Mark some invariants in the vdbesort.c logic when SQLITE_MAX_WORKER_THREADS==0.

FossilOrigin-Name: 721cd965859c9ccc24d2a1d2851c914229e584b3

manifest

@@ -1,5 +1,5 @@
-C Merge\srecent\strunk\schanges,\sand\sespecially\sthe\sfix\sfor\sthe\sCREATE\sUNIQUE\sINDEX\nproblem\sof\sticket\s[9a6daf340df99ba9].
-D 2014-07-30T14:44:24.940
+C Mark\ssome\sinvariants\sin\sthe\svdbesort.c\slogic\swhen\sSQLITE_MAX_WORKER_THREADS==0.
+D 2014-07-30T17:21:37.320
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in cf57f673d77606ab0f2d9627ca52a9ba1464146a
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -291,7 +291,7 @@ F src/vdbeapi.c 24e40422382beb774daab11fe9fe9d37e8a04949
 F src/vdbeaux.c 3f1d2baa4a8cbdad33cb255a5f4fd1af7a414683
 F src/vdbeblob.c 9205ce9d3b064d9600f8418a897fc88b5687d9ac
 F src/vdbemem.c d90a1e8acf8b63dc9d14cbbea12bfec6cec31394
-F src/vdbesort.c cab84b480d5c616e830d9b20c8903e42de3b60b3
+F src/vdbesort.c e37e494274fb9a05955b44eb61ead2230ae3e321
 F src/vdbetrace.c 6f52bc0c51e144b7efdcfb2a8f771167a8816767
 F src/vtab.c 21b932841e51ebd7d075e2d0ad1415dce8d2d5fd
 F src/wal.c 264df50a1b33124130b23180ded2e2c5663c652a
@@ -1190,7 +1190,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 0abfd78ceb09b7f7c27c688c8e3fe93268a13b32
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P bd9ee0ea69181526cfc3cadac33a5ec5190112b0 6b785e92f279cb65746834d5cd25594fd3333342
-R 5abc11219614f612d7ef9f82b784bc0c
+P 5b50a8380b2b678c1646ff303e3696efc1d7d92c
+R 79135dabbf9021221308446429439ade
 U drh
-Z f20a2d1678a8f4c3f64fec3d49fad416
+Z af737cf3847cc90d4e2e364aefe53a30

manifest.uuid

@@ -1 +1 @@
-5b50a8380b2b678c1646ff303e3696efc1d7d92c
+721cd965859c9ccc24d2a1d2851c914229e584b3

src/vdbesort.c

@@ -1860,6 +1860,10 @@ static void vdbeMergeEngineCompare(
 /*
 ** Allowed values for the eMode parameter to vdbeMergeEngineInit()
 ** and vdbePmaReaderIncrMergeInit().
+**
+** Only INCRINIT_NORMAL is valid in single-threaded builds (when
+** SQLITE_MAX_WORKER_THREADS==0).  The other values are only used
+** when there exists one or more separate worker threads.
 */
 #define INCRINIT_NORMAL 0
 #define INCRINIT_TASK   1
@@ -1898,12 +1902,15 @@ static int vdbeMergeEngineInit(
   int i;                          /* For looping over PmaReader objects */
   int nTree = pMerger->nTree;
 
+  /* eMode is always INCRINIT_NORMAL in single-threaded mode */
+  assert( SQLITE_MAX_WORKER_THREADS>0 || eMode==INCRINIT_NORMAL );
+
   /* Verify that the MergeEngine is assigned to a single thread */
   assert( pMerger->pTask==0 ); // || pMerger->pTask==pTask );
   pMerger->pTask = pTask;
 
   for(i=0; i<nTree; i++){
-    if( eMode==INCRINIT_ROOT ){
+    if( SQLITE_MAX_WORKER_THREADS>0 && eMode==INCRINIT_ROOT ){
       /* PmaReaders should be normally initialized in order, as if they are
       ** reading from the same temp file this makes for more linear file IO.
       ** However, in the INCRINIT_ROOT case, if PmaReader aReadr[nTask-1] is
@@ -1962,6 +1969,10 @@ static int vdbeMergeEngineInit(
 static int vdbePmaReaderIncrMergeInit(PmaReader *pReadr, int eMode){
   int rc = SQLITE_OK;
   IncrMerger *pIncr = pReadr->pIncr;
+
+  /* eMode is always INCRINIT_NORMAL in single-threaded mode */
+  assert( SQLITE_MAX_WORKER_THREADS>0 || eMode==INCRINIT_NORMAL );
+
   if( pIncr ){
     SortSubtask *pTask = pIncr->pTask;
     sqlite3 *db = pTask->pSorter->db;
@@ -2005,7 +2016,9 @@ static int vdbePmaReaderIncrMergeInit(PmaReader *pReadr, int eMode){
     }
 #endif
 
-    if( rc==SQLITE_OK && eMode!=INCRINIT_TASK ){
+    if( rc==SQLITE_OK
+     && (SQLITE_MAX_WORKER_THREADS==0 || eMode!=INCRINIT_TASK)
+    ){
       rc = vdbePmaReaderNext(pReadr);
     }
   }
@@ -2186,7 +2199,8 @@ static int vdbeSorterMergeTreeBuild(
 
   for(iTask=0; rc==SQLITE_OK && iTask<pSorter->nTask; iTask++){
     SortSubtask *pTask = &pSorter->aTask[iTask];
-    if( pTask->nPMA ){
+    assert( pTask->nPMA>0 || SQLITE_MAX_WORKER_THREADS>0 );
+    if( SQLITE_MAX_WORKER_THREADS==0 || pTask->nPMA ){
       MergeEngine *pRoot = 0;     /* Root node of tree for this task */
       int nDepth = vdbeSorterTreeDepth(pTask->nPMA);
       i64 iReadOff = 0;