Index: src/select.c
==================================================================
--- src/select.c
+++ src/select.c
@@ -4031,10 +4031,12 @@
                         ** one row of the input to the aggregator has been
                         ** processed */
     int iAbortFlag;     /* Mem address which causes query abort if positive */
     int groupBySort;    /* Rows come from source in GROUP BY order */
     int addrEnd;        /* End of processing for this SELECT */
+    int sortPTab = 0;   /* Pseudotable used to decode sorting results */
+    int sortOut = 0;    /* Output register from the sorter */
 
     /* Remove any and all aliases between the result set and the
     ** GROUP BY clause.
     */
     if( pGroupBy ){
@@ -4092,16 +4094,16 @@
       int addrReset;      /* Subroutine for resetting the accumulator */
       int regReset;       /* Return address register for reset subroutine */
 
       /* If there is a GROUP BY clause we might need a sorting index to
       ** implement it.  Allocate that sorting index now.  If it turns out
-      ** that we do not need it after all, the OpenEphemeral instruction
+      ** that we do not need it after all, the OP_SorterOpen instruction
       ** will be converted into a Noop.  
       */
       sAggInfo.sortingIdx = pParse->nTab++;
       pKeyInfo = keyInfoFromExprList(pParse, pGroupBy);
-      addrSortingIdx = sqlite3VdbeAddOp4(v, OP_OpenEphemeral, 
+      addrSortingIdx = sqlite3VdbeAddOp4(v, OP_SorterOpen, 
           sAggInfo.sortingIdx, sAggInfo.nSortingColumn, 
           0, (char*)pKeyInfo, P4_KEYINFO_HANDOFF);
 
       /* Initialize memory locations used by GROUP BY aggregate processing
       */
@@ -4178,15 +4180,18 @@
             j++;
           }
         }
         regRecord = sqlite3GetTempReg(pParse);
         sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regRecord);
-        sqlite3VdbeAddOp2(v, OP_IdxInsert, sAggInfo.sortingIdx, regRecord);
+        sqlite3VdbeAddOp2(v, OP_SorterInsert, sAggInfo.sortingIdx, regRecord);
         sqlite3ReleaseTempReg(pParse, regRecord);
         sqlite3ReleaseTempRange(pParse, regBase, nCol);
         sqlite3WhereEnd(pWInfo);
-        sqlite3VdbeAddOp2(v, OP_Sort, sAggInfo.sortingIdx, addrEnd);
+        sortPTab = pParse->nTab++;
+        sortOut = sqlite3GetTempReg(pParse);
+        sqlite3VdbeAddOp3(v, OP_OpenPseudo, sortPTab, sortOut, nCol);
+        sqlite3VdbeAddOp2(v, OP_SorterSort, sAggInfo.sortingIdx, addrEnd);
         VdbeComment((v, "GROUP BY sort"));
         sAggInfo.useSortingIdx = 1;
         sqlite3ExprCacheClear(pParse);
       }
 
@@ -4195,13 +4200,17 @@
       ** Then compare the current GROUP BY terms against the GROUP BY terms
       ** from the previous row currently stored in a0, a1, a2...
       */
       addrTopOfLoop = sqlite3VdbeCurrentAddr(v);
       sqlite3ExprCacheClear(pParse);
+      if( groupBySort ){
+        sqlite3VdbeAddOp2(v, OP_SorterData, sAggInfo.sortingIdx, sortOut);
+      }
       for(j=0; j<pGroupBy->nExpr; j++){
         if( groupBySort ){
-          sqlite3VdbeAddOp3(v, OP_Column, sAggInfo.sortingIdx, j, iBMem+j);
+          sqlite3VdbeAddOp3(v, OP_Column, sortPTab, j, iBMem+j);
+          if( j==0 ) sqlite3VdbeChangeP5(v, OPFLAG_CLEARCACHE);
         }else{
           sAggInfo.directMode = 1;
           sqlite3ExprCode(pParse, pGroupBy->a[j].pExpr, iBMem+j);
         }
       }
@@ -4236,11 +4245,11 @@
       VdbeComment((v, "indicate data in accumulator"));
 
       /* End of the loop
       */
       if( groupBySort ){
-        sqlite3VdbeAddOp2(v, OP_Next, sAggInfo.sortingIdx, addrTopOfLoop);
+        sqlite3VdbeAddOp2(v, OP_SorterNext, sAggInfo.sortingIdx, addrTopOfLoop);
       }else{
         sqlite3WhereEnd(pWInfo);
         sqlite3VdbeChangeToNoop(v, addrSortingIdx, 1);
       }
 

Index: test/distinct.test
==================================================================
--- test/distinct.test
+++ test/distinct.test
@@ -43,11 +43,11 @@
 
 proc do_temptables_test {tn sql temptables} {
   uplevel [list do_test $tn [subst -novar {
     set ret ""
     db eval "EXPLAIN [set sql]" {
-      if {$opcode == "OpenEphemeral"} { 
+      if {$opcode == "OpenEphemeral" || $opcode == "SorterOpen"} { 
         if {$p5 != "10" && $p5!="00"} { error "p5 = $p5" }
         if {$p5 == "10"} {
           lappend ret hash
         } else {
           lappend ret btree