diff --git a/manifest b/manifest
index 7252ec3ac5..0a8a624dbd 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Merge\sthe\slatest\strunk\schanges\sinto\sthe\sthreads\sbranch.
-D 2014-05-09T15:00:32.924
+C In\sthe\ssorter,\sonly\suse\slarge\smemory\sallocations\sif\sscratch\smemory\shas\snot\nbeen\sconfigured.\s\sAdd\s#ifdefs\sto\sdisable\sunused\scode\swhen\s\nSQLITE_MAX_WORKER_THREADS\sis\szero.\s\sOther\ssorter\schanges\sin\ssupport\nof\stestability.
+D 2014-05-12T15:30:00.944
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in de92112472618cb869d27249966bad1783e4a853
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -187,7 +187,7 @@ F src/journal.c b4124532212b6952f42eb2c12fa3c25701d8ba8d
 F src/legacy.c 0df0b1550b9cc1f58229644735e317ac89131f12
 F src/lempar.c cdf0a000315332fc9b50b62f3b5e22e080a0952b
 F src/loadext.c 867c7b330b740c6c917af9956b13b81d0a048303
-F src/main.c 2ba4f6eeb84cf8efd8bb632c1abe203dc86adcac
+F src/main.c 274a72f5de174a8eb20d01bbd83393347c092592
 F src/malloc.c 0203ebce9152c6a0e5de520140b8ba65187350be
 F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
 F src/mem1.c c0c990fcaddff810ea277b4fb5d9138603dd5d4b
@@ -289,7 +289,7 @@ F src/vdbeapi.c 0ed6053f947edd0b30f64ce5aeb811872a3450a4
 F src/vdbeaux.c 44d4d1f5711f71eaf0d624de5c3e4976fe4e180b
 F src/vdbeblob.c 9205ce9d3b064d9600f8418a897fc88b5687d9ac
 F src/vdbemem.c 6fc77594c60f6155404f3f8d71bf36d1fdeb4447
-F src/vdbesort.c b36070436d33372237541e9eaa6068e1a61bc402
+F src/vdbesort.c 0daa029978b50d9c1d103d179ac1e2b38d9daa20
 F src/vdbetrace.c 6f52bc0c51e144b7efdcfb2a8f771167a8816767
 F src/vtab.c 21b932841e51ebd7d075e2d0ad1415dce8d2d5fd
 F src/wal.c 76e7fc6de229bea8b30bb2539110f03a494dc3a8
@@ -1175,7 +1175,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh d1a6de74685f360ab718efda6265994b99bbea01
 F tool/win/sqlite.vsix a94fb9b1b1ef06efc2898975cdfcfa9643731f5e
-P ee0ab09c80a648e9202757fc04122952375e7c8c 116bed5af664899a73b46dca528ac0c021fc50c3
-R e8e0d3ce5fd31e02042e8e0c64134243
-U dan
-Z b9842070469fd517448a2bc084149835
+P 9ac8f1e7115bc50663235adedeb0d3e1234c5740
+R 6fb72f0b0bf6c011a8428254c9753d68
+U drh
+Z 8d87c7cf2c9f964aeaecc8906e4a1927
diff --git a/manifest.uuid b/manifest.uuid
index cc8556fc36..695d315026 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-9ac8f1e7115bc50663235adedeb0d3e1234c5740
\ No newline at end of file
+d7e2b0d9cb099eda3341bc934bedff9facfe88bd
\ No newline at end of file
diff --git a/src/main.c b/src/main.c
index d76bcb607e..4f8a128508 100644
--- a/src/main.c
+++ b/src/main.c
@@ -516,9 +516,11 @@ int sqlite3_config(int op, ...){
 #endif
 
     case SQLITE_CONFIG_WORKER_THREADS: {
+#if SQLITE_MAX_WORKER_THREADS>0
       int n = va_arg(ap, int);
       if( n>SQLITE_MAX_WORKER_THREADS ) n = SQLITE_MAX_WORKER_THREADS;
       if( n>=0 ) sqlite3GlobalConfig.nWorker = n;
+#endif
       break;
     }
 
diff --git a/src/vdbesort.c b/src/vdbesort.c
index 9c57135dd3..01404e4f12 100644
--- a/src/vdbesort.c
+++ b/src/vdbesort.c
@@ -449,7 +449,7 @@ static void vdbePmaReaderClear(PmaReader *pIter){
   sqlite3_free(pIter->aAlloc);
   sqlite3_free(pIter->aBuffer);
   if( pIter->aMap ) sqlite3OsUnfetch(pIter->pFile, 0, pIter->aMap);
-  if( pIter->pIncr ) vdbeIncrFree(pIter->pIncr);
+  vdbeIncrFree(pIter->pIncr);
   memset(pIter, 0, sizeof(PmaReader));
 }
 
@@ -828,7 +828,11 @@ int sqlite3VdbeSorterInit(
   int szKeyInfo;                  /* Size of pCsr->pKeyInfo in bytes */
   int sz;                         /* Size of pSorter in bytes */
   int rc = SQLITE_OK;
+#if SQLITE_MAX_WORKER_THREADS==0
+  const int nWorker = 0;
+#else
   int nWorker = (sqlite3GlobalConfig.bCoreMutex?sqlite3GlobalConfig.nWorker:0);
+#endif
 
   assert( pCsr->pKeyInfo && pCsr->pBt==0 );
   szKeyInfo = sizeof(KeyInfo) + (pCsr->pKeyInfo->nField-1)*sizeof(CollSeq*);
@@ -858,10 +862,13 @@ int sqlite3VdbeSorterInit(
       if( mxCache<SORTER_MIN_WORKING ) mxCache = SORTER_MIN_WORKING;
       pSorter->mxPmaSize = mxCache * pgsz;
 
-      /* If the application is using memsys3 or memsys5, use a separate 
-      ** allocation for each sort-key in memory. Otherwise, use a single big
-      ** allocation at pSorter->aMemory for all sort-keys.  */
-      if( sqlite3GlobalConfig.pHeap==0 ){
+      /* If the application has not configure scratch memory using
+      ** SQLITE_CONFIG_SCRATCH then we assume it is OK to do large memory
+      ** allocations.  If scratch memory has been configured, then assume
+      ** large memory allocations should be avoided to prevent heap
+      ** fragmentation.
+      */
+      if( sqlite3GlobalConfig.pScratch==0 ){
         assert( pSorter->iMemory==0 );
         pSorter->nMemory = pgsz;
         pSorter->list.aMemory = (u8*)sqlite3Malloc(pgsz);
@@ -1921,7 +1928,15 @@ static int vdbePmaReaderIncrInit(PmaReader *pIter, int eMode){
     ** only requires a region of pTask->file2. */
     if( rc==SQLITE_OK ){
       int mxSz = pIncr->mxSz;
-      if( pIncr->bUseThread==0 ){
+#if SQLITE_MAX_WORKER_THREADS>0
+      if( pIncr->bUseThread ){
+        rc = vdbeSorterOpenTempFile(db, mxSz, &pIncr->aFile[0].pFd);
+        if( rc==SQLITE_OK ){
+          rc = vdbeSorterOpenTempFile(db, mxSz, &pIncr->aFile[1].pFd);
+        }
+      }else
+#endif
+      /*if( !pIncr->bUseThread )*/{
         if( pTask->file2.pFd==0 ){
           assert( pTask->file2.iEof>0 );
           rc = vdbeSorterOpenTempFile(db, pTask->file2.iEof, &pTask->file2.pFd);
@@ -1932,14 +1947,10 @@ static int vdbePmaReaderIncrInit(PmaReader *pIter, int eMode){
           pIncr->iStartOff = pTask->file2.iEof;
           pTask->file2.iEof += mxSz;
         }
-      }else{
-        rc = vdbeSorterOpenTempFile(db, mxSz, &pIncr->aFile[0].pFd);
-        if( rc==SQLITE_OK ){
-          rc = vdbeSorterOpenTempFile(db, mxSz, &pIncr->aFile[1].pFd);
-        }
       }
     }
 
+#if SQLITE_MAX_WORKER_THREADS>0
     if( rc==SQLITE_OK && pIncr->bUseThread ){
       /* Use the current thread to populate aFile[1], even though this
       ** iterator is multi-threaded. The reason being that this function
@@ -1947,6 +1958,7 @@ static int vdbePmaReaderIncrInit(PmaReader *pIter, int eMode){
       assert( eMode==INCRINIT_ROOT || eMode==INCRINIT_TASK );
       rc = vdbeIncrPopulate(pIncr);
     }
+#endif
 
     if( rc==SQLITE_OK && eMode!=INCRINIT_TASK ){
       rc = vdbePmaReaderNext(pIter);
@@ -2111,6 +2123,7 @@ static int vdbeSorterMergeTreeBuild(VdbeSorter *pSorter, MergeEngine **ppOut){
   int rc = SQLITE_OK;
   int iTask;
 
+#if SQLITE_MAX_WORKER_THREADS>0
   /* If the sorter uses more than one task, then create the top-level 
   ** MergeEngine here. This MergeEngine will read data from exactly 
   ** one PmaReader per sub-task.  */
@@ -2119,6 +2132,7 @@ static int vdbeSorterMergeTreeBuild(VdbeSorter *pSorter, MergeEngine **ppOut){
     pMain = vdbeMergeEngineNew(pSorter->nTask);
     if( pMain==0 ) rc = SQLITE_NOMEM;
   }
+#endif
 
   for(iTask=0; iTask<pSorter->nTask && rc==SQLITE_OK; iTask++){
     SortSubtask *pTask = &pSorter->aTask[iTask];
@@ -2301,10 +2315,13 @@ int sqlite3VdbeSorterNext(sqlite3 *db, const VdbeCursor *pCsr, int *pbEof){
     assert( pSorter->pReader==0 || pSorter->pMerger==0 );
     assert( pSorter->bUseThreads==0 || pSorter->pReader );
     assert( pSorter->bUseThreads==1 || pSorter->pMerger );
+#if SQLITE_MAX_WORKER_THREADS>0
     if( pSorter->bUseThreads ){
       rc = vdbePmaReaderNext(pSorter->pReader);
       *pbEof = (pSorter->pReader->pFile==0);
-    }else{
+    }else
+#endif
+    /*if( !pSorter->bUseThreads )*/ {
       rc = vdbeSorterNext(&pSorter->aTask[0], pSorter->pMerger, pbEof);
     }
   }else{
@@ -2328,9 +2345,15 @@ static void *vdbeSorterRowkey(
 ){
   void *pKey;
   if( pSorter->bUsePMA ){
-    PmaReader *pReader = (pSorter->bUseThreads ?
-        pSorter->pReader : &pSorter->pMerger->aIter[pSorter->pMerger->aTree[1]]
-    );
+    PmaReader *pReader;
+#if SQLITE_MAX_WORKER_THREADS>0
+    if( pSorter->bUseThreads ){
+      pReader = pSorter->pReader;
+    }else
+#endif
+    /*if( !pSorter->bUseThreads )*/{
+      pReader = &pSorter->pMerger->aIter[pSorter->pMerger->aTree[1]];
+    }
     *pnKey = pReader->nKey;
     pKey = pReader->aKey;
   }else{