Index: src/expr.c
==================================================================
--- src/expr.c
+++ src/expr.c
@@ -3760,5 +3760,13 @@
   if( nReg>pParse->nRangeReg ){
     pParse->nRangeReg = nReg;
     pParse->iRangeReg = iReg;
   }
 }
+
+/*
+** Mark all temporary registers as being unavailable for reuse.
+*/
+void sqlite3ClearTempRegCache(Parse *pParse){
+  pParse->nTempReg = 0;
+  pParse->nRangeReg = 0;
+}

Index: src/select.c
==================================================================
--- src/select.c
+++ src/select.c
@@ -3858,11 +3858,11 @@
       pItem->pTab->nRowEst = (unsigned)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);
-
+      sqlite3ClearTempRegCache(pParse);
     }
     if( /*pParse->nErr ||*/ db->mallocFailed ){
       goto select_end;
     }
     pParse->nHeight -= sqlite3SelectExprHeight(p);

Index: src/sqliteInt.h
==================================================================
--- src/sqliteInt.h
+++ src/sqliteInt.h
@@ -2658,10 +2658,11 @@
 void sqlite3FinishCoding(Parse*);
 int sqlite3GetTempReg(Parse*);
 void sqlite3ReleaseTempReg(Parse*,int);
 int sqlite3GetTempRange(Parse*,int);
 void sqlite3ReleaseTempRange(Parse*,int,int);
+void sqlite3ClearTempRegCache(Parse*);
 Expr *sqlite3ExprAlloc(sqlite3*,int,const Token*,int);
 Expr *sqlite3Expr(sqlite3*,int,const char*);
 void sqlite3ExprAttachSubtrees(sqlite3*,Expr*,Expr*,Expr*);
 Expr *sqlite3PExpr(Parse*, int, Expr*, Expr*, const Token*);
 Expr *sqlite3ExprAnd(sqlite3*,Expr*, Expr*);