Index: src/test_tclvar.c
==================================================================
--- src/test_tclvar.c
+++ src/test_tclvar.c
@@ -14,11 +14,11 @@
 ** testing of the SQLite library.
 **
 ** The emphasis of this file is a virtual table that provides
 ** access to TCL variables.
 **
-** $Id: test_tclvar.c,v 1.14 2007/08/21 10:44:16 drh Exp $
+** $Id: test_tclvar.c,v 1.15 2008/05/29 05:23:42 drh Exp $
 */
 #include "sqliteInt.h"
 #include "tcl.h"
 #include <stdlib.h>
 #include <string.h>
@@ -220,11 +220,12 @@
 static int tclvarBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
   int ii;
 
   for(ii=0; ii<pIdxInfo->nConstraint; ii++){
     struct sqlite3_index_constraint const *pCons = &pIdxInfo->aConstraint[ii];
-    if( pCons->iColumn==0 && pCons->op==SQLITE_INDEX_CONSTRAINT_EQ ){
+    if( pCons->iColumn==0 && pCons->usable
+           && pCons->op==SQLITE_INDEX_CONSTRAINT_EQ ){
       struct sqlite3_index_constraint_usage *pUsage;
       pUsage = &pIdxInfo->aConstraintUsage[ii];
       pUsage->omit = 0;
       pUsage->argvIndex = 1;
       return SQLITE_OK;
@@ -231,11 +232,12 @@
     }
   }
 
   for(ii=0; ii<pIdxInfo->nConstraint; ii++){
     struct sqlite3_index_constraint const *pCons = &pIdxInfo->aConstraint[ii];
-    if( pCons->iColumn==0 && pCons->op==SQLITE_INDEX_CONSTRAINT_MATCH ){
+    if( pCons->iColumn==0 && pCons->usable
+           && pCons->op==SQLITE_INDEX_CONSTRAINT_MATCH ){
       struct sqlite3_index_constraint_usage *pUsage;
       pUsage = &pIdxInfo->aConstraintUsage[ii];
       pUsage->omit = 1;
       pUsage->argvIndex = 1;
       return SQLITE_OK;

Index: src/vdbe.c
==================================================================
--- src/vdbe.c
+++ src/vdbe.c
@@ -41,11 +41,11 @@
 ** documentation, headers files, or other derived files.  The formatting
 ** of the code in this file is, therefore, important.  See other comments
 ** in this file for details.  If in doubt, do not deviate from existing
 ** commenting and indentation practices when changing or adding code.
 **
-** $Id: vdbe.c,v 1.742 2008/05/29 03:12:55 drh Exp $
+** $Id: vdbe.c,v 1.743 2008/05/29 05:23:42 drh Exp $
 */
 #include "sqliteInt.h"
 #include <ctype.h>
 #include "vdbeInt.h"
 
@@ -4549,12 +4549,12 @@
 ** to the module implementation.
 **
 ** This opcode invokes the xFilter method on the virtual table specified
 ** by P1.  The integer query plan parameter to xFilter is stored in register
 ** P3. Register P3+1 stores the argc parameter to be passed to the
-** xFilter method. Registers P3+2..P3+1+argc are the argc additional
-** parametersneath additional parameters which are passed to
+** xFilter method. Registers P3+2..P3+1+argc are the argc
+** additional parameters which are passed to
 ** xFilter as argv. Register P3+2 becomes argv[0] when passed to xFilter.
 **
 ** A jump is made to P2 if the result set after filtering would be empty.
 */
 case OP_VFilter: {   /* jump */

Index: src/where.c
==================================================================
--- src/where.c
+++ src/where.c
@@ -14,11 +14,11 @@
 ** generating the code that loops through a table looking for applicable
 ** rows.  Indices are selected and used to speed the search when doing
 ** so is applicable.  Because this module is responsible for selecting
 ** indices, you might also think of this module as the "query optimizer".
 **
-** $Id: where.c,v 1.305 2008/05/28 18:01:45 shane Exp $
+** $Id: where.c,v 1.306 2008/05/29 05:23:42 drh Exp $
 */
 #include "sqliteInt.h"
 
 /*
 ** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
@@ -2361,24 +2361,26 @@
       for(j=1; j<=nConstraint; j++){
         int k;
         for(k=0; k<nConstraint; k++){
           if( aUsage[k].argvIndex==j ){
             int iTerm = aConstraint[k].iTermOffset;
+            assert( pParse->disableColCache );
             sqlite3ExprCode(pParse, wc.a[iTerm].pExpr->pRight, iReg+j+1);
             break;
           }
         }
         if( k==nConstraint ) break;
       }
+      assert( pParse->disableColCache );
       pParse->disableColCache--;
       sqlite3VdbeAddOp2(v, OP_Integer, pBestIdx->idxNum, iReg);
       sqlite3VdbeAddOp2(v, OP_Integer, j-1, iReg+1);
       sqlite3VdbeAddOp4(v, OP_VFilter, iCur, brk, iReg, pBestIdx->idxStr,
                         pBestIdx->needToFreeIdxStr ? P4_MPRINTF : P4_STATIC);
       sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
       pBestIdx->needToFreeIdxStr = 0;
-      for(j=0; j<pBestIdx->nConstraint; j++){
+      for(j=0; j<nConstraint; j++){
         if( aUsage[j].omit ){
           int iTerm = aConstraint[j].iTermOffset;
           disableTerm(pLevel, &wc.a[iTerm]);
         }
       }
@@ -2575,11 +2577,11 @@
       /* Seek the index cursor to the start of the range. */
       nConstraint = nEq;
       if( pRangeStart ){
         int dcc = pParse->disableColCache;
         if( pRangeEnd ){
-          pParse->disableColCache = 1;
+          pParse->disableColCache++;
         }
         sqlite3ExprCode(pParse, pRangeStart->pExpr->pRight, regBase+nEq);
         pParse->disableColCache = dcc;
         sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, nxt);
         nConstraint++;