Index: src/alter.c
==================================================================
--- src/alter.c
+++ src/alter.c
@@ -959,11 +959,10 @@
   p->db = db;
   p->nQueryLoop = 1;
   rc = sqlite3RunParser(p, zSql, &zErr);
   assert( p->zErrMsg==0 );
   assert( rc!=SQLITE_OK || zErr==0 );
-  assert( (0!=p->pNewTable) + (0!=p->pNewIndex) + (0!=p->pNewTrigger)<2 );
   p->zErrMsg = zErr;
   if( db->mallocFailed ) rc = SQLITE_NOMEM;
   if( rc==SQLITE_OK 
    && p->pNewTable==0 && p->pNewIndex==0 && p->pNewTrigger==0 
   ){
@@ -1179,15 +1178,19 @@
 ** 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);
-  if( pParse->pNewIndex ) sqlite3FreeIndex(db, pParse->pNewIndex);
+  while( (pIdx = pParse->pNewIndex)!=0 ){
+    pParse->pNewIndex = pIdx->pNext;
+    sqlite3FreeIndex(db, pIdx);
+  }
   sqlite3DeleteTrigger(db, pParse->pNewTrigger);
   sqlite3DbFree(db, pParse->zErrMsg);
   renameTokenFree(db, pParse->pRename);
   sqlite3ParserReset(pParse);
 }
@@ -1293,10 +1296,13 @@
           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);
         }
       }
 
       for(pFKey=sParse.pNewTable->pFKey; pFKey; pFKey=pFKey->pNextFrom){
         for(i=0; i<pFKey->nCol; i++){

Index: src/build.c
==================================================================
--- src/build.c
+++ src/build.c
@@ -3465,10 +3465,15 @@
           if( pIdx->onError==OE_Default ){
             pIdx->onError = pIndex->onError;
           }
         }
         if( idxType==SQLITE_IDXTYPE_PRIMARYKEY ) pIdx->idxType = idxType;
+        if( IN_RENAME_OBJECT ){
+          pIndex->pNext = pParse->pNewIndex;
+          pParse->pNewIndex = pIndex;
+          pIndex = 0;
+        }
         goto exit_create_index;
       }
     }
   }
 

Index: src/sqliteInt.h
==================================================================
--- src/sqliteInt.h
+++ src/sqliteInt.h
@@ -3132,11 +3132,13 @@
 #endif
   VList *pVList;            /* Mapping between variable names and numbers */
   Vdbe *pReprepare;         /* VM being reprepared (sqlite3Reprepare()) */
   const char *zTail;        /* All SQL text past the last semicolon parsed */
   Table *pNewTable;         /* A table being constructed by CREATE TABLE */
-  Index *pNewIndex;         /* An index being constructed by CREATE INDEX */
+  Index *pNewIndex;         /* An index being constructed by CREATE INDEX.
+                            ** Also used to hold redundant UNIQUE constraints
+                            ** during a RENAME COLUMN */
   Trigger *pNewTrigger;     /* Trigger under construct by a CREATE TRIGGER */
   const char *zAuthContext; /* The 6th parameter to db->xAuth callbacks */
 #ifndef SQLITE_OMIT_VIRTUALTABLE
   Token sArg;               /* Complete text of a module argument */
   Table **apVtabLock;       /* Pointer to virtual tables needing locking */

Index: test/altercol.test
==================================================================
--- test/altercol.test
+++ test/altercol.test
@@ -776,8 +776,34 @@
   SELECT sql FROM sqlite_master WHERE name = 'v2';
 } {
   {CREATE VIEW v2(e) AS SELECT coalesce(t2.c,t1.f) FROM t1, t2 WHERE t1.b=t2.d}
 }
 
+# 2019-01-08: https://www.sqlite.org/src/tktview/bc8d94f0fbd633fd9a051e3
+#
+# ALTER TABLE RENAME COLUMN does not work for tables that have redundant
+# UNIQUE constraints.
+#
+sqlite3 db :memory:
+do_execsql_test 20.100 {
+  CREATE TABLE t1(aaa,b,c,UNIQUE(aaA),PRIMARY KEY(aAa),UNIQUE(aAA));
+  ALTER TABLE t1 RENAME aaa TO bbb;
+  SELECT sql FROM sqlite_master WHERE name='t1';
+} {{CREATE TABLE t1(bbb,b,c,UNIQUE(bbb),PRIMARY KEY(bbb),UNIQUE(bbb))}}
+do_execsql_test 20.105 {
+  DROP TABLE t1;
+  CREATE TABLE t1(aaa,b,c,UNIQUE(aaA),PRIMARY KEY(aAa),UNIQUE(aAA))WITHOUT ROWID;
+  ALTER TABLE t1 RENAME aaa TO bbb;
+  SELECT sql FROM sqlite_master WHERE name='t1';
+} {{CREATE TABLE t1(bbb,b,c,UNIQUE(bbb),PRIMARY KEY(bbb),UNIQUE(bbb))WITHOUT ROWID}}
+do_execsql_test 20.110 {
+  DROP TABLE t1;
+  CREATE TABLE t1(aa UNIQUE,bb UNIQUE,cc UNIQUE,UNIQUE(aA),PRIMARY KEY(bB),UNIQUE(cC));
+  ALTER TABLE t1 RENAME aa TO xx;
+  ALTER TABLE t1 RENAME bb TO yy;
+  ALTER TABLE t1 RENAME cc TO zz;
+  SELECT sql FROM sqlite_master WHERE name='t1';
+} {{CREATE TABLE t1(xx UNIQUE,yy UNIQUE,zz UNIQUE,UNIQUE(xx),PRIMARY KEY(yy),UNIQUE(zz))}}
+
 
 
 finish_test