SQLite

  SortCtx *pSort,        /* Information about the ORDER BY clause */
  Select *pSelect,       /* The whole SELECT statement */
  int regData,           /* First register holding data to be sorted */
  int nData,             /* Number of elements in the data array */
  int nPrefixReg         /* No. of reg prior to regData available for use */
){
  Vdbe *v = pParse->pVdbe;                         /* Stmt under construction */
  int bSeq = ((pSort->sortFlags & SORTFLAG_UseSorter)==0);
  int nExpr = pSort->pOrderBy->nExpr;              /* No. of ORDER BY terms */
  int nBase = nExpr + 1 + nData;                   /* Fields in sorter record */
  int nBase = nExpr + bSeq + nData;                /* Fields in sorter record */
  int regBase;                                     /* Regs for sorter record */
  int regRecord = sqlite3GetTempReg(pParse);       /* Assemblied sorter record */
  int nOBSat = pSort->nOBSat;                      /* No. ORDER BY terms to skip */
  int op;                               /* Opcode to add sorter record to sorter */
  int regRecord = sqlite3GetTempReg(pParse);       /* Assembled sorter record */
  int nOBSat = pSort->nOBSat;                      /* ORDER BY terms to skip */
  int op;                            /* Opcode to add sorter record to sorter */

  assert( bSeq==0 || bSeq==1 );
  if( nPrefixReg ){
    assert( nPrefixReg==nExpr+1 );
    regBase = regData - nExpr - 1;
    assert( nPrefixReg==nExpr+bSeq );
    regBase = regData - nExpr - bSeq;
  }else{
    regBase = sqlite3GetTempRange(pParse, nBase);
  }
  sqlite3ExprCodeExprList(pParse, pSort->pOrderBy, regBase, SQLITE_ECEL_DUP);
  if( bSeq ){
  sqlite3VdbeAddOp2(v, OP_Sequence, pSort->iECursor, regBase+nExpr);
    sqlite3VdbeAddOp2(v, OP_Sequence, pSort->iECursor, regBase+nExpr);
  }
  if( nPrefixReg==0 ){
    sqlite3VdbeAddOp3(v, OP_Move, regData, regBase+nExpr+1, nData);
    sqlite3VdbeAddOp3(v, OP_Move, regData, regBase+nExpr+bSeq, nData);
  }

  sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase+nOBSat, nBase-nOBSat, regRecord);
  if( nOBSat>0 ){
    int regPrevKey;   /* The first nOBSat columns of the previous row */
    int addrFirst;    /* Address of the OP_IfNot opcode */
    int addrJmp;      /* Address of the OP_Jump opcode */
    VdbeOp *pOp;      /* Opcode that opens the sorter */
    int nKey;         /* Number of sorting key columns, including OP_Sequence */
    KeyInfo *pKI;     /* Original KeyInfo on the sorter table */

    regPrevKey = pParse->nMem+1;
    pParse->nMem += pSort->nOBSat;
    nKey = nExpr - pSort->nOBSat + 1;
    addrFirst = sqlite3VdbeAddOp1(v, OP_IfNot, regBase+nExpr); VdbeCoverage(v);
    nKey = nExpr - pSort->nOBSat + bSeq;
    if( bSeq ){
      addrFirst = sqlite3VdbeAddOp1(v, OP_IfNot, regBase+nExpr); 
    }else{
      addrFirst = sqlite3VdbeAddOp1(v, OP_SequenceTest, pSort->iECursor);
    }
    VdbeCoverage(v);
    sqlite3VdbeAddOp3(v, OP_Compare, regPrevKey, regBase, pSort->nOBSat);
    pOp = sqlite3VdbeGetOp(v, pSort->addrSortIndex);
    if( pParse->db->mallocFailed ) return;
    pOp->p2 = nKey + 1;
    pKI = pOp->p4.pKeyInfo;
    memset(pKI->aSortOrder, 0, pKI->nField); /* Makes OP_Jump below testable */
    sqlite3VdbeChangeP4(v, -1, (char*)pKI, P4_KEYINFO);

  /* Pull the requested columns.
  */
  nResultCol = pEList->nExpr;

  if( pDest->iSdst==0 ){
    if( pSort ){
      nPrefixReg = pSort->pOrderBy->nExpr + 1;
      nPrefixReg = pSort->pOrderBy->nExpr;
      if( !(pSort->sortFlags & SORTFLAG_UseSorter) ) nPrefixReg++;
      pParse->nMem += nPrefixReg;
    }
    pDest->iSdst = pParse->nMem+1;
    pParse->nMem += nResultCol;
  }else if( pDest->iSdst+nResultCol > pParse->nMem ){
    /* This is an error condition that can result, for example, when a SELECT
    ** on the right-hand side of an INSERT contains more result columns than

  int regRow;
  int regRowid;
  int nKey;
  int iSortTab;                   /* Sorter cursor to read from */
  int nSortData;                  /* Trailing values to read from sorter */
  u8 p5;                          /* p5 parameter for 1st OP_Column */
  int i;
  int bSeq;                       /* True if sorter record includes seq. no. */
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
  struct ExprList_item *aOutEx = p->pEList->a;
#endif

  if( pSort->labelBkOut ){
    sqlite3VdbeAddOp2(v, OP_Gosub, pSort->regReturn, pSort->labelBkOut);
    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrBreak);

    sqlite3VdbeAddOp3(v, OP_OpenPseudo, iSortTab, regSortOut, nKey+1+nSortData);
    if( addrOnce ) sqlite3VdbeJumpHere(v, addrOnce);
    addr = 1 + sqlite3VdbeAddOp2(v, OP_SorterSort, iTab, addrBreak);
    VdbeCoverage(v);
    codeOffset(v, p->iOffset, addrContinue);
    sqlite3VdbeAddOp2(v, OP_SorterData, iTab, regSortOut);
    p5 = OPFLAG_CLEARCACHE;
    bSeq = 0;
  }else{
    addr = 1 + sqlite3VdbeAddOp2(v, OP_Sort, iTab, addrBreak); VdbeCoverage(v);
    codeOffset(v, p->iOffset, addrContinue);
    iSortTab = iTab;
    p5 = 0;
    bSeq = 1;
  }
  for(i=0; i<nSortData; i++){
    sqlite3VdbeAddOp3(v, OP_Column, iSortTab, nKey+1+i, regRow+i);
    sqlite3VdbeAddOp3(v, OP_Column, iSortTab, nKey+bSeq+i, regRow+i);
    if( i==0 ) sqlite3VdbeChangeP5(v, p5);
    VdbeComment((v, "%s", aOutEx[i].zName ? aOutEx[i].zName : aOutEx[i].zSpan));
  }
  switch( eDest ){
    case SRT_Table:
    case SRT_EphemTab: {
      testcase( eDest==SRT_Table );

  if( pCx==0 ) goto no_mem;
  pCx->pKeyInfo = pOp->p4.pKeyInfo;
  assert( pCx->pKeyInfo->db==db );
  assert( pCx->pKeyInfo->enc==ENC(db) );
  rc = sqlite3VdbeSorterInit(db, pCx);
  break;
}

/* Opcode: SequenceTest P1 P2 * * *
** Synopsis: if( cursor[P1].ctr++ ) pc = P2
**
** P1 is a sorter cursor. If the sequence counter is currently zero, jump
** to P2. Regardless of whether or not the jump is taken, increment the
** the sequence value.
*/
case OP_SequenceTest: {
  VdbeCursor *pC;
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC->pSorter );
  if( (pC->seqCount++)==0 ){
    pc = pOp->p2 - 1;
  }
  break;
}

/* Opcode: OpenPseudo P1 P2 P3 * *
** Synopsis: P3 columns in r[P2]
**
** Open a new cursor that points to a fake table that contains a single
** row of data.  The content of that one row is the content of memory
** register P2.  In other words, cursor P1 becomes an alias for the