SQLite

**
** 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 1.578 2006/10/27 14:06:58 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

  pTos--;
  if( c ) pc = pOp->p2-1;
  break;
}

/* Opcode: IsNull P1 P2 *
**
** Check the top of the stack and jump to P2 if the top of the stack
** is NULL.  If P1 is positive, then pop P1 elements from the stack
** regardless of whether or not the jump is taken.  If P1 is negative,
** pop -P1 elements from the stack only if the jump is taken and leave
** the stack unchanged if the jump is not taken.
*/
case OP_IsNull: {            /* same as TK_ISNULL, no-push */







  if( pTos->flags & MEM_Null ){
    pc = pOp->p2-1;

    if( pOp->p1<0 ){
      popStack(&pTos, -pOp->p1);
    }
  }
  if( pOp->p1>0 ){
    popStack(&pTos, pOp->p1);
  }
  break;
}

/* Opcode: NotNull P1 P2 *
**
** Jump to P2 if the top abs(P1) values on the stack are all not NULL.  
** Regardless of whether or not the jump is taken, pop the stack
** P1 times if P1 is greater than zero.  But if P1 is negative,
** leave the stack unchanged.
*/
case OP_NotNull: {            /* same as TK_NOTNULL, no-push */
  int i, cnt;
  cnt = pOp->p1;
  if( cnt<0 ) cnt = -cnt;
  assert( &pTos[1-cnt] >= p->aStack );
  for(i=0; i<cnt && (pTos[1+i-cnt].flags & MEM_Null)==0; i++){}

    /* Read the serial types for the next element in each key. */
    idx1 += GetVarint( aKey1+idx1, serial_type1 );
    if( d1>=nKey1 && sqlite3VdbeSerialTypeLen(serial_type1)>0 ) break;
    idx2 += GetVarint( aKey2+idx2, serial_type2 );
    if( d2>=nKey2 && sqlite3VdbeSerialTypeLen(serial_type2)>0 ) break;



    /* Extract the values to be compared.

    */
    d1 += sqlite3VdbeSerialGet(&aKey1[d1], serial_type1, &mem1);
    d2 += sqlite3VdbeSerialGet(&aKey2[d2], serial_type2, &mem2);

    /* Do the comparison
    */
    rc = sqlite3MemCompare(&mem1, &mem2, i<nField ? pKeyInfo->aColl[i] : 0);
    if( mem1.flags & MEM_Dyn ) sqlite3VdbeMemRelease(&mem1);
    if( mem2.flags & MEM_Dyn ) sqlite3VdbeMemRelease(&mem2);
    if( rc!=0 ){
      break;
    }
    i++;

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is reponsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.230 2006/10/27 14:06:59 drh Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8)

**    *  Construct a probe entry from the top nColumn entries in
**       the stack with affinities appropriate for index pIdx. 
**       Only nColumn elements are popped from the stack in this case
**       (by OP_MakeRecord).
**
*/
static void buildIndexProbe(
  Vdbe *v,        /* Generate code into this VM */
  int nColumn,    /* The number of columns to check for NULL */
  int nExtra,     /* Number of extra values beyond nColumn */
  int brk,        /* Jump to here if no match is possible */
  Index *pIdx     /* Index that we will be searching */
){
  sqlite3VdbeAddOp(v, OP_NotNull, -nColumn, sqlite3VdbeCurrentAddr(v)+3);
  sqlite3VdbeAddOp(v, OP_Pop, nColumn+nExtra, 0);
  sqlite3VdbeAddOp(v, OP_Goto, 0, brk);
  sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
  sqlite3IndexAffinityStr(v, pIdx);
}

  */
  for(j=0; j<pIdx->nColumn; j++){
    int k = pIdx->aiColumn[j];
    pTerm = findTerm(pWC, iCur, k, notReady, WO_EQ|WO_IN, pIdx);
    if( pTerm==0 ) break;
    assert( (pTerm->flags & TERM_CODED)==0 );
    codeEqualityTerm(pParse, pTerm, brk, pLevel);
#if 0  /* WORK IN PROGRESS */
    sqlite3VdbeAddOp(v, OP_IsNull, termsInMem ? -1 : -(j+1), brk);
#endif
    if( termsInMem ){
      sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem+j+1, 1);
    }
  }
  assert( j==nEq );

  /* Make sure all the constraint values are on the top of the stack