SQLite

  }else{
    sortOrderMask = 0;    /* Ignore DESC */
  }

  /* Analyze the list of expressions that form the terms of the index and
  ** report any errors.  In the common case where the expression is exactly
  ** a table column, store that column in aiColumn[].  For general expressions,
  ** populate pIndex->aColExpr and store XN_EXPR (-2) in aiColumn[].
  **
  ** TODO: Issue a warning if two or more columns of the index are identical.
  ** TODO: Issue a warning if the table primary key is used as part of the
  ** index key.
  */
  for(i=0, pListItem=pList->a; i<pList->nExpr; i++, pListItem++){
    Expr *pCExpr;                  /* The i-th index expression */

        ExprList *pCopy = sqlite3ExprListDup(db, pList, 0);
        pIndex->aColExpr = pCopy;
        if( !db->mallocFailed ){
          assert( pCopy!=0 );
          pListItem = &pCopy->a[i];
        }
      }
      j = XN_EXPR;
      pIndex->aiColumn[i] = XN_EXPR;
      pIndex->uniqNotNull = 0;
    }else{
      j = pCExpr->iColumn;
      assert( j<=0x7fff );
      if( j<0 ){
        j = pTab->iPKey;
      }else if( pTab->aCol[j].notNull==0 ){

        pIndex->azColl[i] = pPk->azColl[j];
        pIndex->aSortOrder[i] = pPk->aSortOrder[j];
        i++;
      }
    }
    assert( i==pIndex->nColumn );
  }else{
    pIndex->aiColumn[i] = XN_ROWID;
    pIndex->azColl[i] = "BINARY";
  }
  sqlite3DefaultRowEst(pIndex);
  if( pParse->pNewTable==0 ) estimateIndexWidth(pIndex);

  if( pTab==pParse->pNewTable ){
    /* This routine has been called to create an automatic index as a

    if( db->flags & SQLITE_CountRows ){
      sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);
    }
  
    /* Extract the rowid or primary key for the current row */
    if( pPk ){
      for(i=0; i<nPk; i++){
        assert( pPk->aiColumn[i]>=0 );
        sqlite3ExprCodeGetColumnOfTable(v, pTab, iTabCur,
                                        pPk->aiColumn[i], iPk+i);
      }
      iKey = iPk;
    }else{
      iKey = pParse->nMem + 1;
      iKey = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iTabCur, iKey, 0);

  }
  nCol = (prefixOnly && pIdx->uniqNotNull) ? pIdx->nKeyCol : pIdx->nColumn;
  regBase = sqlite3GetTempRange(pParse, nCol);
  if( pPrior && (regBase!=regPrior || pPrior->pPartIdxWhere) ) pPrior = 0;
  for(j=0; j<nCol; j++){
    if( pPrior
     && pPrior->aiColumn[j]==pIdx->aiColumn[j]
     && pPrior->aiColumn[j]!=XN_EXPR
    ){
      /* This column was already computed by the previous index */
      continue;
    }
    sqlite3ExprCodeLoadIndexColumn(pParse, pIdx, iDataCur, j, regBase+j);
    /* If the column affinity is REAL but the number is an integer, then it
    ** might be stored in the table as an integer (using a compact

  Parse *pParse,  /* The parsing context */
  Index *pIdx,    /* The index whose column is to be loaded */
  int iTabCur,    /* Cursor pointing to a table row */
  int iIdxCol,    /* The column of the index to be loaded */
  int regOut      /* Store the index column value in this register */
){
  i16 iTabCol = pIdx->aiColumn[iIdxCol];
  if( iTabCol==XN_EXPR ){




    assert( pIdx->aColExpr );
    assert( pIdx->aColExpr->nExpr>iIdxCol );
    pParse->iSelfTab = iTabCur;
    sqlite3ExprCode(pParse, pIdx->aColExpr->a[iIdxCol].pExpr, regOut);
  }else{
    sqlite3ExprCodeGetColumnOfTable(pParse->pVdbe, pIdx->pTable, iTabCur,
                                    iTabCol, regOut);
  }
}

/*
** Generate code to extract the value of the iCol-th column of a table.
*/
void sqlite3ExprCodeGetColumnOfTable(
  Vdbe *v,        /* The VDBE under construction */

        ** the default collation sequences for each column. */
        int i, j;
        for(i=0; i<nCol; i++){
          i16 iCol = pIdx->aiColumn[i];     /* Index of column in parent tbl */
          char *zDfltColl;                  /* Def. collation for column */
          char *zIdxCol;                    /* Name of indexed column */

          if( iCol<0 ) break; /* No foreign keys against expression indexes */

          /* If the index uses a collation sequence that is different from
          ** the default collation sequence for the column, this index is
          ** unusable. Bail out early in this case.  */
          zDfltColl = pParent->aCol[iCol].zColl;
          if( !zDfltColl ){
            zDfltColl = "BINARY";
          }

      ** none of the child key values are).
      */
      if( pTab==pFKey->pFrom && nIncr==1 ){
        int iJump = sqlite3VdbeCurrentAddr(v) + nCol + 1;
        for(i=0; i<nCol; i++){
          int iChild = aiCol[i]+1+regData;
          int iParent = pIdx->aiColumn[i]+1+regData;
          assert( pIdx->aiColumn[i]>=0 );
          assert( aiCol[i]!=pTab->iPKey );
          if( pIdx->aiColumn[i]==pTab->iPKey ){
            /* The parent key is a composite key that includes the IPK column */
            iParent = regData;
          }
          sqlite3VdbeAddOp3(v, OP_Ne, iChild, iJump, iParent); VdbeCoverage(v);
          sqlite3VdbeChangeP5(v, SQLITE_JUMPIFNULL);

      pNe = sqlite3PExpr(pParse, TK_NE, pLeft, pRight, 0);
    }else{
      Expr *pEq, *pAll = 0;
      Index *pPk = sqlite3PrimaryKeyIndex(pTab);
      assert( pIdx!=0 );
      for(i=0; i<pPk->nKeyCol; i++){
        i16 iCol = pIdx->aiColumn[i];
        assert( iCol>=0 );
        pLeft = exprTableRegister(pParse, pTab, regData, iCol);
        pRight = exprTableColumn(db, pTab, pSrc->a[0].iCursor, iCol);
        pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight, 0);
        pAll = sqlite3ExprAnd(db, pAll, pEq);
      }
      pNe = sqlite3PExpr(pParse, TK_NOT, pAll, 0, 0);
    }

      iCol = pFKey->aCol[0].iFrom;
      aiCol = &iCol;
    }
    for(i=0; i<pFKey->nCol; i++){
      if( aiCol[i]==pTab->iPKey ){
        aiCol[i] = -1;
      }
      assert( pIdx==0 || pIdx->aiColumn[i]>=0 );
#ifndef SQLITE_OMIT_AUTHORIZATION
      /* Request permission to read the parent key columns. If the 
      ** authorization callback returns SQLITE_IGNORE, behave as if any
      ** values read from the parent table are NULL. */
      if( db->xAuth ){
        int rcauth;
        char *zCol = pTo->aCol[pIdx ? pIdx->aiColumn[i] : pTo->iPKey].zName;

    for(p=pTab->pFKey; p; p=p->pNextFrom){
      for(i=0; i<p->nCol; i++) mask |= COLUMN_MASK(p->aCol[i].iFrom);
    }
    for(p=sqlite3FkReferences(pTab); p; p=p->pNextTo){
      Index *pIdx = 0;
      sqlite3FkLocateIndex(pParse, pTab, p, &pIdx, 0);
      if( pIdx ){
        for(i=0; i<pIdx->nKeyCol; i++){
          assert( pIdx->aiColumn[i]>=0 );
          mask |= COLUMN_MASK(pIdx->aiColumn[i]);
        }
      }
    }
  }
  return mask;
}

      Token tToCol;               /* Name of column in parent table */
      int iFromCol;               /* Idx of column in child table */
      Expr *pEq;                  /* tFromCol = OLD.tToCol */

      iFromCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
      assert( iFromCol>=0 );
      assert( pIdx!=0 || (pTab->iPKey>=0 && pTab->iPKey<pTab->nCol) );
      assert( pIdx==0 || pIdx->aiColumn[i]>=0 );
      tToCol.z = pTab->aCol[pIdx ? pIdx->aiColumn[i] : pTab->iPKey].zName;
      tFromCol.z = pFKey->pFrom->aCol[iFromCol].zName;

      tToCol.n = sqlite3Strlen30(tToCol.z);
      tFromCol.n = sqlite3Strlen30(tFromCol.z);

      /* Create the expression "OLD.zToCol = zFromCol". It is important

      db->mallocFailed = 1;
      return 0;
    }
    for(n=0; n<pIdx->nColumn; n++){
      i16 x = pIdx->aiColumn[n];
      if( x>=0 ){
        pIdx->zColAff[n] = pTab->aCol[x].affinity;
      }else if( x==XN_ROWID ){
        pIdx->zColAff[n] = SQLITE_AFF_INTEGER;
      }else{
        char aff;
        assert( x==XN_EXPR );
        assert( pIdx->aColExpr!=0 );
        aff = sqlite3ExprAffinity(pIdx->aColExpr->a[n].pExpr);
        if( aff==0 ) aff = SQLITE_AFF_BLOB;
        pIdx->zColAff[n] = aff;
      }
    }
    pIdx->zColAff[n] = 0;

    /* Create a record for this index entry as it should appear after
    ** the insert or update.  Store that record in the aRegIdx[ix] register
    */
    regIdx = sqlite3GetTempRange(pParse, pIdx->nColumn);
    for(i=0; i<pIdx->nColumn; i++){
      int iField = pIdx->aiColumn[i];
      int x;
      if( iField==XN_EXPR ){
        pParse->ckBase = regNewData+1;
        sqlite3ExprCode(pParse, pIdx->aColExpr->a[i].pExpr, regIdx+i);
        pParse->ckBase = 0;
        VdbeComment((v, "%s column %d", pIdx->zName, i));
      }else{
        if( iField==XN_ROWID || iField==pTab->iPKey ){
          if( regRowid==regIdx+i ) continue; /* ROWID already in regIdx+i */
          x = regNewData;
          regRowid =  pIdx->pPartIdxWhere ? -1 : regIdx+i;
        }else{
          x = iField + regNewData + 1;
        }
        sqlite3VdbeAddOp2(v, OP_SCopy, x, regIdx+i);

        }
      }else{
        int x;
        /* Extract the PRIMARY KEY from the end of the index entry and
        ** store it in registers regR..regR+nPk-1 */
        if( pIdx!=pPk ){
          for(i=0; i<pPk->nKeyCol; i++){
            assert( pPk->aiColumn[i]>=0 );
            x = sqlite3ColumnOfIndex(pIdx, pPk->aiColumn[i]);
            sqlite3VdbeAddOp3(v, OP_Column, iThisCur, x, regR+i);
            VdbeComment((v, "%s.%s", pTab->zName,
                         pTab->aCol[pPk->aiColumn[i]].zName));
          }
        }
        if( isUpdate ){

          int addrJump = sqlite3VdbeCurrentAddr(v)+pPk->nKeyCol;
          int op = OP_Ne;
          int regCmp = (IsPrimaryKeyIndex(pIdx) ? regIdx : regR);
  
          for(i=0; i<pPk->nKeyCol; i++){
            char *p4 = (char*)sqlite3LocateCollSeq(pParse, pPk->azColl[i]);
            x = pPk->aiColumn[i];
            assert( x>=0 );
            if( i==(pPk->nKeyCol-1) ){
              addrJump = addrUniqueOk;
              op = OP_Eq;
            }
            sqlite3VdbeAddOp4(v, op, 
                regOldData+1+x, addrJump, regCmp+i, p4, P4_COLLSEQ
            );

  if( pDest->onError!=pSrc->onError ){
    return 0;   /* Different conflict resolution strategies */
  }
  for(i=0; i<pSrc->nKeyCol; i++){
    if( pSrc->aiColumn[i]!=pDest->aiColumn[i] ){
      return 0;   /* Different columns indexed */
    }
    if( pSrc->aiColumn[i]==XN_EXPR ){
      assert( pSrc->aColExpr!=0 && pDest->aColExpr!=0 );
      if( sqlite3ExprCompare(pSrc->aColExpr->a[i].pExpr,
                             pDest->aColExpr->a[i].pExpr, -1)!=0 ){
        return 0;   /* Different expressions in the index */
      }
    }
    if( pSrc->aSortOrder[i]!=pDest->aSortOrder[i] ){

          ** or (2) the next entry has a different key */
          if( IsUniqueIndex(pIdx) ){
            int uniqOk = sqlite3VdbeMakeLabel(v);
            int jmp6;
            int kk;
            for(kk=0; kk<pIdx->nKeyCol; kk++){
              int iCol = pIdx->aiColumn[kk];
              assert( iCol!=XN_ROWID && iCol<pTab->nCol );
              if( iCol>=0 && pTab->aCol[iCol].notNull ) continue;
              sqlite3VdbeAddOp2(v, OP_IsNull, r1+kk, uniqOk);
              VdbeCoverage(v);
            }
            jmp6 = sqlite3VdbeAddOp1(v, OP_Next, iIdxCur+j); VdbeCoverage(v);
            sqlite3VdbeGoto(v, uniqOk);
            sqlite3VdbeJumpHere(v, jmp6);

/* Return true if index X is a PRIMARY KEY index */
#define IsPrimaryKeyIndex(X)  ((X)->idxType==SQLITE_IDXTYPE_PRIMARYKEY)

/* Return true if index X is a UNIQUE index */
#define IsUniqueIndex(X)      ((X)->onError!=OE_None)

/* The Index.aiColumn[] values are normally positive integer.  But
** there are some negative values that have special meaning:
*/
#define XN_ROWID     (-1)     /* Indexed column is the rowid */
#define XN_EXPR      (-2)     /* Indexed column is an expression */

/*
** Each sample stored in the sqlite_stat3 table is represented in memory 
** using a structure of this type.  See documentation at the top of the
** analyze.c source file for additional information.
*/
struct IndexSample {
  void *p;          /* Pointer to sampled record */

    addrOpen = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, iEph, nPk);
    sqlite3VdbeSetP4KeyInfo(pParse, pPk);
    pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0, 0, 
                               WHERE_ONEPASS_DESIRED, iIdxCur);
    if( pWInfo==0 ) goto update_cleanup;
    okOnePass = sqlite3WhereOkOnePass(pWInfo, aiCurOnePass);
    for(i=0; i<nPk; i++){
      assert( pPk->aiColumn[i]>=0 );
      sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, pPk->aiColumn[i],
                                      iPk+i);
    }
    if( okOnePass ){
      sqlite3VdbeChangeToNoop(v, addrOpen);
      nKey = nPk;
      regKey = iPk;

        }
      }
#endif
      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
        int j;
        for(j=0; j<pIdx->nKeyCol; j++){
          /* FIXME: Be smarter about indexes that use expressions */
          if( pIdx->aiColumn[j]==iCol || pIdx->aiColumn[j]==XN_EXPR ){
            zFault = "indexed";
          }
        }
      }
      if( zFault ){
        sqlite3DbFree(db, zErr);
        zErr = sqlite3MPrintf(db, "cannot open %s column for writing", zFault);

  WhereClause *pWC;    /* Shorthand for pScan->pWC */
  WhereTerm *pTerm;    /* The term being tested */
  int k = pScan->k;    /* Where to start scanning */

  while( pScan->iEquiv<=pScan->nEquiv ){
    iCur = pScan->aiCur[pScan->iEquiv-1];
    iColumn = pScan->aiColumn[pScan->iEquiv-1];
    if( iColumn==XN_EXPR && pScan->pIdxExpr==0 ) return 0;
    while( (pWC = pScan->pWC)!=0 ){
      for(pTerm=pWC->a+k; k<pWC->nTerm; k++, pTerm++){
        if( pTerm->leftCursor==iCur
         && pTerm->u.leftColumn==iColumn
         && (iColumn!=XN_EXPR
             || sqlite3ExprCompare(pTerm->pExpr->pLeft,pScan->pIdxExpr,iCur)==0)
         && (pScan->iEquiv<=1 || !ExprHasProperty(pTerm->pExpr, EP_FromJoin))
        ){
          if( (pTerm->eOperator & WO_EQUIV)!=0
           && pScan->nEquiv<ArraySize(pScan->aiCur)
           && (pX = sqlite3ExprSkipCollate(pTerm->pExpr->pRight))->op==TK_COLUMN
          ){

  /* memset(pScan, 0, sizeof(*pScan)); */
  pScan->pOrigWC = pWC;
  pScan->pWC = pWC;
  pScan->pIdxExpr = 0;
  if( pIdx ){
    j = iColumn;
    iColumn = pIdx->aiColumn[j];
    if( iColumn==XN_EXPR ) pScan->pIdxExpr = pIdx->aColExpr->a[j].pExpr;
  }
  if( pIdx && iColumn>=0 ){
    pScan->idxaff = pIdx->pTable->aCol[iColumn].affinity;
    pScan->zCollName = pIdx->azColl[j];
  }else{
    pScan->idxaff = 0;
    pScan->zCollName = 0;

    for(i=BMS-1; i<pTable->nCol; i++){
      pIdx->aiColumn[n] = i;
      pIdx->azColl[n] = "BINARY";
      n++;
    }
  }
  assert( n==nKeyCol );
  pIdx->aiColumn[n] = XN_ROWID;
  pIdx->azColl[n] = "BINARY";

  /* Create the automatic index */
  assert( pLevel->iIdxCur>=0 );
  pLevel->iIdxCur = pParse->nTab++;
  sqlite3VdbeAddOp2(v, OP_OpenAutoindex, pLevel->iIdxCur, nKeyCol+1);
  sqlite3VdbeSetP4KeyInfo(pParse, pIdx);

      assert( nIn>0 );  /* RHS always has 2 or more terms...  The parser
                        ** changes "x IN (?)" into "x=?". */

    }else if( eOp & (WO_EQ|WO_IS) ){
      int iCol = pProbe->aiColumn[saved_nEq];
      pNew->wsFlags |= WHERE_COLUMN_EQ;
      assert( saved_nEq==pNew->u.btree.nEq );
      if( iCol==XN_ROWID 
       || (iCol>0 && nInMul==0 && saved_nEq==pProbe->nKeyCol-1)
      ){
        if( iCol>=0 && pProbe->uniqNotNull==0 ){
          pNew->wsFlags |= WHERE_UNQ_WANTED;
        }else{
          pNew->wsFlags |= WHERE_ONEROW;
        }
      }
    }else if( eOp & WO_ISNULL ){

    if( pExpr->op==TK_COLUMN && pExpr->iTable==iCursor ){
      if( pExpr->iColumn<0 ) return 1;
      for(jj=0; jj<pIndex->nKeyCol; jj++){
        if( pExpr->iColumn==pIndex->aiColumn[jj] ) return 1;
      }
    }else if( (aColExpr = pIndex->aColExpr)!=0 ){
      for(jj=0; jj<pIndex->nKeyCol; jj++){
        if( pIndex->aiColumn[jj]!=XN_EXPR ) continue;
        if( sqlite3ExprCompare(pExpr,aColExpr->a[jj].pExpr,iCursor)==0 ){
          return 1;
        }
      }
    }
  }
  return 0;

        nColumn = 1;
      }else if( (pIndex = pLoop->u.btree.pIndex)==0 || pIndex->bUnordered ){
        return 0;
      }else{
        nKeyCol = pIndex->nKeyCol;
        nColumn = pIndex->nColumn;
        assert( nColumn==nKeyCol+1 || !HasRowid(pIndex->pTable) );
        assert( pIndex->aiColumn[nColumn-1]==XN_ROWID
                          || !HasRowid(pIndex->pTable));
        isOrderDistinct = IsUniqueIndex(pIndex);
      }

      /* Loop through all columns of the index and deal with the ones
      ** that are not constrained by == or IN.
      */
      rev = revSet = 0;

        ** (revIdx) for the j-th column of the index.
        */
        if( pIndex ){
          iColumn = pIndex->aiColumn[j];
          revIdx = pIndex->aSortOrder[j];
          if( iColumn==pIndex->pTable->iPKey ) iColumn = -1;
        }else{
          iColumn = XN_ROWID;
          revIdx = 0;
        }

        /* An unconstrained column that might be NULL means that this
        ** WhereLoop is not well-ordered
        */
        if( isOrderDistinct

        if( pOp->p1!=pLevel->iTabCur ) continue;
        if( pOp->opcode==OP_Column ){
          int x = pOp->p2;
          assert( pIdx->pTable==pTab );
          if( !HasRowid(pTab) ){
            Index *pPk = sqlite3PrimaryKeyIndex(pTab);
            x = pPk->aiColumn[x];
            assert( x>=0 );
          }
          x = sqlite3ColumnOfIndex(pIdx, x);
          if( x>=0 ){
            pOp->p2 = x;
            pOp->p1 = pLevel->iIdxCur;
          }
          assert( (pLoop->wsFlags & WHERE_IDX_ONLY)==0 || x>=0 );

}

/*
** Return the name of the i-th column of the pIdx index.
*/
static const char *explainIndexColumnName(Index *pIdx, int i){
  i = pIdx->aiColumn[i];
  if( i==XN_EXPR ) return "<expr>";
  if( i==XN_ROWID ) return "rowid";
  return pIdx->pTable->aCol[i].zName;
}

/*
** Argument pLevel describes a strategy for scanning table pTab. This 
** function appends text to pStr that describes the subset of table
** rows scanned by the strategy in the form of an SQL expression.

    pLevel->addrSkip = sqlite3VdbeAddOp4Int(v, (bRev?OP_SeekLT:OP_SeekGT),
                            iIdxCur, 0, regBase, nSkip);
    VdbeCoverageIf(v, bRev==0);
    VdbeCoverageIf(v, bRev!=0);
    sqlite3VdbeJumpHere(v, j);
    for(j=0; j<nSkip; j++){
      sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, j, regBase+j);
      testcase( pIdx->aiColumn[j]==XN_EXPR );
      VdbeComment((v, "%s", explainIndexColumnName(pIdx, j)));
    }
  }    

  /* Evaluate the equality constraints
  */
  assert( zAff==0 || (int)strlen(zAff)>=nEq );