Refactor the VdbeCursor object. It is now slightly smaller and faster and is

easier to understand.

FossilOrigin-Name: 9b1d174d862500a627840008ffac4c8419dc97e2

5 files changed, 214 insertions, 160 deletions

diff --git a/src/vdbe.c b/src/vdbe.c
index 5be906c67..7428d5f60 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -165,7 +165,7 @@ int sqlite3_found_count = 0;
        && sqlite3VdbeMemMakeWriteable(P) ){ goto no_mem;}
 
 /* Return true if the cursor was opened using the OP_OpenSorter opcode. */
-#define isSorter(x) ((x)->pSorter!=0)
+#define isSorter(x) ((x)->eCurType==CURTYPE_SORTER)
 
 /*
 ** Allocate VdbeCursor number iCur.  Return a pointer to it.  Return NULL
@@ -176,7 +176,7 @@ static VdbeCursor *allocateCursor(
   int iCur,             /* Index of the new VdbeCursor */
   int nField,           /* Number of fields in the table or index */
   int iDb,              /* Database the cursor belongs to, or -1 */
-  int isBtreeCursor     /* True for B-Tree.  False for pseudo-table or vtab */
+  u8 eCurType           /* Type of the new cursor */
 ){
   /* Find the memory cell that will be used to store the blob of memory
   ** required for this VdbeCursor structure. It is convenient to use a 
@@ -202,7 +202,7 @@ static VdbeCursor *allocateCursor(
   VdbeCursor *pCx = 0;
   nByte = 
       ROUND8(sizeof(VdbeCursor)) + 2*sizeof(u32)*nField + 
-      (isBtreeCursor?sqlite3BtreeCursorSize():0);
+      (eCurType==CURTYPE_BTREE?sqlite3BtreeCursorSize():0);
 
   assert( iCur<p->nCursor );
   if( p->apCsr[iCur] ){
@@ -212,13 +212,14 @@ static VdbeCursor *allocateCursor(
   if( SQLITE_OK==sqlite3VdbeMemClearAndResize(pMem, nByte) ){
     p->apCsr[iCur] = pCx = (VdbeCursor*)pMem->z;
     memset(pCx, 0, sizeof(VdbeCursor));
+    pCx->eCurType = eCurType;
     pCx->iDb = iDb;
     pCx->nField = nField;
     pCx->aOffset = &pCx->aType[nField];
-    if( isBtreeCursor ){
-      pCx->pCursor = (BtCursor*)
+    if( eCurType==CURTYPE_BTREE ){
+      pCx->uc.pCursor = (BtCursor*)
           &pMem->z[ROUND8(sizeof(VdbeCursor))+2*sizeof(u32)*nField];
-      sqlite3BtreeCursorZero(pCx->pCursor);
+      sqlite3BtreeCursorZero(pCx->uc.pCursor);
     }
   }
   return pCx;
@@ -2383,21 +2384,19 @@ case OP_Column: {
   assert( pC!=0 );
   assert( p2<pC->nField );
   aOffset = pC->aOffset;
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-  assert( pC->pVtabCursor==0 ); /* OP_Column never called on virtual table */
-#endif
-  pCrsr = pC->pCursor;
-  assert( pCrsr!=0 || pC->pseudoTableReg>0 ); /* pCrsr NULL on PseudoTables */
-  assert( pCrsr!=0 || pC->nullRow );          /* pC->nullRow on PseudoTables */
+  assert( pC->eCurType!=CURTYPE_VTAB ); /* OP_Column never called on virtual table */
+  assert( pC->eCurType!=CURTYPE_PSEUDO || pC->nullRow );
+  assert( pC->eCurType!=CURTYPE_SORTER );
+  pCrsr = pC->uc.pCursor;
 
   /* If the cursor cache is stale, bring it up-to-date */
   rc = sqlite3VdbeCursorMoveto(pC);
   if( rc ) goto abort_due_to_error;
   if( pC->cacheStatus!=p->cacheCtr ){
     if( pC->nullRow ){
-      if( pCrsr==0 ){
-        assert( pC->pseudoTableReg>0 );
-        pReg = &aMem[pC->pseudoTableReg];
+      if( pC->eCurType==CURTYPE_PSEUDO ){
+        assert( pC->uc.pseudoTableReg>0 );
+        pReg = &aMem[pC->uc.pseudoTableReg];
         assert( pReg->flags & MEM_Blob );
         assert( memIsValid(pReg) );
         pC->payloadSize = pC->szRow = avail = pReg->n;
@@ -2407,6 +2406,7 @@ case OP_Column: {
         goto op_column_out;
       }
     }else{
+      assert( pC->eCurType==CURTYPE_BTREE );
       assert( pCrsr );
       if( pC->isTable==0 ){
         assert( sqlite3BtreeCursorIsValid(pCrsr) );
@@ -2795,7 +2795,8 @@ case OP_Count: {         /* out2 */
   i64 nEntry;
   BtCursor *pCrsr;
 
-  pCrsr = p->apCsr[pOp->p1]->pCursor;
+  assert( p->apCsr[pOp->p1]->eCurType==CURTYPE_BTREE );
+  pCrsr = p->apCsr[pOp->p1]->uc.pCursor;
   assert( pCrsr );
   nEntry = 0;  /* Not needed.  Only used to silence a warning. */
   rc = sqlite3BtreeCount(pCrsr, &nEntry);
@@ -3380,12 +3381,12 @@ case OP_OpenWrite:
   assert( pOp->p1>=0 );
   assert( nField>=0 );
   testcase( nField==0 );  /* Table with INTEGER PRIMARY KEY and nothing else */
-  pCur = allocateCursor(p, pOp->p1, nField, iDb, 1);
+  pCur = allocateCursor(p, pOp->p1, nField, iDb, CURTYPE_BTREE);
   if( pCur==0 ) goto no_mem;
   pCur->nullRow = 1;
   pCur->isOrdered = 1;
   pCur->pgnoRoot = p2;
-  rc = sqlite3BtreeCursor(pX, p2, wrFlag, pKeyInfo, pCur->pCursor);
+  rc = sqlite3BtreeCursor(pX, p2, wrFlag, pKeyInfo, pCur->uc.pCursor);
   pCur->pKeyInfo = pKeyInfo;
   /* Set the VdbeCursor.isTable variable. Previous versions of
   ** SQLite used to check if the root-page flags were sane at this point
@@ -3400,7 +3401,7 @@ open_cursor_set_hints:
 #ifdef SQLITE_ENABLE_CURSOR_HINT
   testcase( pOp->p2 & OPFLAG_SEEKEQ );
 #endif
-  sqlite3BtreeCursorHintFlags(pCur->pCursor,
+  sqlite3BtreeCursorHintFlags(pCur->uc.pCursor,
                                (pOp->p5 & (OPFLAG_BULKCSR|OPFLAG_SEEKEQ)));
   break;
 }
@@ -3444,7 +3445,7 @@ case OP_OpenEphemeral: {
       SQLITE_OPEN_TRANSIENT_DB;
   assert( pOp->p1>=0 );
   assert( pOp->p2>=0 );
-  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, 1);
+  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, CURTYPE_BTREE);
   if( pCx==0 ) goto no_mem;
   pCx->nullRow = 1;
   pCx->isEphemeral = 1;
@@ -3468,11 +3469,11 @@ case OP_OpenEphemeral: {
         assert( pKeyInfo->db==db );
         assert( pKeyInfo->enc==ENC(db) );
         pCx->pKeyInfo = pKeyInfo;
-        rc = sqlite3BtreeCursor(pCx->pBt, pgno, BTREE_WRCSR, pKeyInfo, pCx->pCursor);
+        rc = sqlite3BtreeCursor(pCx->pBt, pgno, BTREE_WRCSR, pKeyInfo, pCx->uc.pCursor);
       }
       pCx->isTable = 0;
     }else{
-      rc = sqlite3BtreeCursor(pCx->pBt, MASTER_ROOT, BTREE_WRCSR, 0, pCx->pCursor);
+      rc = sqlite3BtreeCursor(pCx->pBt, MASTER_ROOT, BTREE_WRCSR, 0, pCx->uc.pCursor);
       pCx->isTable = 1;
     }
   }
@@ -3495,7 +3496,7 @@ case OP_SorterOpen: {
 
   assert( pOp->p1>=0 );
   assert( pOp->p2>=0 );
-  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, 1);
+  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, CURTYPE_SORTER);
   if( pCx==0 ) goto no_mem;
   pCx->pKeyInfo = pOp->p4.pKeyInfo;
   assert( pCx->pKeyInfo->db==db );
@@ -3515,7 +3516,7 @@ case OP_SequenceTest: {
   VdbeCursor *pC;
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   pC = p->apCsr[pOp->p1];
-  assert( pC->pSorter );
+  assert( isSorter(pC) );
   if( (pC->seqCount++)==0 ){
     goto jump_to_p2;
   }
@@ -3543,10 +3544,10 @@ case OP_OpenPseudo: {
 
   assert( pOp->p1>=0 );
   assert( pOp->p3>=0 );
-  pCx = allocateCursor(p, pOp->p1, pOp->p3, -1, 0);
+  pCx = allocateCursor(p, pOp->p1, pOp->p3, -1, CURTYPE_PSEUDO);
   if( pCx==0 ) goto no_mem;
   pCx->nullRow = 1;
-  pCx->pseudoTableReg = pOp->p2;
+  pCx->uc.pseudoTableReg = pOp->p2;
   pCx->isTable = 1;
   assert( pOp->p5==0 );
   break;
@@ -3578,7 +3579,7 @@ case OP_Close: {
 case OP_ColumnsUsed: {
   VdbeCursor *pC;
   pC = p->apCsr[pOp->p1];
-  assert( pC->pCursor );
+  assert( pC->eCurType==CURTYPE_BTREE );
   pC->maskUsed = *(u64*)pOp->p4.pI64;
   break;
 }
@@ -3686,12 +3687,12 @@ case OP_SeekGT: {       /* jump, in3 */
   assert( pOp->p2!=0 );
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
-  assert( pC->pseudoTableReg==0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
   assert( OP_SeekLE == OP_SeekLT+1 );
   assert( OP_SeekGE == OP_SeekLT+2 );
   assert( OP_SeekGT == OP_SeekLT+3 );
   assert( pC->isOrdered );
-  assert( pC->pCursor!=0 );
+  assert( pC->uc.pCursor!=0 );
   oc = pOp->opcode;
   eqOnly = 0;
   pC->nullRow = 0;
@@ -3701,7 +3702,7 @@ case OP_SeekGT: {       /* jump, in3 */
 
   if( pC->isTable ){
     /* The BTREE_SEEK_EQ flag is only set on index cursors */
-    assert( sqlite3BtreeCursorHasHint(pC->pCursor, BTREE_SEEK_EQ)==0 );
+    assert( sqlite3BtreeCursorHasHint(pC->uc.pCursor, BTREE_SEEK_EQ)==0 );
 
     /* The input value in P3 might be of any type: integer, real, string,
     ** blob, or NULL.  But it needs to be an integer before we can do
@@ -3745,7 +3746,7 @@ case OP_SeekGT: {       /* jump, in3 */
         if( (oc & 0x0001)==(OP_SeekLT & 0x0001) ) oc++;
       }
     } 
-    rc = sqlite3BtreeMovetoUnpacked(pC->pCursor, 0, (u64)iKey, 0, &res);
+    rc = sqlite3BtreeMovetoUnpacked(pC->uc.pCursor, 0, (u64)iKey, 0, &res);
     pC->movetoTarget = iKey;  /* Used by OP_Delete */
     if( rc!=SQLITE_OK ){
       goto abort_due_to_error;
@@ -3755,7 +3756,7 @@ case OP_SeekGT: {       /* jump, in3 */
     ** OP_SeekLE opcodes are allowed, and these must be immediately followed
     ** by an OP_IdxGT or OP_IdxLT opcode, respectively, with the same key.
     */
-    if( sqlite3BtreeCursorHasHint(pC->pCursor, BTREE_SEEK_EQ) ){
+    if( sqlite3BtreeCursorHasHint(pC->uc.pCursor, BTREE_SEEK_EQ) ){
       eqOnly = 1;
       assert( pOp->opcode==OP_SeekGE || pOp->opcode==OP_SeekLE );
       assert( pOp[1].opcode==OP_IdxLT || pOp[1].opcode==OP_IdxGT );
@@ -3790,7 +3791,7 @@ case OP_SeekGT: {       /* jump, in3 */
 #endif
     ExpandBlob(r.aMem);
     r.eqSeen = 0;
-    rc = sqlite3BtreeMovetoUnpacked(pC->pCursor, &r, 0, 0, &res);
+    rc = sqlite3BtreeMovetoUnpacked(pC->uc.pCursor, &r, 0, 0, &res);
     if( rc!=SQLITE_OK ){
       goto abort_due_to_error;
     }
@@ -3807,7 +3808,7 @@ case OP_SeekGT: {       /* jump, in3 */
   if( oc>=OP_SeekGE ){  assert( oc==OP_SeekGE || oc==OP_SeekGT );
     if( res<0 || (res==0 && oc==OP_SeekGT) ){
       res = 0;
-      rc = sqlite3BtreeNext(pC->pCursor, &res);
+      rc = sqlite3BtreeNext(pC->uc.pCursor, &res);
       if( rc!=SQLITE_OK ) goto abort_due_to_error;
     }else{
       res = 0;
@@ -3816,13 +3817,13 @@ case OP_SeekGT: {       /* jump, in3 */
     assert( oc==OP_SeekLT || oc==OP_SeekLE );
     if( res>0 || (res==0 && oc==OP_SeekLT) ){
       res = 0;
-      rc = sqlite3BtreePrevious(pC->pCursor, &res);
+      rc = sqlite3BtreePrevious(pC->uc.pCursor, &res);
       if( rc!=SQLITE_OK ) goto abort_due_to_error;
     }else{
       /* res might be negative because the table is empty.  Check to
       ** see if this is the case.
       */
-      res = sqlite3BtreeEof(pC->pCursor);
+      res = sqlite3BtreeEof(pC->uc.pCursor);
     }
   }
 seek_not_found:
@@ -3853,7 +3854,8 @@ case OP_Seek: {    /* in2 */
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
-  assert( pC->pCursor!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->uc.pCursor!=0 );
   assert( pC->isTable );
   pC->nullRow = 0;
   pIn2 = &aMem[pOp->p2];
@@ -3947,7 +3949,8 @@ case OP_Found: {        /* jump, in3 */
   pC->seekOp = pOp->opcode;
 #endif
   pIn3 = &aMem[pOp->p3];
-  assert( pC->pCursor!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->uc.pCursor!=0 );
   assert( pC->isTable==0 );
   pFree = 0;
   if( pOp->p4.i>0 ){
@@ -3984,7 +3987,7 @@ case OP_Found: {        /* jump, in3 */
       }
     }
   }
-  rc = sqlite3BtreeMovetoUnpacked(pC->pCursor, pIdxKey, 0, 0, &res);
+  rc = sqlite3BtreeMovetoUnpacked(pC->uc.pCursor, pIdxKey, 0, 0, &res);
   sqlite3DbFree(db, pFree);
   if( rc!=SQLITE_OK ){
     break;
@@ -4038,8 +4041,8 @@ case OP_NotExists: {        /* jump, in3 */
   pC->seekOp = 0;
 #endif
   assert( pC->isTable );
-  assert( pC->pseudoTableReg==0 );
-  pCrsr = pC->pCursor;
+  assert( pC->eCurType==CURTYPE_BTREE );
+  pCrsr = pC->uc.pCursor;
   assert( pCrsr!=0 );
   res = 0;
   iKey = pIn3->u.i;
@@ -4073,6 +4076,7 @@ case OP_NotExists: {        /* jump, in3 */
 case OP_Sequence: {           /* out2 */
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   assert( p->apCsr[pOp->p1]!=0 );
+  assert( p->apCsr[pOp->p1]->eCurType!=CURTYPE_VTAB );
   pOut = out2Prerelease(p, pOp);
   pOut->u.i = p->apCsr[pOp->p1]->seqCount++;
   break;
@@ -4108,7 +4112,8 @@ case OP_NewRowid: {           /* out2 */
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
-  assert( pC->pCursor!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->uc.pCursor!=0 );
   {
     /* The next rowid or record number (different terms for the same
     ** thing) is obtained in a two-step algorithm.
@@ -4136,15 +4141,15 @@ case OP_NewRowid: {           /* out2 */
 #endif
 
     if( !pC->useRandomRowid ){
-      rc = sqlite3BtreeLast(pC->pCursor, &res);
+      rc = sqlite3BtreeLast(pC->uc.pCursor, &res);
       if( rc!=SQLITE_OK ){
         goto abort_due_to_error;
       }
       if( res ){
         v = 1;   /* IMP: R-61914-48074 */
       }else{
-        assert( sqlite3BtreeCursorIsValid(pC->pCursor) );
-        rc = sqlite3BtreeKeySize(pC->pCursor, &v);
+        assert( sqlite3BtreeCursorIsValid(pC->uc.pCursor) );
+        rc = sqlite3BtreeKeySize(pC->uc.pCursor, &v);
         assert( rc==SQLITE_OK );   /* Cannot fail following BtreeLast() */
         if( v>=MAX_ROWID ){
           pC->useRandomRowid = 1;
@@ -4195,7 +4200,7 @@ case OP_NewRowid: {           /* out2 */
       do{
         sqlite3_randomness(sizeof(v), &v);
         v &= (MAX_ROWID>>1); v++;  /* Ensure that v is greater than zero */
-      }while(  ((rc = sqlite3BtreeMovetoUnpacked(pC->pCursor, 0, (u64)v,
+      }while(  ((rc = sqlite3BtreeMovetoUnpacked(pC->uc.pCursor, 0, (u64)v,
                                                  0, &res))==SQLITE_OK)
             && (res==0)
             && (++cnt<100));
@@ -4275,8 +4280,8 @@ case OP_InsertInt: {
   assert( memIsValid(pData) );
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
-  assert( pC->pCursor!=0 );
-  assert( pC->pseudoTableReg==0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->uc.pCursor!=0 );
   assert( pC->isTable );
   REGISTER_TRACE(pOp->p2, pData);
 
@@ -4305,7 +4310,7 @@ case OP_InsertInt: {
   }else{
     nZero = 0;
   }
-  rc = sqlite3BtreeInsert(pC->pCursor, 0, iKey,
+  rc = sqlite3BtreeInsert(pC->uc.pCursor, 0, iKey,
                           pData->z, pData->n, nZero,
                           (pOp->p5 & OPFLAG_APPEND)!=0, seekResult
   );
@@ -4352,12 +4357,13 @@ case OP_Delete: {
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
-  assert( pC->pCursor!=0 );  /* Only valid for real tables, no pseudotables */
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->uc.pCursor!=0 );
   assert( pC->deferredMoveto==0 );
 
   hasUpdateCallback = db->xUpdateCallback && pOp->p4.z && pC->isTable;
   if( pOp->p5 && hasUpdateCallback ){
-    sqlite3BtreeKeySize(pC->pCursor, &pC->movetoTarget);
+    sqlite3BtreeKeySize(pC->uc.pCursor, &pC->movetoTarget);
   }
 
 #ifdef SQLITE_DEBUG
@@ -4366,12 +4372,12 @@ case OP_Delete: {
   ** is being deleted */
   if( pOp->p4.z && pC->isTable && pOp->p5==0 ){
     i64 iKey = 0;
-    sqlite3BtreeKeySize(pC->pCursor, &iKey);
+    sqlite3BtreeKeySize(pC->uc.pCursor, &iKey);
     assert( pC->movetoTarget==iKey ); 
   }
 #endif
  
-  rc = sqlite3BtreeDelete(pC->pCursor, pOp->p5);
+  rc = sqlite3BtreeDelete(pC->uc.pCursor, pOp->p5);
   pC->cacheStatus = CACHE_STALE;
 
   /* Invoke the update-hook if required. */
@@ -4488,14 +4494,14 @@ case OP_RowData: {
   /* Note that RowKey and RowData are really exactly the same instruction */
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   pC = p->apCsr[pOp->p1];
+  assert( pC!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE );
   assert( isSorter(pC)==0 );
   assert( pC->isTable || pOp->opcode!=OP_RowData );
   assert( pC->isTable==0 || pOp->opcode==OP_RowData );
-  assert( pC!=0 );
   assert( pC->nullRow==0 );
-  assert( pC->pseudoTableReg==0 );
-  assert( pC->pCursor!=0 );
-  pCrsr = pC->pCursor;
+  assert( pC->uc.pCursor!=0 );
+  pCrsr = pC->uc.pCursor;
 
   /* The OP_RowKey and OP_RowData opcodes always follow OP_NotExists or
   ** OP_Rewind/Op_Next with no intervening instructions that might invalidate
@@ -4563,29 +4569,31 @@ case OP_Rowid: {                 /* out2 */
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
-  assert( pC->pseudoTableReg==0 || pC->nullRow );
+  assert( pC->eCurType!=CURTYPE_PSEUDO || pC->nullRow );
   if( pC->nullRow ){
     pOut->flags = MEM_Null;
     break;
   }else if( pC->deferredMoveto ){
     v = pC->movetoTarget;
 #ifndef SQLITE_OMIT_VIRTUALTABLE
-  }else if( pC->pVtabCursor ){
-    pVtab = pC->pVtabCursor->pVtab;
+  }else if( pC->eCurType==CURTYPE_VTAB ){
+    assert( pC->uc.pVCur!=0 );
+    pVtab = pC->uc.pVCur->pVtab;
     pModule = pVtab->pModule;
     assert( pModule->xRowid );
-    rc = pModule->xRowid(pC->pVtabCursor, &v);
+    rc = pModule->xRowid(pC->uc.pVCur, &v);
     sqlite3VtabImportErrmsg(p, pVtab);
 #endif /* SQLITE_OMIT_VIRTUALTABLE */
   }else{
-    assert( pC->pCursor!=0 );
+    assert( pC->eCurType==CURTYPE_BTREE );
+    assert( pC->uc.pCursor!=0 );
     rc = sqlite3VdbeCursorRestore(pC);
     if( rc ) goto abort_due_to_error;
     if( pC->nullRow ){
       pOut->flags = MEM_Null;
       break;
     }
-    rc = sqlite3BtreeKeySize(pC->pCursor, &v);
+    rc = sqlite3BtreeKeySize(pC->uc.pCursor, &v);
     assert( rc==SQLITE_OK );  /* Always so because of CursorRestore() above */
   }
   pOut->u.i = v;
@@ -4606,8 +4614,9 @@ case OP_NullRow: {
   assert( pC!=0 );
   pC->nullRow = 1;
   pC->cacheStatus = CACHE_STALE;
-  if( pC->pCursor ){
-    sqlite3BtreeClearCursor(pC->pCursor);
+  if( pC->eCurType==CURTYPE_BTREE ){
+    assert( pC->uc.pCursor!=0 );
+    sqlite3BtreeClearCursor(pC->uc.pCursor);
   }
   break;
 }
@@ -4632,7 +4641,8 @@ case OP_Last: {        /* jump */
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
-  pCrsr = pC->pCursor;
+  assert( pC->eCurType==CURTYPE_BTREE );
+  pCrsr = pC->uc.pCursor;
   res = 0;
   assert( pCrsr!=0 );
   rc = sqlite3BtreeLast(pCrsr, &res);
@@ -4700,7 +4710,8 @@ case OP_Rewind: {        /* jump */
   if( isSorter(pC) ){
     rc = sqlite3VdbeSorterRewind(pC, &res);
   }else{
-    pCrsr = pC->pCursor;
+    assert( pC->eCurType==CURTYPE_BTREE );
+    pCrsr = pC->uc.pCursor;
     assert( pCrsr );
     rc = sqlite3BtreeFirst(pCrsr, &res);
     pC->deferredMoveto = 0;
@@ -4797,7 +4808,7 @@ case OP_Next:          /* jump */
   res = pOp->p3;
   assert( pC!=0 );
   assert( pC->deferredMoveto==0 );
-  assert( pC->pCursor );
+  assert( pC->eCurType==CURTYPE_BTREE );
   assert( res==0 || (res==1 && pC->isTable==0) );
   testcase( res==1 );
   assert( pOp->opcode!=OP_Next || pOp->p4.xAdvance==sqlite3BtreeNext );
@@ -4814,7 +4825,7 @@ case OP_Next:          /* jump */
        || pC->seekOp==OP_SeekLT || pC->seekOp==OP_SeekLE
        || pC->seekOp==OP_Last );
 
-  rc = pOp->p4.xAdvance(pC->pCursor, &res);
+  rc = pOp->p4.xAdvance(pC->uc.pCursor, &res);
 next_tail:
   pC->cacheStatus = CACHE_STALE;
   VdbeBranchTaken(res==0,2);
@@ -4865,7 +4876,7 @@ case OP_IdxInsert: {        /* in2 */
   pIn2 = &aMem[pOp->p2];
   assert( pIn2->flags & MEM_Blob );
   if( pOp->p5 & OPFLAG_NCHANGE ) p->nChange++;
-  assert( pC->pCursor!=0 );
+  assert( pC->eCurType==CURTYPE_BTREE || pOp->opcode==OP_SorterInsert );
   assert( pC->isTable==0 );
   rc = ExpandBlob(pIn2);
   if( rc==SQLITE_OK ){
@@ -4874,7 +4885,7 @@ case OP_IdxInsert: {        /* in2 */
     }else{
       nKey = pIn2->n;
       zKey = pIn2->z;
-      rc = sqlite3BtreeInsert(pC->pCursor, zKey, nKey, "", 0, 0, pOp->p3, 
+      rc = sqlite3BtreeInsert(pC->uc.pCursor, zKey, nKey, "", 0, 0, pOp->p3, 
           ((pOp->p5 & OPFLAG_USESEEKRESULT) ? pC->seekResult : 0)
           );
       assert( pC->deferredMoveto==0 );
@@ -4902,7 +4913,8 @@ case OP_IdxDelete: {
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
-  pCrsr = pC->pCursor;
+  assert( pC->eCurType==CURTYPE_BTREE );
+  pCrsr = pC->uc.pCursor;
   assert( pCrsr!=0 );
   assert( pOp->p5==0 );
   r.pKeyInfo = pC->pKeyInfo;
@@ -4939,7 +4951,8 @@ case OP_IdxRowid: {              /* out2 */
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
-  pCrsr = pC->pCursor;
+  assert( pC->eCurType==CURTYPE_BTREE );
+  pCrsr = pC->uc.pCursor;
   assert( pCrsr!=0 );
   pOut->flags = MEM_Null;
   assert( pC->isTable==0 );
@@ -5020,7 +5033,8 @@ case OP_IdxGE:  {       /* jump */
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
   assert( pC->isOrdered );
-  assert( pC->pCursor!=0);
+  assert( pC->eCurType==CURTYPE_BTREE );
+  assert( pC->uc.pCursor!=0);
   assert( pC->deferredMoveto==0 );
   assert( pOp->p5==0 || pOp->p5==1 );
   assert( pOp->p4type==P4_INT32 );
@@ -5153,11 +5167,12 @@ case OP_ResetSorter: {
   assert( pOp->p1>=0 && pOp->p1<p->nCursor );
   pC = p->apCsr[pOp->p1];
   assert( pC!=0 );
-  if( pC->pSorter ){
-    sqlite3VdbeSorterReset(db, pC->pSorter);
+  if( isSorter(pC) ){
+    sqlite3VdbeSorterReset(db, pC->uc.pSorter);
   }else{
+    assert( pC->eCurType==CURTYPE_BTREE );
     assert( pC->isEphemeral );
-    rc = sqlite3BtreeClearTableOfCursor(pC->pCursor);
+    rc = sqlite3BtreeClearTableOfCursor(pC->uc.pCursor);
   }
   break;
 }
@@ -6231,33 +6246,33 @@ case OP_VDestroy: {
 */
 case OP_VOpen: {
   VdbeCursor *pCur;
-  sqlite3_vtab_cursor *pVtabCursor;
+  sqlite3_vtab_cursor *pVCur;
   sqlite3_vtab *pVtab;
   const sqlite3_module *pModule;
 
   assert( p->bIsReader );
   pCur = 0;
-  pVtabCursor = 0;
+  pVCur = 0;
   pVtab = pOp->p4.pVtab->pVtab;
   if( pVtab==0 || NEVER(pVtab->pModule==0) ){
     rc = SQLITE_LOCKED;
     break;
   }
   pModule = pVtab->pModule;
-  rc = pModule->xOpen(pVtab, &pVtabCursor);
+  rc = pModule->xOpen(pVtab, &pVCur);
   sqlite3VtabImportErrmsg(p, pVtab);
   if( SQLITE_OK==rc ){
     /* Initialize sqlite3_vtab_cursor base class */
-    pVtabCursor->pVtab = pVtab;
+    pVCur->pVtab = pVtab;
 
     /* Initialize vdbe cursor object */
-    pCur = allocateCursor(p, pOp->p1, 0, -1, 0);
+    pCur = allocateCursor(p, pOp->p1, 0, -1, CURTYPE_VTAB);
     if( pCur ){
-      pCur->pVtabCursor = pVtabCursor;
+      pCur->uc.pVCur = pVCur;
       pVtab->nRef++;
     }else{
       assert( db->mallocFailed );
-      pModule->xClose(pVtabCursor);
+      pModule->xClose(pVCur);
       goto no_mem;
     }
   }
@@ -6291,7 +6306,7 @@ case OP_VFilter: {   /* jump */
   const sqlite3_module *pModule;
   Mem *pQuery;
   Mem *pArgc;
-  sqlite3_vtab_cursor *pVtabCursor;
+  sqlite3_vtab_cursor *pVCur;
   sqlite3_vtab *pVtab;
   VdbeCursor *pCur;
   int res;
@@ -6303,9 +6318,9 @@ case OP_VFilter: {   /* jump */
   pCur = p->apCsr[pOp->p1];
   assert( memIsValid(pQuery) );
   REGISTER_TRACE(pOp->p3, pQuery);
-  assert( pCur->pVtabCursor );
-  pVtabCursor = pCur->pVtabCursor;
-  pVtab = pVtabCursor->pVtab;
+  assert( pCur->eCurType==CURTYPE_VTAB );
+  pVCur = pCur->uc.pVCur;
+  pVtab = pVCur->pVtab;
   pModule = pVtab->pModule;
 
   /* Grab the index number and argc parameters */
@@ -6319,10 +6334,10 @@ case OP_VFilter: {   /* jump */
   for(i = 0; i<nArg; i++){
     apArg[i] = &pArgc[i+1];
   }
-  rc = pModule->xFilter(pVtabCursor, iQuery, pOp->p4.z, nArg, apArg);
+  rc = pModule->xFilter(pVCur, iQuery, pOp->p4.z, nArg, apArg);
   sqlite3VtabImportErrmsg(p, pVtab);
   if( rc==SQLITE_OK ){
-    res = pModule->xEof(pVtabCursor);
+    res = pModule->xEof(pVCur);
   }
   pCur->nullRow = 0;
   VdbeBranchTaken(res!=0,2);
@@ -6346,7 +6361,7 @@ case OP_VColumn: {
   sqlite3_context sContext;
 
   VdbeCursor *pCur = p->apCsr[pOp->p1];
-  assert( pCur->pVtabCursor );
+  assert( pCur->eCurType==CURTYPE_VTAB );
   assert( pOp->p3>0 && pOp->p3<=(p->nMem-p->nCursor) );
   pDest = &aMem[pOp->p3];
   memAboutToChange(p, pDest);
@@ -6354,13 +6369,13 @@ case OP_VColumn: {
     sqlite3VdbeMemSetNull(pDest);
     break;
   }
-  pVtab = pCur->pVtabCursor->pVtab;
+  pVtab = pCur->uc.pVCur->pVtab;
   pModule = pVtab->pModule;
   assert( pModule->xColumn );
   memset(&sContext, 0, sizeof(sContext));
   sContext.pOut = pDest;
   MemSetTypeFlag(pDest, MEM_Null);
-  rc = pModule->xColumn(pCur->pVtabCursor, &sContext, pOp->p2);
+  rc = pModule->xColumn(pCur->uc.pVCur, &sContext, pOp->p2);
   sqlite3VtabImportErrmsg(p, pVtab);
   if( sContext.isError ){
     rc = sContext.isError;
@@ -6391,11 +6406,11 @@ case OP_VNext: {   /* jump */
 
   res = 0;
   pCur = p->apCsr[pOp->p1];
-  assert( pCur->pVtabCursor );
+  assert( pCur->eCurType==CURTYPE_VTAB );
   if( pCur->nullRow ){
     break;
   }
-  pVtab = pCur->pVtabCursor->pVtab;
+  pVtab = pCur->uc.pVCur->pVtab;
   pModule = pVtab->pModule;
   assert( pModule->xNext );
 
@@ -6405,10 +6420,10 @@ case OP_VNext: {   /* jump */
   ** data is available) and the error code returned when xColumn or
   ** some other method is next invoked on the save virtual table cursor.
   */
-  rc = pModule->xNext(pCur->pVtabCursor);
+  rc = pModule->xNext(pCur->uc.pVCur);
   sqlite3VtabImportErrmsg(p, pVtab);
   if( rc==SQLITE_OK ){
-    res = pModule->xEof(pCur->pVtabCursor);
+    res = pModule->xEof(pCur->uc.pVCur);
   }
   VdbeBranchTaken(!res,2);
   if( !res ){
@@ -6632,7 +6647,8 @@ case OP_CursorHint: {
   assert( pOp->p4type==P4_EXPR );
   pC = p->apCsr[pOp->p1];
   if( pC ){
-    sqlite3BtreeCursorHint(pC->pCursor, BTREE_HINT_RANGE, pOp->p4.pExpr, aMem);
+    assert( pC->eCurType==CURTYPE_BTREE );
+    sqlite3BtreeCursorHint(pC->uc.pCursor, BTREE_HINT_RANGE, pOp->p4.pExpr, aMem);
   }
   break;
 }
diff --git a/src/vdbeInt.h b/src/vdbeInt.h
index 729304bd8..d1de55eb1 100644
--- a/src/vdbeInt.h
+++ b/src/vdbeInt.h
@@ -58,42 +58,48 @@ typedef struct Explain Explain;
 /* Elements of the linked list at Vdbe.pAuxData */
 typedef struct AuxData AuxData;
 
+/* Types of VDBE cursors */
+#define CURTYPE_BTREE       0
+#define CURTYPE_SORTER      1
+#define CURTYPE_VTAB        2
+#define CURTYPE_PSEUDO      3
+
 /*
-** A cursor is a pointer into a single BTree within a database file.
-** The cursor can seek to a BTree entry with a particular key, or
-** loop over all entries of the Btree.  You can also insert new BTree
-** entries or retrieve the key or data from the entry that the cursor
-** is currently pointing to.
+** A VdbeCursor is an superclass (a wrapper) for various cursor objects:
 **
-** Cursors can also point to virtual tables, sorters, or "pseudo-tables".
-** A pseudo-table is a single-row table implemented by registers.
-** 
-** Every cursor that the virtual machine has open is represented by an
-** instance of the following structure.
+**      * A b-tree cursor
+**          -  In the main database or in an ephemeral database
+**          -  On either an index or a table
+**      * A sorter
+**      * A virtual table
+**      * A one-row "pseudotable" stored in a single register
 */
 struct VdbeCursor {
-  BtCursor *pCursor;    /* The cursor structure of the backend */
-  Btree *pBt;           /* Separate file holding temporary table */
-  KeyInfo *pKeyInfo;    /* Info about index keys needed by index cursors */
-  int seekResult;       /* Result of previous sqlite3BtreeMoveto() */
-  int pseudoTableReg;   /* Register holding pseudotable content. */
-  i16 nField;           /* Number of fields in the header */
-  u16 nHdrParsed;       /* Number of header fields parsed so far */
-#ifdef SQLITE_DEBUG
-  u8 seekOp;            /* Most recent seek operation on this cursor */
-#endif
+  u8 eCurType;          /* One of the CURTYPE_* values above */
   i8 iDb;               /* Index of cursor database in db->aDb[] (or -1) */
   u8 nullRow;           /* True if pointing to a row with no data */
   u8 deferredMoveto;    /* A call to sqlite3BtreeMoveto() is needed */
+  u8 isTable;           /* True for rowid tables.  False for indexes */
+#ifdef SQLITE_DEBUG
+  u8 seekOp;            /* Most recent seek operation on this cursor */
+#endif
   Bool isEphemeral:1;   /* True for an ephemeral table */
   Bool useRandomRowid:1;/* Generate new record numbers semi-randomly */
-  Bool isTable:1;       /* True if a table requiring integer keys */
   Bool isOrdered:1;     /* True if the underlying table is BTREE_UNORDERED */
   Pgno pgnoRoot;        /* Root page of the open btree cursor */
-  sqlite3_vtab_cursor *pVtabCursor;  /* The cursor for a virtual table */
+  i16 nField;           /* Number of fields in the header */
+  u16 nHdrParsed;       /* Number of header fields parsed so far */
+  union {
+    BtCursor *pCursor;          /* CURTYPE_BTREE.  Btree cursor */
+    sqlite3_vtab_cursor *pVCur; /* CURTYPE_VTAB.   Vtab cursor */
+    int pseudoTableReg;         /* CURTYPE_PSEUDO. Reg holding content. */
+    VdbeSorter *pSorter;        /* CURTYPE_SORTER. Sorter object */
+  } uc;
+  Btree *pBt;           /* Separate file holding temporary table */
+  KeyInfo *pKeyInfo;    /* Info about index keys needed by index cursors */
+  int seekResult;       /* Result of previous sqlite3BtreeMoveto() */
   i64 seqCount;         /* Sequence counter */
   i64 movetoTarget;     /* Argument to the deferred sqlite3BtreeMoveto() */
-  VdbeSorter *pSorter;  /* Sorter object for OP_SorterOpen cursors */
 #ifdef SQLITE_ENABLE_COLUMN_USED_MASK
   u64 maskUsed;         /* Mask of columns used by this cursor */
 #endif
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index a5bc0b71a..9ced9480b 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -1930,23 +1930,34 @@ void sqlite3VdbeFreeCursor(Vdbe *p, VdbeCursor *pCx){
   if( pCx==0 ){
     return;
   }
-  sqlite3VdbeSorterClose(p->db, pCx);
-  if( pCx->pBt ){
-    sqlite3BtreeClose(pCx->pBt);
-    /* The pCx->pCursor will be close automatically, if it exists, by
-    ** the call above. */
-  }else if( pCx->pCursor ){
-    sqlite3BtreeCloseCursor(pCx->pCursor);
-  }
+  assert( pCx->pBt==0 || pCx->eCurType==CURTYPE_BTREE );
+  switch( pCx->eCurType ){
+    case CURTYPE_SORTER: {
+      sqlite3VdbeSorterClose(p->db, pCx);
+      break;
+    }
+    case CURTYPE_BTREE: {
+      if( pCx->pBt ){
+        sqlite3BtreeClose(pCx->pBt);
+        /* The pCx->pCursor will be close automatically, if it exists, by
+        ** the call above. */
+      }else{
+        assert( pCx->uc.pCursor!=0 );
+        sqlite3BtreeCloseCursor(pCx->uc.pCursor);
+      }
+      break;
+    }
 #ifndef SQLITE_OMIT_VIRTUALTABLE
-  else if( pCx->pVtabCursor ){
-    sqlite3_vtab_cursor *pVtabCursor = pCx->pVtabCursor;
-    const sqlite3_module *pModule = pVtabCursor->pVtab->pModule;
-    assert( pVtabCursor->pVtab->nRef>0 );
-    pVtabCursor->pVtab->nRef--;
-    pModule->xClose(pVtabCursor);
-  }
+    case CURTYPE_VTAB: {
+      sqlite3_vtab_cursor *pVCur = pCx->uc.pVCur;
+      const sqlite3_module *pModule = pVCur->pVtab->pModule;
+      assert( pVCur->pVtab->nRef>0 );
+      pVCur->pVtab->nRef--;
+      pModule->xClose(pVCur);
+      break;
+    }
 #endif
+  }
 }
 
 /*
@@ -2933,7 +2944,8 @@ static int SQLITE_NOINLINE handleDeferredMoveto(VdbeCursor *p){
 #endif
   assert( p->deferredMoveto );
   assert( p->isTable );
-  rc = sqlite3BtreeMovetoUnpacked(p->pCursor, 0, p->movetoTarget, 0, &res);
+  assert( p->eCurType==CURTYPE_BTREE );
+  rc = sqlite3BtreeMovetoUnpacked(p->uc.pCursor, 0, p->movetoTarget, 0, &res);
   if( rc ) return rc;
   if( res!=0 ) return SQLITE_CORRUPT_BKPT;
 #ifdef SQLITE_TEST
@@ -2953,9 +2965,10 @@ static int SQLITE_NOINLINE handleDeferredMoveto(VdbeCursor *p){
 */
 static int SQLITE_NOINLINE handleMovedCursor(VdbeCursor *p){
   int isDifferentRow, rc;
-  assert( p->pCursor!=0 );
-  assert( sqlite3BtreeCursorHasMoved(p->pCursor) );
-  rc = sqlite3BtreeCursorRestore(p->pCursor, &isDifferentRow);
+  assert( p->eCurType==CURTYPE_BTREE );
+  assert( p->uc.pCursor!=0 );
+  assert( sqlite3BtreeCursorHasMoved(p->uc.pCursor) );
+  rc = sqlite3BtreeCursorRestore(p->uc.pCursor, &isDifferentRow);
   p->cacheStatus = CACHE_STALE;
   if( isDifferentRow ) p->nullRow = 1;
   return rc;
@@ -2966,7 +2979,8 @@ static int SQLITE_NOINLINE handleMovedCursor(VdbeCursor *p){
 ** if need be.  Return any I/O error from the restore operation.
 */
 int sqlite3VdbeCursorRestore(VdbeCursor *p){
-  if( sqlite3BtreeCursorHasMoved(p->pCursor) ){
+  assert( p->eCurType==CURTYPE_BTREE );
+  if( sqlite3BtreeCursorHasMoved(p->uc.pCursor) ){
     return handleMovedCursor(p);
   }
   return SQLITE_OK;
@@ -2986,11 +3000,13 @@ int sqlite3VdbeCursorRestore(VdbeCursor *p){
 ** not been deleted out from under the cursor, then this routine is a no-op.
 */
 int sqlite3VdbeCursorMoveto(VdbeCursor *p){
-  if( p->deferredMoveto ){
-    return handleDeferredMoveto(p);
-  }
-  if( p->pCursor && sqlite3BtreeCursorHasMoved(p->pCursor) ){
-    return handleMovedCursor(p);
+  if( p->eCurType==CURTYPE_BTREE ){
+    if( p->deferredMoveto ){
+      return handleDeferredMoveto(p);
+    }
+    if( sqlite3BtreeCursorHasMoved(p->uc.pCursor) ){
+      return handleMovedCursor(p);
+    }
   }
   return SQLITE_OK;
 }
@@ -4303,9 +4319,11 @@ int sqlite3VdbeIdxKeyCompare(
 ){
   i64 nCellKey = 0;
   int rc;
-  BtCursor *pCur = pC->pCursor;
+  BtCursor *pCur;
   Mem m;
 
+  assert( pC->eCurType==CURTYPE_BTREE );
+  pCur = pC->uc.pCursor;
   assert( sqlite3BtreeCursorIsValid(pCur) );
   VVA_ONLY(rc =) sqlite3BtreeKeySize(pCur, &nCellKey);
   assert( rc==SQLITE_OK );    /* pCur is always valid so KeySize cannot fail */
@@ -4316,7 +4334,7 @@ int sqlite3VdbeIdxKeyCompare(
     return SQLITE_CORRUPT_BKPT;
   }
   sqlite3VdbeMemInit(&m, db, 0);
-  rc = sqlite3VdbeMemFromBtree(pC->pCursor, 0, (u32)nCellKey, 1, &m);
+  rc = sqlite3VdbeMemFromBtree(pCur, 0, (u32)nCellKey, 1, &m);
   if( rc ){
     return rc;
   }
diff --git a/src/vdbeblob.c b/src/vdbeblob.c
index 30a329189..a4718efac 100644
--- a/src/vdbeblob.c
+++ b/src/vdbeblob.c
@@ -76,7 +76,7 @@ static int blobSeekToRow(Incrblob *p, sqlite3_int64 iRow, char **pzErr){
     }else{
       p->iOffset = pC->aType[p->iCol + pC->nField];
       p->nByte = sqlite3VdbeSerialTypeLen(type);
-      p->pCsr =  pC->pCursor;
+      p->pCsr =  pC->uc.pCursor;
       sqlite3BtreeIncrblobCursor(p->pCsr);
     }
   }
diff --git a/src/vdbesort.c b/src/vdbesort.c
index 9840bed31..54e538fd5 100644
--- a/src/vdbesort.c
+++ b/src/vdbesort.c
@@ -961,11 +961,12 @@ int sqlite3VdbeSorterInit(
 #endif
 
   assert( pCsr->pKeyInfo && pCsr->pBt==0 );
+  assert( pCsr->eCurType==CURTYPE_SORTER );
   szKeyInfo = sizeof(KeyInfo) + (pCsr->pKeyInfo->nField-1)*sizeof(CollSeq*);
   sz = sizeof(VdbeSorter) + nWorker * sizeof(SortSubtask);
 
   pSorter = (VdbeSorter*)sqlite3DbMallocZero(db, sz + szKeyInfo);
-  pCsr->pSorter = pSorter;
+  pCsr->uc.pSorter = pSorter;
   if( pSorter==0 ){
     rc = SQLITE_NOMEM;
   }else{
@@ -1249,12 +1250,14 @@ void sqlite3VdbeSorterReset(sqlite3 *db, VdbeSorter *pSorter){
 ** Free any cursor components allocated by sqlite3VdbeSorterXXX routines.
 */
 void sqlite3VdbeSorterClose(sqlite3 *db, VdbeCursor *pCsr){
-  VdbeSorter *pSorter = pCsr->pSorter;
+  VdbeSorter *pSorter;
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
   if( pSorter ){
     sqlite3VdbeSorterReset(db, pSorter);
     sqlite3_free(pSorter->list.aMemory);
     sqlite3DbFree(db, pSorter);
-    pCsr->pSorter = 0;
+    pCsr->uc.pSorter = 0;
   }
 }
 
@@ -1752,15 +1755,16 @@ int sqlite3VdbeSorterWrite(
   const VdbeCursor *pCsr,         /* Sorter cursor */
   Mem *pVal                       /* Memory cell containing record */
 ){
-  VdbeSorter *pSorter = pCsr->pSorter;
+  VdbeSorter *pSorter;
   int rc = SQLITE_OK;             /* Return Code */
   SorterRecord *pNew;             /* New list element */
-
   int bFlush;                     /* True to flush contents of memory to PMA */
   int nReq;                       /* Bytes of memory required */
   int nPMA;                       /* Bytes of PMA space required */
   int t;                          /* serial type of first record field */
 
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
   getVarint32((const u8*)&pVal->z[1], t);
   if( t>0 && t<10 && t!=7 ){
     pSorter->typeMask &= SORTER_TYPE_INTEGER;
@@ -2552,9 +2556,11 @@ static int vdbeSorterSetupMerge(VdbeSorter *pSorter){
 ** in sorted order.
 */
 int sqlite3VdbeSorterRewind(const VdbeCursor *pCsr, int *pbEof){
-  VdbeSorter *pSorter = pCsr->pSorter;
+  VdbeSorter *pSorter;
   int rc = SQLITE_OK;             /* Return code */
 
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
   assert( pSorter );
 
   /* If no data has been written to disk, then do not do so now. Instead,
@@ -2598,9 +2604,11 @@ int sqlite3VdbeSorterRewind(const VdbeCursor *pCsr, int *pbEof){
 ** Advance to the next element in the sorter.
 */
 int sqlite3VdbeSorterNext(sqlite3 *db, const VdbeCursor *pCsr, int *pbEof){
-  VdbeSorter *pSorter = pCsr->pSorter;
+  VdbeSorter *pSorter;
   int rc;                         /* Return code */
 
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
   assert( pSorter->bUsePMA || (pSorter->pReader==0 && pSorter->pMerger==0) );
   if( pSorter->bUsePMA ){
     assert( pSorter->pReader==0 || pSorter->pMerger==0 );
@@ -2660,9 +2668,11 @@ static void *vdbeSorterRowkey(
 ** Copy the current sorter key into the memory cell pOut.
 */
 int sqlite3VdbeSorterRowkey(const VdbeCursor *pCsr, Mem *pOut){
-  VdbeSorter *pSorter = pCsr->pSorter;
+  VdbeSorter *pSorter;
   void *pKey; int nKey;           /* Sorter key to copy into pOut */
 
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
   pKey = vdbeSorterRowkey(pSorter, &nKey);
   if( sqlite3VdbeMemClearAndResize(pOut, nKey) ){
     return SQLITE_NOMEM;
@@ -2696,12 +2706,16 @@ int sqlite3VdbeSorterCompare(
   int nKeyCol,                    /* Compare this many columns */
   int *pRes                       /* OUT: Result of comparison */
 ){
-  VdbeSorter *pSorter = pCsr->pSorter;
-  UnpackedRecord *r2 = pSorter->pUnpacked;
-  KeyInfo *pKeyInfo = pCsr->pKeyInfo;
+  VdbeSorter *pSorter;
+  UnpackedRecord *r2;
+  KeyInfo *pKeyInfo;
   int i;
   void *pKey; int nKey;           /* Sorter key to compare pVal with */
 
+  assert( pCsr->eCurType==CURTYPE_SORTER );
+  pSorter = pCsr->uc.pSorter;
+  r2 = pSorter->pUnpacked;
+  pKeyInfo = pCsr->pKeyInfo;
   if( r2==0 ){
     char *p;
     r2 = pSorter->pUnpacked = sqlite3VdbeAllocUnpackedRecord(pKeyInfo,0,0,&p);