTHORIZATION
   sqlite3_xauth xAuth = db->xAuth;
@@ -1740,8 +1758,8 @@ static void renameTableTest(
       }
     }
 
-    if( rc!=SQLITE_OK ){
-      renameColumnParseError(context, 1, argv[2], argv[3], &sParse);
+    if( rc!=SQLITE_OK && zWhen ){
+      renameColumnParseError(context, zWhen, argv[2], argv[3],&sParse);
     }
     renameParseCleanup(&sParse);
   }
@@ -1751,14 +1769,207 @@ static void renameTableTest(
 #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.
+**  argv[3]: Byte offset of first byte after last column definition in argv[1]
+**
+** 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]);
+  int iAddColOffset = sqlite3_value_int(argv[3]);
+  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
+
+  rc = renameParseSql(&sParse, zDb, db, zSql, iSchema==1);
+  if( rc!=SQLITE_OK ) goto drop_column_done;
+  pTab = sParse.pNewTable;
+  if( 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].zName);
+  if( iCol<pTab->nCol-1 ){
+    RenameToken *pEnd;
+    pEnd = renameTokenFind(&sParse, 0, (void*)pTab->aCol[iCol+1].zName);
+    zEnd = (const char*)pEnd->t.z;
+  }else{
+    zEnd = (const char*)&zSql[iAddColOffset];
+    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, 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: \"%s\"", zCol);
+    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;
+  renameTestSchema(pParse, zDb, iDb==1, "");
+  sqlite3NestedParse(pParse, 
+      "UPDATE \"%w\"." DFLT_SCHEMA_TABLE " SET "
+      "sql = sqlite_drop_column(%d, sql, %d, %d) "
+      "WHERE (type=='table' AND tbl_name=%Q COLLATE nocase)"
+      , zDb, iDb, iCol, pTab->addColOffset, pTab->zName
+  );
+
+  /* Drop and reload the database schema. */
+  renameReloadSchema(pParse, iDb, INITFLAG_AlterDrop);
+  renameTestSchema(pParse, zDb, iDb==1, "after drop column");
+
+  /* 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;
+    pParse->nMem += pTab->nCol;
+    if( HasRowid(pTab) ){
+      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, reg);
+    }else{
+      pPk = sqlite3PrimaryKeyIndex(pTab);
+    }
+    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);
+          regOut = reg+1+iPos-(iPos>iColPos);
+        }else{
+          regOut = reg+1+nField;
+        }
+        sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, i, regOut);
+        nField++;
+      }
+    }
+    regRec = reg + pTab->nCol;
+    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);
+    }
+
+    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,   5, renameTableTest),
+    INTERNAL_FUNCTION(sqlite_rename_column,  9, renameColumnFunc),
+    INTERNAL_FUNCTION(sqlite_rename_table,   7, renameTableFunc),
+    INTERNAL_FUNCTION(sqlite_rename_test,    6, renameTableTest),
+    INTERNAL_FUNCTION(sqlite_drop_column,    4, dropColumnFunc),
   };
   sqlite3InsertBuiltinFuncs(aAlterTableFuncs, ArraySize(aAlterTableFuncs));
 }
diff --git a/src/build.c b/src/build.c
index 3bb084cbf4..bb6610f100 100644
--- a/src/build.c
+++ b/src/build.c
@@ -2641,7 +2641,7 @@ void sqlite3EndTable(
 
     /* Reparse everything to update our internal data structures */
     sqlite3VdbeAddParseSchemaOp(v, iDb,
-           sqlite3MPrintf(db, "tbl_name='%q' AND type!='trigger'", p->zName));
+           sqlite3MPrintf(db, "tbl_name='%q' AND type!='trigger'", p->zName),0);
   }
 
   /* Add the table to the in-memory representation of the database.
@@ -4129,7 +4129,7 @@ void sqlite3CreateIndex(
         sqlite3RefillIndex(pParse, pIndex, iMem);
         sqlite3ChangeCookie(pParse, iDb);
         sqlite3VdbeAddParseSchemaOp(v, iDb,
-            sqlite3MPrintf(db, "name='%q' AND type='index'", pIndex->zName));
+            sqlite3MPrintf(db, "name='%q' AND type='index'", pIndex->zName), 0);
         sqlite3VdbeAddOp2(v, OP_Expire, 0, 1);
       }
 
diff --git a/src/parse.y b/src/parse.y
index 591cde3b9d..82f760ede5 100644
--- a/src/parse.y
+++ b/src/parse.y
@@ -1621,6 +1621,10 @@ cmd ::= ALTER TABLE add_column_fullname
   Y.n = (int)(pParse->sLastToken.z-Y.z) + pParse->sLastToken.n;
   sqlite3AlterFinishAddColumn(pParse, &Y);
 }
+cmd ::= ALTER TABLE fullname(X) DROP kwcolumn_opt nm(Y). {
+  sqlite3AlterDropColumn(pParse, X, &Y);
+}
+
 add_column_fullname ::= fullname(X). {
   disableLookaside(pParse);
   sqlite3AlterBeginAddColumn(pParse, X);
diff --git a/src/prepare.c b/src/prepare.c
index a990350223..dfa20e2b5d 100644
--- a/src/prepare.c
+++ b/src/prepare.c
@@ -21,7 +21,7 @@
 */
 static void corruptSchema(
   InitData *pData,     /* Initialization context */
-  const char *zObj,    /* Object being parsed at the point of error */
+  char **azObj,        /* Type and name of object being parsed */
   const char *zExtra   /* Error information */
 ){
   sqlite3 *db = pData->db;
@@ -29,14 +29,18 @@ static void corruptSchema(
     pData->rc = SQLITE_NOMEM_BKPT;
   }else if( pData->pzErrMsg[0]!=0 ){
     /* A error message has already been generated.  Do not overwrite it */
-  }else if( pData->mInitFlags & INITFLAG_AlterTable ){
-    *pData->pzErrMsg = sqlite3DbStrDup(db, zExtra);
+  }else if( pData->mInitFlags & (INITFLAG_AlterRename|INITFLAG_AlterDrop) ){
+    *pData->pzErrMsg = sqlite3MPrintf(db, 
+        "error in %s %s after %s: %s", azObj[0], azObj[1], 
+        (pData->mInitFlags & INITFLAG_AlterRename) ? "rename" : "drop column",
+        zExtra
+    );
     pData->rc = SQLITE_ERROR;
   }else if( db->flags & SQLITE_WriteSchema ){
     pData->rc = SQLITE_CORRUPT_BKPT;
   }else{
     char *z;
-    if( zObj==0 ) zObj = "?";
+    const char *zObj = azObj[1] ? azObj[1] : "?";
     z = sqlite3MPrintf(db, "malformed database schema (%s)", zObj);
     if( zExtra && zExtra[0] ) z = sqlite3MPrintf(db, "%z - %s", z, zExtra);
     *pData->pzErrMsg = z;
@@ -94,14 +98,14 @@ int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
   db->mDbFlags |= DBFLAG_EncodingFixed;
   pData->nInitRow++;
   if( db->mallocFailed ){
-    corruptSchema(pData, argv[1], 0);
+    corruptSchema(pData, argv, 0);
     return 1;
   }
 
   assert( iDb>=0 && iDb<db->nDb );
   if( argv==0 ) return 0;   /* Might happen if EMPTY_RESULT_CALLBACKS are on */
   if( argv[3]==0 ){
-    corruptSchema(pData, argv[1], 0);
+    corruptSchema(pData, argv, 0);
   }else if( argv[4]
          && 'c'==sqlite3UpperToLower[(unsigned char)argv[4][0]]
          && 'r'==sqlite3UpperToLower[(unsigned char)argv[4][1]] ){
@@ -126,7 +130,7 @@ int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
      || (db->init.newTnum>pData->mxPage && pData->mxPage>0)
     ){
       if( sqlite3Config.bExtraSchemaChecks ){
-        corruptSchema(pData, argv[1], "invalid rootpage");
+        corruptSchema(pData, argv, "invalid rootpage");
       }
     }
     db->init.orphanTrigger = 0;
@@ -145,13 +149,13 @@ int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
         if( rc==SQLITE_NOMEM ){
           sqlite3OomFault(db);
         }else if( rc!=SQLITE_INTERRUPT && (rc&0xFF)!=SQLITE_LOCKED ){
-          corruptSchema(pData, argv[1], sqlite3_errmsg(db));
+          corruptSchema(pData, argv, sqlite3_errmsg(db));
         }
       }
     }
     sqlite3_finalize(pStmt);
   }else if( argv[1]==0 || (argv[4]!=0 && argv[4][0]!=0) ){
-    corruptSchema(pData, argv[1], 0);
+    corruptSchema(pData, argv, 0);
   }else{
     /* If the SQL column is blank it means this is an index that
     ** was created to be the PRIMARY KEY or to fulfill a UNIQUE
@@ -162,7 +166,7 @@ int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
     Index *pIndex;
     pIndex = sqlite3FindIndex(db, argv[1], db->aDb[iDb].zDbSName);
     if( pIndex==0 ){
-      corruptSchema(pData, argv[1], "orphan index");
+      corruptSchema(pData, argv, "orphan index");
     }else
     if( sqlite3GetUInt32(argv[3],&pIndex->tnum)==0
      || pIndex->tnum<2
@@ -170,7 +174,7 @@ int sqlite3InitCallback(void *pInit, int argc, char **argv, char **NotUsed){
      || sqlite3IndexHasDuplicateRootPage(pIndex)
     ){
       if( sqlite3Config.bExtraSchemaChecks ){
-        corruptSchema(pData, argv[1], "invalid rootpage");
+        corruptSchema(pData, argv, "invalid rootpage");
       }
     }
   }
diff --git a/src/select.c b/src/select.c
index 9e275db712..6d5f049f33 100644
--- a/src/select.c
+++ b/src/select.c
@@ -262,7 +262,7 @@ int sqlite3JoinType(Parse *pParse, Token *pA, Token *pB, Token *pC){
 ** Return the index of a column in a table.  Return -1 if the column
 ** is not contained in the table.
 */
-static int columnIndex(Table *pTab, const char *zCol){
+int sqlite3ColumnIndex(Table *pTab, const char *zCol){
   int i;
   u8 h = sqlite3StrIHash(zCol);
   Column *pCol;
@@ -294,7 +294,7 @@ static int tableAndColumnIndex(
 
   assert( (piTab==0)==(piCol==0) );  /* Both or neither are NULL */
   for(i=0; i<N; i++){
-    iCol = columnIndex(pSrc->a[i].pTab, zCol);
+    iCol = sqlite3ColumnIndex(pSrc->a[i].pTab, zCol);
     if( iCol>=0 
      && (bIgnoreHidden==0 || IsHiddenColumn(&pSrc->a[i].pTab->aCol[iCol])==0)
     ){
@@ -504,7 +504,7 @@ static int sqliteProcessJoin(Parse *pParse, Select *p){
         int iRightCol;   /* Column number of matching column on the right */
 
         zName = pList->a[j].zName;
-        iRightCol = columnIndex(pRightTab, zName);
+        iRightCol = sqlite3ColumnIndex(pRightTab, zName);
         if( iRightCol<0
          || !tableAndColumnIndex(pSrc, i+1, zName, &iLeft, &iLeftCol, 0)
         ){
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 811b9665e7..961a6ed86f 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -3716,7 +3716,8 @@ typedef struct {
 /*
 ** Allowed values for mInitFlags
 */
-#define INITFLAG_AlterTable   0x0001  /* This is a reparse after ALTER TABLE */
+#define INITFLAG_AlterRename   0x0001  /* Reparse after a RENAME */
+#define INITFLAG_AlterDrop     0x0002  /* Reparse after a DROP COLUMN */
 
 /*
 ** Structure containing global configuration data for the SQLite library.
@@ -4536,6 +4537,7 @@ void sqlite3MaterializeView(Parse*, Table*, Expr*, ExprList*,Expr*,int);
 #endif
 
 int sqlite3JoinType(Parse*, Token*, Token*, Token*);
+int sqlite3ColumnIndex(Table *pTab, const char *zCol);
 void sqlite3SetJoinExpr(Expr*,int);
 void sqlite3CreateForeignKey(Parse*, ExprList*, Token*, ExprList*, int);
 void sqlite3DeferForeignKey(Parse*, int);
@@ -4720,6 +4722,7 @@ int sqlite3ResolveOrderGroupBy(Parse*, Select*, ExprList*, const char*);
 void sqlite3ColumnDefault(Vdbe *, Table *, int, int);
 void sqlite3AlterFinishAddColumn(Parse *, Token *);
 void sqlite3AlterBeginAddColumn(Parse *, SrcList *);
+void sqlite3AlterDropColumn(Parse*, SrcList*, Token*);
 void *sqlite3RenameTokenMap(Parse*, void*, Token*);
 void sqlite3RenameTokenRemap(Parse*, void *pTo, void *pFrom);
 void sqlite3RenameExprUnmap(Parse*, Expr*);
diff --git a/src/trigger.c b/src/trigger.c
index 1d4c2790c3..689c7c741e 100644
--- a/src/trigger.c
+++ b/src/trigger.c
@@ -356,7 +356,7 @@ void sqlite3FinishTrigger(
     sqlite3DbFree(db, z);
     sqlite3ChangeCookie(pParse, iDb);
     sqlite3VdbeAddParseSchemaOp(v, iDb,
-        sqlite3MPrintf(db, "type='trigger' AND name='%q'", zName));
+        sqlite3MPrintf(db, "type='trigger' AND name='%q'", zName), 0);
   }
 
   if( db->init.busy ){
diff --git a/src/vdbe.c b/src/vdbe.c
index 97cd696de3..153ed40b75 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -6330,7 +6330,7 @@ case OP_ParseSchema: {
   if( pOp->p4.z==0 ){
     sqlite3SchemaClear(db->aDb[iDb].pSchema);
     db->mDbFlags &= ~DBFLAG_SchemaKnownOk;
-    rc = sqlite3InitOne(db, iDb, &p->zErrMsg, INITFLAG_AlterTable);
+    rc = sqlite3InitOne(db, iDb, &p->zErrMsg, pOp->p5);
     db->mDbFlags |= DBFLAG_SchemaChange;
     p->expired = 0;
   }else
diff --git a/src/vdbe.h b/src/vdbe.h
index 17f11fdd77..3257ff68a1 100644
--- a/src/vdbe.h
+++ b/src/vdbe.h
@@ -223,7 +223,7 @@ VdbeOp *sqlite3VdbeAddOpList(Vdbe*, int nOp, VdbeOpList const *aOp,int iLineno);
 #else
 # define sqlite3ExplainBreakpoint(A,B) /*no-op*/
 #endif
-void sqlite3VdbeAddParseSchemaOp(Vdbe*,int,char*);
+void sqlite3VdbeAddParseSchemaOp(Vdbe*, int, char*, u16);
 void sqlite3VdbeChangeOpcode(Vdbe*, int addr, u8);
 void sqlite3VdbeChangeP1(Vdbe*, int addr, int P1);
 void sqlite3VdbeChangeP2(Vdbe*, int addr, int P2);
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index 7ee4f629e0..ede652dfac 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -471,9 +471,10 @@ void sqlite3VdbeExplainPop(Parse *pParse){
 ** The zWhere string must have been obtained from sqlite3_malloc().
 ** This routine will take ownership of the allocated memory.
 */
-void sqlite3VdbeAddParseSchemaOp(Vdbe *p, int iDb, char *zWhere){
+void sqlite3VdbeAddParseSchemaOp(Vdbe *p, int iDb, char *zWhere, u16 p5){
   int j;
   sqlite3VdbeAddOp4(p, OP_ParseSchema, iDb, 0, 0, zWhere, P4_DYNAMIC);
+  sqlite3VdbeChangeP5(p, p5);
   for(j=0; j<p->db->nDb; j++) sqlite3VdbeUsesBtree(p, j);
   sqlite3MayAbort(p->pParse);
 }
diff --git a/src/vtab.c b/src/vtab.c
index 24144902fe..ded12c13bb 100644
--- a/src/vtab.c
+++ b/src/vtab.c
@@ -489,7 +489,7 @@ void sqlite3VtabFinishParse(Parse *pParse, Token *pEnd){
 
     sqlite3VdbeAddOp0(v, OP_Expire);
     zWhere = sqlite3MPrintf(db, "name=%Q AND sql=%Q", pTab->zName, zStmt);
-    sqlite3VdbeAddParseSchemaOp(v, iDb, zWhere);
+    sqlite3VdbeAddParseSchemaOp(v, iDb, zWhere, 0);
     sqlite3DbFree(db, zStmt);
 
     iReg = ++pParse->nMem;
diff --git a/test/alterauth2.test b/test/alterauth2.test
index bd589cda1d..a411408b58 100644
--- a/test/alterauth2.test
+++ b/test/alterauth2.test
@@ -95,4 +95,21 @@ do_auth_test 1.2 {
   {SQLITE_UPDATE sqlite_temp_master sql temp {}}
 }
 
+do_auth_test 1.3 {
+  ALTER TABLE t2 DROP COLUMN c;
+} {
+  {SQLITE_FUNCTION {} like {} {}} 
+  {SQLITE_FUNCTION {} sqlite_drop_column {} {}}
+  {SQLITE_FUNCTION {} sqlite_rename_test {} {}} 
+  {SQLITE_READ sqlite_master name main {}} 
+  {SQLITE_READ sqlite_master sql main {}} 
+  {SQLITE_READ sqlite_master tbl_name main {}} 
+  {SQLITE_READ sqlite_master type main {}} 
+  {SQLITE_READ sqlite_temp_master name temp {}} 
+  {SQLITE_READ sqlite_temp_master sql temp {}} 
+  {SQLITE_READ sqlite_temp_master type temp {}} 
+  {SQLITE_SELECT {} {} {} {}} 
+  {SQLITE_UPDATE sqlite_master sql main {}}
+}
+
 finish_test
diff --git a/test/altercorrupt.test b/test/altercorrupt.test
new file mode 100644
index 0000000000..84a67e281c
--- /dev/null
+++ b/test/altercorrupt.test
@@ -0,0 +1,100 @@
+# 2019-01-11
+#
+# 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.
+#
+#***********************************************************************
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix altercorrupt
+
+database_may_be_corrupt
+
+#--------------------------------------------------------------------------
+reset_db
+do_test 1.0 {
+  sqlite3 db {}
+  db deserialize [decode_hexdb {
+.open --hexdb
+| size 24576 pagesize 4096 filename crash-685346d89b5e5f.db
+| page 1 offset 0
+|      0: 53 51 4c 69 74 65 20 66 6f 72 6d 61 74 20 33 00   SQLite format 3.
+|     16: 10 00 01 01 00 40 20 20 00 00 00 00 00 00 00 06   .....@  ........
+|     32: 00 00 63 00 00 05 f0 00 00 00 00 04 10 00 00 04   ..c.............
+|     48: 00 00 00 00 00 00 0f f0 00 00 00 01 00 00 00 00   ................
+|     64: 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
+|     96: 00 00 00 00 0d 0f f8 00 05 0e cf 00 0f 79 0f d3   .............y..
+|    112: 0f 2e 0e f3 0e cf 00 00 00 00 00 00 00 00 00 00   ................
+|   3776: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 22   ................
+|   3792: 05 06 17 11 11 01 31 74 61 62 6c 65 74 34 74 34   ......1tablet4t4
+|   3808: 06 43 52 45 41 54 45 20 54 41 42 4c 45 20 74 34   .CREATE TABLE t4
+|   3824: 28 7a 29 39 04 06 17 11 11 01 5f 74 61 62 6c 65   (z)9......_table
+|   3840: 74 33 74 33 05 43 52 45 41 54 45 20 54 41 42 4c   t3t3.CREATE TABL
+|   3856: 45 20 74 33 28 78 20 49 4e 54 45 47 45 52 20 50   E t3(x INTEGER P
+|   3872: 52 49 4d 41 52 59 20 4b 45 59 2c 20 79 29 49 03   RIMARY KEY, y)I.
+|   3888: 06 17 11 11 01 7f 74 61 62 6c 65 74 32 74 32 04   ......tablet2t2.
+|   3904: 43 52 45 41 54 45 20 54 41 42 4c 45 20 74 32 28   CREATE TABLE t2(
+|   3920: 61 2c 62 2c 63 20 50 52 49 4d 41 52 59 20 4b 45   a,b,c PRIMARY KE
+|   3936: 59 2c 20 64 2c 20 65 2c 20 66 29 20 57 49 54 48   Y, d, e, f) WITH
+|   3952: 4f 55 54 20 52 4f 57 49 44 58 03 07 17 11 11 01   OUT ROWIDX......
+|   3968: 81 1b 74 61 62 6c 65 74 31 74 31 02 43 52 45 41   ..tablet1t1.CREA
+|   3984: 54 45 20 54 41 42 4c 45 20 74 31 28 61 2c 62 2c   TE TABLE t1(a,b,
+|   4000: 63 20 41 53 20 28 2d 62 29 20 56 49 52 54 55 41   c AS (-b) VIRTUA
+|   4016: 4c 2c 64 20 43 48 45 43 4b 28 64 3e 35 29 2c 65   L,d CHECK(d>5),e
+|   4032: 20 55 4e 49 51 55 45 2c 20 66 20 41 53 20 28 2b    UNIQUE, f AS (+
+|   4048: 62 29 29 23 02 06 17 37 11 01 00 69 6e 64 65 78   b))#...7...index
+|   4064: 73 71 6c 69 74 65 5f 61 75 74 6f 69 6e 64 65 78   sqlite_autoindex
+|   4080: 5f 74 31 5f 31 74 31 03 00 00 00 08 00 00 00 00   _t1_1t1.........
+| page 2 offset 4096
+|      0: 0d 00 00 00 0a 0f 93 00 0f f6 0f eb 0f e0 0f d5   ................
+|     16: 0f ca 0f 8f 0f b4 0f a9 0f 9e 0f 93 00 00 00 00   ................
+|   3984: 00 00 00 09 0a 05 01 01 01 01 0a 64 6e 14 09 09   ...........dn...
+|   4000: 05 01 01 01 01 09 5a 6d 12 09 08 05 01 01 01 01   ......Zm........
+|   4016: 08 50 6c 10 09 07 05 01 01 01 01 07 46 6b 0e 09   .Pl.........Fk..
+|   4032: 06 05 01 01 01 01 06 3c 6a 0c 09 05 05 01 01 01   .......<j.......
+|   4048: 01 05 32 69 0a 09 04 05 01 01 01 01 04 28 68 08   ..2i.........(h.
+|   4064: 09 03 05 01 01 01 01 03 1e 67 06 09 02 05 01 01   .........g......
+|   4080: 01 01 02 14 66 04 08 01 05 09 01 01 01 0a 65 02   ....f.........e.
+| page 3 offset 8192
+|      0: 0a 00 00 00 0a 0f c5 00 0f fb 0f f5 0f ef 0f e9   ................
+|     16: 0f e3 0f dd 0f d7 0f d1 0f cb 0f c5 00 00 00 00   ................
+|   4032: 00 00 00 00 00 05 03 01 01 14 0a 05 03 01 01 12   ................
+|   4048: 09 05 03 01 01 10 08 05 03 01 01 0e 07 05 03 01   ................
+|   4064: 01 0c 06 05 03 01 01 0a 05 05 03 01 01 08 04 05   ................
+|   4080: 03 01 01 06 03 05 03 01 01 04 02 04 03 01 09 02   ................
+| page 4 offset 12288
+|      0: 0a 00 00 00 0a 0f 75 00 0f 75 0f 83 0f 91 0f 9f   ......u..u......
+|     16: 0f ad 0f bb 0f 00 00 00 00 00 00 00 00 00 00 00   ................
+|   3952: 00 00 00 00 00 0d 07 01 01 01 01 01 01 9c 0a 64   ...............d
+|   3968: 6e 14 64 0d 07 02 01 01 01 01 01 a6 09 5a 6d 12   n.d..........Zm.
+|   3984: 5a 0d 07 01 01 01 01 01 01 b0 08 50 6c 10 50 0d   Z..........Pl.P.
+|   4000: 07 01 01 01 01 01 01 ba 07 46 6b 0e 46 0d 07 01   .........Fk.F...
+|   4016: 01 01 01 01 01 c4 06 3c 6a 0c 3c 0d 07 01 01 01   .......<j.<.....
+|   4032: 01 01 01 ce 05 32 69 0a 32 0d 07 01 01 01 01 01   .....2i.2.......
+|   4048: 01 d8 04 28 68 08 28 0d 07 01 01 01 01 01 01 e2   ...(h.(.........
+|   4064: 03 1e 67 06 1e 0d 07 01 01 01 01 01 01 ec 02 14   ..g.............
+|   4080: 66 04 14 0c 07 01 09 01 01 01 01 f6 0a 65 02 0a   f............e..
+| page 5 offset 16384
+|      0: 0d 00 00 00 03 0f e9 00 0f e9 0f fb 0f f6 00 00   ................
+|     16: 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00   ................
+|   4064: 00 00 00 00 00 00 00 00 00 03 ff ff ff ff ff ff   ................
+|   4080: ff ff 9c 03 00 00 03 64 03 00 00 03 01 03 00 00   .......d........
+| page 6 offset 20480
+|      0: 0d 00 00 00 00 10 00 00 00 00 00 00 00 00 00 00   ................
+| end crash-685346d89b5e5f.db
+}]} {}
+
+do_execsql_test 1.1 {
+  ALTER TABLE t2 DROP COLUMN e;
+}
+do_catchsql_test 1.2 {
+  ALTER TABLE t1 DROP COLUMN f;
+} {1 {database disk image is malformed}}
+
+finish_test
diff --git a/test/alterdropcol.test b/test/alterdropcol.test
new file mode 100644
index 0000000000..1087f66328
--- /dev/null
+++ b/test/alterdropcol.test
@@ -0,0 +1,258 @@
+# 2021 February 16
+#
+# 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.
+#
+#*************************************************************************
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix alterdropcol
+
+# If SQLITE_OMIT_ALTERTABLE is defined, omit this file.
+ifcapable !altertable {
+  finish_test
+  return
+}
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(a, b, c);
+  CREATE VIEW v1 AS SELECT * FROM t1;
+
+  CREATE TABLE t2(x INTEGER PRIMARY KEY, y, z UNIQUE);
+  CREATE INDEX t2y ON t2(y);
+
+  CREATE TABLE t3(q, r, s);
+  CREATE INDEX t3rs ON t3(r+s);
+}
+
+do_catchsql_test 1.1 {
+  ALTER TABLE nosuch DROP COLUMN z;
+} {1 {no such table: nosuch}}
+
+do_catchsql_test 1.2 {
+  ALTER TABLE v1 DROP COLUMN c;
+} {1 {cannot drop column from view "v1"}}
+
+ifcapable fts5 {
+  do_execsql_test 1.3.1 {
+    CREATE VIRTUAL TABLE ft1 USING fts5(one, two);
+  }
+  do_catchsql_test 1.3.2 {
+    ALTER TABLE ft1 DROP COLUMN two;
+  } {1 {cannot drop column from virtual table "ft1"}}
+}
+
+do_catchsql_test 1.4 {
+  ALTER TABLE sqlite_schema DROP COLUMN sql;
+} {1 {table sqlite_master may not be altered}}
+
+do_catchsql_test 1.5 {
+  ALTER TABLE t1 DROP COLUMN d;
+} {1 {no such column: "d"}}
+
+do_execsql_test 1.6.1 {
+  ALTER TABLE t1 DROP COLUMN b;
+}
+do_execsql_test 1.6.2 {
+  SELECT sql FROM sqlite_schema WHERE name = 't1'
+} {{CREATE TABLE t1(a, c)}}
+
+do_execsql_test 1.7.1 {
+  ALTER TABLE t1 DROP COLUMN c;
+}
+do_execsql_test 1.7.2 {
+  SELECT sql FROM sqlite_schema WHERE name = 't1'
+} {{CREATE TABLE t1(a)}}
+
+do_catchsql_test 1.7.3 {
+  ALTER TABLE t1 DROP COLUMN a;
+} {1 {cannot drop column "a": no other columns exist}}
+
+
+do_catchsql_test 1.8 {
+  ALTER TABLE t2 DROP COLUMN z
+} {1 {cannot drop UNIQUE column: "z"}}
+
+do_catchsql_test 1.9 {
+  ALTER TABLE t2 DROP COLUMN x
+} {1 {cannot drop PRIMARY KEY column: "x"}}
+
+do_catchsql_test 1.10 {
+  ALTER TABLE t2 DROP COLUMN y
+} {1 {error in index t2y after drop column: no such column: y}}
+
+do_catchsql_test 1.11 {
+  ALTER TABLE t3 DROP COLUMN s
+} {1 {error in index t3rs after drop column: no such column: s}}
+
+#-------------------------------------------------------------------------
+
+foreach {tn wo} {
+  1 {}
+  2 {WITHOUT ROWID}
+} { eval [string map [list %TN% $tn %WO% $wo] {
+
+  reset_db
+  do_execsql_test 2.%TN%.0 {
+    CREATE TABLE t1(x, y INTEGER PRIMARY KEY, z) %WO% ;
+    INSERT INTO t1 VALUES(1, 2, 3);
+    INSERT INTO t1 VALUES(4, 5, 6);
+    INSERT INTO t1 VALUES(7, 8, 9);
+  }
+  
+  do_execsql_test 2.%TN%.1 {
+    ALTER TABLE t1 DROP COLUMN x;
+    SELECT * FROM t1;
+  } {
+    2 3  5 6  8 9
+  }
+  do_execsql_test 2.%TN%.2 {
+    ALTER TABLE t1 DROP COLUMN z;
+    SELECT * FROM t1;
+  } {
+    2 5 8
+  }
+}]}
+
+#-------------------------------------------------------------------------
+reset_db
+
+do_execsql_test 3.0 {
+  CREATE TABLE t12(a, b, c, CHECK(c>10));
+  CREATE TABLE t13(a, b, c CHECK(c>10));
+}
+do_catchsql_test 3.1 {
+  ALTER TABLE t12 DROP COLUMN c;
+} {1 {error in table t12 after drop column: no such column: c}}
+
+do_catchsql_test 3.2 {
+  ALTER TABLE t13 DROP COLUMN c;
+} {0 {}}
+
+#-------------------------------------------------------------------------
+# Test that generated columns can be dropped. And that other columns from
+# tables that contain generated columns can be dropped.
+#
+foreach {tn wo vs} {
+  1 ""              ""
+  2 ""              VIRTUAL
+  3 ""              STORED
+  4 "WITHOUT ROWID" STORED
+  5 "WITHOUT ROWID" VIRTUAL
+} {
+  reset_db
+
+  do_execsql_test 4.$tn.0 "
+    CREATE TABLE 'my table'(a, b PRIMARY KEY, c AS (a+b) $vs, d) $wo
+  "
+  do_execsql_test 4.$tn.1 {
+    INSERT INTO "my table"(a, b, d) VALUES(1, 2, 'hello');
+    INSERT INTO "my table"(a, b, d) VALUES(3, 4, 'world');
+
+    SELECT * FROM "my table"
+  } {
+    1 2 3 hello
+    3 4 7 world
+  }
+
+  do_execsql_test 4.$tn.2 {
+    ALTER TABLE "my table" DROP COLUMN c;
+  }
+  do_execsql_test 4.$tn.3 {
+    SELECT * FROM "my table"
+  } {
+    1 2 hello
+    3 4 world
+  }
+  
+  do_execsql_test 4.$tn.4 "
+    CREATE TABLE x1(a, b, c PRIMARY KEY, d AS (b+c) $vs, e) $wo
+  "
+  do_execsql_test 4.$tn.5 {
+    INSERT INTO x1(a, b, c, e) VALUES(1, 2, 3, 4);
+    INSERT INTO x1(a, b, c, e) VALUES(5, 6, 7, 8);
+    INSERT INTO x1(a, b, c, e) VALUES(9, 10, 11, 12);
+    SELECT * FROM x1;
+  } {
+    1 2 3 5 4
+    5 6 7 13 8
+    9 10 11 21 12
+  }
+
+  do_execsql_test 4.$tn.6 {
+    ALTER TABLE x1 DROP COLUMN a
+  }
+  do_execsql_test 4.$tn.7 {
+    SELECT * FROM x1
+  } {
+    2 3 5 4
+    6 7 13 8
+    10 11 21 12
+  }
+  do_execsql_test 4.$tn.8 {
+    ALTER TABLE x1 DROP COLUMN e
+  }
+  do_execsql_test 4.$tn.9 {
+    SELECT * FROM x1
+  } {
+    2 3 5
+    6 7 13
+    10 11 21
+  }
+}
+
+#-------------------------------------------------------------------------
+reset_db
+do_execsql_test 5.0 {
+  CREATE TABLE p1(a PRIMARY KEY, b UNIQUE);
+  CREATE TABLE c1(x, y, z REFERENCES p1(c));
+  CREATE TABLE c2(x, y, z, w REFERENCES p1(b));
+}
+do_execsql_test 5.1 {
+  ALTER TABLE c1 DROP COLUMN z;
+  ALTER TABLE c2 DROP COLUMN z;
+  SELECT sql FROM sqlite_schema WHERE name IN ('c1', 'c2');
+} {
+  {CREATE TABLE c1(x, y)} 
+  {CREATE TABLE c2(x, y, w REFERENCES p1(b))}
+}
+
+do_execsql_test 5.2.1 {
+  CREATE VIEW v1 AS SELECT d, e FROM p1
+}
+do_catchsql_test 5.2.2 {
+  ALTER TABLE c1 DROP COLUMN x
+} {1 {error in view v1: no such column: d}}
+do_execsql_test 5.3.1 {
+  DROP VIEW v1;
+  CREATE VIEW v1 AS SELECT x, y FROM c1;
+}
+do_catchsql_test 5.3.2 {
+  ALTER TABLE c1 DROP COLUMN x
+} {1 {error in view v1 after drop column: no such column: x}}
+
+do_execsql_test 5.4.1 {
+  CREATE TRIGGER tr AFTER INSERT ON c1 BEGIN
+    INSERT INTO p1 VALUES(new.y, new.xyz);
+  END;
+}
+do_catchsql_test 5.4.2 {
+  ALTER TABLE c1 DROP COLUMN y
+} {1 {error in trigger tr: no such column: new.xyz}}
+do_execsql_test 5.5.1 {
+  DROP TRIGGER tr;
+  CREATE TRIGGER tr AFTER INSERT ON c1 BEGIN
+    INSERT INTO p1 VALUES(new.y, new.z);
+  END;
+}
+do_catchsql_test 5.5.2 {
+  ALTER TABLE c1 DROP COLUMN y
+} {1 {error in trigger tr: no such column: new.z}}
+
+finish_test
diff --git a/test/alterlegacy.test b/test/alterlegacy.test
index 47d8bcfba9..dfa1716467 100644
--- a/test/alterlegacy.test
+++ b/test/alterlegacy.test
@@ -40,7 +40,7 @@ do_execsql_test 1.1 {
 # slightly different - it rejects the change and rolls back the transaction.
 do_catchsql_test 1.2 {
   ALTER TABLE t1 RENAME TO t1new;
-} {1 {no such column: t1.a}}
+} {1 {error in table t1new after rename: no such column: t1.a}}
 
 do_execsql_test 1.3 {
   CREATE TABLE t3(c, d);
@@ -59,7 +59,7 @@ do_execsql_test 1.4 {
 
 do_catchsql_test 1.3 {
   ALTER TABLE t2 RENAME TO t2new;
-} {1 {no such column: t2.b}}
+} {1 {error in index t2expr after rename: no such column: t2.b}}
 do_execsql_test 1.4 {
   SELECT sql FROM sqlite_master
 } {
diff --git a/test/altermalloc3.test b/test/altermalloc3.test
new file mode 100644
index 0000000000..d84f6bbc94
--- /dev/null
+++ b/test/altermalloc3.test
@@ -0,0 +1,40 @@
+# 2021 February 18
+#
+# 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.
+#
+#*************************************************************************
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+source $testdir/malloc_common.tcl
+set testprefix altermalloc3
+
+# If SQLITE_OMIT_ALTERTABLE is defined, omit this file.
+ifcapable !altertable {
+  finish_test
+  return
+}
+
+do_execsql_test 1.0 {
+  CREATE TABLE t1(a, b, c, d, PRIMARY KEY(d, b)) WITHOUT ROWID;
+  INSERT INTO t1 VALUES(1, 2, 3, 4);
+}
+faultsim_save_and_close
+
+do_faultsim_test 1 -prep {
+  faultsim_restore_and_reopen
+} -body {
+  execsql { ALTER TABLE t1 DROP COLUMN c }
+} -test {
+  faultsim_test_result {0 {}}
+}
+
+
+finish_test
+
diff --git a/test/fts4rename.test b/test/fts4rename.test
index c647d6928e..5571ea7b15 100644
--- a/test/fts4rename.test
+++ b/test/fts4rename.test
@@ -29,7 +29,7 @@ do_execsql_test 1.0 {
 
 do_catchsql_test 1.1 {
   ALTER TABLE t1_content RENAME c0a TO docid;
-} {1 {duplicate column name: docid}}
+} {1 {error in table t1_content after rename: duplicate column name: docid}}
 
 do_catchsql_test 1.2 {
   UPDATE t1 SET Col0 = 1 ;