Index: src/select.c
==================================================================
--- src/select.c
+++ src/select.c
@@ -4876,10 +4876,36 @@
   }
 }
 #else
 # define explainSimpleCount(a,b,c)
 #endif
+
+/*
+** Check to see if the pThis entry of pTabList is a self-join of a prior view.
+** If it is, then return the SrcList_item for the prior view.  If it is not,
+** then return 0.
+*/
+static struct SrcList_item *isSelfJoinView(
+  SrcList *pTabList,           /* Search for self-joins in this FROM clause */
+  struct SrcList_item *pThis   /* Search for prior reference to this subquery */
+){
+  struct SrcList_item *pItem;
+  for(pItem = pTabList->a; pItem<pThis; pItem++){
+    if( pItem->pSelect==0 ) continue;
+    if( pItem->fg.viaCoroutine ) continue;
+    if( pItem->zName==0 ) continue;
+    if( sqlite3_stricmp(pItem->zDatabase, pThis->zDatabase)!=0 ) continue;
+    if( sqlite3_stricmp(pItem->zName, pThis->zName)!=0 ) continue;
+    if( sqlite3ExprCompare(pThis->pSelect->pWhere, pItem->pSelect->pWhere, -1) ){
+      /* The view was modified by some other optimization such as
+      ** pushDownWhereTerms() */
+      continue;
+    }
+    return pItem;
+  }
+  return 0;
+}
 
 /*
 ** Generate code for the SELECT statement given in the p argument.  
 **
 ** The results are returned according to the SelectDest structure.
@@ -5111,10 +5137,12 @@
       ** is a register allocated to hold the subroutine return address
       */
       int topAddr;
       int onceAddr = 0;
       int retAddr;
+      struct SrcList_item *pPrior;
+
       assert( pItem->addrFillSub==0 );
       pItem->regReturn = ++pParse->nMem;
       topAddr = sqlite3VdbeAddOp2(v, OP_Integer, 0, pItem->regReturn);
       pItem->addrFillSub = topAddr+1;
       if( pItem->fg.isCorrelated==0 ){
@@ -5124,13 +5152,18 @@
         onceAddr = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
         VdbeComment((v, "materialize \"%s\"", pItem->pTab->zName));
       }else{
         VdbeNoopComment((v, "materialize \"%s\"", pItem->pTab->zName));
       }
-      sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
-      explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
-      sqlite3Select(pParse, pSub, &dest);
+      pPrior = isSelfJoinView(pTabList, pItem);
+      if( pPrior ){
+        sqlite3VdbeAddOp2(v, OP_OpenDup, pItem->iCursor, pPrior->iCursor);
+      }else{
+        sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
+        explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
+        sqlite3Select(pParse, pSub, &dest);
+      }
       pItem->pTab->nRowLogEst = pSub->nSelectRow;
       if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
       retAddr = sqlite3VdbeAddOp1(v, OP_Return, pItem->regReturn);
       VdbeComment((v, "end %s", pItem->pTab->zName));
       sqlite3VdbeChangeP1(v, topAddr, retAddr);

Index: src/vdbe.c
==================================================================
--- src/vdbe.c
+++ src/vdbe.c
@@ -3537,10 +3537,38 @@
   sqlite3BtreeCursorHintFlags(pCur->uc.pCursor,
                                (pOp->p5 & (OPFLAG_BULKCSR|OPFLAG_SEEKEQ)));
   if( rc ) goto abort_due_to_error;
   break;
 }
+
+/* Opcode: OpenDup P1 P2 * * *
+**
+** Open a new cursor P1 that points to the same ephemeral table as
+** cursor P2.  The P2 cursor must have been opened by a prior OP_OpenEphemeral
+** opcode.  Only ephemeral cursors may be duplicated.
+**
+** Duplicate ephemeral cursors are used for self-joins of materialized views.
+*/
+case OP_OpenDup: {
+  VdbeCursor *pOrig;    /* The original cursor to be duplicated */
+  VdbeCursor *pCx;      /* The new cursor */
+
+  pOrig = p->apCsr[pOp->p2];
+  assert( pOrig->pBtx!=0 );  /* Only ephemeral cursors can be duplicated */
+
+  pCx = allocateCursor(p, pOp->p1, pOrig->nField, -1, CURTYPE_BTREE);
+  if( pCx==0 ) goto no_mem;
+  pCx->nullRow = 1;
+  pCx->isEphemeral = 1;
+  pCx->pKeyInfo = pOrig->pKeyInfo;
+  pCx->isTable = pOrig->isTable;
+  rc = sqlite3BtreeCursor(pOrig->pBtx, MASTER_ROOT, BTREE_WRCSR,
+                          pCx->pKeyInfo, pCx->uc.pCursor);
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+
 
 /* Opcode: OpenEphemeral P1 P2 * P4 P5
 ** Synopsis: nColumn=P2
 **
 ** Open a new cursor P1 to a transient table.

Index: src/vdbeaux.c
==================================================================
--- src/vdbeaux.c
+++ src/vdbeaux.c
@@ -2033,12 +2033,12 @@
     case CURTYPE_SORTER: {
       sqlite3VdbeSorterClose(p->db, pCx);
       break;
     }
     case CURTYPE_BTREE: {
-      if( pCx->pBtx ){
-        sqlite3BtreeClose(pCx->pBtx);
+      if( pCx->isEphemeral ){
+        if( pCx->pBtx ) sqlite3BtreeClose(pCx->pBtx);
         /* The pCx->pCursor will be close automatically, if it exists, by
         ** the call above. */
       }else{
         assert( pCx->uc.pCursor!=0 );
         sqlite3BtreeCloseCursor(pCx->uc.pCursor);