**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.435 2008/06/24 12:46:31 drh Exp $
*/
#include "sqliteInt.h"


/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.
................................................................................
  sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nExpr + 2, regRecord);
  sqlite3VdbeAddOp2(v, OP_IdxInsert, pOrderBy->iECursor, regRecord);
  sqlite3ReleaseTempReg(pParse, regRecord);
  sqlite3ReleaseTempRange(pParse, regBase, nExpr+2);
  if( pSelect->iLimit ){
    int addr1, addr2;
    int iLimit;
    if( pSelect->pOffset ){
      iLimit = pSelect->iOffset+1;
    }else{
      iLimit = pSelect->iLimit;
    }
    addr1 = sqlite3VdbeAddOp1(v, OP_IfZero, iLimit);
    sqlite3VdbeAddOp2(v, OP_AddImm, iLimit, -1);
    addr2 = sqlite3VdbeAddOp0(v, OP_Goto);
................................................................................
  */
  if( nColumn>0 ){
    nResultCol = nColumn;
  }else{
    nResultCol = pEList->nExpr;
  }
  if( pDest->iMem==0 ){
    pDest->iMem = sqlite3GetTempRange(pParse, nResultCol);
    pDest->nMem = nResultCol;

  }else if( pDest->nMem!=nResultCol ){
    /* This happens when two SELECTs of a compound SELECT have differing
    ** numbers of result columns.  The error message will be generated by
    ** a higher-level routine. */
    return;
  }
  regResult = pDest->iMem;
................................................................................
** SELECT statements.
*/
static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
  Vdbe *v = 0;
  int iLimit = 0;
  int iOffset;
  int addr1;


  /* 
  ** "LIMIT -1" always shows all rows.  There is some
  ** contraversy about what the correct behavior should be.
  ** The current implementation interprets "LIMIT 0" to mean
  ** no rows.
  */
................................................................................
  if( p->pEList->nExpr!=pPrior->pEList->nExpr ){
    sqlite3ErrorMsg(pParse, "SELECTs to the left and right of %s"
      " do not have the same number of result columns", selectOpName(p->op));
    rc = 1;
    goto multi_select_end;
  }

#if 0
  if( p->pOrderBy ){
    return multiSelectOrderBy(pParse, p, pDest, aff);
  }
#endif

  /* Generate code for the left and right SELECT statements.
  */
................................................................................
  return rc;
}
#endif /* SQLITE_OMIT_COMPOUND_SELECT */

/*
** Code an output subroutine for a coroutine implementation of a
** SELECT statment.
















*/
static int outputSubroutine(
  Parse *pParse,          /* Parsing context */
  Select *p,              /* The SELECT statement */
  SelectDest *pIn,        /* Coroutine supplying data */
  SelectDest *pDest,      /* Where to send the data */
  int regReturn,          /* The return address register */



  int iBreak              /* Jump here if we hit the LIMIT */
){
  Vdbe *v = pParse->pVdbe;
  int iContinue;
  int addr;
  if( v==0 ) return 0;

  addr = sqlite3VdbeCurrentAddr(v);
  iContinue = sqlite3VdbeMakeLabel(v);
















  codeOffset(v, p, iContinue);

  switch( pDest->eDest ){
    /* Store the result as data using a unique key.
    */
    case SRT_Table:
    case SRT_EphemTab: {
................................................................................
  /* Jump to the end of the loop if the LIMIT is reached.
  */
  if( p->iLimit ){
    sqlite3VdbeAddOp2(v, OP_AddImm, p->iLimit, -1);
    sqlite3VdbeAddOp2(v, OP_IfZero, p->iLimit, iBreak);
  }

  /* Advance the coroutine to its next value.
  */
  sqlite3VdbeResolveLabel(v, iContinue);
  sqlite3VdbeAddOp1(v, OP_Yield, pIn->iParm);

  /* Generate the subroutine return
  */
  sqlite3VdbeAddOp1(v, OP_Return, regReturn);

  return addr;
}

/*
** Alternative compound select code generator for cases when there
................................................................................
**
** The implementation of the latter five subroutines depend on which 
** <operator> is used:
**
**
**             UNION ALL         UNION            EXCEPT          INTERSECT
**          -------------  -----------------  --------------  -----------------
**   AltB:   outA, nextA      outA, nextA       outA, nextA        nextA
**
**   AeqB:   outA, nextA         nextA             nextA           outA
**                                                            nextA while A==B
**
**   AgtB:   outB, nextB      outB, nextB          nextB           nextB
**
**   EofA:   outB, nextB      A<-B, outB,          halt            halt
**                          nextB while A==B
**
**   EofB:   outA, nextA      B<-A, outA        outA, nextA        halt


**                          nextA while A==B







**
** The implementation plan is to implement the two coroutines and seven
** subroutines first, then put the control logic at the bottom.  Like this:
**
**          goto Init
**     coA: coroutine for left query (A)
**     coB: coroutine for right query (B)
................................................................................
*/
static int multiSelectOrderBy(
  Parse *pParse,        /* Parsing context */
  Select *p,            /* The right-most of SELECTs to be coded */
  SelectDest *pDest,    /* What to do with query results */
  char *aff             /* If eDest is SRT_Union, the affinity string */
){

  Select *pPrior;       /* Another SELECT immediately to our left */
  Vdbe *v;              /* Generate code to this VDBE */
  SelectDest destA;     /* Destination for coroutine A */
  SelectDest destB;     /* Destination for coroutine B */
  int regAddrA;         /* Address register for select-A coroutine */
  int regEofA;          /* Flag to indicate when select-A is complete */
  int regAddrB;         /* Address register for select-B coroutine */
................................................................................
  int addrEofA;         /* Address of the select-A-exhausted subroutine */
  int addrEofB;         /* Address of the select-B-exhausted subroutine */
  int addrAltB;         /* Address of the A<B subroutine */
  int addrAeqB;         /* Address of the A==B subroutine */
  int addrAgtB;         /* Address of the A>B subroutine */
  int regLimitA;        /* Limit register for select-A */
  int regLimitB;        /* Limit register for select-A */

  int savedLimit;       /* Saved value of p->iLimit */
  int savedOffset;      /* Saved value of p->iOffset */
  int labelCmpr;        /* Label for the start of the merge algorithm */
  int labelEnd;         /* Label for the end of the overall SELECT stmt */
  int j1, j2, j3;       /* Jump instructions that get retargetted */
  int op;               /* One of TK_ALL, TK_UNION, TK_EXCEPT, TK_INTERSECT */
  KeyInfo *pKeyInfo;    /* Type data for comparisons */
  int p4type;           /* P4 type used for pKeyInfo */






  assert( p->pOrderBy!=0 );

  v = pParse->pVdbe;
  if( v==0 ) return SQLITE_NOMEM;
  labelEnd = sqlite3VdbeMakeLabel(v);
  labelCmpr = sqlite3VdbeMakeLabel(v);
  pKeyInfo = keyInfoFromExprList(pParse, p->pEList);
  p4type = P4_KEYINFO_HANDOFF;


  /* Patch up the ORDER BY clause
  */
  op = p->op;  
  pPrior = p->pPrior;
  assert( pPrior->pOrderBy==0 );


  if( processCompoundOrderBy(pParse, p, 0) ){
    return SQLITE_ERROR;
  }






































































  pPrior->pOrderBy = sqlite3ExprListDup(pParse->db, p->pOrderBy);
 
























  /* Separate the left and the right query from one another
  */
  p->pPrior = 0;
  pPrior->pRightmost = 0;



  

  /* Compute the limit registers */
  computeLimitRegisters(pParse, p, labelEnd);
  if( p->iLimit ){
    regLimitA = ++pParse->nMem;
    regLimitB = ++pParse->nMem;
    sqlite3VdbeAddOp2(v, OP_Copy, p->iOffset ? p->iOffset+1 : p->iLimit,
                                  regLimitA);
    sqlite3VdbeAddOp2(v, OP_Copy, regLimitA, regLimitB);
  }else{
    regLimitA = regLimitB = 0;
  }





  regAddrA = ++pParse->nMem;
  regEofA = ++pParse->nMem;
  regAddrB = ++pParse->nMem;
  regEofB = ++pParse->nMem;
  regOutA = ++pParse->nMem;
  regOutB = ++pParse->nMem;
................................................................................
  sqlite3SelectDestInit(&destB, SRT_Coroutine, regAddrB);

  /* Jump past the various subroutines and coroutines to the main
  ** merge loop
  */
  j1 = sqlite3VdbeAddOp0(v, OP_Goto);
  addrSelectA = sqlite3VdbeCurrentAddr(v);


  /* Generate a coroutine to evaluate the SELECT statement to the
  ** left of the compound operator - the "A" select. */

  VdbeNoopComment((v, "Begin coroutine for left SELECT"));
  pPrior->iLimit = regLimitA;
  sqlite3Select(pParse, pPrior, &destA, 0, 0, 0, 0);
  sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofA);
  sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
  VdbeNoopComment((v, "End coroutine for left SELECT"));

................................................................................
  p->iLimit = savedLimit;
  p->iOffset = savedOffset;
  sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofB);
  sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
  VdbeNoopComment((v, "End coroutine for right SELECT"));

  /* Generate a subroutine that outputs the current row of the A
  ** select as the next output row of the compound select and then
  ** advances the A select to its next row
  */
  VdbeNoopComment((v, "Output routine for A"));

  addrOutA = outputSubroutine(pParse, p, &destA, pDest, regOutA, labelEnd);

  
  /* Generate a subroutine that outputs the current row of the B
  ** select as the next output row of the compound select and then
  ** advances the B select to its next row
  */

  VdbeNoopComment((v, "Output routine for B"));

  addrOutB = outputSubroutine(pParse, p, &destB, pDest, regOutB, labelEnd);



  /* Generate a subroutine to run when the results from select A
  ** are exhausted and only data in select B remains.
  */
  VdbeNoopComment((v, "eof-A subroutine"));
  addrEofA = sqlite3VdbeCurrentAddr(v);
  if( op==TK_EXCEPT || op==TK_INTERSECT ){
    sqlite3VdbeAddOp2(v, OP_Goto, 0, labelEnd);
  }else{  
    if( op==TK_ALL ){
      j2 = sqlite3VdbeAddOp2(v, OP_If, regEofB, labelEnd);
      sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
      sqlite3VdbeAddOp2(v, OP_Goto, 0, j2);
    }else{
      assert( op==TK_UNION );
      sqlite3ExprCodeCopy(pParse, destB.iMem, destA.iMem, destB.nMem);
      j2 = sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
      sqlite3VdbeAddOp2(v, OP_If, regEofB, labelEnd);
      sqlite3VdbeAddOp4(v, OP_Compare, destA.iMem, destB.iMem, destB.nMem,
                           (char*)pKeyInfo, p4type);
      p4type = P4_KEYINFO_STATIC;
      sqlite3VdbeAddOp3(v, OP_Jump, j2, j2+4, j2);
      sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
      sqlite3VdbeAddOp2(v, OP_Goto, 0, j2+1);
    }
  }

  /* Generate a subroutine to run when the results from select B
  ** are exhausted and only data in select A remains.
  */
  if( op==TK_INTERSECT ){
    addrEofB = addrEofA;
  }else{  
    VdbeNoopComment((v, "eof-B subroutine"));
    addrEofB = sqlite3VdbeCurrentAddr(v);
    if( op==TK_ALL || op==TK_EXCEPT ){
      j2 = sqlite3VdbeAddOp2(v, OP_If, regEofA, labelEnd);
      sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
      sqlite3VdbeAddOp2(v, OP_Goto, 0, j2);
    }else{
      assert( op==TK_UNION );
      sqlite3VdbeAddOp2(v, OP_If, regEofA, labelEnd);
      sqlite3ExprCodeCopy(pParse, destA.iMem, destB.iMem, destA.nMem);
      j2 = sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
      sqlite3VdbeAddOp2(v, OP_If, regEofA, labelEnd);
      sqlite3VdbeAddOp4(v, OP_Compare, destA.iMem, destB.iMem, destB.nMem,
                           (char*)pKeyInfo, p4type);
      p4type = P4_KEYINFO_STATIC;
      sqlite3VdbeAddOp3(v, OP_Jump, j2, j2+4, j2);
      sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
      sqlite3VdbeAddOp2(v, OP_Goto, 0, j2+1);
    }
  }

  /* Generate code to handle the case of A<B
  */
  VdbeNoopComment((v, "A-lt-B subroutine"));
  addrAltB = sqlite3VdbeCurrentAddr(v);
  if( op==TK_INTERSECT ){
    sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
  }else{
    sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
  }
  sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
  sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);

  /* Generate code to handle the case of A==B
  */
  if( op==TK_ALL ){
    addrAeqB = addrAltB;



  }else{
    VdbeNoopComment((v, "A-eq-B subroutine"));
    addrAeqB = sqlite3VdbeCurrentAddr(v);
    if( op==TK_INTERSECT ){
      sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
      j2 = sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
      sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
      sqlite3VdbeAddOp4(v, OP_Compare, destA.iMem, destB.iMem, destA.nMem,
                           (char*)pKeyInfo, p4type);
      p4type = P4_KEYINFO_STATIC;
      j3 = sqlite3VdbeCurrentAddr(v)+1;
      sqlite3VdbeAddOp3(v, OP_Jump, j3, j2, j3);
      sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
    }else{
      sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
      sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
      sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
    }
  }

  /* Generate code to handle the case of A>B
  */
  VdbeNoopComment((v, "A-gt-B subroutine"));
  addrAgtB = sqlite3VdbeCurrentAddr(v);
  if( op==TK_ALL || op==TK_UNION ){
    sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
  }else{
    sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
  }

  sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);
  sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);

  /* This code runs once to initialize everything.
  */
  sqlite3VdbeJumpHere(v, j1);
  sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofA);
  sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofB);
  sqlite3VdbeAddOp2(v, OP_Integer, addrSelectB, regAddrB);
  sqlite3VdbeAddOp2(v, OP_Gosub, regAddrA, addrSelectA);
  sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
  sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
  sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);

  /* Implement the main merge loop
  */
  sqlite3VdbeResolveLabel(v, labelCmpr);

  sqlite3VdbeAddOp4(v, OP_Compare, destA.iMem, destB.iMem, destA.nMem,
                         (char*)pKeyInfo, p4type);
  p4type = P4_KEYINFO_STATIC;
  sqlite3VdbeAddOp3(v, OP_Jump, addrAltB, addrAeqB, addrAgtB);







  /* Jump to the this point in order to terminate the query.
  */
  sqlite3VdbeResolveLabel(v, labelEnd);

  /* Set the number of output columns
  */
  if( pDest->eDest==SRT_Callback ){
    Select *pFirst = p;
    while( pFirst->pPrior ) pFirst = pFirst->pPrior;
    generateColumnNames(pParse, 0, pFirst->pEList);
  }

  /* Free the KeyInfo if unused.
  */
  if( p4type==P4_KEYINFO_HANDOFF ){
    sqlite3_free(pKeyInfo);
  }

  /*** TBD:  Insert subroutine calls to close cursors on incomplete
  **** subqueries ****/
  return SQLITE_OK;
}

#ifndef SQLITE_OMIT_VIEW

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.436 2008/06/25 00:12:41 drh Exp $
*/
#include "sqliteInt.h"


/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.
................................................................................
  sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nExpr + 2, regRecord);
  sqlite3VdbeAddOp2(v, OP_IdxInsert, pOrderBy->iECursor, regRecord);
  sqlite3ReleaseTempReg(pParse, regRecord);
  sqlite3ReleaseTempRange(pParse, regBase, nExpr+2);
  if( pSelect->iLimit ){
    int addr1, addr2;
    int iLimit;
    if( pSelect->iOffset ){
      iLimit = pSelect->iOffset+1;
    }else{
      iLimit = pSelect->iLimit;
    }
    addr1 = sqlite3VdbeAddOp1(v, OP_IfZero, iLimit);
    sqlite3VdbeAddOp2(v, OP_AddImm, iLimit, -1);
    addr2 = sqlite3VdbeAddOp0(v, OP_Goto);
................................................................................
  */
  if( nColumn>0 ){
    nResultCol = nColumn;
  }else{
    nResultCol = pEList->nExpr;
  }
  if( pDest->iMem==0 ){
    pDest->iMem = pParse->nMem+1;
    pDest->nMem = nResultCol;
    pParse->nMem += nResultCol;
  }else if( pDest->nMem!=nResultCol ){
    /* This happens when two SELECTs of a compound SELECT have differing
    ** numbers of result columns.  The error message will be generated by
    ** a higher-level routine. */
    return;
  }
  regResult = pDest->iMem;
................................................................................
** SELECT statements.
*/
static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
  Vdbe *v = 0;
  int iLimit = 0;
  int iOffset;
  int addr1;
  if( p->iLimit ) return;

  /* 
  ** "LIMIT -1" always shows all rows.  There is some
  ** contraversy about what the correct behavior should be.
  ** The current implementation interprets "LIMIT 0" to mean
  ** no rows.
  */
................................................................................
  if( p->pEList->nExpr!=pPrior->pEList->nExpr ){
    sqlite3ErrorMsg(pParse, "SELECTs to the left and right of %s"
      " do not have the same number of result columns", selectOpName(p->op));
    rc = 1;
    goto multi_select_end;
  }

#if 1
  if( p->pOrderBy ){
    return multiSelectOrderBy(pParse, p, pDest, aff);
  }
#endif

  /* Generate code for the left and right SELECT statements.
  */
................................................................................
  return rc;
}
#endif /* SQLITE_OMIT_COMPOUND_SELECT */

/*
** Code an output subroutine for a coroutine implementation of a
** SELECT statment.
**
** The data to be output is contained in pIn->iMem.  There are
** pIn->nMem columns to be output.  pDest is where the output should
** be sent.
**
** regReturn is the number of the register holding the subroutine
** return address.
**
** If regPrev>0 then it is a the first register in a vector that
** records the previous output.  mem[regPrev] is a flag that is false
** if there has been no previous output.  If regPrev>0 then code is
** generated to suppress duplicates.  pKeyInfo is used for comparing
** keys.
**
** If the LIMIT found in p->iLimit is reached, jump immediately to
** iBreak.
*/
static int generateOutputSubroutine(
  Parse *pParse,          /* Parsing context */
  Select *p,              /* The SELECT statement */
  SelectDest *pIn,        /* Coroutine supplying data */
  SelectDest *pDest,      /* Where to send the data */
  int regReturn,          /* The return address register */
  int regPrev,            /* Previous result register.  No uniqueness if 0 */
  KeyInfo *pKeyInfo,      /* For comparing with previous entry */
  int p4type,             /* The p4 type for pKeyInfo */
  int iBreak              /* Jump here if we hit the LIMIT */
){
  Vdbe *v = pParse->pVdbe;
  int iContinue;
  int addr;
  if( v==0 ) return 0;

  addr = sqlite3VdbeCurrentAddr(v);
  iContinue = sqlite3VdbeMakeLabel(v);

  /* Suppress duplicates for UNION, EXCEPT, and INTERSECT 
  */
  if( regPrev ){
    int j1, j2;
    j1 = sqlite3VdbeAddOp1(v, OP_IfNot, regPrev);
    j2 = sqlite3VdbeAddOp4(v, OP_Compare, pIn->iMem, regPrev+1, pIn->nMem,
                              (char*)pKeyInfo, p4type);
    sqlite3VdbeAddOp3(v, OP_Jump, j2+2, iContinue, j2+2);
    sqlite3VdbeJumpHere(v, j1);
    sqlite3ExprCodeCopy(pParse, pIn->iMem, regPrev+1, pIn->nMem);
    sqlite3VdbeAddOp2(v, OP_Integer, 1, regPrev);
  }

  /* Suppress the the first OFFSET entries if there is an OFFSET clause
  */
  codeOffset(v, p, iContinue);

  switch( pDest->eDest ){
    /* Store the result as data using a unique key.
    */
    case SRT_Table:
    case SRT_EphemTab: {
................................................................................
  /* Jump to the end of the loop if the LIMIT is reached.
  */
  if( p->iLimit ){
    sqlite3VdbeAddOp2(v, OP_AddImm, p->iLimit, -1);
    sqlite3VdbeAddOp2(v, OP_IfZero, p->iLimit, iBreak);
  }

  /* Generate the subroutine return
  */
  sqlite3VdbeResolveLabel(v, iContinue);




  sqlite3VdbeAddOp1(v, OP_Return, regReturn);

  return addr;
}

/*
** Alternative compound select code generator for cases when there
................................................................................
**
** The implementation of the latter five subroutines depend on which 
** <operator> is used:
**
**
**             UNION ALL         UNION            EXCEPT          INTERSECT
**          -------------  -----------------  --------------  -----------------
**   AltB:   outA, nextA      outA, nextA       outA, nextA         nextA
**
**   AeqB:   outA, nextA         nextA             nextA         outA, nextA

**
**   AgtB:   outB, nextB      outB, nextB          nextB            nextB
**
**   EofA:   outB, nextB      outB, nextB          halt             halt

**
**   EofB:   outA, nextA      outA, nextA       outA, nextA         halt
**
** In the AltB, AeqB, and AgtB subroutines, an EOF on A following nextA
** causes an immediate jump to EofA and an EOF on B following nextB causes
** an immediate jump to EofB.  Within EofA and EofB, and EOF on entry or
** following nextX causes a jump to the end of the select processing.
**
** Duplicate removal in the UNION, EXCEPT, and INTERSECT cases is handled
** within the output subroutine.  The regPrev register set holds the previously
** output value.  A comparison is made against this value and the output
** is skipped if the next results would be the same as the previous.
**
** The implementation plan is to implement the two coroutines and seven
** subroutines first, then put the control logic at the bottom.  Like this:
**
**          goto Init
**     coA: coroutine for left query (A)
**     coB: coroutine for right query (B)
................................................................................
*/
static int multiSelectOrderBy(
  Parse *pParse,        /* Parsing context */
  Select *p,            /* The right-most of SELECTs to be coded */
  SelectDest *pDest,    /* What to do with query results */
  char *aff             /* If eDest is SRT_Union, the affinity string */
){
  int i, j;             /* Loop counters */
  Select *pPrior;       /* Another SELECT immediately to our left */
  Vdbe *v;              /* Generate code to this VDBE */
  SelectDest destA;     /* Destination for coroutine A */
  SelectDest destB;     /* Destination for coroutine B */
  int regAddrA;         /* Address register for select-A coroutine */
  int regEofA;          /* Flag to indicate when select-A is complete */
  int regAddrB;         /* Address register for select-B coroutine */
................................................................................
  int addrEofA;         /* Address of the select-A-exhausted subroutine */
  int addrEofB;         /* Address of the select-B-exhausted subroutine */
  int addrAltB;         /* Address of the A<B subroutine */
  int addrAeqB;         /* Address of the A==B subroutine */
  int addrAgtB;         /* Address of the A>B subroutine */
  int regLimitA;        /* Limit register for select-A */
  int regLimitB;        /* Limit register for select-A */
  int regPrev;          /* A range of registers to hold previous output */
  int savedLimit;       /* Saved value of p->iLimit */
  int savedOffset;      /* Saved value of p->iOffset */
  int labelCmpr;        /* Label for the start of the merge algorithm */
  int labelEnd;         /* Label for the end of the overall SELECT stmt */
  int j1;               /* Jump instructions that get retargetted */
  int op;               /* One of TK_ALL, TK_UNION, TK_EXCEPT, TK_INTERSECT */
  KeyInfo *pKeyDup;     /* Comparison information for duplicate removal */
  KeyInfo *pKeyMerge;   /* Comparison information for merging rows */
  sqlite3 *db;          /* Database connection */
  ExprList *pOrderBy;   /* The ORDER BY clause */
  int nOrderBy;         /* Number of terms in the ORDER BY clause */
  int *aPermute;        /* Mapping from ORDER BY terms to result set columns */
  u8 NotUsed;           /* Dummy variables */

  assert( p->pOrderBy!=0 );
  db = pParse->db;
  v = pParse->pVdbe;
  if( v==0 ) return SQLITE_NOMEM;
  labelEnd = sqlite3VdbeMakeLabel(v);
  labelCmpr = sqlite3VdbeMakeLabel(v);




  /* Patch up the ORDER BY clause
  */
  op = p->op;  
  pPrior = p->pPrior;
  assert( pPrior->pOrderBy==0 );
  pOrderBy = p->pOrderBy;
  if( pOrderBy ){
    if( processCompoundOrderBy(pParse, p, 0) ){
      return SQLITE_ERROR;
    }
    nOrderBy = pOrderBy->nExpr;
  }else{
    nOrderBy = 0;
  }
  /* For operators other than UNION ALL we have to make sure that
  ** the ORDER BY clause covers every term of the result set.  Add
  ** terms to the ORDER BY clause as necessary.
  */
  if( op!=TK_ALL ){
    for(i=1; db->mallocFailed==0 && i<=p->pEList->nExpr; i++){
      for(j=0; j<nOrderBy; j++){
        Expr *pTerm = pOrderBy->a[j].pExpr;
        assert( pTerm->op==TK_INTEGER );
        assert( (pTerm->flags & EP_IntValue)!=0 );
        if( pTerm->iTable==i ) break;
      }
      if( j==nOrderBy ){
        Expr *pNew = sqlite3PExpr(pParse, TK_INTEGER, 0, 0, 0);
        if( pNew==0 ) return SQLITE_NOMEM;
        pNew->flags |= EP_IntValue;
        pNew->iTable = i;
        pOrderBy = sqlite3ExprListAppend(pParse, pOrderBy, pNew, 0);
        nOrderBy++;
      }
    }
  }

  /* Compute the comparison permutation and keyinfo that is used with
  ** the permutation in order to comparisons to determine if the next
  ** row of results comes from selectA or selectB.  Also add explicit
  ** collations to the ORDER BY clause terms so that when the subqueries
  ** to the right and the left are evaluated, they use the correct
  ** collation.
  */
  aPermute = sqlite3DbMallocRaw(db, sizeof(int)*nOrderBy);
  if( aPermute ){
    for(i=0; i<nOrderBy; i++){
      Expr *pTerm = pOrderBy->a[i].pExpr;
      assert( pTerm->op==TK_INTEGER );
      assert( (pTerm->flags & EP_IntValue)!=0 );
      aPermute[i] = pTerm->iTable-1;
      assert( aPermute[i]>=0 && aPermute[i]<p->pEList->nExpr );
    }
    pKeyMerge =
      sqlite3DbMallocRaw(db, sizeof(*pKeyMerge)+nOrderBy*(sizeof(CollSeq*)+1));
    if( pKeyMerge ){
      pKeyMerge->aSortOrder = (u8*)&pKeyMerge->aColl[nOrderBy];
      pKeyMerge->nField = nOrderBy;
      pKeyMerge->enc = ENC(db);
      for(i=0; i<nOrderBy; i++){
        CollSeq *pColl;
        Expr *pTerm = pOrderBy->a[i].pExpr;
        if( pTerm->flags & EP_ExpCollate ){
          pColl = pTerm->pColl;
        }else{
          pColl = multiSelectCollSeq(pParse, p, aPermute[i]);
          pTerm->flags |= EP_ExpCollate;
          pTerm->pColl = pColl;
        }
        pKeyMerge->aColl[i] = pColl;
        pKeyMerge->aSortOrder[i] = pOrderBy->a[i].sortOrder;
      }
    }
  }else{
    pKeyMerge = 0;
  }

  /* Reattach the ORDER BY clause to the query.
  */
  p->pOrderBy = pOrderBy;
  pPrior->pOrderBy = sqlite3ExprListDup(pParse->db, pOrderBy);

  /* Allocate a range of temporary registers and the KeyInfo needed
  ** for the logic that removes duplicate result rows when the
  ** operator is UNION, EXCEPT, or INTERSECT (but not UNION ALL).
  */
  if( op==TK_ALL ){
    regPrev = 0;
  }else{
    int nExpr = p->pEList->nExpr;
    assert( nOrderBy>=nExpr );
    regPrev = sqlite3GetTempRange(pParse, nExpr+1);
    sqlite3VdbeAddOp2(v, OP_Integer, 0, regPrev);
    pKeyDup = sqlite3DbMallocZero(db,
                  sizeof(*pKeyDup) + nExpr*(sizeof(CollSeq*)+1) );
    if( pKeyDup ){
      pKeyDup->aSortOrder = (u8*)&pKeyDup->aColl[nExpr];
      pKeyDup->nField = nExpr;
      pKeyDup->enc = ENC(db);
      for(i=0; i<nExpr; i++){
        pKeyDup->aColl[i] = multiSelectCollSeq(pParse, p, i);
        pKeyDup->aSortOrder[i] = 0;
      }
    }
  }
 
  /* Separate the left and the right query from one another
  */
  p->pPrior = 0;
  pPrior->pRightmost = 0;
  processOrderGroupBy(pParse, p, p->pOrderBy, 1, &NotUsed);
  if( pPrior->pPrior==0 ){
    processOrderGroupBy(pParse, pPrior, pPrior->pOrderBy, 1, &NotUsed);
  }

  /* Compute the limit registers */
  computeLimitRegisters(pParse, p, labelEnd);
  if( p->iLimit && op==TK_ALL ){
    regLimitA = ++pParse->nMem;
    regLimitB = ++pParse->nMem;
    sqlite3VdbeAddOp2(v, OP_Copy, p->iOffset ? p->iOffset+1 : p->iLimit,
                                  regLimitA);
    sqlite3VdbeAddOp2(v, OP_Copy, regLimitA, regLimitB);
  }else{
    regLimitA = regLimitB = 0;
  }
  sqlite3ExprDelete(p->pLimit);
  p->pLimit = 0;
  sqlite3ExprDelete(p->pOffset);
  p->pOffset = 0;

  regAddrA = ++pParse->nMem;
  regEofA = ++pParse->nMem;
  regAddrB = ++pParse->nMem;
  regEofB = ++pParse->nMem;
  regOutA = ++pParse->nMem;
  regOutB = ++pParse->nMem;
................................................................................
  sqlite3SelectDestInit(&destB, SRT_Coroutine, regAddrB);

  /* Jump past the various subroutines and coroutines to the main
  ** merge loop
  */
  j1 = sqlite3VdbeAddOp0(v, OP_Goto);
  addrSelectA = sqlite3VdbeCurrentAddr(v);


  /* Generate a coroutine to evaluate the SELECT statement to the
  ** left of the compound operator - the "A" select.
  */
  VdbeNoopComment((v, "Begin coroutine for left SELECT"));
  pPrior->iLimit = regLimitA;
  sqlite3Select(pParse, pPrior, &destA, 0, 0, 0, 0);
  sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofA);
  sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
  VdbeNoopComment((v, "End coroutine for left SELECT"));

................................................................................
  p->iLimit = savedLimit;
  p->iOffset = savedOffset;
  sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofB);
  sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
  VdbeNoopComment((v, "End coroutine for right SELECT"));

  /* Generate a subroutine that outputs the current row of the A
  ** select as the next output row of the compound select.

  */
  VdbeNoopComment((v, "Output routine for A"));
  addrOutA = generateOutputSubroutine(pParse,
                 p, &destA, pDest, regOutA,
                 regPrev, pKeyDup, P4_KEYINFO_HANDOFF, labelEnd);
  
  /* Generate a subroutine that outputs the current row of the B
  ** select as the next output row of the compound select.

  */
  if( op==TK_ALL || op==TK_UNION ){
    VdbeNoopComment((v, "Output routine for B"));
    addrOutB = generateOutputSubroutine(pParse,
                 p, &destB, pDest, regOutB,
                 regPrev, pKeyDup, P4_KEYINFO_STATIC, labelEnd);
  }

  /* Generate a subroutine to run when the results from select A
  ** are exhausted and only data in select B remains.
  */
  VdbeNoopComment((v, "eof-A subroutine"));

  if( op==TK_EXCEPT || op==TK_INTERSECT ){
    addrEofA = sqlite3VdbeAddOp2(v, OP_Goto, 0, labelEnd);
  }else{  

    addrEofA = sqlite3VdbeAddOp2(v, OP_If, regEofB, labelEnd);
    sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);










    sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEofA);

  }

  /* Generate a subroutine to run when the results from select B
  ** are exhausted and only data in select A remains.
  */
  if( op==TK_INTERSECT ){
    addrEofB = addrEofA;
  }else{  
    VdbeNoopComment((v, "eof-B subroutine"));


    addrEofB = sqlite3VdbeAddOp2(v, OP_If, regEofA, labelEnd);
    sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);











    sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
    sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEofB);

  }

  /* Generate code to handle the case of A<B
  */
  VdbeNoopComment((v, "A-lt-B subroutine"));
  addrAltB = sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);

  sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);



  sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
  sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);

  /* Generate code to handle the case of A==B
  */
  if( op==TK_ALL ){
    addrAeqB = addrAltB;
  }else if( op==TK_INTERSECT ){
    addrAeqB = addrAltB;
    addrAltB++;
  }else{
    VdbeNoopComment((v, "A-eq-B subroutine"));
    addrAeqB =











    sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
    sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
    sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);

  }

  /* Generate code to handle the case of A>B
  */
  VdbeNoopComment((v, "A-gt-B subroutine"));
  addrAgtB = sqlite3VdbeCurrentAddr(v);
  if( op==TK_ALL || op==TK_UNION ){
    sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);


  }
  sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
  sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);
  sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);

  /* This code runs once to initialize everything.
  */
  sqlite3VdbeJumpHere(v, j1);
  sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofA);
  sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofB);
  sqlite3VdbeAddOp2(v, OP_Gosub, regAddrA, addrSelectA);
  sqlite3VdbeAddOp2(v, OP_Gosub, regAddrB, addrSelectB);
  sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);

  sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);

  /* Implement the main merge loop
  */
  sqlite3VdbeResolveLabel(v, labelCmpr);
  sqlite3VdbeAddOp4(v, OP_Permutation, 0, 0, 0, (char*)aPermute, P4_INTARRAY);
  sqlite3VdbeAddOp4(v, OP_Compare, destA.iMem, destB.iMem, nOrderBy,

                         (char*)pKeyMerge, P4_KEYINFO_HANDOFF);
  sqlite3VdbeAddOp3(v, OP_Jump, addrAltB, addrAeqB, addrAgtB);

  /* Release temporary registers
  */
  if( regPrev ){
    sqlite3ReleaseTempRange(pParse, regPrev, nOrderBy+1);
  }

  /* Jump to the this point in order to terminate the query.
  */
  sqlite3VdbeResolveLabel(v, labelEnd);

  /* Set the number of output columns
  */
  if( pDest->eDest==SRT_Callback ){
    Select *pFirst = pPrior;
    while( pFirst->pPrior ) pFirst = pFirst->pPrior;
    generateColumnNames(pParse, 0, pFirst->pEList);
  }

  /* Reassembly the compound query so that it will be freed correctly
  ** by the calling function */
  p->pPrior = pPrior;



  /*** TBD:  Insert subroutine calls to close cursors on incomplete
  **** subqueries ****/
  return SQLITE_OK;
}

#ifndef SQLITE_OMIT_VIEW

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.754 2008/06/23 18:49:44 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor
................................................................................
  Op *pOp;                   /* Current operation */
  int rc = SQLITE_OK;        /* Value to return */
  sqlite3 *db = p->db;       /* The database */
  u8 encoding = ENC(db);     /* The database encoding */
  Mem *pIn1, *pIn2, *pIn3;   /* Input operands */
  Mem *pOut;                 /* Output operand */
  u8 opProperty;


#ifdef VDBE_PROFILE
  u64 start;                 /* CPU clock count at start of opcode */
  int origPc;                /* Program counter at start of opcode */
#endif
#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
  int nProgressOps = 0;      /* Opcodes executed since progress callback. */
#endif
................................................................................
  assert( p1+n<p->nMem );
  pIn1 = &p->aMem[p1];
  assert( p2>0 );
  assert( p2+n<p->nMem );
  pOut = &p->aMem[p2];
  assert( p1+n<=p2 || p2+n<=p1 );
  while( n-- ){
    REGISTER_TRACE(p1++, pIn1);
    zMalloc = pOut->zMalloc;
    pOut->zMalloc = 0;
    sqlite3VdbeMemMove(pOut, pIn1);
    pIn1->zMalloc = zMalloc;
    REGISTER_TRACE(p2++, pOut);
    pIn1++;
    pOut++;
................................................................................
** This instruction makes a deep copy of the value.  A duplicate
** is made of any string or blob constant.  See also OP_SCopy.
*/
case OP_Copy: {
  assert( pOp->p1>0 );
  assert( pOp->p1<=p->nMem );
  pIn1 = &p->aMem[pOp->p1];
  REGISTER_TRACE(pOp->p1, pIn1);
  assert( pOp->p2>0 );
  assert( pOp->p2<=p->nMem );
  pOut = &p->aMem[pOp->p2];
  assert( pOut!=pIn1 );
  sqlite3VdbeMemShallowCopy(pOut, pIn1, MEM_Ephem);
  Deephemeralize(pOut);
  REGISTER_TRACE(pOp->p2, pOut);
................................................................................
  ** and have an assigned type.  The results are de-ephemeralized as
  ** as side effect.
  */
  pMem = p->pResultSet = &p->aMem[pOp->p1];
  for(i=0; i<pOp->p2; i++){
    sqlite3VdbeMemNulTerminate(&pMem[i]);
    storeTypeInfo(&pMem[i], encoding);

  }
  if( db->mallocFailed ) goto no_mem;

  /* Return SQLITE_ROW
  */
  p->nCallback++;
  p->pc = pc + 1;
................................................................................
    pOut->u.i = res;
    REGISTER_TRACE(pOp->p2, pOut);
  }else if( res ){
    pc = pOp->p2-1;
  }
  break;
}

















/* Opcode: Compare P1 P2 P3 P4 *
**
** Compare to vectors of registers in reg(P1)..reg(P1+P3-1) (all this
** one "A") and in reg(P2)..reg(P2+P3-1) ("B").  Save the result of
** the comparison for use by the next OP_Jump instruct.
**
** P4 is a KeyInfo structure that defines collating sequences usedused for affinity purposes.  The
** comparison is done for sorting purposes, so NULLs compare



** equal, NULLs are less than numbers, numbers are less than strings,
** and strings are less than blobs.
*/
case OP_Compare: {
  int n = pOp->p3;
  int i, p1, p2;
  const KeyInfo *pKeyInfo = pOp->p4.pKeyInfo;
  assert( n>0 );
  p1 = pOp->p1;
  assert( p1>0 && p1+n-1<p->nMem );
  p2 = pOp->p2;
  assert( p2>0 && p2+n-1<p->nMem );
  for(i=0; i<n; i++, p1++, p2++){




    REGISTER_TRACE(p1, &p->aMem[p1]);
    REGISTER_TRACE(p2, &p->aMem[p2]);








    p->iCompare = sqlite3MemCompare(&p->aMem[p1], &p->aMem[p2],
                   pKeyInfo && i<pKeyInfo->nField ? pKeyInfo->aColl[i] : 0);
    if( p->iCompare ) break;


  }


  break;
}

/* Opcode: Jump P1 P2 P3 * *
**
** Jump to the instruction at address P1, P2, or P3 depending on whether
** in the most recent OP_Compare instruction the P1 vector was less than
** equal to, or greater than the P2 vector, respectively.
*/
case OP_Jump: {
  if( p->iCompare<0 ){
    pc = pOp->p1 - 1;
  }else if( p->iCompare==0 ){
    pc = pOp->p2 - 1;
  }else{
    pc = pOp->p3 - 1;
  }
  break;
}

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.755 2008/06/25 00:12:41 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor
................................................................................
  Op *pOp;                   /* Current operation */
  int rc = SQLITE_OK;        /* Value to return */
  sqlite3 *db = p->db;       /* The database */
  u8 encoding = ENC(db);     /* The database encoding */
  Mem *pIn1, *pIn2, *pIn3;   /* Input operands */
  Mem *pOut;                 /* Output operand */
  u8 opProperty;
  int iCompare = 0;          /* Result of last OP_Compare operation */
  int *aPermute = 0;         /* Permuation of columns for OP_Compare */
#ifdef VDBE_PROFILE
  u64 start;                 /* CPU clock count at start of opcode */
  int origPc;                /* Program counter at start of opcode */
#endif
#ifndef SQLITE_OMIT_PROGRESS_CALLBACK
  int nProgressOps = 0;      /* Opcodes executed since progress callback. */
#endif
................................................................................
  assert( p1+n<p->nMem );
  pIn1 = &p->aMem[p1];
  assert( p2>0 );
  assert( p2+n<p->nMem );
  pOut = &p->aMem[p2];
  assert( p1+n<=p2 || p2+n<=p1 );
  while( n-- ){

    zMalloc = pOut->zMalloc;
    pOut->zMalloc = 0;
    sqlite3VdbeMemMove(pOut, pIn1);
    pIn1->zMalloc = zMalloc;
    REGISTER_TRACE(p2++, pOut);
    pIn1++;
    pOut++;
................................................................................
** This instruction makes a deep copy of the value.  A duplicate
** is made of any string or blob constant.  See also OP_SCopy.
*/
case OP_Copy: {
  assert( pOp->p1>0 );
  assert( pOp->p1<=p->nMem );
  pIn1 = &p->aMem[pOp->p1];

  assert( pOp->p2>0 );
  assert( pOp->p2<=p->nMem );
  pOut = &p->aMem[pOp->p2];
  assert( pOut!=pIn1 );
  sqlite3VdbeMemShallowCopy(pOut, pIn1, MEM_Ephem);
  Deephemeralize(pOut);
  REGISTER_TRACE(pOp->p2, pOut);
................................................................................
  ** and have an assigned type.  The results are de-ephemeralized as
  ** as side effect.
  */
  pMem = p->pResultSet = &p->aMem[pOp->p1];
  for(i=0; i<pOp->p2; i++){
    sqlite3VdbeMemNulTerminate(&pMem[i]);
    storeTypeInfo(&pMem[i], encoding);
    REGISTER_TRACE(pOp->p1+i, &pMem[i]);
  }
  if( db->mallocFailed ) goto no_mem;

  /* Return SQLITE_ROW
  */
  p->nCallback++;
  p->pc = pc + 1;
................................................................................
    pOut->u.i = res;
    REGISTER_TRACE(pOp->p2, pOut);
  }else if( res ){
    pc = pOp->p2-1;
  }
  break;
}

/* Opcode: Permutation * * * P4 *
**
** Set the permuation used by the OP_Compare operator to be the array
** of integers in P4.
**
** The permutation is only valid until the next OP_Permutation, OP_Compare,
** OP_Halt, or OP_ResultRow.  Typically the OP_Permutation should occur
** immediately prior to the OP_Compare.
*/
case OP_Permutation: {
  assert( pOp->p4type==P4_INTARRAY );
  assert( pOp->p4.ai );
  aPermute = pOp->p4.ai;
  break;
}

/* Opcode: Compare P1 P2 P3 P4 *
**
** Compare to vectors of registers in reg(P1)..reg(P1+P3-1) (all this
** one "A") and in reg(P2)..reg(P2+P3-1) ("B").  Save the result of
** the comparison for use by the next OP_Jump instruct.
**
** P4 is a KeyInfo structure that defines collating sequences and sort
** orders for the comparison.  The permutation applies to registers
** only.  The KeyInfo elements are used sequentially.
**
** The comparison is a sort comparison, so NULLs compare equal,
** NULLs are less than numbers, numbers are less than strings,
** and strings are less than blobs.
*/
case OP_Compare: {
  int n = pOp->p3;
  int i, p1, p2;
  const KeyInfo *pKeyInfo = pOp->p4.pKeyInfo;
  assert( n>0 );
  p1 = pOp->p1;
  assert( p1>0 && p1+n-1<p->nMem );
  p2 = pOp->p2;
  assert( p2>0 && p2+n-1<p->nMem );
  for(i=0; i<n; i++){
    int idx = aPermute ? aPermute[i] : i;
    CollSeq *pColl;    /* Collating sequence to use on this term */
    int bRev;          /* True for DESCENDING sort order */
    assert( pKeyInfo==0 || i<pKeyInfo->nField );
    REGISTER_TRACE(p1+idx, &p->aMem[p1+idx]);
    REGISTER_TRACE(p2+idx, &p->aMem[p2+idx]);
    if( pKeyInfo ){
      assert( i<pKeyInfo->nField );
      pColl = pKeyInfo->aColl[i];
      bRev = pKeyInfo->aSortOrder[i];
    }else{
      pColl = 0;
      bRev = 0;
    }
    iCompare = sqlite3MemCompare(&p->aMem[p1+idx], &p->aMem[p2+idx], pColl);

    if( iCompare ){
      if( bRev ) iCompare = -iCompare;
      break;
    }
  }
  aPermute = 0;
  break;
}

/* Opcode: Jump P1 P2 P3 * *
**
** Jump to the instruction at address P1, P2, or P3 depending on whether
** in the most recent OP_Compare instruction the P1 vector was less than
** equal to, or greater than the P2 vector, respectively.
*/
case OP_Jump: {             /* jump */
  if( iCompare<0 ){
    pc = pOp->p1 - 1;
  }else if( iCompare==0 ){
    pc = pOp->p2 - 1;
  }else{
    pc = pOp->p3 - 1;
  }
  break;
}

*************************************************************************
** Header file for the Virtual DataBase Engine (VDBE)
**
** This header defines the interface to the virtual database engine
** or VDBE.  The VDBE implements an abstract machine that runs a
** simple program to access and modify the underlying database.
**
** $Id: vdbe.h,v 1.133 2008/06/20 18:13:25 drh Exp $
*/
#ifndef _SQLITE_VDBE_H_
#define _SQLITE_VDBE_H_
#include <stdio.h>

/*
** A single VDBE is an opaque structure named "Vdbe".  Only routines
................................................................................
    double *pReal;         /* Used when p4type is P4_REAL */
    FuncDef *pFunc;        /* Used when p4type is P4_FUNCDEF */
    VdbeFunc *pVdbeFunc;   /* Used when p4type is P4_VDBEFUNC */
    CollSeq *pColl;        /* Used when p4type is P4_COLLSEQ */
    Mem *pMem;             /* Used when p4type is P4_MEM */
    sqlite3_vtab *pVtab;   /* Used when p4type is P4_VTAB */
    KeyInfo *pKeyInfo;     /* Used when p4type is P4_KEYINFO */

  } p4;
#ifdef SQLITE_DEBUG
  char *zComment;          /* Comment to improve readability */
#endif
#ifdef VDBE_PROFILE
  int cnt;                 /* Number of times this instruction was executed */
  u64 cycles;              /* Total time spent executing this instruction */
................................................................................
#define P4_MEM      (-8)  /* P4 is a pointer to a Mem*    structure */
#define P4_TRANSIENT (-9) /* P4 is a pointer to a transient string */
#define P4_VTAB     (-10) /* P4 is a pointer to an sqlite3_vtab structure */
#define P4_MPRINTF  (-11) /* P4 is a string obtained from sqlite3_mprintf() */
#define P4_REAL     (-12) /* P4 is a 64-bit floating point value */
#define P4_INT64    (-13) /* P4 is a 64-bit signed integer */
#define P4_INT32    (-14) /* P4 is a 32-bit signed integer */


/* When adding a P4 argument using P4_KEYINFO, a copy of the KeyInfo structure
** is made.  That copy is freed when the Vdbe is finalized.  But if the
** argument is P4_KEYINFO_HANDOFF, the passed in pointer is used.  It still
** gets freed when the Vdbe is finalized so it still should be obtained
** from a single sqliteMalloc().  But no copy is made and the calling
** function should *not* try to free the KeyInfo.
*/
#define P4_KEYINFO_HANDOFF (-15)
#define P4_KEYINFO_STATIC  (-16)

/*
** The Vdbe.aColName array contains 5n Mem structures, where n is the 
** number of columns of data returned by the statement.
*/
#define COLNAME_NAME     0
#define COLNAME_DECLTYPE 1

*************************************************************************
** Header file for the Virtual DataBase Engine (VDBE)
**
** This header defines the interface to the virtual database engine
** or VDBE.  The VDBE implements an abstract machine that runs a
** simple program to access and modify the underlying database.
**
** $Id: vdbe.h,v 1.134 2008/06/25 00:12:41 drh Exp $
*/
#ifndef _SQLITE_VDBE_H_
#define _SQLITE_VDBE_H_
#include <stdio.h>

/*
** A single VDBE is an opaque structure named "Vdbe".  Only routines
................................................................................
    double *pReal;         /* Used when p4type is P4_REAL */
    FuncDef *pFunc;        /* Used when p4type is P4_FUNCDEF */
    VdbeFunc *pVdbeFunc;   /* Used when p4type is P4_VDBEFUNC */
    CollSeq *pColl;        /* Used when p4type is P4_COLLSEQ */
    Mem *pMem;             /* Used when p4type is P4_MEM */
    sqlite3_vtab *pVtab;   /* Used when p4type is P4_VTAB */
    KeyInfo *pKeyInfo;     /* Used when p4type is P4_KEYINFO */
    int *ai;               /* Used when p4type is P4_INTARRAY */
  } p4;
#ifdef SQLITE_DEBUG
  char *zComment;          /* Comment to improve readability */
#endif
#ifdef VDBE_PROFILE
  int cnt;                 /* Number of times this instruction was executed */
  u64 cycles;              /* Total time spent executing this instruction */
................................................................................
#define P4_MEM      (-8)  /* P4 is a pointer to a Mem*    structure */
#define P4_TRANSIENT (-9) /* P4 is a pointer to a transient string */
#define P4_VTAB     (-10) /* P4 is a pointer to an sqlite3_vtab structure */
#define P4_MPRINTF  (-11) /* P4 is a string obtained from sqlite3_mprintf() */
#define P4_REAL     (-12) /* P4 is a 64-bit floating point value */
#define P4_INT64    (-13) /* P4 is a 64-bit signed integer */
#define P4_INT32    (-14) /* P4 is a 32-bit signed integer */
#define P4_INTARRAY (-15) /* P4 is a vector of 32-bit integers */

/* When adding a P4 argument using P4_KEYINFO, a copy of the KeyInfo structure
** is made.  That copy is freed when the Vdbe is finalized.  But if the
** argument is P4_KEYINFO_HANDOFF, the passed in pointer is used.  It still
** gets freed when the Vdbe is finalized so it still should be obtained
** from a single sqliteMalloc().  But no copy is made and the calling
** function should *not* try to free the KeyInfo.
*/
#define P4_KEYINFO_HANDOFF (-16)
#define P4_KEYINFO_STATIC  (-17)

/*
** The Vdbe.aColName array contains 5n Mem structures, where n is the 
** number of columns of data returned by the statement.
*/
#define COLNAME_NAME     0
#define COLNAME_DECLTYPE 1

*************************************************************************
** This is the header file for information that is private to the
** VDBE.  This information used to all be at the top of the single
** source code file "vdbe.c".  When that file became too big (over
** 6000 lines long) it was split up into several smaller files and
** this header information was factored out.
**
** $Id: vdbeInt.h,v 1.148 2008/06/20 18:13:25 drh Exp $
*/
#ifndef _VDBEINT_H_
#define _VDBEINT_H_

/*
** intToKey() and keyToInt() used to transform the rowid.  But with
** the latest versions of the design they are no-ops.
................................................................................
  Mem *pResultSet;        /* Pointer to an array of results */
  u8 explain;             /* True if EXPLAIN present on SQL command */
  u8 changeCntOn;         /* True to update the change-counter */
  u8 aborted;             /* True if ROLLBACK in another VM causes an abort */
  u8 expired;             /* True if the VM needs to be recompiled */
  u8 minWriteFileFormat;  /* Minimum file format for writable database files */
  u8 inVtabMethod;        /* See comments above */
  int iCompare;           /* Result of most recent OP_Compare comparison */
  int nChange;            /* Number of db changes made since last reset */
  i64 startTime;          /* Time when query started - used for profiling */
  int btreeMask;          /* Bitmask of db->aDb[] entries referenced */
  BtreeMutexArray aMutex; /* An array of Btree used here and needing locks */
  int nSql;             /* Number of bytes in zSql */
  char *zSql;           /* Text of the SQL statement that generated this */
#ifdef SQLITE_DEBUG

*************************************************************************
** This is the header file for information that is private to the
** VDBE.  This information used to all be at the top of the single
** source code file "vdbe.c".  When that file became too big (over
** 6000 lines long) it was split up into several smaller files and
** this header information was factored out.
**
** $Id: vdbeInt.h,v 1.149 2008/06/25 00:12:41 drh Exp $
*/
#ifndef _VDBEINT_H_
#define _VDBEINT_H_

/*
** intToKey() and keyToInt() used to transform the rowid.  But with
** the latest versions of the design they are no-ops.
................................................................................
  Mem *pResultSet;        /* Pointer to an array of results */
  u8 explain;             /* True if EXPLAIN present on SQL command */
  u8 changeCntOn;         /* True to update the change-counter */
  u8 aborted;             /* True if ROLLBACK in another VM causes an abort */
  u8 expired;             /* True if the VM needs to be recompiled */
  u8 minWriteFileFormat;  /* Minimum file format for writable database files */
  u8 inVtabMethod;        /* See comments above */

  int nChange;            /* Number of db changes made since last reset */
  i64 startTime;          /* Time when query started - used for profiling */
  int btreeMask;          /* Bitmask of db->aDb[] entries referenced */
  BtreeMutexArray aMutex; /* An array of Btree used here and needing locks */
  int nSql;             /* Number of bytes in zSql */
  char *zSql;           /* Text of the SQL statement that generated this */
#ifdef SQLITE_DEBUG

**
*************************************************************************
** This file contains code used for creating, destroying, and populating
** a VDBE (or an "sqlite3_stmt" as it is known to the outside world.)  Prior
** to version 2.8.7, all this code was combined into the vdbe.c source file.
** But that file was getting too big so this subroutines were split out.
**
** $Id: vdbeaux.c,v 1.392 2008/06/23 13:57:22 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
#include "vdbeInt.h"



................................................................................
    sqlite3_free(pDef);
  }
}

/*
** Delete a P4 value if necessary.
*/
static void freeP4(int p4type, void *p3){
  if( p3 ){
    switch( p4type ){
      case P4_REAL:
      case P4_INT64:
      case P4_MPRINTF:
      case P4_DYNAMIC:
      case P4_KEYINFO:

      case P4_KEYINFO_HANDOFF: {
        sqlite3_free(p3);
        break;
      }
      case P4_VDBEFUNC: {
        VdbeFunc *pVdbeFunc = (VdbeFunc *)p3;
        freeEphemeralFunction(pVdbeFunc->pFunc);
        sqlite3VdbeDeleteAuxData(pVdbeFunc, 0);
        sqlite3_free(pVdbeFunc);
        break;
      }
      case P4_FUNCDEF: {
        freeEphemeralFunction((FuncDef*)p3);
        break;
      }
      case P4_MEM: {
        sqlite3ValueFree((sqlite3_value*)p3);
        break;
      }
    }
  }
}


................................................................................
#ifndef SQLITE_OMIT_VIRTUALTABLE
    case P4_VTAB: {
      sqlite3_vtab *pVtab = pOp->p4.pVtab;
      sqlite3_snprintf(nTemp, zTemp, "vtab:%p:%p", pVtab, pVtab->pModule);
      break;
    }
#endif




    default: {
      zP4 = pOp->p4.z;
      if( zP4==0 ){
        zP4 = zTemp;
        zTemp[0] = 0;
      }
    }

**
*************************************************************************
** This file contains code used for creating, destroying, and populating
** a VDBE (or an "sqlite3_stmt" as it is known to the outside world.)  Prior
** to version 2.8.7, all this code was combined into the vdbe.c source file.
** But that file was getting too big so this subroutines were split out.
**
** $Id: vdbeaux.c,v 1.393 2008/06/25 00:12:42 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>
#include "vdbeInt.h"



................................................................................
    sqlite3_free(pDef);
  }
}

/*
** Delete a P4 value if necessary.
*/
static void freeP4(int p4type, void *p4){
  if( p4 ){
    switch( p4type ){
      case P4_REAL:
      case P4_INT64:
      case P4_MPRINTF:
      case P4_DYNAMIC:
      case P4_KEYINFO:
      case P4_INTARRAY:
      case P4_KEYINFO_HANDOFF: {
        sqlite3_free(p4);
        break;
      }
      case P4_VDBEFUNC: {
        VdbeFunc *pVdbeFunc = (VdbeFunc *)p4;
        freeEphemeralFunction(pVdbeFunc->pFunc);
        sqlite3VdbeDeleteAuxData(pVdbeFunc, 0);
        sqlite3_free(pVdbeFunc);
        break;
      }
      case P4_FUNCDEF: {
        freeEphemeralFunction((FuncDef*)p4);
        break;
      }
      case P4_MEM: {
        sqlite3ValueFree((sqlite3_value*)p4);
        break;
      }
    }
  }
}


................................................................................
#ifndef SQLITE_OMIT_VIRTUALTABLE
    case P4_VTAB: {
      sqlite3_vtab *pVtab = pOp->p4.pVtab;
      sqlite3_snprintf(nTemp, zTemp, "vtab:%p:%p", pVtab, pVtab->pModule);
      break;
    }
#endif
    case P4_INTARRAY: {
      sqlite3_snprintf(nTemp, zTemp, "intarray");
      break;
    }
    default: {
      zP4 = pOp->p4.z;
      if( zP4==0 ){
        zP4 = zTemp;
        zTemp[0] = 0;
      }
    }