Index: src/sqliteInt.h
==================================================================
--- src/sqliteInt.h
+++ src/sqliteInt.h
@@ -954,10 +954,11 @@
 #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_IdxRealAsInt   0x80        /* Store REAL as INT in indices */
+#define SQLITE_DistinctOpt    0x80        /* DISTINCT using indexes */
 #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/where.c
==================================================================
--- src/where.c
+++ src/where.c
@@ -4595,10 +4595,14 @@
   pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
   pWInfo->pWC = pWC = (WhereClause *)&((u8 *)pWInfo)[nByteWInfo];
   pWInfo->wctrlFlags = wctrlFlags;
   pWInfo->savedNQueryLoop = pParse->nQueryLoop;
   pMaskSet = (WhereMaskSet*)&pWC[1];
+
+  /* Disable the DISTINCT optimization if SQLITE_DistinctOpt is set via
+  ** sqlite3_test_ctrl(SQLITE_TESTCTRL_OPTIMIZATIONS,...) */
+  if( db->flags & SQLITE_DistinctOpt ) pDistinct = 0;
 
   /* Split the WHERE clause into separate subexpressions where each
   ** subexpression is separated by an AND operator.
   */
   initMaskSet(pMaskSet);