Merge recent enhancements from trunk, and especially the fix for

ticket [1b266395d6bc10].

FossilOrigin-Name: b2face9aa95ade96a5666c70b6b31064c1ad0977

20 files changed, 344 insertions, 167 deletions

diff --git a/src/btree.c b/src/btree.c
index c7d6fabba..1eae0ac5d 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -661,7 +661,7 @@ static int saveCursorPosition(BtCursor *pCur){
     pCur->eState = CURSOR_REQUIRESEEK;
   }
 
-  invalidateOverflowCache(pCur);
+  pCur->curFlags &= ~(BTCF_ValidNKey|BTCF_ValidOvfl|BTCF_AtLast);
   return rc;
 }
 
@@ -7624,7 +7624,7 @@ static int balance_nonroot(
     ** by smaller than the child due to the database header, and so all the
     ** free space needs to be up front.
     */
-    assert( nNew==1 );
+    assert( nNew==1 || CORRUPT_DB );
     rc = defragmentPage(apNew[0]);
     testcase( rc!=SQLITE_OK );
     assert( apNew[0]->nFree == 
diff --git a/src/build.c b/src/build.c
index eee62ee15..ea89e501d 100644
--- a/src/build.c
+++ b/src/build.c
@@ -192,6 +192,8 @@ void sqlite3FinishCoding(Parse *pParse){
           db->aDb[iDb].pSchema->iGeneration  /* P4 */
         );
         if( db->init.busy==0 ) sqlite3VdbeChangeP5(v, 1);
+        VdbeComment((v,
+              "usesStmtJournal=%d", pParse->mayAbort && pParse->isMultiWrite));
       }
 #ifndef SQLITE_OMIT_VIRTUALTABLE
       for(i=0; i<pParse->nVtabLock; i++){
@@ -2082,8 +2084,7 @@ void sqlite3CreateView(
 
   if( pParse->nVar>0 ){
     sqlite3ErrorMsg(pParse, "parameters are not allowed in views");
-    sqlite3SelectDelete(db, pSelect);
-    return;
+    goto create_view_fail;
   }
   sqlite3StartTable(pParse, pName1, pName2, isTemp, 1, 0, noErr);
   p = pParse->pNewTable;
@@ -3135,7 +3136,7 @@ Index *sqlite3CreateIndex(
   /* Analyze the list of expressions that form the terms of the index and
   ** report any errors.  In the common case where the expression is exactly
   ** a table column, store that column in aiColumn[].  For general expressions,
-  ** populate pIndex->aColExpr and store -2 in aiColumn[].
+  ** populate pIndex->aColExpr and store XN_EXPR (-2) in aiColumn[].
   **
   ** TODO: Issue a warning if two or more columns of the index are identical.
   ** TODO: Issue a warning if the table primary key is used as part of the
@@ -3164,8 +3165,8 @@ Index *sqlite3CreateIndex(
           pListItem = &pCopy->a[i];
         }
       }
-      j = -2;
-      pIndex->aiColumn[i] = -2;
+      j = XN_EXPR;
+      pIndex->aiColumn[i] = XN_EXPR;
       pIndex->uniqNotNull = 0;
     }else{
       j = pCExpr->iColumn;
@@ -3218,7 +3219,7 @@ Index *sqlite3CreateIndex(
     }
     assert( i==pIndex->nColumn );
   }else{
-    pIndex->aiColumn[i] = -1;
+    pIndex->aiColumn[i] = XN_ROWID;
     pIndex->azColl[i] = "BINARY";
   }
   sqlite3DefaultRowEst(pIndex);
diff --git a/src/delete.c b/src/delete.c
index 914b3dfae..9abefda1a 100644
--- a/src/delete.c
+++ b/src/delete.c
@@ -414,7 +414,7 @@ void sqlite3DeleteFrom(
     pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0, 0, wcf, iTabCur+1);
     if( pWInfo==0 ) goto delete_from_cleanup;
     eOnePass = sqlite3WhereOkOnePass(pWInfo, aiCurOnePass);
-    assert( IsVirtual(pTab)==0 || eOnePass==ONEPASS_OFF );
+    assert( IsVirtual(pTab)==0 || eOnePass!=ONEPASS_MULTI );
     assert( IsVirtual(pTab) || bComplex || eOnePass!=ONEPASS_OFF );
   
     /* Keep track of the number of rows to be deleted */
@@ -425,7 +425,7 @@ void sqlite3DeleteFrom(
     /* Extract the rowid or primary key for the current row */
     if( pPk ){
       for(i=0; i<nPk; i++){
-        assert( pPk->aiColumn[i]>=(-1) );
+        assert( pPk->aiColumn[i]>=0 );
         sqlite3ExprCodeGetColumnOfTable(v, pTab, iTabCur,
                                         pPk->aiColumn[i], iPk+i);
       }
@@ -497,7 +497,7 @@ void sqlite3DeleteFrom(
     */
     if( eOnePass!=ONEPASS_OFF ){
       assert( nKey==nPk );  /* OP_Found will use an unpacked key */
-      if( aToOpen[iDataCur-iTabCur] ){
+      if( !IsVirtual(pTab) && aToOpen[iDataCur-iTabCur] ){
         assert( pPk!=0 || pTab->pSelect!=0 );
         sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, addrBypass, iKey, nKey);
         VdbeCoverage(v);
@@ -519,7 +519,11 @@ void sqlite3DeleteFrom(
       sqlite3VtabMakeWritable(pParse, pTab);
       sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iKey, pVTab, P4_VTAB);
       sqlite3VdbeChangeP5(v, OE_Abort);
+      assert( eOnePass==ONEPASS_OFF || eOnePass==ONEPASS_SINGLE );
       sqlite3MayAbort(pParse);
+      if( eOnePass==ONEPASS_SINGLE && sqlite3IsToplevel(pParse) ){
+        pParse->isMultiWrite = 0;
+      }
     }else
 #endif
     {
@@ -862,7 +866,7 @@ int sqlite3GenerateIndexKey(
   for(j=0; j<nCol; j++){
     if( pPrior
      && pPrior->aiColumn[j]==pIdx->aiColumn[j]
-     && pPrior->aiColumn[j]>=(-1)
+     && pPrior->aiColumn[j]!=XN_EXPR
     ){
       /* This column was already computed by the previous index */
       continue;
diff --git a/src/expr.c b/src/expr.c
index 3141cd9db..b52e814f3 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -2443,15 +2443,15 @@ void sqlite3ExprCodeLoadIndexColumn(
   int regOut      /* Store the index column value in this register */
 ){
   i16 iTabCol = pIdx->aiColumn[iIdxCol];
-  if( iTabCol>=(-1) ){
+  if( iTabCol==XN_EXPR ){
+    assert( pIdx->aColExpr );
+    assert( pIdx->aColExpr->nExpr>iIdxCol );
+    pParse->iSelfTab = iTabCur;
+    sqlite3ExprCode(pParse, pIdx->aColExpr->a[iIdxCol].pExpr, regOut);
+  }else{
     sqlite3ExprCodeGetColumnOfTable(pParse->pVdbe, pIdx->pTable, iTabCur,
                                     iTabCol, regOut);
-    return;
   }
-  assert( pIdx->aColExpr );
-  assert( pIdx->aColExpr->nExpr>iIdxCol );
-  pParse->iSelfTab = iTabCur;
-  sqlite3ExprCode(pParse, pIdx->aColExpr->a[iIdxCol].pExpr, regOut);
 }
 
 /*
diff --git a/src/fkey.c b/src/fkey.c
index a087889f4..b55e2a981 100644
--- a/src/fkey.c
+++ b/src/fkey.c
@@ -252,6 +252,8 @@ int sqlite3FkLocateIndex(
           char *zDfltColl;                  /* Def. collation for column */
           char *zIdxCol;                    /* Name of indexed column */
 
+          if( iCol<0 ) break; /* No foreign keys against expression indexes */
+
           /* If the index uses a collation sequence that is different from
           ** the default collation sequence for the column, this index is
           ** unusable. Bail out early in this case.  */
@@ -404,6 +406,7 @@ static void fkLookupParent(
         for(i=0; i<nCol; i++){
           int iChild = aiCol[i]+1+regData;
           int iParent = pIdx->aiColumn[i]+1+regData;
+          assert( pIdx->aiColumn[i]>=0 );
           assert( aiCol[i]!=pTab->iPKey );
           if( pIdx->aiColumn[i]==pTab->iPKey ){
             /* The parent key is a composite key that includes the IPK column */
@@ -612,6 +615,7 @@ static void fkScanChildren(
       assert( pIdx!=0 );
       for(i=0; i<pPk->nKeyCol; i++){
         i16 iCol = pIdx->aiColumn[i];
+        assert( iCol>=0 );
         pLeft = exprTableRegister(pParse, pTab, regData, iCol);
         pRight = exprTableColumn(db, pTab, pSrc->a[0].iCursor, iCol);
         pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight, 0);
@@ -931,6 +935,7 @@ void sqlite3FkCheck(
       if( aiCol[i]==pTab->iPKey ){
         aiCol[i] = -1;
       }
+      assert( pIdx==0 || pIdx->aiColumn[i]>=0 );
 #ifndef SQLITE_OMIT_AUTHORIZATION
       /* Request permission to read the parent key columns. If the 
       ** authorization callback returns SQLITE_IGNORE, behave as if any
@@ -1062,7 +1067,10 @@ u32 sqlite3FkOldmask(
       Index *pIdx = 0;
       sqlite3FkLocateIndex(pParse, pTab, p, &pIdx, 0);
       if( pIdx ){
-        for(i=0; i<pIdx->nKeyCol; i++) mask |= COLUMN_MASK(pIdx->aiColumn[i]);
+        for(i=0; i<pIdx->nKeyCol; i++){
+          assert( pIdx->aiColumn[i]>=0 );
+          mask |= COLUMN_MASK(pIdx->aiColumn[i]);
+        }
       }
     }
   }
@@ -1185,6 +1193,7 @@ static Trigger *fkActionTrigger(
       iFromCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
       assert( iFromCol>=0 );
       assert( pIdx!=0 || (pTab->iPKey>=0 && pTab->iPKey<pTab->nCol) );
+      assert( pIdx==0 || pIdx->aiColumn[i]>=0 );
       tToCol.z = pTab->aCol[pIdx ? pIdx->aiColumn[i] : pTab->iPKey].zName;
       tFromCol.z = pFKey->pFrom->aCol[iFromCol].zName;
 
diff --git a/src/insert.c b/src/insert.c
index 746f58db3..4108c8879 100644
--- a/src/insert.c
+++ b/src/insert.c
@@ -90,11 +90,11 @@ const char *sqlite3IndexAffinityStr(sqlite3 *db, Index *pIdx){
       i16 x = pIdx->aiColumn[n];
       if( x>=0 ){
         pIdx->zColAff[n] = pTab->aCol[x].affinity;
-      }else if( x==(-1) ){
+      }else if( x==XN_ROWID ){
         pIdx->zColAff[n] = SQLITE_AFF_INTEGER;
       }else{
         char aff;
-        assert( x==(-2) );
+        assert( x==XN_EXPR );
         assert( pIdx->aColExpr!=0 );
         aff = sqlite3ExprAffinity(pIdx->aColExpr->a[n].pExpr);
         if( aff==0 ) aff = SQLITE_AFF_BLOB;
@@ -260,7 +260,7 @@ void sqlite3AutoincrementBegin(Parse *pParse){
   /* This routine is never called during trigger-generation.  It is
   ** only called from the top-level */
   assert( pParse->pTriggerTab==0 );
-  assert( pParse==sqlite3ParseToplevel(pParse) );
+  assert( sqlite3IsToplevel(pParse) );
 
   assert( v );   /* We failed long ago if this is not so */
   for(p = pParse->pAinc; p; p = p->pNext){
@@ -1417,13 +1417,13 @@ void sqlite3GenerateConstraintChecks(
     for(i=0; i<pIdx->nColumn; i++){
       int iField = pIdx->aiColumn[i];
       int x;
-      if( iField==(-2) ){
+      if( iField==XN_EXPR ){
         pParse->ckBase = regNewData+1;
         sqlite3ExprCode(pParse, pIdx->aColExpr->a[i].pExpr, regIdx+i);
         pParse->ckBase = 0;
         VdbeComment((v, "%s column %d", pIdx->zName, i));
       }else{
-        if( iField==(-1) || iField==pTab->iPKey ){
+        if( iField==XN_ROWID || iField==pTab->iPKey ){
           if( regRowid==regIdx+i ) continue; /* ROWID already in regIdx+i */
           x = regNewData;
           regRowid =  pIdx->pPartIdxWhere ? -1 : regIdx+i;
@@ -1482,6 +1482,7 @@ void sqlite3GenerateConstraintChecks(
         ** store it in registers regR..regR+nPk-1 */
         if( pIdx!=pPk ){
           for(i=0; i<pPk->nKeyCol; i++){
+            assert( pPk->aiColumn[i]>=0 );
             x = sqlite3ColumnOfIndex(pIdx, pPk->aiColumn[i]);
             sqlite3VdbeAddOp3(v, OP_Column, iThisCur, x, regR+i);
             VdbeComment((v, "%s.%s", pTab->zName,
@@ -1503,6 +1504,7 @@ void sqlite3GenerateConstraintChecks(
           for(i=0; i<pPk->nKeyCol; i++){
             char *p4 = (char*)sqlite3LocateCollSeq(pParse, pPk->azColl[i]);
             x = pPk->aiColumn[i];
+            assert( x>=0 );
             if( i==(pPk->nKeyCol-1) ){
               addrJump = addrUniqueOk;
               op = OP_Eq;
@@ -1754,7 +1756,7 @@ static int xferCompatibleIndex(Index *pDest, Index *pSrc){
     if( pSrc->aiColumn[i]!=pDest->aiColumn[i] ){
       return 0;   /* Different columns indexed */
     }
-    if( pSrc->aiColumn[i]==(-2) ){
+    if( pSrc->aiColumn[i]==XN_EXPR ){
       assert( pSrc->aColExpr!=0 && pDest->aColExpr!=0 );
       if( sqlite3ExprCompare(pSrc->aColExpr->a[i].pExpr,
                              pDest->aColExpr->a[i].pExpr, -1)!=0 ){
diff --git a/src/main.c b/src/main.c
index fbb7da437..2aca573b0 100644
--- a/src/main.c
+++ b/src/main.c
@@ -2917,6 +2917,13 @@ static int openDatabase(
   }
 #endif
 
+#ifdef SQLITE_ENABLE_JSON1
+  if( !db->mallocFailed && rc==SQLITE_OK){
+    extern int sqlite3Json1Init(sqlite3*);
+    rc = sqlite3Json1Init(db);
+  }
+#endif
+
   /* -DSQLITE_DEFAULT_LOCKING_MODE=1 makes EXCLUSIVE the default locking
   ** mode.  -DSQLITE_DEFAULT_LOCKING_MODE=0 make NORMAL the default locking
   ** mode.  Doing nothing at all also makes NORMAL the default.
diff --git a/src/mutex_unix.c b/src/mutex_unix.c
index cebb96c90..dbdaa225b 100644
--- a/src/mutex_unix.c
+++ b/src/mutex_unix.c
@@ -81,7 +81,9 @@ static int pthreadMutexNotheld(sqlite3_mutex *p){
 #endif
 
 /*
-** Try to provide a memory barrier operation, needed for initialization only.
+** Try to provide a memory barrier operation, needed for initialization
+** and also for the implementation of xShmBarrier in the VFS in cases
+** where SQLite is compiled without mutexes.
 */
 void sqlite3MemoryBarrier(void){
 #if defined(SQLITE_MEMORY_BARRIER)
diff --git a/src/mutex_w32.c b/src/mutex_w32.c
index 90be07db2..7d28e4def 100644
--- a/src/mutex_w32.c
+++ b/src/mutex_w32.c
@@ -78,7 +78,9 @@ static int winMutexNotheld(sqlite3_mutex *p){
 #endif
 
 /*
-** Try to provide a memory barrier operation, needed for initialization only.
+** Try to provide a memory barrier operation, needed for initialization
+** and also for the xShmBarrier method of the VFS in cases when SQLite is
+** compiled without mutexes (SQLITE_THREADSAFE=0).
 */
 void sqlite3MemoryBarrier(void){
 #if defined(SQLITE_MEMORY_BARRIER)
diff --git a/src/pragma.c b/src/pragma.c
index 2dcad614f..e5e7e54a2 100644
--- a/src/pragma.c
+++ b/src/pragma.c
@@ -1524,8 +1524,8 @@ void sqlite3Pragma(
             int kk;
             for(kk=0; kk<pIdx->nKeyCol; kk++){
               int iCol = pIdx->aiColumn[kk];
-              assert( iCol>=0 && iCol<pTab->nCol );
-              if( pTab->aCol[iCol].notNull ) continue;
+              assert( iCol!=XN_ROWID && iCol<pTab->nCol );
+              if( iCol>=0 && pTab->aCol[iCol].notNull ) continue;
               sqlite3VdbeAddOp2(v, OP_IsNull, r1+kk, uniqOk);
               VdbeCoverage(v);
             }
diff --git a/src/select.c b/src/select.c
index a4aaa0eca..8430a00f3 100644
--- a/src/select.c
+++ b/src/select.c
@@ -4221,17 +4221,9 @@ static int selectExpander(Walker *pWalker, Select *p){
   */
   for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
     Table *pTab;
-    assert( pFrom->fg.isRecursive==0 || pFrom->pTab );
+    assert( pFrom->fg.isRecursive==0 || pFrom->pTab!=0 );
     if( pFrom->fg.isRecursive ) continue;
-    if( pFrom->pTab!=0 ){
-      /* This statement has already been prepared.  There is no need
-      ** to go further. */
-      assert( i==0 );
-#ifndef SQLITE_OMIT_CTE
-      selectPopWith(pWalker, p);
-#endif
-      return WRC_Prune;
-    }
+    assert( pFrom->pTab==0 );
 #ifndef SQLITE_OMIT_CTE
     if( withExpand(pWalker, pFrom) ) return WRC_Abort;
     if( pFrom->pTab ) {} else
@@ -4523,19 +4515,19 @@ static void selectAddSubqueryTypeInfo(Walker *pWalker, Select *p){
   struct SrcList_item *pFrom;
 
   assert( p->selFlags & SF_Resolved );
-  if( (p->selFlags & SF_HasTypeInfo)==0 ){
-    p->selFlags |= SF_HasTypeInfo;
-    pParse = pWalker->pParse;
-    pTabList = p->pSrc;
-    for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
-      Table *pTab = pFrom->pTab;
-      if( ALWAYS(pTab!=0) && (pTab->tabFlags & TF_Ephemeral)!=0 ){
-        /* A sub-query in the FROM clause of a SELECT */
-        Select *pSel = pFrom->pSelect;
-        if( pSel ){
-          while( pSel->pPrior ) pSel = pSel->pPrior;
-          selectAddColumnTypeAndCollation(pParse, pTab, pSel);
-        }
+  assert( (p->selFlags & SF_HasTypeInfo)==0 );
+  p->selFlags |= SF_HasTypeInfo;
+  pParse = pWalker->pParse;
+  pTabList = p->pSrc;
+  for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
+    Table *pTab = pFrom->pTab;
+    assert( pTab!=0 );
+    if( (pTab->tabFlags & TF_Ephemeral)!=0 ){
+      /* A sub-query in the FROM clause of a SELECT */
+      Select *pSel = pFrom->pSelect;
+      if( pSel ){
+        while( pSel->pPrior ) pSel = pSel->pPrior;
+        selectAddColumnTypeAndCollation(pParse, pTab, pSel);
       }
     }
   }
@@ -4861,7 +4853,17 @@ int sqlite3Select(
     struct SrcList_item *pItem = &pTabList->a[i];
     Select *pSub = pItem->pSelect;
     int isAggSub;
+    Table *pTab = pItem->pTab;
     if( pSub==0 ) continue;
+
+    /* Catch mismatch in the declared columns of a view and the number of
+    ** columns in the SELECT on the RHS */
+    if( pTab->nCol!=pSub->pEList->nExpr ){
+      sqlite3ErrorMsg(pParse, "expected %d columns for '%s' but got %d",
+                      pTab->nCol, pTab->zName, pSub->pEList->nExpr);
+      goto select_end;
+    }
+
     isAggSub = (pSub->selFlags & SF_Aggregate)!=0;
     if( flattenSubquery(pParse, p, i, isAgg, isAggSub) ){
       /* This subquery can be absorbed into its parent. */
diff --git a/src/shell.c b/src/shell.c
index 277473099..ca8e37186 100644
--- a/src/shell.c
+++ b/src/shell.c
@@ -2701,6 +2701,22 @@ static int shell_dbinfo_command(ShellState *p, int nArg, char **azArg){
   return 0;
 }
 
+/*
+** Print the current sqlite3_errmsg() value to stderr and return 1.
+*/
+static int shellDatabaseError(sqlite3 *db){
+  const char *zErr = sqlite3_errmsg(db);
+  fprintf(stderr, "Error: %s\n", zErr);
+  return 1;
+}
+
+/*
+** Print an out-of-memory message to stderr and return 1.
+*/
+static int shellNomemError(void){
+  fprintf(stderr, "Error: out of memory\n");
+  return 1;
+}
 
 /*
 ** If an input line begins with "." then invoke this routine to
@@ -3994,13 +4010,17 @@ static int do_meta_command(char *zLine, ShellState *p){
     int ii;
     open_db(p, 0);
     rc = sqlite3_prepare_v2(p->db, "PRAGMA database_list", -1, &pStmt, 0);
-    if( rc ) return rc;
+    if( rc ) return shellDatabaseError(p->db);
+
+    /* Create an SQL statement to query for the list of tables in the
+    ** main and all attached databases where the table name matches the
+    ** LIKE pattern bound to variable "?1". */
     zSql = sqlite3_mprintf(
         "SELECT name FROM sqlite_master"
         " WHERE type IN ('table','view')"
         "   AND name NOT LIKE 'sqlite_%%'"
         "   AND name LIKE ?1");
-    while( sqlite3_step(pStmt)==SQLITE_ROW ){
+    while( zSql && sqlite3_step(pStmt)==SQLITE_ROW ){
       const char *zDbName = (const char*)sqlite3_column_text(pStmt, 1);
       if( zDbName==0 || strcmp(zDbName,"main")==0 ) continue;
       if( strcmp(zDbName,"temp")==0 ){
@@ -4019,11 +4039,17 @@ static int do_meta_command(char *zLine, ShellState *p){
                  "   AND name LIKE ?1", zSql, zDbName, zDbName);
       }
     }
-    sqlite3_finalize(pStmt);
-    zSql = sqlite3_mprintf("%z ORDER BY 1", zSql);
-    rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+    rc = sqlite3_finalize(pStmt);
+    if( zSql && rc==SQLITE_OK ){
+      zSql = sqlite3_mprintf("%z ORDER BY 1", zSql);
+      if( zSql ) rc = sqlite3_prepare_v2(p->db, zSql, -1, &pStmt, 0);
+    }
     sqlite3_free(zSql);
-    if( rc ) return rc;
+    if( !zSql ) return shellNomemError();
+    if( rc ) return shellDatabaseError(p->db);
+
+    /* Run the SQL statement prepared by the above block. Store the results
+    ** as an array of nul-terminated strings in azResult[].  */
     nRow = nAlloc = 0;
     azResult = 0;
     if( nArg>1 ){
@@ -4037,17 +4063,25 @@ static int do_meta_command(char *zLine, ShellState *p){
         int n2 = nAlloc*2 + 10;
         azNew = sqlite3_realloc64(azResult, sizeof(azResult[0])*n2);
         if( azNew==0 ){
-          fprintf(stderr, "Error: out of memory\n");
+          rc = shellNomemError();
           break;
         }
         nAlloc = n2;
         azResult = azNew;
       }
       azResult[nRow] = sqlite3_mprintf("%s", sqlite3_column_text(pStmt, 0));
-      if( azResult[nRow] ) nRow++;
+      if( 0==azResult[nRow] ){
+        rc = shellNomemError();
+        break;
+      }
+      nRow++;
+    }
+    if( sqlite3_finalize(pStmt)!=SQLITE_OK ){
+      rc = shellDatabaseError(p->db);
     }
-    sqlite3_finalize(pStmt);        
-    if( nRow>0 ){
+
+    /* Pretty-print the contents of array azResult[] to the output */
+    if( rc==0 && nRow>0 ){
       int len, maxlen = 0;
       int i, j;
       int nPrintCol, nPrintRow;
@@ -4066,6 +4100,7 @@ static int do_meta_command(char *zLine, ShellState *p){
         fprintf(p->out, "\n");
       }
     }
+
     for(ii=0; ii<nRow; ii++) sqlite3_free(azResult[ii]);
     sqlite3_free(azResult);
   }else
@@ -4900,7 +4935,7 @@ int SQLITE_CDECL main(int argc, char **argv){
   }
   data.out = stdout;
 
-#ifdef SQLITE_ENABLE_JSON1
+#ifdef SQLITE_SHELL_JSON1
   {
     extern int sqlite3_json_init(sqlite3*);
     sqlite3_auto_extension((void(*)(void))sqlite3_json_init);
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index 471b7f526..8934d729e 100644
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -4360,7 +4360,7 @@ int sqlite3_value_type(sqlite3_value*);
 int sqlite3_value_numeric_type(sqlite3_value*);
 
 /*
-** CAPI3REF: Obtaining SQL Values
+** CAPI3REF: Finding The Subtype Of SQL Values
 ** METHOD: sqlite3_value
 **
 ** The sqlite3_value_subtype(V) function returns the subtype for
@@ -5634,13 +5634,31 @@ struct sqlite3_module {
 ** ^The estimatedRows value is an estimate of the number of rows that
 ** will be returned by the strategy.
 **
+** The xBestIndex method may optionally populate the idxFlags field with a 
+** mask of SQLITE_INDEX_SCAN_* flags. Currently there is only one such flag -
+** SQLITE_INDEX_SCAN_UNIQUE. If the xBestIndex method sets this flag, SQLite
+** assumes that the strategy may visit at most one row. 
+**
+** Additionally, if xBestIndex sets the SQLITE_INDEX_SCAN_UNIQUE flag, then
+** SQLite also assumes that if a call to the xUpdate() method is made as
+** part of the same statement to delete or update a virtual table row and the
+** implementation returns SQLITE_CONSTRAINT, then there is no need to rollback
+** any database changes. In other words, if the xUpdate() returns
+** SQLITE_CONSTRAINT, the database contents must be exactly as they were
+** before xUpdate was called. By contrast, if SQLITE_INDEX_SCAN_UNIQUE is not
+** set and xUpdate returns SQLITE_CONSTRAINT, any database changes made by
+** the xUpdate method are automatically rolled back by SQLite.
+**
 ** IMPORTANT: The estimatedRows field was added to the sqlite3_index_info
 ** structure for SQLite version 3.8.2. If a virtual table extension is
 ** used with an SQLite version earlier than 3.8.2, the results of attempting 
 ** to read or write the estimatedRows field are undefined (but are likely 
 ** to included crashing the application). The estimatedRows field should
 ** therefore only be used if [sqlite3_libversion_number()] returns a
-** value greater than or equal to 3008002.
+** value greater than or equal to 3008002. Similarly, the idxFlags field
+** was added for version 3.8.12. It may therefore only be used if
+** sqlite3_libversion_number() returns a value greater than or equal to
+** 3008012.
 */
 struct sqlite3_index_info {
   /* Inputs */
@@ -5668,9 +5686,16 @@ struct sqlite3_index_info {
   double estimatedCost;           /* Estimated cost of using this index */
   /* Fields below are only available in SQLite 3.8.2 and later */
   sqlite3_int64 estimatedRows;    /* Estimated number of rows returned */
+  /* Fields below are only available in SQLite 3.8.12 and later */
+  int idxFlags;              /* Mask of SQLITE_INDEX_SCAN_* flags */
 };
 
 /*
+** CAPI3REF: Virtual Table Scan Flags
+*/
+#define SQLITE_INDEX_SCAN_UNIQUE      1     /* Scan visits at most 1 row */
+
+/*
 ** CAPI3REF: Virtual Table Constraint Operator Codes
 **
 ** These macros defined the allowed values for the
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 6b999374b..450eb7cc5 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1925,6 +1925,12 @@ struct Index {
 /* Return true if index X is a UNIQUE index */
 #define IsUniqueIndex(X)      ((X)->onError!=OE_None)
 
+/* The Index.aiColumn[] values are normally positive integer.  But
+** there are some negative values that have special meaning:
+*/
+#define XN_ROWID     (-1)     /* Indexed column is the rowid */
+#define XN_EXPR      (-2)     /* Indexed column is an expression */
+
 /*
 ** Each sample stored in the sqlite_stat3 table is represented in memory 
 ** using a structure of this type.  See documentation at the top of the
@@ -3516,6 +3522,7 @@ void sqlite3MaterializeView(Parse*, Table*, Expr*, int);
   void sqlite3UnlinkAndDeleteTrigger(sqlite3*,int,const char*);
   u32 sqlite3TriggerColmask(Parse*,Trigger*,ExprList*,int,int,Table*,int);
 # define sqlite3ParseToplevel(p) ((p)->pToplevel ? (p)->pToplevel : (p))
+# define sqlite3IsToplevel(p) ((p)->pToplevel==0)
 #else
 # define sqlite3TriggersExist(B,C,D,E,F) 0
 # define sqlite3DeleteTrigger(A,B)
@@ -3525,6 +3532,7 @@ void sqlite3MaterializeView(Parse*, Table*, Expr*, int);
 # define sqlite3CodeRowTriggerDirect(A,B,C,D,E,F)
 # define sqlite3TriggerList(X, Y) 0
 # define sqlite3ParseToplevel(p) p
+# define sqlite3IsToplevel(p) 1
 # define sqlite3TriggerColmask(A,B,C,D,E,F,G) 0
 #endif
 
diff --git a/src/threads.c b/src/threads.c
index 4ce612227..251b9b763 100644
--- a/src/threads.c
+++ b/src/threads.c
@@ -67,6 +67,10 @@ int sqlite3ThreadCreate(
   memset(p, 0, sizeof(*p));
   p->xTask = xTask;
   p->pIn = pIn;
+  /* If the SQLITE_TESTCTRL_FAULT_INSTALL callback is registered to a 
+  ** function that returns SQLITE_ERROR when passed the argument 200, that
+  ** forces worker threads to run sequentially and deterministically 
+  ** for testing purposes. */
   if( sqlite3FaultSim(200) ){
     rc = 1;
   }else{    
@@ -151,7 +155,12 @@ int sqlite3ThreadCreate(
   *ppThread = 0;
   p = sqlite3Malloc(sizeof(*p));
   if( p==0 ) return SQLITE_NOMEM;
-  if( sqlite3GlobalConfig.bCoreMutex==0 ){
+  /* If the SQLITE_TESTCTRL_FAULT_INSTALL callback is registered to a 
+  ** function that returns SQLITE_ERROR when passed the argument 200, that
+  ** forces worker threads to run sequentially and deterministically 
+  ** (via the sqlite3FaultSim() term of the conditional) for testing
+  ** purposes. */
+  if( sqlite3GlobalConfig.bCoreMutex==0 || sqlite3FaultSim(200) ){
     memset(p, 0, sizeof(*p));
   }else{
     p->xTask = xTask;
@@ -179,7 +188,7 @@ int sqlite3ThreadJoin(SQLiteThread *p, void **ppOut){
   assert( ppOut!=0 );
   if( NEVER(p==0) ) return SQLITE_NOMEM;
   if( p->xTask==0 ){
-    assert( p->id==GetCurrentThreadId() );
+    /* assert( p->id==GetCurrentThreadId() ); */
     rc = WAIT_OBJECT_0;
     assert( p->tid==0 );
   }else{
diff --git a/src/update.c b/src/update.c
index aa13e7f7d..fba7762aa 100644
--- a/src/update.c
+++ b/src/update.c
@@ -134,9 +134,9 @@ void sqlite3Update(
 
   /* Register Allocations */
   int regRowCount = 0;   /* A count of rows changed */
-  int regOldRowid;       /* The old rowid */
-  int regNewRowid;       /* The new rowid */
-  int regNew;            /* Content of the NEW.* table in triggers */
+  int regOldRowid = 0;   /* The old rowid */
+  int regNewRowid = 0;   /* The new rowid */
+  int regNew = 0;        /* Content of the NEW.* table in triggers */
   int regOld = 0;        /* Content of OLD.* table in triggers */
   int regRowSet = 0;     /* Rowset of rows to be updated */
   int regKey = 0;        /* composite PRIMARY KEY value */
@@ -300,29 +300,20 @@ void sqlite3Update(
   if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
   sqlite3BeginWriteOperation(pParse, 1, iDb);
 
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-  /* Virtual tables must be handled separately */
-  if( IsVirtual(pTab) ){
-    updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,
-                       pWhere, onError);
-    pWhere = 0;
-    pTabList = 0;
-    goto update_cleanup;
-  }
-#endif
-
   /* Allocate required registers. */
-  regRowSet = ++pParse->nMem;
-  regOldRowid = regNewRowid = ++pParse->nMem;
-  if( chngPk || pTrigger || hasFK ){
-    regOld = pParse->nMem + 1;
+  if( !IsVirtual(pTab) ){
+    regRowSet = ++pParse->nMem;
+    regOldRowid = regNewRowid = ++pParse->nMem;
+    if( chngPk || pTrigger || hasFK ){
+      regOld = pParse->nMem + 1;
+      pParse->nMem += pTab->nCol;
+    }
+    if( chngKey || pTrigger || hasFK ){
+      regNewRowid = ++pParse->nMem;
+    }
+    regNew = pParse->nMem + 1;
     pParse->nMem += pTab->nCol;
   }
-  if( chngKey || pTrigger || hasFK ){
-    regNewRowid = ++pParse->nMem;
-  }
-  regNew = pParse->nMem + 1;
-  pParse->nMem += pTab->nCol;
 
   /* Start the view context. */
   if( isView ){
@@ -345,6 +336,15 @@ void sqlite3Update(
     goto update_cleanup;
   }
 
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+  /* Virtual tables must be handled separately */
+  if( IsVirtual(pTab) ){
+    updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,
+                       pWhere, onError);
+    goto update_cleanup;
+  }
+#endif
+
   /* Begin the database scan
   */
   if( HasRowid(pTab) ){
@@ -384,7 +384,7 @@ void sqlite3Update(
     if( pWInfo==0 ) goto update_cleanup;
     okOnePass = sqlite3WhereOkOnePass(pWInfo, aiCurOnePass);
     for(i=0; i<nPk; i++){
-      assert( pPk->aiColumn[i]>=(-1) );
+      assert( pPk->aiColumn[i]>=0 );
       sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, pPk->aiColumn[i],
                                       iPk+i);
     }
@@ -507,7 +507,6 @@ void sqlite3Update(
   newmask = sqlite3TriggerColmask(
       pParse, pTrigger, pChanges, 1, TRIGGER_BEFORE, pTab, onError
   );
-  /*sqlite3VdbeAddOp3(v, OP_Null, 0, regNew, regNew+pTab->nCol-1);*/
   for(i=0; i<pTab->nCol; i++){
     if( i==pTab->iPKey ){
       sqlite3VdbeAddOp2(v, OP_Null, 0, regNew+i);
@@ -698,21 +697,23 @@ update_cleanup:
 /*
 ** Generate code for an UPDATE of a virtual table.
 **
-** The strategy is that we create an ephemeral table that contains
+** There are two possible strategies - the default and the special 
+** "onepass" strategy. Onepass is only used if the virtual table 
+** implementation indicates that pWhere may match at most one row.
+**
+** The default strategy is to create an ephemeral table that contains
 ** for each row to be changed:
 **
 **   (A)  The original rowid of that row.
-**   (B)  The revised rowid for the row. (note1)
+**   (B)  The revised rowid for the row.
 **   (C)  The content of every column in the row.
 **
-** Then we loop over this ephemeral table and for each row in
-** the ephemeral table call VUpdate.
-**
-** When finished, drop the ephemeral table.
+** Then loop through the contents of this ephemeral table executing a
+** VUpdate for each row. When finished, drop the ephemeral table.
 **
-** (note1) Actually, if we know in advance that (A) is always the same
-** as (B) we only store (A), then duplicate (A) when pulling
-** it out of the ephemeral table before calling VUpdate.
+** The "onepass" strategy does not use an ephemeral table. Instead, it
+** stores the same values (A, B and C above) in a register array and
+** makes a single invocation of VUpdate.
 */
 static void updateVirtualTable(
   Parse *pParse,       /* The parsing context */
@@ -725,65 +726,95 @@ static void updateVirtualTable(
   int onError          /* ON CONFLICT strategy */
 ){
   Vdbe *v = pParse->pVdbe;  /* Virtual machine under construction */
-  ExprList *pEList = 0;     /* The result set of the SELECT statement */
-  Select *pSelect = 0;      /* The SELECT statement */
-  Expr *pExpr;              /* Temporary expression */
   int ephemTab;             /* Table holding the result of the SELECT */
   int i;                    /* Loop counter */
-  int addr;                 /* Address of top of loop */
-  int iReg;                 /* First register in set passed to OP_VUpdate */
   sqlite3 *db = pParse->db; /* Database connection */
   const char *pVTab = (const char*)sqlite3GetVTable(db, pTab);
-  SelectDest dest;
-
-  /* Construct the SELECT statement that will find the new values for
-  ** all updated rows. 
-  */
-  pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db, TK_ID, "_rowid_"));
+  WhereInfo *pWInfo;
+  int nArg = 2 + pTab->nCol;      /* Number of arguments to VUpdate */
+  int regArg;                     /* First register in VUpdate arg array */
+  int regRec;                     /* Register in which to assemble record */
+  int regRowid;                   /* Register for ephem table rowid */
+  int iCsr = pSrc->a[0].iCursor;  /* Cursor used for virtual table scan */
+  int aDummy[2];                  /* Unused arg for sqlite3WhereOkOnePass() */
+  int bOnePass;                   /* True to use onepass strategy */
+  int addr;                       /* Address of OP_OpenEphemeral */
+
+  /* Allocate nArg registers to martial the arguments to VUpdate. Then
+  ** create and open the ephemeral table in which the records created from
+  ** these arguments will be temporarily stored. */
+  assert( v );
+  ephemTab = pParse->nTab++;
+  addr= sqlite3VdbeAddOp2(v, OP_OpenEphemeral, ephemTab, nArg);
+  regArg = pParse->nMem + 1;
+  pParse->nMem += nArg;
+  regRec = ++pParse->nMem;
+  regRowid = ++pParse->nMem;
+
+  /* Start scanning the virtual table */
+  pWInfo = sqlite3WhereBegin(pParse, pSrc, pWhere, 0,0,WHERE_ONEPASS_DESIRED,0);
+  if( pWInfo==0 ) return;
+
+  /* Populate the argument registers. */
+  sqlite3VdbeAddOp2(v, OP_Rowid, iCsr, regArg);
   if( pRowid ){
-    pEList = sqlite3ExprListAppend(pParse, pEList,
-                                   sqlite3ExprDup(db, pRowid, 0));
+    sqlite3ExprCode(pParse, pRowid, regArg+1);
+  }else{
+    sqlite3VdbeAddOp2(v, OP_Rowid, iCsr, regArg+1);
   }
-  assert( pTab->iPKey<0 );
   for(i=0; i<pTab->nCol; i++){
     if( aXRef[i]>=0 ){
-      pExpr = sqlite3ExprDup(db, pChanges->a[aXRef[i]].pExpr, 0);
+      sqlite3ExprCode(pParse, pChanges->a[aXRef[i]].pExpr, regArg+2+i);
     }else{
-      pExpr = sqlite3Expr(db, TK_ID, pTab->aCol[i].zName);
+      sqlite3VdbeAddOp3(v, OP_VColumn, iCsr, i, regArg+2+i);
     }
-    pEList = sqlite3ExprListAppend(pParse, pEList, pExpr);
   }
-  pSelect = sqlite3SelectNew(pParse, pEList, pSrc, pWhere, 0, 0, 0, 0, 0, 0);
-  
-  /* Create the ephemeral table into which the update results will
-  ** be stored.
-  */
-  assert( v );
-  ephemTab = pParse->nTab++;
 
-  /* fill the ephemeral table 
-  */
-  sqlite3SelectDestInit(&dest, SRT_EphemTab, ephemTab);
-  sqlite3Select(pParse, pSelect, &dest);
-
-  /* Generate code to scan the ephemeral table and call VUpdate. */
-  iReg = ++pParse->nMem;
-  pParse->nMem += pTab->nCol+1;
-  addr = sqlite3VdbeAddOp2(v, OP_Rewind, ephemTab, 0); VdbeCoverage(v);
-  sqlite3VdbeAddOp3(v, OP_Column,  ephemTab, 0, iReg);
-  sqlite3VdbeAddOp3(v, OP_Column, ephemTab, (pRowid?1:0), iReg+1);
-  for(i=0; i<pTab->nCol; i++){
-    sqlite3VdbeAddOp3(v, OP_Column, ephemTab, i+1+(pRowid!=0), iReg+2+i);
+  bOnePass = sqlite3WhereOkOnePass(pWInfo, aDummy);
+
+  if( bOnePass ){
+    /* If using the onepass strategy, no-op out the OP_OpenEphemeral coded
+    ** above. Also, if this is a top-level parse (not a trigger), clear the
+    ** multi-write flag so that the VM does not open a statement journal */
+    sqlite3VdbeChangeToNoop(v, addr);
+    if( sqlite3IsToplevel(pParse) ){
+      pParse->isMultiWrite = 0;
+    }
+  }else{
+    /* Create a record from the argument register contents and insert it into
+    ** the ephemeral table. */
+    sqlite3VdbeAddOp3(v, OP_MakeRecord, regArg, nArg, regRec);
+    sqlite3VdbeAddOp2(v, OP_NewRowid, ephemTab, regRowid);
+    sqlite3VdbeAddOp3(v, OP_Insert, ephemTab, regRec, regRowid);
+  }
+
+
+  if( bOnePass==0 ){
+    /* End the virtual table scan */
+    sqlite3WhereEnd(pWInfo);
+
+    /* Begin scannning through the ephemeral table. */
+    addr = sqlite3VdbeAddOp1(v, OP_Rewind, ephemTab); VdbeCoverage(v);
+
+    /* Extract arguments from the current row of the ephemeral table and 
+    ** invoke the VUpdate method.  */
+    for(i=0; i<nArg; i++){
+      sqlite3VdbeAddOp3(v, OP_Column, ephemTab, i, regArg+i);
+    }
   }
   sqlite3VtabMakeWritable(pParse, pTab);
-  sqlite3VdbeAddOp4(v, OP_VUpdate, 0, pTab->nCol+2, iReg, pVTab, P4_VTAB);
+  sqlite3VdbeAddOp4(v, OP_VUpdate, 0, nArg, regArg, pVTab, P4_VTAB);
   sqlite3VdbeChangeP5(v, onError==OE_Default ? OE_Abort : onError);
   sqlite3MayAbort(pParse);
-  sqlite3VdbeAddOp2(v, OP_Next, ephemTab, addr+1); VdbeCoverage(v);
-  sqlite3VdbeJumpHere(v, addr);
-  sqlite3VdbeAddOp2(v, OP_Close, ephemTab, 0);
 
-  /* Cleanup */
-  sqlite3SelectDelete(db, pSelect);  
+  /* End of the ephemeral table scan. Or, if using the onepass strategy,
+  ** jump to here if the scan visited zero rows. */
+  if( bOnePass==0 ){
+    sqlite3VdbeAddOp2(v, OP_Next, ephemTab, addr+1); VdbeCoverage(v);
+    sqlite3VdbeJumpHere(v, addr);
+    sqlite3VdbeAddOp2(v, OP_Close, ephemTab, 0);
+  }else{
+    sqlite3WhereEnd(pWInfo);
+  }
 }
 #endif /* SQLITE_OMIT_VIRTUALTABLE */
diff --git a/src/vdbeblob.c b/src/vdbeblob.c
index ae40a9c09..80608ecec 100644
--- a/src/vdbeblob.c
+++ b/src/vdbeblob.c
@@ -252,7 +252,7 @@ int sqlite3_blob_open(
         int j;
         for(j=0; j<pIdx->nKeyCol; j++){
           /* FIXME: Be smarter about indexes that use expressions */
-          if( pIdx->aiColumn[j]==iCol || pIdx->aiColumn[j]==(-2) ){
+          if( pIdx->aiColumn[j]==iCol || pIdx->aiColumn[j]==XN_EXPR ){
             zFault = "indexed";
           }
         }
diff --git a/src/vtab.c b/src/vtab.c
index 041805ca4..cc293e806 100644
--- a/src/vtab.c
+++ b/src/vtab.c
@@ -937,7 +937,9 @@ int sqlite3VtabBegin(sqlite3 *db, VTable *pVTab){
     if( rc==SQLITE_OK ){
       rc = pModule->xBegin(pVTab->pVtab);
       if( rc==SQLITE_OK ){
+        int iSvpt = db->nStatement + db->nSavepoint;
         addToVTrans(db, pVTab);
+        if( iSvpt ) rc = sqlite3VtabSavepoint(db, SAVEPOINT_BEGIN, iSvpt-1);
       }
     }
   }
diff --git a/src/where.c b/src/where.c
index 1e13cf0ed..af8e2f35f 100644
--- a/src/where.c
+++ b/src/where.c
@@ -87,6 +87,13 @@ int sqlite3WhereBreakLabel(WhereInfo *pWInfo){
 */
 int sqlite3WhereOkOnePass(WhereInfo *pWInfo, int *aiCur){
   memcpy(aiCur, pWInfo->aiCurOnePass, sizeof(int)*2);
+#ifdef WHERETRACE_ENABLED
+  if( sqlite3WhereTrace && pWInfo->eOnePass!=ONEPASS_OFF ){
+    sqlite3DebugPrintf("%s cursors: %d %d\n",
+         pWInfo->eOnePass==ONEPASS_SINGLE ? "ONEPASS_SINGLE" : "ONEPASS_MULTI",
+         aiCur[0], aiCur[1]);
+  }
+#endif
   return pWInfo->eOnePass;
 }
 
@@ -182,13 +189,13 @@ static WhereTerm *whereScanNext(WhereScan *pScan){
   while( pScan->iEquiv<=pScan->nEquiv ){
     iCur = pScan->aiCur[pScan->iEquiv-1];
     iColumn = pScan->aiColumn[pScan->iEquiv-1];
-    if( iColumn==(-2) && pScan->pIdxExpr==0 ) return 0;
+    if( iColumn==XN_EXPR && pScan->pIdxExpr==0 ) return 0;
     while( (pWC = pScan->pWC)!=0 ){
       for(pTerm=pWC->a+k; k<pWC->nTerm; k++, pTerm++){
         if( pTerm->leftCursor==iCur
          && pTerm->u.leftColumn==iColumn
-         && (iColumn!=(-2)
-               || sqlite3ExprCompare(pTerm->pExpr->pLeft,pScan->pIdxExpr,iCur)==0)
+         && (iColumn!=XN_EXPR
+             || sqlite3ExprCompare(pTerm->pExpr->pLeft,pScan->pIdxExpr,iCur)==0)
          && (pScan->iEquiv<=1 || !ExprHasProperty(pTerm->pExpr, EP_FromJoin))
         ){
           if( (pTerm->eOperator & WO_EQUIV)!=0
@@ -281,7 +288,7 @@ static WhereTerm *whereScanInit(
   if( pIdx ){
     j = iColumn;
     iColumn = pIdx->aiColumn[j];
-    if( iColumn==(-2) ) pScan->pIdxExpr = pIdx->aColExpr->a[j].pExpr;
+    if( iColumn==XN_EXPR ) pScan->pIdxExpr = pIdx->aColExpr->a[j].pExpr;
   }
   if( pIdx && iColumn>=0 ){
     pScan->idxaff = pIdx->pTable->aCol[iColumn].affinity;
@@ -720,7 +727,7 @@ static void constructAutomaticIndex(
     }
   }
   assert( n==nKeyCol );
-  pIdx->aiColumn[n] = -1;
+  pIdx->aiColumn[n] = XN_ROWID;
   pIdx->azColl[n] = "BINARY";
 
   /* Create the automatic index */
@@ -1159,6 +1166,7 @@ static LogEst whereRangeAdjust(WhereTerm *pTerm, LogEst nNew){
 ** Return the affinity for a single column of an index.
 */
 static char sqlite3IndexColumnAffinity(sqlite3 *db, Index *pIdx, int iCol){
+  assert( iCol>=0 && iCol<pIdx->nColumn );
   if( !pIdx->zColAff ){
     if( sqlite3IndexAffinityStr(db, pIdx)==0 ) return SQLITE_AFF_BLOB;
   }
@@ -1216,8 +1224,7 @@ static int whereRangeSkipScanEst(
   int nLower = -1;
   int nUpper = p->nSample+1;
   int rc = SQLITE_OK;
-  int iCol = p->aiColumn[nEq];
-  u8 aff = sqlite3IndexColumnAffinity(db, p, iCol);
+  u8 aff = sqlite3IndexColumnAffinity(db, p, nEq);
   CollSeq *pColl;
   
   sqlite3_value *p1 = 0;          /* Value extracted from pLower */
@@ -2235,7 +2242,9 @@ static int whereLoopAddBtreeIndex(
       int iCol = pProbe->aiColumn[saved_nEq];
       pNew->wsFlags |= WHERE_COLUMN_EQ;
       assert( saved_nEq==pNew->u.btree.nEq );
-      if( iCol==(-1) || (iCol>0 && nInMul==0 && saved_nEq==pProbe->nKeyCol-1) ){
+      if( iCol==XN_ROWID 
+       || (iCol>0 && nInMul==0 && saved_nEq==pProbe->nKeyCol-1)
+      ){
         if( iCol>=0 && pProbe->uniqNotNull==0 ){
           pNew->wsFlags |= WHERE_UNQ_WANTED;
         }else{
@@ -2421,18 +2430,25 @@ static int indexMightHelpWithOrderBy(
   int iCursor
 ){
   ExprList *pOB;
+  ExprList *aColExpr;
   int ii, jj;
 
   if( pIndex->bUnordered ) return 0;
   if( (pOB = pBuilder->pWInfo->pOrderBy)==0 ) return 0;
   for(ii=0; ii<pOB->nExpr; ii++){
     Expr *pExpr = sqlite3ExprSkipCollate(pOB->a[ii].pExpr);
-    if( pExpr->op!=TK_COLUMN ) return 0;
-    if( pExpr->iTable==iCursor ){
+    if( pExpr->op==TK_COLUMN && pExpr->iTable==iCursor ){
       if( pExpr->iColumn<0 ) return 1;
       for(jj=0; jj<pIndex->nKeyCol; jj++){
         if( pExpr->iColumn==pIndex->aiColumn[jj] ) return 1;
       }
+    }else if( (aColExpr = pIndex->aColExpr)!=0 ){
+      for(jj=0; jj<pIndex->nKeyCol; jj++){
+        if( pIndex->aiColumn[jj]!=XN_EXPR ) continue;
+        if( sqlite3ExprCompare(pExpr,aColExpr->a[jj].pExpr,iCursor)==0 ){
+          return 1;
+        }
+      }
     }
   }
   return 0;
@@ -2580,7 +2596,7 @@ static int whereLoopAddBtree(
    && (pWInfo->pParse->db->flags & SQLITE_AutoIndex)!=0
    && pSrc->pIBIndex==0      /* Has no INDEXED BY clause */
    && !pSrc->fg.notIndexed   /* Has no NOT INDEXED clause */
-   && HasRowid(pTab)         /* Is not a WITHOUT ROWID table. (FIXME: Why not?) */
+   && HasRowid(pTab)         /* Not WITHOUT ROWID table. (FIXME: Why not?) */
    && !pSrc->fg.isCorrelated /* Not a correlated subquery */
    && !pSrc->fg.isRecursive  /* Not a recursive common table expression. */
   ){
@@ -2825,6 +2841,7 @@ static int whereLoopAddVirtual(
     pIdxInfo->orderByConsumed = 0;
     pIdxInfo->estimatedCost = SQLITE_BIG_DBL / (double)2;
     pIdxInfo->estimatedRows = 25;
+    pIdxInfo->idxFlags = 0;
     rc = vtabBestIndex(pParse, pTab, pIdxInfo);
     if( rc ) goto whereLoopAddVtab_exit;
     pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
@@ -2870,6 +2887,7 @@ static int whereLoopAddVirtual(
           ** (2) Multiple outputs from a single IN value will not merge
           ** together.  */
           pIdxInfo->orderByConsumed = 0;
+          pIdxInfo->idxFlags &= ~SQLITE_INDEX_SCAN_UNIQUE;
         }
       }
     }
@@ -2885,6 +2903,14 @@ static int whereLoopAddVirtual(
       pNew->rSetup = 0;
       pNew->rRun = sqlite3LogEstFromDouble(pIdxInfo->estimatedCost);
       pNew->nOut = sqlite3LogEst(pIdxInfo->estimatedRows);
+
+      /* Set the WHERE_ONEROW flag if the xBestIndex() method indicated
+      ** that the scan will visit at most one row. Clear it otherwise. */
+      if( pIdxInfo->idxFlags & SQLITE_INDEX_SCAN_UNIQUE ){
+        pNew->wsFlags |= WHERE_ONEROW;
+      }else{
+        pNew->wsFlags &= ~WHERE_ONEROW;
+      }
       whereLoopInsert(pBuilder, pNew);
       if( pNew->u.vtab.needFree ){
         sqlite3_free(pNew->u.vtab.idxStr);
@@ -3206,7 +3232,8 @@ static i8 wherePathSatisfiesOrderBy(
         nKeyCol = pIndex->nKeyCol;
         nColumn = pIndex->nColumn;
         assert( nColumn==nKeyCol+1 || !HasRowid(pIndex->pTable) );
-        assert( pIndex->aiColumn[nColumn-1]==(-1) || !HasRowid(pIndex->pTable));
+        assert( pIndex->aiColumn[nColumn-1]==XN_ROWID
+                          || !HasRowid(pIndex->pTable));
         isOrderDistinct = IsUniqueIndex(pIndex);
       }
 
@@ -3238,7 +3265,7 @@ static i8 wherePathSatisfiesOrderBy(
           revIdx = pIndex->aSortOrder[j];
           if( iColumn==pIndex->pTable->iPKey ) iColumn = -1;
         }else{
-          iColumn = -1;
+          iColumn = XN_ROWID;
           revIdx = 0;
         }
 
@@ -3264,9 +3291,15 @@ static i8 wherePathSatisfiesOrderBy(
           testcase( wctrlFlags & WHERE_GROUPBY );
           testcase( wctrlFlags & WHERE_DISTINCTBY );
           if( (wctrlFlags & (WHERE_GROUPBY|WHERE_DISTINCTBY))==0 ) bOnce = 0;
-          if( pOBExpr->op!=TK_COLUMN ) continue;
-          if( pOBExpr->iTable!=iCur ) continue;
-          if( pOBExpr->iColumn!=iColumn ) continue;
+          if( iColumn>=(-1) ){
+            if( pOBExpr->op!=TK_COLUMN ) continue;
+            if( pOBExpr->iTable!=iCur ) continue;
+            if( pOBExpr->iColumn!=iColumn ) continue;
+          }else{
+            if( sqlite3ExprCompare(pOBExpr,pIndex->aColExpr->a[j].pExpr,iCur) ){
+              continue;
+            }
+          }
           if( iColumn>=0 ){
             pColl = sqlite3ExprCollSeq(pWInfo->pParse, pOrderBy->a[i].pExpr);
             if( !pColl ) pColl = db->pDfltColl;
@@ -4097,7 +4130,8 @@ WhereInfo *sqlite3WhereBegin(
   }
 
   /* Construct the WhereLoop objects */
-  WHERETRACE(0xffff,("*** Optimizer Start ***\n"));
+  WHERETRACE(0xffff,("*** Optimizer Start *** (wctrlFlags: 0x%x)\n",
+             wctrlFlags));
 #if defined(WHERETRACE_ENABLED)
   if( sqlite3WhereTrace & 0x100 ){ /* Display all terms of the WHERE clause */
     int i;
@@ -4516,7 +4550,10 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
     }else if( pLoop->wsFlags & WHERE_MULTI_OR ){
       pIdx = pLevel->u.pCovidx;
     }
-    if( pIdx && !db->mallocFailed ){
+    if( pIdx
+     && (pWInfo->eOnePass==ONEPASS_OFF || !HasRowid(pIdx->pTable))
+     && !db->mallocFailed
+    ){
       last = sqlite3VdbeCurrentAddr(v);
       k = pLevel->addrBody;
       pOp = sqlite3VdbeGetOp(v, k);
@@ -4528,6 +4565,7 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
           if( !HasRowid(pTab) ){
             Index *pPk = sqlite3PrimaryKeyIndex(pTab);
             x = pPk->aiColumn[x];
+            assert( x>=0 );
           }
           x = sqlite3ColumnOfIndex(pIdx, x);
           if( x>=0 ){
diff --git a/src/wherecode.c b/src/wherecode.c
index 77b8be4be..a6c45f032 100644
--- a/src/wherecode.c
+++ b/src/wherecode.c
@@ -46,8 +46,8 @@ static void explainAppendTerm(
 */
 static const char *explainIndexColumnName(Index *pIdx, int i){
   i = pIdx->aiColumn[i];
-  if( i==(-2) ) return "<expr>";
-  if( i==(-1) ) return "rowid";
+  if( i==XN_EXPR ) return "<expr>";
+  if( i==XN_ROWID ) return "rowid";
   return pIdx->pTable->aCol[i].zName;
 }
 
@@ -514,7 +514,7 @@ static int codeAllEqualityTerms(
     sqlite3VdbeJumpHere(v, j);
     for(j=0; j<nSkip; j++){
       sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, j, regBase+j);
-      testcase( pIdx->aiColumn[j]==(-2) );
+      testcase( pIdx->aiColumn[j]==XN_EXPR );
       VdbeComment((v, "%s", explainIndexColumnName(pIdx, j)));
     }
   }    
@@ -700,8 +700,8 @@ Bitmask sqlite3WhereCodeOneLoopStart(
         disableTerm(pLevel, pLoop->aLTerm[j]);
       }
     }
-    pLevel->op = OP_VNext;
     pLevel->p1 = iCur;
+    pLevel->op = pWInfo->eOnePass ? OP_Noop : OP_VNext;
     pLevel->p2 = sqlite3VdbeCurrentAddr(v);
     sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
     sqlite3ExprCachePop(pParse);