Index: src/build.c
==================================================================
--- src/build.c
+++ src/build.c
@@ -1926,10 +1926,14 @@
     for(i=0, j=pIdx->nKeyCol; i<nPk; i++){
       if( !isDupColumn(pIdx, pIdx->nKeyCol, pPk, i) ){
         testcase( hasColumn(pIdx->aiColumn, pIdx->nKeyCol, pPk->aiColumn[i]) );
         pIdx->aiColumn[j] = pPk->aiColumn[i];
         pIdx->azColl[j] = pPk->azColl[i];
+        if( pPk->aSortOrder[i] ){
+          /* See ticket https://www.sqlite.org/src/info/bba7b69f9849b5bf */
+          pIdx->bAscKeyBug = 1;
+        }
         j++;
       }
     }
     assert( pIdx->nColumn>=pIdx->nKeyCol+n );
     assert( pIdx->nColumn>=j );
@@ -3047,11 +3051,20 @@
     sqlite3VdbeJumpHere(v, j2);
   }else{
     addr2 = sqlite3VdbeCurrentAddr(v);
   }
   sqlite3VdbeAddOp3(v, OP_SorterData, iSorter, regRecord, iIdx);
-  sqlite3VdbeAddOp1(v, OP_SeekEnd, iIdx);
+  if( !pIndex->bAscKeyBug ){
+    /* This OP_SeekEnd opcode makes index insert for a REINDEX go much
+    ** faster by avoiding unnecessary seeks.  But the optimization does
+    ** not work for UNIQUE constraint indexes on WITHOUT ROWID tables
+    ** with DESC primary keys, since those indexes have there keys in
+    ** a different order from the main table.
+    ** See ticket: https://www.sqlite.org/src/info/bba7b69f9849b5bf
+    */
+    sqlite3VdbeAddOp1(v, OP_SeekEnd, iIdx);
+  }
   sqlite3VdbeAddOp2(v, OP_IdxInsert, iIdx, regRecord);
   sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
   sqlite3ReleaseTempReg(pParse, regRecord);
   sqlite3VdbeAddOp2(v, OP_SorterNext, iSorter, addr2); VdbeCoverage(v);
   sqlite3VdbeJumpHere(v, addr1);

Index: src/sqliteInt.h
==================================================================
--- src/sqliteInt.h
+++ src/sqliteInt.h
@@ -2251,10 +2251,11 @@
   unsigned isResized:1;    /* True if resizeIndexObject() has been called */
   unsigned isCovering:1;   /* True if this is a covering index */
   unsigned noSkipScan:1;   /* Do not try to use skip-scan if true */
   unsigned hasStat1:1;     /* aiRowLogEst values come from sqlite_stat1 */
   unsigned bNoQuery:1;     /* Do not use this index to optimize queries */
+  unsigned bAscKeyBug:1;   /* True if the bba7b69f9849b5bf bug applies */
 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
   int nSample;             /* Number of elements in aSample[] */
   int nSampleCol;          /* Size of IndexSample.anEq[] and so on */
   tRowcnt *aAvgEq;         /* Average nEq values for keys not in aSample */
   IndexSample *aSample;    /* Samples of the left-most key */

Index: test/without_rowid1.test
==================================================================
--- test/without_rowid1.test
+++ test/without_rowid1.test
@@ -397,7 +397,17 @@
   CREATE INDEX t11a ON t11(a COLLATE NOCASE);
   INSERT INTO t11(a,b) VALUES ('A',1),('a',2);
   PRAGMA integrity_check;
   SELECT a FROM t11 ORDER BY a COLLATE binary;
 } {ok A a}
+
+# 2019-05-13 ticket https://www.sqlite.org/src/info/bba7b69f9849b5b
+do_execsql_test 12.1 {
+  DROP TABLE IF EXISTS t0;
+  CREATE TABLE t0 (c0 INTEGER PRIMARY KEY DESC, c1 UNIQUE DEFAULT NULL) WITHOUT ROWID;
+  INSERT INTO t0(c0) VALUES (1), (2), (3), (4), (5);
+  REINDEX;
+  PRAGMA integrity_check;
+} {ok}
+
   
 finish_test