Index: src/expr.c
==================================================================
--- src/expr.c
+++ src/expr.c
@@ -3038,14 +3038,26 @@
 
 /*
 ** Preevaluate constant subexpressions within pExpr and store the
 ** results in registers.  Modify pExpr so that the constant subexpresions
 ** are TK_REGISTER opcodes that refer to the precomputed values.
+**
+** This routine is a no-op if the jump to the cookie-check code has
+** already occur.  Since the cookie-check jump is generated prior to
+** any other serious processing, this check ensures that there is no
+** way to accidently bypass the constant initializations.
+**
+** This routine is also a no-op if the SQLITE_FactorOutConst optimization
+** is disabled via the sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS)
+** interface.  This allows test logic to verify that the same answer is
+** obtained for queries regardless of whether or not constants are
+** precomputed into registers or if they are inserted in-line.
 */
 void sqlite3ExprCodeConstants(Parse *pParse, Expr *pExpr){
   Walker w;
   if( pParse->cookieGoto ) return;
+  if( (pParse->db->flags & SQLITE_FactorOutConst)!=0 ) return;
   w.xExprCallback = evalConstExpr;
   w.xSelectCallback = 0;
   w.pParse = pParse;
   sqlite3WalkExpr(&w, pExpr);
 }

Index: src/sqliteInt.h
==================================================================
--- src/sqliteInt.h
+++ src/sqliteInt.h
@@ -932,10 +932,11 @@
 #define SQLITE_ColumnCache    0x02        /* Disable the column cache */
 #define SQLITE_IndexSort      0x04        /* Disable indexes for sorting */
 #define SQLITE_IndexSearch    0x08        /* Disable indexes for searching */
 #define SQLITE_IndexCover     0x10        /* Disable index covering table */
 #define SQLITE_GroupByOrder   0x20        /* Disable GROUPBY cover of ORDERBY */
+#define SQLITE_FactorOutConst 0x40        /* Disable factoring out constants */
 #define SQLITE_OptMask        0xff        /* Mask of all disablable opts */
 
 /*
 ** Possible values for the sqlite.magic field.
 ** The numbers are obtained at random and have no special meaning, other

Index: src/test1.c
==================================================================
--- src/test1.c
+++ src/test1.c
@@ -5314,10 +5314,68 @@
   rc = printExplainQueryPlan(pStmt);
   Tcl_SetResult(interp, (char *)t1ErrorName(rc), 0);
   return TCL_OK;
 }
 #endif /* SQLITE_OMIT_EXPLAIN */
+
+/*
+**      optimization_control DB OPT BOOLEAN
+**
+** Enable or disable query optimizations using the sqlite3_test_control()
+** interface.  Disable if BOOLEAN is false and enable if BOOLEAN is true.
+** OPT is the name of the optimization to be disabled.
+*/
+static int optimization_control(
+  void * clientData,
+  Tcl_Interp *interp,
+  int objc,
+  Tcl_Obj *CONST objv[]
+){
+  int i;
+  sqlite3 *db;
+  const char *zOpt;
+  int onoff;
+  int mask;
+  static const struct {
+    const char *zOptName;
+    int mask;
+  } aOpt[] = {
+    { "all",              SQLITE_OptMask        },
+    { "query-flattener",  SQLITE_QueryFlattener },
+    { "column-cache",     SQLITE_ColumnCache    },
+    { "index-sort",       SQLITE_IndexSort      },
+    { "index-search",     SQLITE_IndexSearch    },
+    { "index-cover",      SQLITE_IndexCover     },
+    { "groupby-order",    SQLITE_GroupByOrder   },
+    { "factor-constants", SQLITE_FactorOutConst },
+  };
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB OPT BOOLEAN");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
+  if( Tcl_GetBooleanFromObj(interp, objv[3], &onoff) ) return TCL_ERROR;
+  zOpt = Tcl_GetString(objv[2]);
+  for(i=0; i<sizeof(aOpt)/sizeof(aOpt[0]); i++){
+    if( strcmp(zOpt, aOpt[i].zOptName)==0 ){
+      mask = aOpt[i].mask;
+      break;
+    }
+  }
+  if( onoff ) mask = ~mask;
+  if( i>=sizeof(aOpt)/sizeof(aOpt[0]) ){
+    Tcl_AppendResult(interp, "unknown optimization - should be one of:",
+                     (char*)0);
+    for(i=0; i<sizeof(aOpt)/sizeof(aOpt[0]); i++){
+      Tcl_AppendResult(interp, " ", aOpt[i].zOptName);
+    }
+    return TCL_ERROR;
+  }
+  sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS, db, mask);
+  return TCL_OK;
+}
 
 /*
 ** Register commands with the TCL interpreter.
 */
 int Sqlitetest1_Init(Tcl_Interp *interp){
@@ -5432,10 +5490,11 @@
      { "sqlite3_limit",                 test_limit,                 0},
 
      { "save_prng_state",               save_prng_state,    0 },
      { "restore_prng_state",            restore_prng_state, 0 },
      { "reset_prng_state",              reset_prng_state,   0 },
+     { "optimization_control",          optimization_control,0},
      { "tcl_objproc",                   runAsObjProc,       0 },
 
      /* sqlite3_column_*() API */
      { "sqlite3_column_count",          test_column_count  ,0 },
      { "sqlite3_data_count",            test_data_count    ,0 },

Index: test/tkt-80ba201079.test
==================================================================
--- test/tkt-80ba201079.test
+++ test/tkt-80ba201079.test
@@ -37,10 +37,39 @@
     SELECT * FROM t1, t2
      WHERE (a='A' AND b='X')
         OR (a='A' AND EXISTS (SELECT * FROM t3 WHERE c='C'));
   }
 } {A B}
+do_test tkt-80ba2-102 {
+  optimization_control db factor-constants 0
+  db cache flush
+  db eval {
+    SELECT * FROM t1, t2
+     WHERE (a='A' AND b='X')
+        OR (a='A' AND EXISTS (SELECT * FROM t3 WHERE c='C'));
+  }
+} {A B}
+optimization_control db all 1
+
+# Verify that the optimization_control command is actually working
+#
+do_test tkt-80ba2-150 {
+  optimization_control db factor-constants 1
+  db cache flush
+  set x1 [db eval {EXPLAIN 
+    SELECT * FROM t1, t2
+     WHERE (a='A' AND b='X')
+        OR (a='A' AND EXISTS (SELECT * FROM t3 WHERE c='C'));}]
+  optimization_control db factor-constants 0
+  db cache flush
+  set x2 [db eval {EXPLAIN 
+    SELECT * FROM t1, t2
+     WHERE (a='A' AND b='X')
+        OR (a='A' AND EXISTS (SELECT * FROM t3 WHERE c='C'));}]
+
+  expr {$x1==$x2}
+} {0}
 
 do_test tkt-80ba2-200 {
   db eval {
     CREATE TABLE entry_types (
                         id     integer primary key,
@@ -79,10 +108,25 @@
   }
 } {300 object_change 2048}
 do_test tkt-80ba2-201 {
   db eval {
     CREATE INDEX timeline_entry_id_idx on timeline(entry_id);
+    SELECT entry_type,
+           entry_types.name,
+           entry_id
+      FROM timeline JOIN entry_types ON entry_type = entry_types.id
+     WHERE (entry_types.name = 'cli_command' AND entry_id=2114)
+        OR (entry_types.name = 'object_change'
+             AND entry_id IN (SELECT change_id
+                              FROM object_changes
+                               WHERE obj_context = 'exported_pools'));
+  }
+} {300 object_change 2048}
+do_test tkt-80ba2-202 {
+  optimization_control db factor-constants 0
+  db cache flush
+  db eval {
     SELECT entry_type,
            entry_types.name,
            entry_id
       FROM timeline JOIN entry_types ON entry_type = entry_types.id
      WHERE (entry_types.name = 'cli_command' AND entry_id=2114)