SQLite

  Bitmask prereq;       /* Bitmask of other loops that must run first */
  Bitmask maskSelf;     /* Bitmask identifying table iTab */
#ifdef SQLITE_DEBUG
  char cId;             /* Symbolic ID of this loop for debugging use */
#endif
  u8 iTab;              /* Position in FROM clause of table for this loop */
  u8 iSortIdx;          /* Sorting index number.  0==None */
  u16 nLTerm;           /* Number of entries in aLTerm[] */
  u16 nLSlot;           /* Number of slots allocated for aLTerm[] */
  u32 wsFlags;          /* WHERE_* flags describing the plan */
  WhereCost rSetup;     /* One-time setup cost (ex: create transient index) */
  WhereCost rRun;       /* Cost of running each loop */
  WhereCost nOut;       /* Estimated number of output rows */
  union {
    struct {               /* Information for internal btree tables */
      int nEq;               /* Number of equality constraints */
      Index *pIndex;         /* Index used, or NULL */
    } btree;
    struct {               /* Information for virtual tables */
      int idxNum;            /* Index number */
      u8 needFree;           /* True if sqlite3_free(idxStr) is needed */
      u8 isOrdered;          /* True if satisfies ORDER BY */
      u16 omitMask;          /* Terms that may be omitted */
      char *idxStr;          /* Index identifier string */
    } vtab;
  } u;
  u32 wsFlags;          /* WHERE_* flags describing the plan */
  u16 nLTerm;           /* Number of entries in aLTerm[] */
  /**** whereLoopXfer() copies fields above ***********************/
# define WHERE_LOOP_XFER_SZ offsetof(WhereLoop,nLSlot)
  u16 nLSlot;           /* Number of slots allocated for aLTerm[] */
  WhereTerm **aLTerm;   /* WhereTerms used */
  WhereLoop *pNextLoop; /* Next WhereLoop object in the WhereClause */
  WhereTerm *aLTermSpace[4];  /* Initial aLTerm[] space */
};

/* Forward declaration of methods */
static int whereLoopResize(sqlite3*, WhereLoop*, int);

/*
** Transfer content from the second pLoop into the first.
*/
static int whereLoopXfer(sqlite3 *db, WhereLoop *pTo, WhereLoop *pFrom){
  if( whereLoopResize(db, pTo, pFrom->nLTerm) ) return SQLITE_NOMEM;
  whereLoopClearUnion(db, pTo);
  pTo->prereq = pFrom->prereq;
  pTo->maskSelf = pFrom->maskSelf;
  pTo->iTab = pFrom->iTab;
  memcpy(pTo, pFrom, WHERE_LOOP_XFER_SZ);
  pTo->iSortIdx = pFrom->iSortIdx;
  pTo->nLTerm = pFrom->nLTerm;
  pTo->rSetup = pFrom->rSetup;
  pTo->rRun = pFrom->rRun;
  pTo->nOut = pFrom->nOut;
  if( pTo->nLTerm ){
    memcpy(pTo->aLTerm, pFrom->aLTerm, pTo->nLTerm*sizeof(pTo->aLTerm[0]));
  memcpy(pTo->aLTerm, pFrom->aLTerm, pTo->nLTerm*sizeof(pTo->aLTerm[0]));
  }
  pTo->wsFlags = pFrom->wsFlags;
  pTo->u = pFrom->u;
  if( pFrom->wsFlags & WHERE_VIRTUALTABLE ){
    pFrom->u.vtab.needFree = 0;
  }else if( (pFrom->wsFlags & WHERE_TEMP_INDEX)!=0 ){
    pFrom->u.btree.pIndex = 0;
  }
  return SQLITE_OK;
}

  Bitmask mPrior = 0;
  int iTab;
  SrcList *pTabList = pWInfo->pTabList;
  struct SrcList_item *pItem;
  sqlite3 *db = pWInfo->pParse->db;
  int nTabList = pWInfo->nLevel;
  int rc = SQLITE_OK;
  WhereLoop *pNew;
  WhereLoop *pNew, sNew;

  /* 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->pNew = pNew = &sNew;
  whereLoopInit(pNew);
  pNew->aLTerm = pNew->aLTermSpace;
  pNew->nLSlot = ArraySize(pNew->aLTermSpace);
  for(iTab=0, pItem=pTabList->a; iTab<nTabList; iTab++, pItem++){
    pNew->iTab = iTab;
    pNew->maskSelf = getMask(&pWInfo->sMaskSet, pItem->iCursor);
    if( (pItem->jointype & (JT_LEFT|JT_CROSS))!=0 ){
      mExtra = mPrior;
    }
    if( IsVirtual(pItem->pTab) ){
      rc = whereLoopAddVirtual(pBuilder, mExtra);
    }else{
      rc = whereLoopAddBtree(pBuilder, mExtra);
    }
    if( rc==SQLITE_OK ){
      rc = whereLoopAddOr(pBuilder, mExtra);
    }
    mPrior |= pNew->maskSelf;
    if( rc || db->mallocFailed ) break;
  }
  whereLoopDelete(db, pBuilder->pNew);
  whereLoopClear(db, pNew);
  pBuilder->pNew = 0;
  return rc;
}

/*
** Examine a WherePath (with the addition of the extra WhereLoop of the 5th
** parameters) to see if it outputs rows in the requested ORDER BY