SQLite

  WhereInfo *pWInfo;        /* Information about this WHERE */
  sqlite3 *db;              /* Database connection */
  Parse *pParse;            /* Parsing context */
  WhereClause *pWC;         /* WHERE clause terms */
  SrcList *pTabList;        /* FROM clause */
  ExprList *pOrderBy;       /* ORDER BY clause */
  WhereLoop *pNew;          /* Template WhereLoop */
  int mxTerm;               /* Maximum number of aTerm[] entries on pNew */
};

/*
** Bitmasks for the operators that indices are able to exploit.  An
** OR-ed combination of these values can be used when searching for
** terms in the where clause.
*/

  WhereLoop *pNew;                /* Template WhereLoop under construction */
  WhereTerm *pTerm;               /* A WhereTerm under consideration */
  int opMask;                     /* Valid operators for constraints */
  WhereScan scan;                 /* Iterator for WHERE terms */
  WhereLoop savedLoop;            /* Saved original content of pNew[] */
  int iCol;                       /* Index of the column in the table */
  int rc = SQLITE_OK;             /* Return code */
  double rLogSize;                /* Logarithm of table size */

  db = pBuilder->db;
  pNew = pBuilder->pNew;
  if( db->mallocFailed ) return SQLITE_NOMEM;

  assert( (pNew->wsFlags & WHERE_VIRTUALTABLE)==0 );
  assert( pNew->u.btree.nEq<pProbe->nColumn );

  }

  iCol = pProbe->aiColumn[pNew->u.btree.nEq];
  pTerm = whereScanInit(&scan, pBuilder->pWC, pSrc->iCursor, iCol,
                        opMask, iCol>=0 ? pProbe : 0);
  savedLoop = *pNew;
  pNew->rSetup = (double)0;
  rLogSize = estLog(pProbe->aiRowEst[0]);
  for(; rc==SQLITE_OK && pTerm!=0; pTerm = whereScanNext(&scan)){
    int nIn = 1;
    pNew->u.btree.nEq = savedLoop.u.btree.nEq;
    pNew->nTerm = savedLoop.nTerm;
    if( pNew->nTerm>=pBuilder->mxTerm ) break; /* Repeated column in index */
    pNew->aTerm[pNew->nTerm++] = pTerm;
    pNew->prereq = (savedLoop.prereq | pTerm->prereqRight) & ~pNew->maskSelf;
    if( pTerm->eOperator & WO_IN ){
      Expr *pExpr = pTerm->pExpr;
      pNew->wsFlags |= WHERE_COLUMN_IN;
      if( ExprHasProperty(pExpr, EP_xIsSelect) ){
        /* "x IN (SELECT ...)":  Assume the SELECT returns 25 rows */

    }else if( pTerm->eOperator & (WO_GT|WO_GE) ){
      pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_BTM_LIMIT;
      pNew->nOut = savedLoop.nOut/3;
    }else if( pTerm->eOperator & (WO_LT|WO_LE) ){
      pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_TOP_LIMIT;
      pNew->nOut = savedLoop.nOut/3;
    }
    pNew->rRun = rLogSize*nIn;  /* Cost for nIn binary searches */
    if( pNew->wsFlags & (WHERE_IDX_ONLY|WHERE_IPK) ){
      pNew->rRun += pNew->nOut;  /* Unit step cost to reach each row */
    }else{
      /* Each row involves a step of the index, then a binary search of
      ** the main table */
      pNew->rRun += pNew->nOut*(1 + rLogSize);
    }
    /* TBD: Adjust nOut and rRun for STAT3 range values */
    /* TBD: Adjust nOut for additional constraints */
    rc = whereLoopInsert(pBuilder->pWInfo, pNew);
    if( (pNew->wsFlags & WHERE_TOP_LIMIT)==0
     && pNew->u.btree.nEq<pProbe->nColumn
    ){
      whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, nInMul*nIn);
    }
  }

  Index *pProbe;              /* An index we are evaluating */
  Index sPk;                  /* A fake index object for the primary key */
  tRowcnt aiRowEstPk[2];      /* The aiRowEst[] value for the sPk index */
  int aiColumnPk = -1;        /* The aColumn[] value for the sPk index */
  struct SrcList_item *pSrc;  /* The FROM clause btree term to add */
  WhereLoop *pNew;            /* Template WhereLoop object */
  int rc = SQLITE_OK;         /* Return code */
  double rSize;               /* number of rows in the table */
  double rLogSize;            /* Logarithm of the number of rows in the table */

  pNew = pBuilder->pNew;
  pSrc = pBuilder->pTabList->a + pNew->iTab;

  if( pSrc->pIndex ){
    /* An INDEXED BY clause specifies a particular index to use */
    pProbe = pSrc->pIndex;

    if( pSrc->notIndexed==0 ){
      /* The real indices of the table are only considered if the
      ** NOT INDEXED qualifier is omitted from the FROM clause */
      sPk.pNext = pFirst;
    }
    pProbe = &sPk;
  }
  rSize = (double)pSrc->pTab->nRowEst;
  rLogSize = estLog(rSize);

  /* Automatic indexes */
  if( (pBuilder->pParse->db->flags & SQLITE_AutoIndex)!=0 
   && !pSrc->viaCoroutine
   && !pSrc->notIndexed
   && !pSrc->isCorrelated
  ){
    /* Generate auto-index WhereLoops */
    WhereClause *pWC = pBuilder->pWC;
    WhereTerm *pTerm;
    WhereTerm *pWCEnd = pWC->a + pWC->nTerm;
    for(pTerm=pWC->a; rc==SQLITE_OK && pTerm<pWCEnd; pTerm++){
      if( termCanDriveIndex(pTerm, pSrc, 0) ){
        pNew->u.btree.nEq = 1;
        pNew->nTerm = 1;
        pNew->aTerm[0] = pTerm;
        pNew->rSetup = 2*rLogSize*pSrc->pTab->nRowEst;
        pNew->nOut = (double)10;
        pNew->rRun = rLogSize + pNew->nOut;
        pNew->wsFlags = WHERE_TEMP_INDEX;
        pNew->prereq = mExtra | pTerm->prereqRight;
        rc = whereLoopInsert(pBuilder->pWInfo, pNew);
      }
    }
  }

  /* Insert a full table scan */
  pNew->u.btree.nEq = 0;
  pNew->nTerm = 0;
  pNew->rSetup = (double)0;
  pNew->prereq = mExtra;
  pNew->u.btree.pIndex = 0;
  pNew->wsFlags = 0;

  pNew->nOut = rSize;
  pNew->rRun = rSize + rLogSize;
  /* TBD: Reduce nOut using constraints */
  rc = whereLoopInsert(pBuilder->pWInfo, pNew);



  /* Loop over all indices
  */
  for(; rc==SQLITE_OK && pProbe; pProbe=pProbe->pNext){
    pNew->u.btree.nEq = 0;
    pNew->nTerm = 0;
    if( pProbe->tnum<=0 ){
      /* Integer primary key index */

    pIdxInfo->orderByConsumed = 0;
    /* ((double)2) In case of SQLITE_OMIT_FLOATING_POINT... */
    pIdxInfo->estimatedCost = SQLITE_BIG_DBL / ((double)2);
    rc = vtabBestIndex(pParse, pTab, pIdxInfo);
    if( rc ) goto whereLoopAddVtab_exit;
    pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
    pNew->prereq = 0;
    assert( pIdxInfo->nConstraint<=pBuilder->mxTerm );
    for(i=0; i<pIdxInfo->nConstraint; i++) pNew->aTerm[i] = 0;
    mxTerm = -1;
    for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
      if( (iTerm = pUsage[i].argvIndex - 1)>=0 ){
        j = pIdxCons->iTermOffset;
        if( iTerm>=pIdxInfo->nConstraint
         || j<0

  int nTabList = pBuilder->pWInfo->nLevel;
  int rc = SQLITE_OK;
  WhereLoop *pNew;

  /* Loop over the tables in the join, from left to right */
  pBuilder->pNew = pNew = sqlite3DbMallocZero(db, sizeof(WhereLoop));
  if( pNew==0 ) return SQLITE_NOMEM;
  pBuilder->mxTerm = pWC->nTerm+1;
  while( pWC->pOuter ){
    pWC = pWC->pOuter;
    pBuilder->mxTerm += pWC->nTerm;
  }
  pWC = pBuilder->pWC;
  pNew->aTerm = sqlite3DbMallocZero(db,pBuilder->mxTerm*sizeof(pNew->aTerm[0]));
  if( pNew->aTerm==0 ){
    rc = SQLITE_NOMEM;
    goto whereLoopAddAll_end;
  }
  for(iTab=0, pItem=pTabList->a; iTab<nTabList; iTab++, pItem++){
    pNew->iTab = iTab;
    pNew->maskSelf = getMask(pWC->pMaskSet, pItem->iCursor);

  */
  assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
  if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 && (andFlags & WHERE_UNIQUE)!=0 ){
    pWInfo->okOnePass = 1;
    pWInfo->a[0].plan.wsFlags &= ~WHERE_IDX_ONLY;
  }

#if 0
  /* Scaffolding:  Check the new query plan against the old.  Report any
  ** discrepencies */
  for(ii=0; ii<nTabList; ii++){
    if( pWInfo->a[ii].iFrom!=pWInfo->a[ii].pWLoop->iTab ){
      sqlite3DebugPrintf("(QP-Mismatch)");
      break;
    }
  }
#endif

  /* Open all tables in the pTabList and any indices selected for
  ** searching those tables.
  */
  sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
  notReady = ~(Bitmask)0;
  pWInfo->nRowOut = (double)1;
  for(ii=0, pLevel=pWInfo->a; ii<nTabList; ii++, pLevel++){