SQLite

**
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** 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 1.597 2007/03/30 11:23:45 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*

    sqlite3VdbeMemNulTerminate(pRec);
    if( (pRec->flags&MEM_Str)
         && sqlite3IsNumber(pRec->z, &realnum, pRec->enc) ){
      i64 value;
      sqlite3VdbeChangeEncoding(pRec, SQLITE_UTF8);
      if( !realnum && sqlite3atoi64(pRec->z, &value) ){
        sqlite3VdbeMemRelease(pRec);
        pRec->u.i = value;
        pRec->flags = MEM_Int;
      }else{
        sqlite3VdbeMemRealify(pRec);
      }
    }
  }
}

/* Opcode: Integer P1 * *
**
** The 32-bit integer value P1 is pushed onto the stack.
*/
case OP_Integer: {
  pTos++;
  pTos->flags = MEM_Int;
  pTos->u.i = pOp->p1;
  break;
}

/* Opcode: Int64 * * P3
**
** P3 is a string representation of an integer.  Convert that integer
** to a 64-bit value and push it onto the stack.
*/
case OP_Int64: {
  pTos++;
  assert( pOp->p3!=0 );
  pTos->flags = MEM_Str|MEM_Static|MEM_Term;
  pTos->z = pOp->p3;
  pTos->n = strlen(pTos->z);
  pTos->enc = SQLITE_UTF8;
  pTos->u.i = sqlite3VdbeIntValue(pTos);
  pTos->flags |= MEM_Int;
  break;
}

/* Opcode: Real * * P3
**
** The string value P3 is converted to a real and pushed on to the stack.

  if( (flags & MEM_Null)!=0 ){
    Release(pTos);
    pTos--;
    Release(pTos);
    pTos->flags = MEM_Null;
  }else if( (pTos->flags & pNos->flags & MEM_Int)==MEM_Int ){
    i64 a, b;
    a = pTos->u.i;
    b = pNos->u.i;
    switch( pOp->opcode ){
      case OP_Add:         b += a;       break;
      case OP_Subtract:    b -= a;       break;
      case OP_Multiply:    b *= a;       break;
      case OP_Divide: {
        if( a==0 ) goto divide_by_zero;
        b /= a;
        break;
      }
      default: {
        if( a==0 ) goto divide_by_zero;
        b %= a;
        break;
      }
    }
    Release(pTos);
    pTos--;
    Release(pTos);
    pTos->u.i = b;
    pTos->flags = MEM_Int;
  }else{
    double a, b;
    a = sqlite3VdbeRealValue(pTos);
    b = sqlite3VdbeRealValue(pNos);
    switch( pOp->opcode ){
      case OP_Add:         b += a;       break;

    case OP_ShiftLeft:   a <<= b;    break;
    case OP_ShiftRight:  a >>= b;    break;
    default:   /* CANT HAPPEN */     break;
  }
  Release(pTos);
  pTos--;
  Release(pTos);
  pTos->u.i = a;
  pTos->flags = MEM_Int;
  break;
}

/* Opcode: AddImm  P1 * *
** 
** Add the value P1 to whatever is on top of the stack.  The result
** is always an integer.
**
** To force the top of the stack to be an integer, just add 0.
*/
case OP_AddImm: {            /* no-push */
  assert( pTos>=p->aStack );
  sqlite3VdbeMemIntegerify(pTos);
  pTos->u.i += pOp->p1;
  break;
}

/* Opcode: ForceInt P1 P2 *
**
** Convert the top of the stack into an integer.  If the current top of
** the stack is not numeric (meaning that is is a NULL or a string that

  if( (pTos->flags & (MEM_Int|MEM_Real))==0 ){
    Release(pTos);
    pTos--;
    pc = pOp->p2 - 1;
    break;
  }
  if( pTos->flags & MEM_Int ){
    v = pTos->u.i + (pOp->p1!=0);
  }else{
    /* FIX ME:  should this not be assert( pTos->flags & MEM_Real ) ??? */
    sqlite3VdbeMemRealify(pTos);
    v = (int)pTos->r;
    if( pTos->r>(double)v ) v++;
    if( pOp->p1 && pTos->r==(double)v ) v++;
  }
  Release(pTos);
  pTos->u.i = v;
  pTos->flags = MEM_Int;
  break;
}

/* Opcode: MustBeInt P1 P2 *
** 
** Force the top of the stack to be an integer.  If the top of the

  if( pOp->p2 ){
    if( res ){
      pc = pOp->p2-1;
    }
  }else{
    pTos++;
    pTos->flags = MEM_Int;
    pTos->u.i = res;
  }
  break;
}

/* Opcode: And * * *
**
** Pop two values off the stack.  Take the logical AND of the

  int v1, v2;    /* 0==TRUE, 1==FALSE, 2==UNKNOWN or NULL */

  assert( pNos>=p->aStack );
  if( pTos->flags & MEM_Null ){
    v1 = 2;
  }else{
    sqlite3VdbeMemIntegerify(pTos);
    v1 = pTos->u.i==0;
  }
  if( pNos->flags & MEM_Null ){
    v2 = 2;
  }else{
    sqlite3VdbeMemIntegerify(pNos);
    v2 = pNos->u.i==0;
  }
  if( pOp->opcode==OP_And ){
    static const unsigned char and_logic[] = { 0, 1, 2, 1, 1, 1, 2, 1, 2 };
    v1 = and_logic[v1*3+v2];
  }else{
    static const unsigned char or_logic[] = { 0, 0, 0, 0, 1, 2, 0, 2, 2 };
    v1 = or_logic[v1*3+v2];
  }
  popStack(&pTos, 2);
  pTos++;
  if( v1==2 ){
    pTos->flags = MEM_Null;
  }else{
    pTos->u.i = v1==0;
    pTos->flags = MEM_Int;
  }
  break;
}

/* Opcode: Negative * * *
**

    Release(pTos);
    if( pOp->opcode==OP_Negative || pTos->r<0.0 ){
      pTos->r = -pTos->r;
    }
    pTos->flags = MEM_Real;
  }else if( pTos->flags & MEM_Int ){
    Release(pTos);
    if( pOp->opcode==OP_Negative || pTos->u.i<0 ){
      pTos->u.i = -pTos->u.i;
    }
    pTos->flags = MEM_Int;
  }else if( pTos->flags & MEM_Null ){
    /* Do nothing */
  }else{
    sqlite3VdbeMemNumerify(pTos);
    goto neg_abs_real_case;

** is unchanged.
*/
case OP_Not: {                /* same as TK_NOT, no-push */
  assert( pTos>=p->aStack );
  if( pTos->flags & MEM_Null ) break;  /* Do nothing to NULLs */
  sqlite3VdbeMemIntegerify(pTos);
  assert( (pTos->flags & MEM_Dyn)==0 );
  pTos->u.i = !pTos->u.i;
  pTos->flags = MEM_Int;
  break;
}

/* Opcode: BitNot * * *
**
** Interpret the top of the stack as an value.  Replace it
** with its ones-complement.  If the top of the stack is NULL its
** value is unchanged.
*/
case OP_BitNot: {             /* same as TK_BITNOT, no-push */
  assert( pTos>=p->aStack );
  if( pTos->flags & MEM_Null ) break;  /* Do nothing to NULLs */
  sqlite3VdbeMemIntegerify(pTos);
  assert( (pTos->flags & MEM_Dyn)==0 );
  pTos->u.i = ~pTos->u.i;
  pTos->flags = MEM_Int;
  break;
}

/* Opcode: Noop * * *
**
** Do nothing.  This instruction is often useful as a jump

  ** be the number of free pages in the database (a read-only value)
  ** and meta[1] to be the schema cookie.  The schema layer considers
  ** meta[1] to be the schema cookie.  So we have to shift the index
  ** by one in the following statement.
  */
  rc = sqlite3BtreeGetMeta(db->aDb[pOp->p1].pBt, 1 + pOp->p2, (u32 *)&iMeta);
  pTos++;
  pTos->u.i = iMeta;
  pTos->flags = MEM_Int;
  break;
}

/* Opcode: SetCookie P1 P2 *
**
** Write the top of the stack into cookie number P2 of database P1.

  assert( pOp->p2<SQLITE_N_BTREE_META );
  assert( pOp->p1>=0 && pOp->p1<db->nDb );
  pDb = &db->aDb[pOp->p1];
  assert( pDb->pBt!=0 );
  assert( pTos>=p->aStack );
  sqlite3VdbeMemIntegerify(pTos);
  /* See note about index shifting on OP_ReadCookie */
  rc = sqlite3BtreeUpdateMeta(pDb->pBt, 1+pOp->p2, (int)pTos->u.i);
  if( pOp->p2==0 ){
    /* When the schema cookie changes, record the new cookie internally */
    pDb->pSchema->schema_cookie = pTos->u.i;
    db->flags |= SQLITE_InternChanges;
  }else if( pOp->p2==1 ){
    /* Record changes in the file format */
    pDb->pSchema->file_format = pTos->u.i;
  }
  assert( (pTos->flags & MEM_Dyn)==0 );
  pTos--;
  if( pOp->p1==1 ){
    /* Invalidate all prepared statements whenever the TEMP database
    ** schema is changed.  Ticket #1644 */
    sqlite3ExpirePreparedStatements(db);

  Btree *pX;
  int iDb;
  Cursor *pCur;
  Db *pDb;
  
  assert( pTos>=p->aStack );
  sqlite3VdbeMemIntegerify(pTos);
  iDb = pTos->u.i;
  assert( (pTos->flags & MEM_Dyn)==0 );
  pTos--;
  assert( iDb>=0 && iDb<db->nDb );
  pDb = &db->aDb[iDb];
  pX = pDb->pBt;
  assert( pX!=0 );
  if( pOp->opcode==OP_OpenWrite ){
    wrFlag = 1;
    if( pDb->pSchema->file_format < p->minWriteFileFormat ){
      p->minWriteFileFormat = pDb->pSchema->file_format;
    }
  }else{
    wrFlag = 0;
  }
  if( p2<=0 ){
    assert( pTos>=p->aStack );
    sqlite3VdbeMemIntegerify(pTos);
    p2 = pTos->u.i;
    assert( (pTos->flags & MEM_Dyn)==0 );
    pTos--;
    assert( p2>=2 );
  }
  assert( i>=0 );
  pCur = allocateCursor(p, i, iDb);
  if( pCur==0 ) goto no_mem;

    int res, oc;
    oc = pOp->opcode;
    pC->nullRow = 0;
    *pC->pIncrKey = oc==OP_MoveGt || oc==OP_MoveLe;
    if( pC->isTable ){
      i64 iKey;
      sqlite3VdbeMemIntegerify(pTos);
      iKey = intToKey(pTos->u.i);
      if( pOp->p2==0 && pOp->opcode==OP_MoveGe ){
        pC->movetoTarget = iKey;
        pC->deferredMoveto = 1;
        assert( (pTos->flags & MEM_Dyn)==0 );
        pTos--;
        break;
      }
      rc = sqlite3BtreeMoveto(pC->pCursor, 0, (u64)iKey, 0, &res);
      if( rc!=SQLITE_OK ){
        goto abort_due_to_error;
      }
      pC->lastRowid = pTos->u.i;
      pC->rowidIsValid = res==0;
    }else{
      assert( pTos->flags & MEM_Blob );
      /* Stringify(pTos, encoding); */
      rc = sqlite3BtreeMoveto(pC->pCursor, pTos->z, pTos->n, 0, &res);
      if( rc!=SQLITE_OK ){
        goto abort_due_to_error;

  BtCursor *pCrsr;
  i64 R;

  /* Pop the value R off the top of the stack
  */
  assert( pNos>=p->aStack );
  sqlite3VdbeMemIntegerify(pTos);
  R = pTos->u.i;
  assert( (pTos->flags & MEM_Dyn)==0 );
  pTos--;
  assert( i>=0 && i<p->nCursor );
  pCx = p->apCsr[i];
  assert( pCx!=0 );
  pCrsr = pCx->pCursor;
  if( pCrsr!=0 ){

    }

    /* The final varint of the key is different from R.  Push it onto
    ** the stack.  (The record number of an entry that violates a UNIQUE
    ** constraint.)
    */
    pTos++;
    pTos->u.i = v;
    pTos->flags = MEM_Int;
  }
  break;
}

/* Opcode: NotExists P1 P2 *
**

  assert( i>=0 && i<p->nCursor );
  assert( p->apCsr[i]!=0 );
  if( (pCrsr = (pC = p->apCsr[i])->pCursor)!=0 ){
    int res;
    u64 iKey;
    assert( pTos->flags & MEM_Int );
    assert( p->apCsr[i]->isTable );
    iKey = intToKey(pTos->u.i);
    rc = sqlite3BtreeMoveto(pCrsr, 0, iKey, 0,&res);
    pC->lastRowid = pTos->u.i;
    pC->rowidIsValid = res==0;
    pC->nullRow = 0;
    pC->cacheStatus = CACHE_STALE;
    /* res might be uninitialized if rc!=SQLITE_OK.  But if rc!=SQLITE_OK
    ** processing is about to abort so we really do not care whether or not
    ** the following jump is taken. */
    if( res!=0 ){

*/
case OP_Sequence: {
  int i = pOp->p1;
  assert( pTos>=p->aStack );
  assert( i>=0 && i<p->nCursor );
  assert( p->apCsr[i]!=0 );
  pTos++;
  pTos->u.i = p->apCsr[i]->seqCount++;
  pTos->flags = MEM_Int;
  break;
}


/* Opcode: NewRowid P1 P2 *
**

#ifndef SQLITE_OMIT_AUTOINCREMENT
      if( pOp->p2 ){
        Mem *pMem;
        assert( pOp->p2>0 && pOp->p2<p->nMem );  /* P2 is a valid memory cell */
        pMem = &p->aMem[pOp->p2];
        sqlite3VdbeMemIntegerify(pMem);
        assert( (pMem->flags & MEM_Int)!=0 );  /* mem(P2) holds an integer */
        if( pMem->u.i==MAX_ROWID || pC->useRandomRowid ){
          rc = SQLITE_FULL;
          goto abort_due_to_error;
        }
        if( v<pMem->u.i+1 ){
          v = pMem->u.i + 1;
        }
        pMem->u.i = v;
      }
#endif

      if( v<MAX_ROWID ){
        pC->nextRowidValid = 1;
        pC->nextRowid = v+1;
      }else{

      }
    }
    pC->rowidIsValid = 0;
    pC->deferredMoveto = 0;
    pC->cacheStatus = CACHE_STALE;
  }
  pTos++;
  pTos->u.i = v;
  pTos->flags = MEM_Int;
  break;
}

/* Opcode: Insert P1 P2 P3
**
** Write an entry into the table of cursor P1.  A new entry is

  assert( i>=0 && i<p->nCursor );
  assert( p->apCsr[i]!=0 );
  if( ((pC = p->apCsr[i])->pCursor!=0 || pC->pseudoTable) ){
    i64 iKey;   /* The integer ROWID or key for the record to be inserted */

    assert( pNos->flags & MEM_Int );
    assert( pC->isTable );
    iKey = intToKey(pNos->u.i);

    if( pOp->p2 & OPFLAG_NCHANGE ) p->nChange++;
    if( pOp->p2 & OPFLAG_LASTROWID ) db->lastRowid = pNos->u.i;
    if( pC->nextRowidValid && pNos->u.i>=pC->nextRowid ){
      pC->nextRowidValid = 0;
    }
    if( pTos->flags & MEM_Null ){
      pTos->z = 0;
      pTos->n = 0;
    }else{
      assert( pTos->flags & (MEM_Blob|MEM_Str) );

    pTos->flags = MEM_Null;
    break;
  }else{
    assert( pC->pCursor!=0 );
    sqlite3BtreeKeySize(pC->pCursor, &v);
    v = keyToInt(v);
  }
  pTos->u.i = v;
  pTos->flags = MEM_Int;
  break;
}

/* Opcode: NullRow P1 * *
**
** Move the cursor P1 to a null row.  Any OP_Column operations

      pTos->flags = MEM_Null;
    }else{
      rc = sqlite3VdbeIdxRowid(pCrsr, &rowid);
      if( rc!=SQLITE_OK ){
        goto abort_due_to_error;
      }
      pTos->flags = MEM_Int;
      pTos->u.i = rowid;
    }
  }
  break;
}

/* Opcode: IdxGT P1 P2 *
**

  if( iCnt>1 ){
    rc = SQLITE_LOCKED;
  }else{
    assert( iCnt==1 );
    rc = sqlite3BtreeDropTable(db->aDb[pOp->p2].pBt, pOp->p1, &iMoved);
    pTos++;
    pTos->flags = MEM_Int;
    pTos->u.i = iMoved;
#ifndef SQLITE_OMIT_AUTOVACUUM
    if( rc==SQLITE_OK && iMoved!=0 ){
      sqlite3RootPageMoved(&db->aDb[pOp->p2], iMoved, pOp->p1);
    }
#endif
  }
  break;

    flags = BTREE_LEAFDATA|BTREE_INTKEY;
  }else{
    flags = BTREE_ZERODATA;
  }
  rc = sqlite3BtreeCreateTable(pDb->pBt, &pgno, flags);
  pTos++;
  if( rc==SQLITE_OK ){
    pTos->u.i = pgno;
    pTos->flags = MEM_Int;
  }else{
    pTos->flags = MEM_Null;
  }
  break;
}

  if( aRoot==0 ) goto no_mem;
  j = pOp->p1;
  assert( j>=0 && j<p->nMem );
  pnErr = &p->aMem[j];
  assert( (pnErr->flags & MEM_Int)!=0 );
  for(j=0; j<nRoot; j++){
    Mem *pMem = &pTos[-j];
    aRoot[j] = pMem->u.i;
  }
  aRoot[j] = 0;
  popStack(&pTos, nRoot);
  pTos++;
  z = sqlite3BtreeIntegrityCheck(db->aDb[pOp->p2].pBt, aRoot, nRoot,
                                 pnErr->u.i, &nErr);
  pnErr->u.i -= nErr;
  if( nErr==0 ){
    assert( z==0 );
    pTos->flags = MEM_Null;
  }else{
    pTos->z = z;
    pTos->n = strlen(z);
    pTos->flags = MEM_Str | MEM_Dyn | MEM_Term;

**
** Write the integer on the top of the stack
** into the Fifo.
*/
case OP_FifoWrite: {        /* no-push */
  assert( pTos>=p->aStack );
  sqlite3VdbeMemIntegerify(pTos);
  sqlite3VdbeFifoPush(&p->sFifo, pTos->u.i);
  assert( (pTos->flags & MEM_Dyn)==0 );
  pTos--;
  break;
}

/* Opcode: FifoRead * P2 *
**
** Attempt to read a single integer from the Fifo
** and push it onto the stack.  If the Fifo is empty
** push nothing but instead jump to P2.
*/
case OP_FifoRead: {
  i64 v;
  CHECK_FOR_INTERRUPT;
  if( sqlite3VdbeFifoPop(&p->sFifo, &v)==SQLITE_DONE ){
    pc = pOp->p2 - 1;
  }else{
    pTos++;
    pTos->u.i = v;
    pTos->flags = MEM_Int;
  }
  break;
}

#ifndef SQLITE_OMIT_TRIGGER
/* Opcode: ContextPush * * * 

  int i = pOp->p1;
  Mem *pMem;
  assert( pTos>=p->aStack );
  assert( i>=0 && i<p->nMem );
  pMem = &p->aMem[i];
  sqlite3VdbeMemIntegerify(pMem);
  sqlite3VdbeMemIntegerify(pTos);
  if( pMem->u.i<pTos->u.i){
    pMem->u.i = pTos->u.i;
  }
  break;
}
#endif /* SQLITE_OMIT_AUTOINCREMENT */

/* Opcode: MemIncr P1 P2 *
**
** Increment the integer valued memory cell P2 by the value in P1.
**
** It is illegal to use this instruction on a memory cell that does
** not contain an integer.  An assertion fault will result if you try.
*/
case OP_MemIncr: {        /* no-push */
  int i = pOp->p2;
  Mem *pMem;
  assert( i>=0 && i<p->nMem );
  pMem = &p->aMem[i];
  assert( pMem->flags==MEM_Int );
  pMem->u.i += pOp->p1;
  break;
}

/* Opcode: IfMemPos P1 P2 *
**
** If the value of memory cell P1 is 1 or greater, jump to P2.
**
** It is illegal to use this instruction on a memory cell that does
** not contain an integer.  An assertion fault will result if you try.
*/
case OP_IfMemPos: {        /* no-push */
  int i = pOp->p1;
  Mem *pMem;
  assert( i>=0 && i<p->nMem );
  pMem = &p->aMem[i];
  assert( pMem->flags==MEM_Int );
  if( pMem->u.i>0 ){
     pc = pOp->p2 - 1;
  }
  break;
}

/* Opcode: IfMemNeg P1 P2 *
**
** If the value of memory cell P1 is less than zero, jump to P2. 
**
** It is illegal to use this instruction on a memory cell that does
** not contain an integer.  An assertion fault will result if you try.
*/
case OP_IfMemNeg: {        /* no-push */
  int i = pOp->p1;
  Mem *pMem;
  assert( i>=0 && i<p->nMem );
  pMem = &p->aMem[i];
  assert( pMem->flags==MEM_Int );
  if( pMem->u.i<0 ){
     pc = pOp->p2 - 1;
  }
  break;
}

/* Opcode: IfMemZero P1 P2 *
**
** If the value of memory cell P1 is exactly 0, jump to P2. 
**
** It is illegal to use this instruction on a memory cell that does
** not contain an integer.  An assertion fault will result if you try.
*/
case OP_IfMemZero: {        /* no-push */
  int i = pOp->p1;
  Mem *pMem;
  assert( i>=0 && i<p->nMem );
  pMem = &p->aMem[i];
  assert( pMem->flags==MEM_Int );
  if( pMem->u.i==0 ){
     pc = pOp->p2 - 1;
  }
  break;
}

/* Opcode: MemNull P1 * *
**

  Cursor *pCur = p->apCsr[pOp->p1];
  assert( pCur->pVtabCursor );
  pModule = pCur->pVtabCursor->pVtab->pModule;

  /* Grab the index number and argc parameters off the top of the stack. */
  assert( (&pTos[-1])>=p->aStack );
  assert( (pTos[0].flags&MEM_Int)!=0 && pTos[-1].flags==MEM_Int );
  nArg = pTos[-1].u.i;

  /* Invoke the xFilter method */
  {
    int res = 0;
    int i;
    Mem **apArg = p->apArg;
    for(i = 0; i<nArg; i++){
      apArg[i] = &pTos[i+1-2-nArg];
      storeTypeInfo(apArg[i], 0);
    }

    if( sqlite3SafetyOff(db) ) goto abort_due_to_misuse;
    p->inVtabMethod = 1;
    rc = pModule->xFilter(pCur->pVtabCursor, pTos->u.i, pOp->p3, nArg, apArg);
    p->inVtabMethod = 0;
    if( rc==SQLITE_OK ){
      res = pModule->xEof(pCur->pVtabCursor);
    }
    if( sqlite3SafetyOn(db) ) goto abort_due_to_misuse;

    if( res ){

    if( sqlite3SafetyOff(db) ) goto abort_due_to_misuse;
    rc = pModule->xRowid(pCur->pVtabCursor, &iRow);
    if( sqlite3SafetyOn(db) ) goto abort_due_to_misuse;

    pTos++;
    pTos->flags = MEM_Int;
    pTos->u.i = iRow;
  }

  break;
}
#endif /* SQLITE_OMIT_VIRTUALTABLE */

#ifndef SQLITE_OMIT_VIRTUALTABLE

    if( p->trace && pTos>=p->aStack ){
      int i;
      fprintf(p->trace, "Stack:");
      for(i=0; i>-5 && &pTos[i]>=p->aStack; i--){
        if( pTos[i].flags & MEM_Null ){
          fprintf(p->trace, " NULL");
        }else if( (pTos[i].flags & (MEM_Int|MEM_Str))==(MEM_Int|MEM_Str) ){
          fprintf(p->trace, " si:%lld", pTos[i].u.i);
        }else if( pTos[i].flags & MEM_Int ){
          fprintf(p->trace, " i:%lld", pTos[i].u.i);
        }else if( pTos[i].flags & MEM_Real ){
          fprintf(p->trace, " r:%g", pTos[i].r);
        }else{
          char zBuf[100];
          sqlite3VdbeMemPrettyPrint(&pTos[i], zBuf);
          fprintf(p->trace, " ");
          fprintf(p->trace, "%s", zBuf);

** in a Mem struct is returned by the MemType(Mem*) macro. The type is
** one of SQLITE_NULL, SQLITE_INTEGER, SQLITE_REAL, SQLITE_TEXT or
** SQLITE_BLOB.
*/
struct Mem {
  union {
    i64 i;              /* Integer value. Or FuncDef* when flags==MEM_Agg */
    FuncDef *pDef;      /* Used only when flags==MEM_Agg */
  } u;
  double r;           /* Real value */
  char *z;            /* String or BLOB value */
  int n;              /* Number of characters in string value, including '\0' */
  u16 flags;          /* Some combination of MEM_Null, MEM_Str, MEM_Dyn, etc. */
  u8  type;           /* One of MEM_Null, MEM_Str, etc. */
  u8  enc;            /* TEXT_Utf8, TEXT_Utf16le, or TEXT_Utf16be */
  void (*xDel)(void *);  /* If not null, call this function to delete Mem.z */

  if( (pMem->flags & MEM_Agg)==0 ){
    if( nByte==0 ){
      assert( pMem->flags==MEM_Null );
      pMem->z = 0;
    }else{
      pMem->flags = MEM_Agg;
      pMem->xDel = sqlite3FreeX;
      pMem->u.pDef = p->pFunc;
      if( nByte<=NBFS ){
        pMem->z = pMem->zShort;
        memset(pMem->z, 0, nByte);
      }else{
        pMem->z = sqliteMalloc( nByte );
      }
    }

    rc = SQLITE_ERROR;
    sqlite3SetString(&p->zErrMsg, sqlite3ErrStr(p->rc), (char*)0);
  }else{
    Op *pOp = &p->aOp[i];
    Mem *pMem = p->aStack;
    pMem->flags = MEM_Int;
    pMem->type = SQLITE_INTEGER;
    pMem->u.i = i;                                /* Program counter */
    pMem++;

    pMem->flags = MEM_Static|MEM_Str|MEM_Term;
    pMem->z = (char*)sqlite3OpcodeNames[pOp->opcode];  /* Opcode */
    assert( pMem->z!=0 );
    pMem->n = strlen(pMem->z);
    pMem->type = SQLITE_TEXT;
    pMem->enc = SQLITE_UTF8;
    pMem++;

    pMem->flags = MEM_Int;
    pMem->u.i = pOp->p1;                          /* P1 */
    pMem->type = SQLITE_INTEGER;
    pMem++;

    pMem->flags = MEM_Int;
    pMem->u.i = pOp->p2;                          /* P2 */
    pMem->type = SQLITE_INTEGER;
    pMem++;

    pMem->flags = MEM_Ephem|MEM_Str|MEM_Term;   /* P3 */
    pMem->z = displayP3(pOp, pMem->zShort, sizeof(pMem->zShort));
    assert( pMem->z!=0 );
    pMem->n = strlen(pMem->z);

  if( flags&MEM_Null ){
    return 0;
  }
  if( flags&MEM_Int ){
    /* Figure out whether to use 1, 2, 4, 6 or 8 bytes. */
#   define MAX_6BYTE ((((i64)0x00001000)<<32)-1)
    i64 i = pMem->u.i;
    u64 u;
    if( file_format>=4 && (i&1)==i ){
      return 8+i;
    }
    u = i<0 ? -i : i;
    if( u<=127 ) return 1;
    if( u<=32767 ) return 2;

  if( serial_type<=7 && serial_type>0 ){
    u64 v;
    int i;
    if( serial_type==7 ){
      assert( sizeof(v)==sizeof(pMem->r) );
      memcpy(&v, &pMem->r, sizeof(v));
    }else{
      v = pMem->u.i;
    }
    len = i = sqlite3VdbeSerialTypeLen(serial_type);
    while( i-- ){
      buf[i] = (v&0xFF);
      v >>= 8;
    }
    return len;

    case 10:   /* Reserved for future use */
    case 11:   /* Reserved for future use */
    case 0: {  /* NULL */
      pMem->flags = MEM_Null;
      break;
    }
    case 1: { /* 1-byte signed integer */
      pMem->u.i = (signed char)buf[0];
      pMem->flags = MEM_Int;
      return 1;
    }
    case 2: { /* 2-byte signed integer */
      pMem->u.i = (((signed char)buf[0])<<8) | buf[1];
      pMem->flags = MEM_Int;
      return 2;
    }
    case 3: { /* 3-byte signed integer */
      pMem->u.i = (((signed char)buf[0])<<16) | (buf[1]<<8) | buf[2];
      pMem->flags = MEM_Int;
      return 3;
    }
    case 4: { /* 4-byte signed integer */
      pMem->u.i = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
      pMem->flags = MEM_Int;
      return 4;
    }
    case 5: { /* 6-byte signed integer */
      u64 x = (((signed char)buf[0])<<8) | buf[1];
      u32 y = (buf[2]<<24) | (buf[3]<<16) | (buf[4]<<8) | buf[5];
      x = (x<<32) | y;
      pMem->u.i = *(i64*)&x;
      pMem->flags = MEM_Int;
      return 6;
    }
    case 6:   /* 8-byte signed integer */
    case 7: { /* IEEE floating point */
      u64 x;
      u32 y;
#if !defined(NDEBUG) && !defined(SQLITE_OMIT_FLOATING_POINT)
      /* Verify that integers and floating point values use the same
      ** byte order.  The byte order differs on some (broken) architectures.
      */
      static const u64 t1 = ((u64)0x3ff00000)<<32;
      static const double r1 = 1.0;
      assert( sizeof(r1)==sizeof(t1) && memcmp(&r1, &t1, sizeof(r1))==0 );
#endif

      x = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
      y = (buf[4]<<24) | (buf[5]<<16) | (buf[6]<<8) | buf[7];
      x = (x<<32) | y;
      if( serial_type==6 ){
        pMem->u.i = *(i64*)&x;
        pMem->flags = MEM_Int;
      }else{
        assert( sizeof(x)==8 && sizeof(pMem->r)==8 );
        memcpy(&pMem->r, &x, sizeof(x));
        /* pMem->r = *(double*)&x; */
        pMem->flags = MEM_Real;
      }
      return 8;
    }
    case 8:    /* Integer 0 */
    case 9: {  /* Integer 1 */
      pMem->u.i = serial_type-8;
      pMem->flags = MEM_Int;
      return 0;
    }
    default: {
      int len = (serial_type-12)/2;
      pMem->z = (char *)buf;
      pMem->n = len;

  if( rc ){
    return rc;
  }
  sqlite3GetVarint32((u8*)m.z, &szHdr);
  sqlite3GetVarint32((u8*)&m.z[szHdr-1], &typeRowid);
  lenRowid = sqlite3VdbeSerialTypeLen(typeRowid);
  sqlite3VdbeSerialGet((u8*)&m.z[m.n-lenRowid], typeRowid, &v);
  *rowid = v.u.i;
  sqlite3VdbeMemRelease(&m);
  return SQLITE_OK;
}

/*
** Compare the key of the index entry that cursor pC is point to against
** the key string in pKey (of length nKey).  Write into *pRes a number

  /* For a Real or Integer, use sqlite3_snprintf() to produce the UTF-8
  ** string representation of the value. Then, if the required encoding
  ** is UTF-16le or UTF-16be do a translation.
  ** 
  ** FIX ME: It would be better if sqlite3_snprintf() could do UTF-16.
  */
  if( fg & MEM_Int ){
    sqlite3_snprintf(NBFS, z, "%lld", pMem->u.i);
  }else{
    assert( fg & MEM_Real );
    sqlite3_snprintf(NBFS, z, "%!.15g", pMem->r);
  }
  pMem->n = strlen(z);
  pMem->z = z;
  pMem->enc = SQLITE_UTF8;

** Return SQLITE_ERROR if the finalizer reports an error.  SQLITE_OK
** otherwise.
*/
int sqlite3VdbeMemFinalize(Mem *pMem, FuncDef *pFunc){
  int rc = SQLITE_OK;
  if( pFunc && pFunc->xFinalize ){
    sqlite3_context ctx;
    assert( (pMem->flags & MEM_Null)!=0 || pFunc==pMem->u.pDef );
    ctx.s.flags = MEM_Null;
    ctx.s.z = pMem->zShort;
    ctx.pMem = pMem;
    ctx.pFunc = pFunc;
    ctx.isError = 0;
    pFunc->xFinalize(&ctx);
    if( pMem->z && pMem->z!=pMem->zShort ){

** inconsistent state, for example with (Mem.z==0) and
** (Mem.type==SQLITE_TEXT).
*/
void sqlite3VdbeMemRelease(Mem *p){
  if( p->flags & (MEM_Dyn|MEM_Agg) ){
    if( p->xDel ){
      if( p->flags & MEM_Agg ){
        sqlite3VdbeMemFinalize(p, p->u.pDef);
        assert( (p->flags & MEM_Agg)==0 );
        sqlite3VdbeMemRelease(p);
      }else{
        p->xDel((void *)p->z);
      }
    }else{
      sqliteFree(p->z);

** it into a integer and return that.  If pMem is NULL, return 0.
**
** If pMem is a string, its encoding might be changed.
*/
i64 sqlite3VdbeIntValue(Mem *pMem){
  int flags = pMem->flags;
  if( flags & MEM_Int ){
    return pMem->u.i;
  }else if( flags & MEM_Real ){
    return (i64)pMem->r;
  }else if( flags & (MEM_Str|MEM_Blob) ){
    i64 value;
    if( sqlite3VdbeChangeEncoding(pMem, SQLITE_UTF8)
       || sqlite3VdbeMemNulTerminate(pMem) ){
      return 0;

** value.  If it is a string or blob, try to convert it to a double.
** If it is a NULL, return 0.0.
*/
double sqlite3VdbeRealValue(Mem *pMem){
  if( pMem->flags & MEM_Real ){
    return pMem->r;
  }else if( pMem->flags & MEM_Int ){
    return (double)pMem->u.i;
  }else if( pMem->flags & (MEM_Str|MEM_Blob) ){
    double val = 0.0;
    if( sqlite3VdbeChangeEncoding(pMem, SQLITE_UTF8)
       || sqlite3VdbeMemNulTerminate(pMem) ){
      return 0.0;
    }
    assert( pMem->z );
    sqlite3AtoF(pMem->z, &val);
    return val;
  }else{
    return 0.0;
  }
}

/*
** The MEM structure is already a MEM_Real.  Try to also make it a
** MEM_Int if we can.
*/
void sqlite3VdbeIntegerAffinity(Mem *pMem){
  assert( pMem->flags & MEM_Real );
  pMem->u.i = pMem->r;
  if( ((double)pMem->u.i)==pMem->r ){
    pMem->flags |= MEM_Int;
  }
}

/*
** Convert pMem to type integer.  Invalidate any prior representations.
*/
int sqlite3VdbeMemIntegerify(Mem *pMem){
  pMem->u.i = sqlite3VdbeIntValue(pMem);
  sqlite3VdbeMemRelease(pMem);
  pMem->flags = MEM_Int;
  return SQLITE_OK;
}

/*
** Convert pMem so that it is of type MEM_Real.

/*
** Delete any previous value and set the value stored in *pMem to val,
** manifest type INTEGER.
*/
void sqlite3VdbeMemSetInt64(Mem *pMem, i64 val){
  sqlite3VdbeMemRelease(pMem);
  pMem->u.i = val;
  pMem->flags = MEM_Int;
  pMem->type = SQLITE_INTEGER;
}

/*
** Delete any previous value and set the value stored in *pMem to val,
** manifest type REAL.

    }
    if( !(f2&(MEM_Int|MEM_Real)) ){
      return -1;
    }
    if( (f1 & f2 & MEM_Int)==0 ){
      double r1, r2;
      if( (f1&MEM_Real)==0 ){
        r1 = pMem1->u.i;
      }else{
        r1 = pMem1->r;
      }
      if( (f2&MEM_Real)==0 ){
        r2 = pMem2->u.i;
      }else{
        r2 = pMem2->r;
      }
      if( r1<r2 ) return -1;
      if( r1>r2 ) return 1;
      return 0;
    }else{
      assert( f1&MEM_Int );
      assert( f2&MEM_Int );
      if( pMem1->u.i < pMem2->u.i ) return -1;
      if( pMem1->u.i > pMem2->u.i ) return 1;
      return 0;
    }
  }

  /* If one value is a string and the other is a blob, the string is less.
  ** If both are strings, compare using the collating functions.
  */

    assert( pMem->xDel==0 );
  }
  /* MEM_Null excludes all other types */
  assert( (pMem->flags&(MEM_Str|MEM_Int|MEM_Real|MEM_Blob))==0
          || (pMem->flags&MEM_Null)==0 );
  /* If the MEM is both real and integer, the values are equal */
  assert( (pMem->flags & (MEM_Int|MEM_Real))!=(MEM_Int|MEM_Real) 
          || pMem->r==pMem->u.i );
}
#endif

/* This function is only available internally, it is not part of the
** external API. It works in a similar way to sqlite3_value_text(),
** except the data returned is in the encoding specified by the second
** parameter, which must be one of SQLITE_UTF16BE, SQLITE_UTF16LE or

    if( (op==TK_INTEGER || op==TK_FLOAT ) && affinity==SQLITE_AFF_NONE ){
      sqlite3ValueApplyAffinity(pVal, SQLITE_AFF_NUMERIC, enc);
    }else{
      sqlite3ValueApplyAffinity(pVal, affinity, enc);
    }
  }else if( op==TK_UMINUS ) {
    if( SQLITE_OK==sqlite3ValueFromExpr(pExpr->pLeft, enc, affinity, &pVal) ){
      pVal->u.i = -1 * pVal->u.i;
      pVal->r = -1.0 * pVal->r;
    }
  }
#ifndef SQLITE_OMIT_BLOB_LITERAL
  else if( op==TK_BLOB ){
    int nVal;
    pVal = sqlite3ValueNew();