SQLite

  WhereCost *pCost            /* Lowest cost query plan */
){
  double nTableRow;           /* Rows in the input table */
  double logN;                /* log(nTableRow) */
  double costTempIdx;         /* per-query cost of the transient index */
  WhereTerm *pTerm;           /* A single term of the WHERE clause */
  WhereTerm *pWCEnd;          /* End of pWC->a[] */
  Table *pTable;              /* Table tht might be indexed */

  if( (pCost->plan.wsFlags & WHERE_NOT_FULLSCAN)!=0 ){
    /* We already have some kind of index in use for this query. */
    return;
  }
  if( pSrc->notIndexed ){
    /* The NOT INDEXED clause appears in the SQL. */

  if( costTempIdx>=pCost->rCost ){
    /* The cost of creating the transient table would be greater than
    ** doing the full table scan */
    return;
  }

  /* Search for any equality comparison term */
  pTable = pSrc->pTab;
  pWCEnd = &pWC->a[pWC->nTerm];
  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
    if( pTerm->leftCursor==pSrc->iCursor
       && (pTerm->prereqRight & notReady)==0
       && (pTerm->eOperator & WO_EQ)!=0
       && sqlite3IndexAffinityOk(pTerm->pExpr,
                                 pTable->aCol[pTerm->u.leftColumn].affinity)
    ){
      WHERETRACE(("auto-index reduces cost from %.2f to %.2f\n",
                    pCost->rCost, costTempIdx));
      pCost->rCost = costTempIdx;
      pCost->nRow = logN + 1;
      pCost->plan.wsFlags = WHERE_TEMP_INDEX;
      pCost->used = pTerm->prereqRight;

  int regIsInit;              /* Register set by initialization */
  int addrInit;               /* Address of the initialization bypass jump */
  Table *pTable;              /* The table being indexed */
  KeyInfo *pKeyinfo;          /* Key information for the index */   
  int addrTop;                /* Top of the index fill loop */
  int regRecord;              /* Register holding an index record */
  int n;                      /* Column counter */
  CollSeq *pColl;             /* Collating sequence to on a column */

  /* Generate code to skip over the creation and initialization of the
  ** transient index on 2nd and subsequent iterations of the loop. */
  v = pParse->pVdbe;
  assert( v!=0 );
  regIsInit = ++pParse->nMem;
  addrInit = sqlite3VdbeAddOp1(v, OP_If, regIsInit);
  sqlite3VdbeAddOp2(v, OP_Integer, 1, regIsInit);

  /* Count the number of columns that will be added to the index */
  nColumn = 0;
  pTable = pSrc->pTab;
  pWCEnd = &pWC->a[pWC->nTerm];
  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
    if( pTerm->leftCursor==pSrc->iCursor
       && (pTerm->prereqRight & notReady)==0
       && (pTerm->eOperator & WO_EQ)!=0
       && sqlite3IndexAffinityOk(pTerm->pExpr,
                                 pTable->aCol[pTerm->u.leftColumn].affinity)
    ){
      nColumn++;
    }
  }
  assert( nColumn>0 );
  pLevel->plan.nEq = nColumn;
  pLevel->plan.wsFlags = WHERE_COLUMN_EQ | WO_EQ;

  /* Construct the Index object to describe this index */
  nByte = sizeof(Index);
  nByte += nColumn*sizeof(int);     /* Index.aiColumn */
  nByte += nColumn*sizeof(char*);   /* Index.azColl */
  nByte += nColumn;                 /* Index.aSortOrder */
  pIdx = sqlite3DbMallocZero(pParse->db, nByte);
  if( pIdx==0 ) return;
  pLevel->plan.u.pIdx = pIdx;
  pIdx->azColl = (char**)&pIdx[1];
  pIdx->aiColumn = (int*)&pIdx->azColl[nColumn];
  pIdx->aSortOrder = (u8*)&pIdx->aiColumn[nColumn];
  pIdx->zName = "auto-index";
  pIdx->nColumn = nColumn;
  pIdx->pTable = pTable;
  n = 0;
  for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
    if( pTerm->leftCursor==pSrc->iCursor
       && (pTerm->prereqRight & notReady)==0
       && (pTerm->eOperator & WO_EQ)!=0
       && sqlite3IndexAffinityOk(pTerm->pExpr,
                                 pTable->aCol[pTerm->u.leftColumn].affinity)
    ){
      int iCol = pTerm->u.leftColumn;
      Expr *pX;
      pIdx->aiColumn[n] = iCol;
      pX = pTerm->pExpr;
      pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
      pIdx->azColl[n] = pColl->zName;

      n++;
    }
  }
  assert( n==pIdx->nColumn );

  /* Create the transient index */
  pKeyinfo = sqlite3IndexKeyinfo(pParse, pIdx);
  assert( pLevel->iIdxCur>=0 );
  sqlite3VdbeAddOp4(v, OP_OpenEphemeral, pLevel->iIdxCur, nColumn+1, 0,
                    (char*)pKeyinfo, P4_KEYINFO_HANDOFF);
  VdbeComment((v, "auto-idx for %s", pTable->zName));

  /* Fill the transient index with content */
  addrTop = sqlite3VdbeAddOp1(v, OP_Rewind, pLevel->iTabCur);
  regRecord = sqlite3GetTempReg(pParse);
  sqlite3GenerateIndexKey(pParse, pIdx, pLevel->iTabCur, regRecord, 1);
  sqlite3VdbeAddOp2(v, OP_IdxInsert, pLevel->iIdxCur, regRecord);
  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);

        zMsg = sqlite3MAppendf(db, zMsg, "%s ORDER BY", zMsg);
      }
      sqlite3VdbeAddOp4(v, OP_Explain, i, pLevel->iFrom, 0, zMsg, P4_DYNAMIC);
    }
#endif /* SQLITE_OMIT_EXPLAIN */
    pTabItem = &pTabList->a[pLevel->iFrom];
    pTab = pTabItem->pTab;
    pLevel->iTabCur = pTabItem->iCursor;
    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
    if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
      if( pLevel->plan.wsFlags & WHERE_TEMP_INDEX ){
        constructTransientIndex(pParse, pWC, pTabItem, notReady, pLevel);
      }
      continue;
    }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
      const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
      int iCur = pTabItem->iCursor;
      sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
    }else
#endif

        sqlite3VdbeChangeP4(v, sqlite3VdbeCurrentAddr(v)-1, 
                            SQLITE_INT_TO_PTR(n), P4_INT32);
        assert( n<=pTab->nCol );
      }
    }else{
      sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
    }

    if( (pLevel->plan.wsFlags & WHERE_TEMP_INDEX)!=0 ){
      constructTransientIndex(pParse, pWC, pTabItem, notReady, pLevel);
    }else if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
      Index *pIx = pLevel->plan.u.pIdx;
      KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
      int iIdxCur = pLevel->iIdxCur;
      assert( pIx->pSchema==pTab->pSchema );