if( iIdxCol<pIdx->nColumn ){
    iRet = pIdx->aiColumn[iIdxCol];
  }else if( pPk && iIdxCol<(pIdx->nColumn + pPk->nColumn) ){
    iRet = pPk->aiColumn[iIdxCol - pIdx->nColumn];
  }
  return iRet;
}

















/*
** Return the total number of fields in the index pIdx, including any
** trailing primary key fields.
*/
static int idxColumnCount(Index *pIdx, Index *pPk){
  return (pIdx->nColumn + (pIdx==pPk ? 0 : pPk->nColumn));
................................................................................
  pScan->pWC = pWC;
  if( pIdx && iColumn>=0 ){
    Index *pPk = sqlite4FindPrimaryKey(pIdx->pTable, 0);
    pScan->idxaff = pIdx->pTable->aCol[iColumn].affinity;
    for(j=0; idxColumnNumber(pIdx, pPk, j)!=iColumn; j++){
      if( NEVER(j>=idxColumnCount(pIdx, pPk)) ) return 0;
    }
    pScan->zCollName = pIdx->azColl[j];
  }else{
    pScan->idxaff = 0;
    pScan->zCollName = 0;
  }
  pScan->opMask = opMask;
  pScan->k = 0;
  pScan->aEquiv[0] = iCur;
................................................................................
  zAff = sqlite4DbStrDup(pParse->db, sqlite4IndexAffinityStr(v, pIdx));
  if( !zAff ){
    pParse->db->mallocFailed = 1;
  }

  /* Evaluate the equality constraints
  */
  assert( pIdx->nColumn>=nEq );
  for(j=0; j<nEq; j++){
    int r1;
    pTerm = pLoop->aLTerm[j];
    assert( pTerm!=0 );
    /* The following true for indices with redundant columns. 
    ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
    testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
................................................................................
    */
    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
    SrcList *pOrTab;       /* Shortened table list or OR-clause generation */
    Index *pCov = 0;             /* Potential covering index (or NULL) */
    int iCovCur = pParse->nTab++;  /* Cursor used for index scans (if any) */

    int regReturn = ++pParse->nMem;           /* Register used with OP_Gosub */
    int regRowset = 0;                        /* Register for RowSet object */
    int regRowid = 0;                         /* Register holding rowid */
    int iLoopBody = sqlite4VdbeMakeLabel(v);  /* Start of loop body */
    int iRetInit;                             /* Address of regReturn init */
    int untestedTerms = 0;             /* Some terms not completely tested */
    int ii;                            /* Loop counter */
    Expr *pAndExpr = 0;                /* An ".. AND (...)" expression */
   
    pTerm = pLoop->aLTerm[0];
................................................................................
      for(k=1; k<=nNotReady; k++){
        memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
      }
    }else{
      pOrTab = pWInfo->pTabList;
    }

    /* Initialize the rowset register to contain NULL. An SQL NULL is 
    ** equivalent to an empty rowset.
    **
    ** Also initialize regReturn to contain the address of the instruction 
    ** immediately following the OP_Return at the bottom of the loop. This
    ** is required in a few obscure LEFT JOIN cases where control jumps
    ** over the top of the loop into the body of it. In this case the 
    ** correct response for the end-of-loop code (the OP_Return) is to 
    ** fall through to the next instruction, just as an OP_Next does if
    ** called on an uninitialized cursor.
    */
    if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
      regRowset = ++pParse->nMem;
      regRowid = ++pParse->nMem;
      sqlite4VdbeAddOp2(v, OP_Null, 0, regRowset);
    }
    iRetInit = sqlite4VdbeAddOp2(v, OP_Integer, 0, regReturn);

    /* If the original WHERE clause is z of the form:  (x1 OR x2 OR ...) AND y
    ** Then for every term xN, evaluate as the subexpression: xN AND z
    ** That way, terms in y that are factored into the disjunction will
    ** be picked up by the recursive calls to sqlite4WhereBegin() below.
................................................................................
        if( pSubWInfo ){
          WhereLoop *pSubLoop;
          explainOneScan(
              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
          );
          if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
            int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
            int r;
            r = sqlite4ExprCodeGetColumn(pParse, pTabItem->pTab, -1, iCur, 
                                         regRowid);
            sqlite4VdbeAddOp4Int(v, OP_RowSetTest, regRowset,
                                 sqlite4VdbeCurrentAddr(v)+2, r, iSet);
          }
          sqlite4VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);

          /* The pSubWInfo->untestedTerms flag means that this OR term
          ** contained one or more AND term from a notReady table.  The
          ** terms from the notReady table could not be tested and will
          ** need to be tested later.
................................................................................
          ** If the call to sqlite4WhereBegin() above resulted in a scan that
          ** uses an index, and this is either the first OR-connected term
          ** processed or the index is the same as that used by all previous
          ** terms, set pCov to the candidate covering index. Otherwise, set 
          ** pCov to NULL to indicate that no candidate covering index will 
          ** be available.
          */

          pSubLoop = pSubWInfo->a[0].pWLoop;
          assert( (pSubLoop->wsFlags & WHERE_AUTO_INDEX)==0 );
          if( (pSubLoop->wsFlags & WHERE_INDEXED)!=0
           && (ii==0 || pSubLoop->u.btree.pIndex==pCov)
          ){
            assert( pSubWInfo->a[0].iIdxCur==iCovCur );
            pCov = pSubLoop->u.btree.pIndex;
          }else{
            pCov = 0;
          }


          /* Finish the loop through table entries that match term pOrTerm. */
          sqlite4WhereEnd(pSubWInfo);
        }
      }
    }
    pLevel->u.pCovidx = pCov;
................................................................................
**    (5)  The template uses more terms of the same index but has no additional
**         dependencies          
*/
static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
  WhereLoop **ppPrev, *p, *pNext = 0;
  WhereInfo *pWInfo = pBuilder->pWInfo;
  sqlite4 *db = pWInfo->pParse->db;



  /* If pBuilder->pBest is defined, then only keep track of the single
  ** best WhereLoop.  pBuilder->pBest->maskSelf==0 indicates that no
  ** prior WhereLoops have been evaluated and that the current pTemplate
  ** is therefore the first and hence the best and should be retained.
  */
  if( (p = pBuilder->pBest)!=0 ){
................................................................................
        pNew->wsFlags = WHERE_AUTO_INDEX;
        pNew->prereq = mExtra | pTerm->prereqRight;
        rc = whereLoopInsert(pBuilder, pNew);
      }
    }
  }
#endif /* ifndef SQLITE4_OMIT_AUTOMATIC_INDEX */



















  /* Loop through the set of indices being considered. */
  for(; rc==SQLITE4_OK && pProbe; pProbe=pProbe->pNext, iSortIdx++){

    if( pProbe->eIndexType==SQLITE4_INDEX_FTS5 ) continue;

    pNew->u.btree.nEq = 0;

  if( iIdxCol<pIdx->nColumn ){
    iRet = pIdx->aiColumn[iIdxCol];
  }else if( pPk && iIdxCol<(pIdx->nColumn + pPk->nColumn) ){
    iRet = pPk->aiColumn[iIdxCol - pIdx->nColumn];
  }
  return iRet;
}

/*
** Return a pointer to a buffer containing the name of the collation 
** sequence used with the iIdxCol'th field in index pIdx, including any
** appended PRIMARY KEY fields.
*/
static char *idxColumnCollation(Index *pIdx, Index *pPk, int iIdxCol){
  char *zColl;
  assert( iIdxCol<(pIdx->nColumn + pPk->nColumn) );
  if( iIdxCol<pIdx->nColumn ){
    zColl = pIdx->azColl[iIdxCol];
  }else if( pPk && iIdxCol<(pIdx->nColumn + pPk->nColumn) ){
    zColl = pPk->azColl[iIdxCol - pIdx->nColumn];
  }
  return zColl;
}

/*
** Return the total number of fields in the index pIdx, including any
** trailing primary key fields.
*/
static int idxColumnCount(Index *pIdx, Index *pPk){
  return (pIdx->nColumn + (pIdx==pPk ? 0 : pPk->nColumn));
................................................................................
  pScan->pWC = pWC;
  if( pIdx && iColumn>=0 ){
    Index *pPk = sqlite4FindPrimaryKey(pIdx->pTable, 0);
    pScan->idxaff = pIdx->pTable->aCol[iColumn].affinity;
    for(j=0; idxColumnNumber(pIdx, pPk, j)!=iColumn; j++){
      if( NEVER(j>=idxColumnCount(pIdx, pPk)) ) return 0;
    }
    pScan->zCollName = idxColumnCollation(pIdx, pPk, j);
  }else{
    pScan->idxaff = 0;
    pScan->zCollName = 0;
  }
  pScan->opMask = opMask;
  pScan->k = 0;
  pScan->aEquiv[0] = iCur;
................................................................................
  zAff = sqlite4DbStrDup(pParse->db, sqlite4IndexAffinityStr(v, pIdx));
  if( !zAff ){
    pParse->db->mallocFailed = 1;
  }

  /* Evaluate the equality constraints
  */
  assert( idxColumnCount(pIdx, sqlite4FindPrimaryKey(pIdx->pTable, 0))>=nEq );
  for(j=0; j<nEq; j++){
    int r1;
    pTerm = pLoop->aLTerm[j];
    assert( pTerm!=0 );
    /* The following true for indices with redundant columns. 
    ** Ex: CREATE INDEX i1 ON t1(a,b,a); SELECT * FROM t1 WHERE a=0 AND b=0; */
    testcase( (pTerm->wtFlags & TERM_CODED)!=0 );
................................................................................
    */
    WhereClause *pOrWc;    /* The OR-clause broken out into subterms */
    SrcList *pOrTab;       /* Shortened table list or OR-clause generation */
    Index *pCov = 0;             /* Potential covering index (or NULL) */
    int iCovCur = pParse->nTab++;  /* Cursor used for index scans (if any) */

    int regReturn = ++pParse->nMem;           /* Register used with OP_Gosub */
    int regKeyset = 0;                        /* Register for RowSet object */
    int regKey = 0;                           /* Register holding key */
    int iLoopBody = sqlite4VdbeMakeLabel(v);  /* Start of loop body */
    int iRetInit;                             /* Address of regReturn init */
    int untestedTerms = 0;             /* Some terms not completely tested */
    int ii;                            /* Loop counter */
    Expr *pAndExpr = 0;                /* An ".. AND (...)" expression */
   
    pTerm = pLoop->aLTerm[0];
................................................................................
      for(k=1; k<=nNotReady; k++){
        memcpy(&pOrTab->a[k], &origSrc[pLevel[k].iFrom], sizeof(pOrTab->a[k]));
      }
    }else{
      pOrTab = pWInfo->pTabList;
    }

    /* Initialize the keyset register to contain NULL. An SQL NULL is 
    ** equivalent to an empty keyset.
    **
    ** Also initialize regReturn to contain the address of the instruction 
    ** immediately following the OP_Return at the bottom of the loop. This
    ** is required in a few obscure LEFT JOIN cases where control jumps
    ** over the top of the loop into the body of it. In this case the 
    ** correct response for the end-of-loop code (the OP_Return) is to 
    ** fall through to the next instruction, just as an OP_Next does if
    ** called on an uninitialized cursor.
    */
    if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
      regKeyset = ++pParse->nMem;
      regKey = ++pParse->nMem;
      sqlite4VdbeAddOp2(v, OP_Null, 0, regKeyset);
    }
    iRetInit = sqlite4VdbeAddOp2(v, OP_Integer, 0, regReturn);

    /* If the original WHERE clause is z of the form:  (x1 OR x2 OR ...) AND y
    ** Then for every term xN, evaluate as the subexpression: xN AND z
    ** That way, terms in y that are factored into the disjunction will
    ** be picked up by the recursive calls to sqlite4WhereBegin() below.
................................................................................
        if( pSubWInfo ){
          WhereLoop *pSubLoop;
          explainOneScan(
              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0
          );
          if( (pWInfo->wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
            int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
            sqlite4VdbeAddOp2(v, OP_RowKey, iCur, regKey);


            sqlite4VdbeAddOp4Int(v, OP_RowSetTest, regKeyset,
                                 sqlite4VdbeCurrentAddr(v)+2, regKey, iSet);
          }
          sqlite4VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);

          /* The pSubWInfo->untestedTerms flag means that this OR term
          ** contained one or more AND term from a notReady table.  The
          ** terms from the notReady table could not be tested and will
          ** need to be tested later.
................................................................................
          ** If the call to sqlite4WhereBegin() above resulted in a scan that
          ** uses an index, and this is either the first OR-connected term
          ** processed or the index is the same as that used by all previous
          ** terms, set pCov to the candidate covering index. Otherwise, set 
          ** pCov to NULL to indicate that no candidate covering index will 
          ** be available.
          */
#if 0
          pSubLoop = pSubWInfo->a[0].pWLoop;
          assert( (pSubLoop->wsFlags & WHERE_AUTO_INDEX)==0 );
          if( (pSubLoop->wsFlags & WHERE_INDEXED)!=0
           && (ii==0 || pSubLoop->u.btree.pIndex==pCov)
          ){
            assert( pSubWInfo->a[0].iIdxCur==iCovCur );
            pCov = pSubLoop->u.btree.pIndex;
          }else{
            pCov = 0;
          }
#endif

          /* Finish the loop through table entries that match term pOrTerm. */
          sqlite4WhereEnd(pSubWInfo);
        }
      }
    }
    pLevel->u.pCovidx = pCov;
................................................................................
**    (5)  The template uses more terms of the same index but has no additional
**         dependencies          
*/
static int whereLoopInsert(WhereLoopBuilder *pBuilder, WhereLoop *pTemplate){
  WhereLoop **ppPrev, *p, *pNext = 0;
  WhereInfo *pWInfo = pBuilder->pWInfo;
  sqlite4 *db = pWInfo->pParse->db;

  assert( pTemplate->u.btree.pIndex || !(pTemplate->wsFlags & WHERE_INDEXED) );

  /* If pBuilder->pBest is defined, then only keep track of the single
  ** best WhereLoop.  pBuilder->pBest->maskSelf==0 indicates that no
  ** prior WhereLoops have been evaluated and that the current pTemplate
  ** is therefore the first and hence the best and should be retained.
  */
  if( (p = pBuilder->pBest)!=0 ){
................................................................................
        pNew->wsFlags = WHERE_AUTO_INDEX;
        pNew->prereq = mExtra | pTerm->prereqRight;
        rc = whereLoopInsert(pBuilder, pNew);
      }
    }
  }
#endif /* ifndef SQLITE4_OMIT_AUTOMATIC_INDEX */

  /* If this table has no primary key, then it is either a materialized
  ** view or ephemeral table. Either way, add an entry for a full-scan 
  ** of it.  */
  if( pPk==0 ){
    assert( pSrc->pTab->pSelect || (pSrc->pTab->tabFlags & TF_Ephemeral) );
    pNew->u.btree.nEq = 0;
    pNew->nLTerm = 0;
    pNew->iSortIdx = 0;
    pNew->rSetup = 0;
    pNew->prereq = mExtra;
    pNew->nOut = rSize;
    pNew->u.btree.pIndex = 0;
    pNew->iSortIdx = 0;
    pNew->wsFlags = 0;
    pNew->rRun = whereCostAdd(rSize,rLogSize) + 16;
    rc = whereLoopInsert(pBuilder, pNew);
  }

  /* Loop through the set of indices being considered. */
  for(; rc==SQLITE4_OK && pProbe; pProbe=pProbe->pNext, iSortIdx++){

    if( pProbe->eIndexType==SQLITE4_INDEX_FTS5 ) continue;

    pNew->u.btree.nEq = 0;