**
** 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 1.857 2009/06/19 22:23:42 drh Exp $
*/
#include "sqliteInt.h"
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor
** moves, either by the OP_SeekXX, OP_Next, or OP_Prev opcodes.  The test
................................................................................
  **
  ** In case this is such a statement, close any statement transaction
  ** opened by this VM before returning control to the user. This is to
  ** ensure that statement-transactions are always nested, not overlapping.
  ** If the open statement-transaction is not closed here, then the user
  ** may step another VM that opens its own statement transaction. This
  ** may lead to overlapping statement transactions.



  */
  assert( p->iStatement==0 || db->flags&SQLITE_CountRows );
  if( SQLITE_OK!=(rc = sqlite3VdbeCloseStatement(p, SAVEPOINT_RELEASE)) ){

    break;
  }

  /* Invalidate all ephemeral cursor row caches */
  p->cacheCtr = (p->cacheCtr + 2)|1;

  /* Make sure the results of the current row are \000 terminated
................................................................................
    if( pC->nullRow ){
      payloadSize = 0;
    }else if( pC->cacheStatus==p->cacheCtr ){
      payloadSize = pC->payloadSize;
      zRec = (char*)pC->aRow;
    }else if( pC->isIndex ){
      sqlite3BtreeKeySize(pCrsr, &payloadSize64);
      if( (payloadSize64 & SQLITE_MAX_U32)!=(u64)payloadSize64 ){
        rc = SQLITE_CORRUPT_BKPT;
        goto abort_due_to_error;
      }
      payloadSize = (u32)payloadSize64;
    }else{
      sqlite3BtreeDataSize(pCrsr, &payloadSize);
    }
    nField = pC->nField;
  }else{
    assert( pC->pseudoTable );
................................................................................
  }
  if( pOp->p5 ){
    assert( p2>0 );
    assert( p2<=p->nMem );
    pIn2 = &p->aMem[p2];
    sqlite3VdbeMemIntegerify(pIn2);
    p2 = (int)pIn2->u.i;
    if( p2<2 ) {
      rc = SQLITE_CORRUPT_BKPT;
      goto abort_due_to_error;
    }
  }
  assert( i>=0 );
  if( pOp->p4type==P4_KEYINFO ){
    pKeyInfo = pOp->p4.pKeyInfo;
................................................................................
  pCur = allocateCursor(p, i, nField, iDb, 1);
  if( pCur==0 ) goto no_mem;
  pCur->nullRow = 1;
  rc = sqlite3BtreeCursor(pX, p2, wrFlag, pKeyInfo, pCur->pCursor);
  pCur->pKeyInfo = pKeyInfo;

  switch( rc ){
    case SQLITE_BUSY: {
      p->pc = pc;
      p->rc = rc = SQLITE_BUSY;
      goto vdbe_return;
    }
    case SQLITE_OK: {
      flags = sqlite3BtreeFlags(pCur->pCursor);

      /* Sanity checking.  Only the lower four bits of the flags byte should
      ** be used.  Bit 3 (mask 0x08) is unpredictable.  The lower 3 bits
      ** (mask 0x07) should be either 5 (intkey+leafdata for tables) or
      ** 2 (zerodata for indices).  If these conditions are not met it can
      ** only mean that we are dealing with a corrupt database file

      */
      if( (flags & 0xf0)!=0 || ((flags & 0x07)!=5 && (flags & 0x07)!=2) ){
        rc = SQLITE_CORRUPT_BKPT;
        goto abort_due_to_error;
      }
      pCur->isTable = (flags & BTREE_INTKEY)!=0 ?1:0;
      pCur->isIndex = (flags & BTREE_ZERODATA)!=0 ?1:0;
      /* If P4==0 it means we are expected to open a table.  If P4!=0 then
      ** we expect to be opening an index.  If this is not what happened,
      ** then the database is corrupt
      */
      if( (pCur->isTable && pOp->p4type==P4_KEYINFO)
................................................................................
      pCur->isTable = pOp->p4type!=P4_KEYINFO;
      pCur->isIndex = !pCur->isTable;
      pCur->pCursor = 0;
      rc = SQLITE_OK;
      break;
    }
    default: {

      goto abort_due_to_error;
    }
  }
  break;
}

/* Opcode: OpenEphemeral P1 P2 * P4 *
................................................................................
          break;
        }
        /* If we reach this point, then the P3 value must be a floating
        ** point number. */
        assert( (pIn3->flags & MEM_Real)!=0 );

        if( iKey==SMALLEST_INT64 && (pIn3->r<(double)iKey || pIn3->r>0) ){
          /* The P3 value is to large in magnitude to be expressed as an
          ** integer. */
          res = 1;
          if( pIn3->r<0 ){
            if( oc==OP_SeekGt || oc==OP_SeekGe ){
              rc = sqlite3BtreeFirst(pC->pCursor, &res);
              if( rc!=SQLITE_OK ) goto abort_due_to_error;
            }
................................................................................
        res = sqlite3BtreeEof(pC->pCursor);
      }
    }
    assert( pOp->p2>0 );
    if( res ){
      pc = pOp->p2 - 1;
    }
  }else if( !pC->pseudoTable ){
    /* This happens when attempting to open the sqlite3_master table
    ** for read access returns SQLITE_EMPTY. In this case always
    ** take the jump (since there are no records in the table).
    */

    pc = pOp->p2 - 1;
  }
  break;
}

/* Opcode: Seek P1 P2 * * *
**
................................................................................
  int i;
  VdbeCursor *pC;

  i = pOp->p1;
  assert( i>=0 && i<p->nCursor );
  pC = p->apCsr[i];
  assert( pC!=0 );
  if( pC->pCursor!=0 ){
    assert( pC->isTable );
    pC->nullRow = 0;
    pC->movetoTarget = sqlite3VdbeIntValue(pIn2);
    pC->rowidIsValid = 0;
    pC->deferredMoveto = 1;
  }
  break;
................................................................................
** to P2.  If an entry does existing, fall through.  The cursor is left
** pointing to the entry that matches.
**
** See also: Found, NotExists, IsUnique
*/
case OP_NotFound:       /* jump, in3 */
case OP_Found: {        /* jump, in3 */
  int i;
  int alreadyExists;
  VdbeCursor *pC;
  int res;
  UnpackedRecord *pIdxKey;
  char aTempRec[ROUND8(sizeof(UnpackedRecord)) + sizeof(Mem)*3 + 7];

  i = pOp->p1;
  alreadyExists = 0;
  assert( i>=0 && i<p->nCursor );

  assert( p->apCsr[i]!=0 );
  if( (pC = p->apCsr[i])->pCursor!=0 ){

    assert( pC->isTable==0 );
    assert( pIn3->flags & MEM_Blob );
    pIdxKey = sqlite3VdbeRecordUnpack(pC->pKeyInfo, pIn3->n, pIn3->z,
                                      aTempRec, sizeof(aTempRec));
    if( pIdxKey==0 ){
      goto no_mem;
................................................................................
** operation assumes the key is an integer and that P1 is a table whereas
** NotFound assumes key is a blob constructed from MakeRecord and
** P1 is an index.
**
** See also: Found, NotFound, IsUnique
*/
case OP_NotExists: {        /* jump, in3 */
  int i;
  VdbeCursor *pC;
  BtCursor *pCrsr;
  int res;
  u64 iKey;

  i = pOp->p1;
  assert( i>=0 && i<p->nCursor );
  assert( p->apCsr[i]!=0 );
  if( (pCrsr = (pC = p->apCsr[i])->pCursor)!=0 ){



    res = 0;
    assert( pIn3->flags & MEM_Int );
    assert( p->apCsr[i]->isTable );
    iKey = intToKey(pIn3->u.i);
    rc = sqlite3BtreeMovetoUnpacked(pCrsr, 0, iKey, 0, &res);
    pC->lastRowid = pIn3->u.i;
    pC->rowidIsValid = res==0 ?1:0;
    pC->nullRow = 0;
    pC->cacheStatus = CACHE_STALE;
    pC->deferredMoveto = 0;
    if( res!=0 ){
      pc = pOp->p2 - 1;
      assert( pC->rowidIsValid==0 );
    }
    pC->seekResult = res;
  }else if( !pC->pseudoTable ){
    /* This happens when an attempt to open a read cursor on the 
    ** sqlite_master table returns SQLITE_EMPTY.
    */

    assert( pC->isTable );
    pc = pOp->p2 - 1;
    assert( pC->rowidIsValid==0 );
    pC->seekResult = 0;
  }
  break;
}
................................................................................
** generated record number.  No new record numbers are allowed to be less
** than this value.  When this value reaches its maximum, a SQLITE_FULL
** error is generated.  The P3 register is updated with the generated
** record number.  This P3 mechanism is used to help implement the
** AUTOINCREMENT feature.
*/
case OP_NewRowid: {           /* out2-prerelease */
  int i;
  i64 v;
  VdbeCursor *pC;

  int res;
  int rx;
  int cnt;
  i64 x;
  Mem *pMem;

  i = pOp->p1;
  v = 0;
  res = 0;
  rx = SQLITE_OK;
  assert( i>=0 && i<p->nCursor );

  assert( p->apCsr[i]!=0 );
  if( (pC = p->apCsr[i])->pCursor==0 ){
    /* The zero initialization above is all that is needed */
  }else{
    /* The next rowid or record number (different terms for the same
    ** thing) is obtained in a two-step algorithm.
    **
    ** First we attempt to find the largest existing rowid and add one
    ** to that.  But if the largest existing rowid is already the maximum
    ** positive integer, we have to fall through to the second
    ** probabilistic algorithm
    **
    ** The second algorithm is to select a rowid at random and see if
    ** it already exists in the table.  If it does not exist, we have
    ** succeeded.  If the random rowid does exist, we select a new one
    ** and try again, up to 1000 times.
    **
    ** For a table with less than 2 billion entries, the probability
    ** of not finding a unused rowid is about 1.0e-300.  This is a 
    ** non-zero probability, but it is still vanishingly small and should
    ** never cause a problem.  You are much, much more likely to have a
    ** hardware failure than for this algorithm to fail.
    **
    ** The analysis in the previous paragraph assumes that you have a good
    ** source of random numbers.  Is a library function like lrand48()
    ** good enough?  Maybe. Maybe not. It's hard to know whether there
    ** might be subtle bugs is some implementations of lrand48() that
    ** could cause problems. To avoid uncertainty, SQLite uses its own 
    ** random number generator based on the RC4 algorithm.
    **
    ** To promote locality of reference for repetitive inserts, the
    ** first few attempts at choosing a random rowid pick values just a little
    ** larger than the previous rowid.  This has been shown experimentally
    ** to double the speed of the COPY operation.
    */

    cnt = 0;
    if( (sqlite3BtreeFlags(pC->pCursor)&(BTREE_INTKEY|BTREE_ZERODATA)) !=
          BTREE_INTKEY ){
      rc = SQLITE_CORRUPT_BKPT;
      goto abort_due_to_error;
    }
    assert( (sqlite3BtreeFlags(pC->pCursor) & BTREE_INTKEY)!=0 );
    assert( (sqlite3BtreeFlags(pC->pCursor) & BTREE_ZERODATA)==0 );

#ifdef SQLITE_32BIT_ROWID
#   define MAX_ROWID 0x7fffffff
#else
    /* Some compilers complain about constants of the form 0x7fffffffffffffff.
    ** Others complain about 0x7ffffffffffffffffLL.  The following macro seems
    ** to provide the constant while making all compilers happy.
................................................................................
        if( rc!=SQLITE_OK ){
          goto abort_due_to_error;
        }
        if( res ){
          v = 1;
        }else{
          sqlite3BtreeKeySize(pC->pCursor, &v);
          v = keyToInt(v);
          if( v==MAX_ROWID ){
            pC->useRandomRowid = 1;
          }else{
            v++;
          }
        }
      }
................................................................................
        pMem->u.i = v;
      }
#endif

      sqlite3BtreeSetCachedRowid(pC->pCursor, v<MAX_ROWID ? v+1 : 0);
    }
    if( pC->useRandomRowid ){
      assert( pOp->p3==0 );  /* SQLITE_FULL must have occurred prior to this */

      v = db->priorNewRowid;
      cnt = 0;
      do{
        if( cnt==0 && (v&0xffffff)==v ){
          v++;
        }else{
          sqlite3_randomness(sizeof(v), &v);
          if( cnt<5 ) v &= 0xffffff;
        }
        if( v==0 ) continue;
        x = intToKey(v);
        rx = sqlite3BtreeMovetoUnpacked(pC->pCursor, 0, (u64)x, 0, &res);
        cnt++;
      }while( cnt<100 && rx==SQLITE_OK && res==0 );
      db->priorNewRowid = v;
      if( rx==SQLITE_OK && res==0 ){
        rc = SQLITE_FULL;
        goto abort_due_to_error;
      }
    }
    pC->rowidIsValid = 0;
    pC->deferredMoveto = 0;
    pC->cacheStatus = CACHE_STALE;
................................................................................
  assert( pC!=0 );
  assert( pC->pCursor!=0 || pC->pseudoTable );
  assert( pKey->flags & MEM_Int );
  assert( pC->isTable );
  REGISTER_TRACE(pOp->p2, pData);
  REGISTER_TRACE(pOp->p3, pKey);

  iKey = intToKey(pKey->u.i);
  if( pOp->p5 & OPFLAG_NCHANGE ) p->nChange++;
  if( pOp->p5 & OPFLAG_LASTROWID ) db->lastRowid = pKey->u.i;
  if( pData->flags & MEM_Null ){
    pData->z = 0;
    pData->n = 0;
  }else{
    assert( pData->flags & (MEM_Blob|MEM_Str) );
................................................................................
  assert( pC!=0 );
  if( pC->nullRow ){
    /* Do nothing so that reg[P2] remains NULL */
    break;
  }else if( pC->deferredMoveto ){
    v = pC->movetoTarget;
  }else if( pC->pseudoTable ){
    v = keyToInt(pC->iKey);
#ifndef SQLITE_OMIT_VIRTUALTABLE
  }else if( pC->pVtabCursor ){
    pVtab = pC->pVtabCursor->pVtab;
    pModule = pVtab->pModule;
    assert( pModule->xRowid );
    if( sqlite3SafetyOff(db) ) goto abort_due_to_misuse;
    rc = pModule->xRowid(pC->pVtabCursor, &v);
................................................................................
    rc = sqlite3VdbeCursorMoveto(pC);
    if( rc ) goto abort_due_to_error;
    if( pC->rowidIsValid ){
      v = pC->lastRowid;
    }else{
      assert( pC->pCursor!=0 );
      sqlite3BtreeKeySize(pC->pCursor, &v);
      v = keyToInt(v);
    }
  }
  pOut->u.i = v;
  MemSetTypeFlag(pOut, MEM_Int);
  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 1.858 2009/06/22 00:55:31 drh Exp $
*/
#include "sqliteInt.h"
#include "vdbeInt.h"

/*
** The following global variable is incremented every time a cursor
** moves, either by the OP_SeekXX, OP_Next, or OP_Prev opcodes.  The test
................................................................................
  **
  ** In case this is such a statement, close any statement transaction
  ** opened by this VM before returning control to the user. This is to
  ** ensure that statement-transactions are always nested, not overlapping.
  ** If the open statement-transaction is not closed here, then the user
  ** may step another VM that opens its own statement transaction. This
  ** may lead to overlapping statement transactions.
  **
  ** The statement transaction is never a top-level transaction.  Hence
  ** the RELEASE call below can never fail.
  */
  assert( p->iStatement==0 || db->flags&SQLITE_CountRows );
  rc = sqlite3VdbeCloseStatement(p, SAVEPOINT_RELEASE);
  if( NEVER(rc!=SQLITE_OK) ){
    break;
  }

  /* Invalidate all ephemeral cursor row caches */
  p->cacheCtr = (p->cacheCtr + 2)|1;

  /* Make sure the results of the current row are \000 terminated
................................................................................
    if( pC->nullRow ){
      payloadSize = 0;
    }else if( pC->cacheStatus==p->cacheCtr ){
      payloadSize = pC->payloadSize;
      zRec = (char*)pC->aRow;
    }else if( pC->isIndex ){
      sqlite3BtreeKeySize(pCrsr, &payloadSize64);
      /* sqlite3BtreeParseCellPtr() uses getVarint32() to extract the
      ** payload size, so it is impossible for payloadSize64 to be
      ** larger than 32 bits. */
      assert( (payloadSize64 & SQLITE_MAX_U32)==(u64)payloadSize64 );
      payloadSize = (u32)payloadSize64;
    }else{
      sqlite3BtreeDataSize(pCrsr, &payloadSize);
    }
    nField = pC->nField;
  }else{
    assert( pC->pseudoTable );
................................................................................
  }
  if( pOp->p5 ){
    assert( p2>0 );
    assert( p2<=p->nMem );
    pIn2 = &p->aMem[p2];
    sqlite3VdbeMemIntegerify(pIn2);
    p2 = (int)pIn2->u.i;
    if( NEVER(p2<2) ) {
      rc = SQLITE_CORRUPT_BKPT;
      goto abort_due_to_error;
    }
  }
  assert( i>=0 );
  if( pOp->p4type==P4_KEYINFO ){
    pKeyInfo = pOp->p4.pKeyInfo;
................................................................................
  pCur = allocateCursor(p, i, nField, iDb, 1);
  if( pCur==0 ) goto no_mem;
  pCur->nullRow = 1;
  rc = sqlite3BtreeCursor(pX, p2, wrFlag, pKeyInfo, pCur->pCursor);
  pCur->pKeyInfo = pKeyInfo;

  switch( rc ){





    case SQLITE_OK: {
      flags = sqlite3BtreeFlags(pCur->pCursor);

      /* Sanity checking.  Only the lower four bits of the flags byte should
      ** be used.  Bit 3 (mask 0x08) is unpredictable.  The lower 3 bits
      ** (mask 0x07) should be either 5 (intkey+leafdata for tables) or
      ** 2 (zerodata for indices).  If these conditions are not met it can
      ** only mean that we are dealing with a corrupt database file.
      ** Note:  All of the above is checked already in sqlite3BtreeCursor().
      */

      assert( (flags & 0xf0)==0 );
      assert( (flags & 0x07)==5 || (flags & 0x07)==2 );

      pCur->isTable = (flags & BTREE_INTKEY)!=0 ?1:0;
      pCur->isIndex = (flags & BTREE_ZERODATA)!=0 ?1:0;
      /* If P4==0 it means we are expected to open a table.  If P4!=0 then
      ** we expect to be opening an index.  If this is not what happened,
      ** then the database is corrupt
      */
      if( (pCur->isTable && pOp->p4type==P4_KEYINFO)
................................................................................
      pCur->isTable = pOp->p4type!=P4_KEYINFO;
      pCur->isIndex = !pCur->isTable;
      pCur->pCursor = 0;
      rc = SQLITE_OK;
      break;
    }
    default: {
      assert( rc!=SQLITE_BUSY );  /* Busy conditions detected earlier */
      goto abort_due_to_error;
    }
  }
  break;
}

/* Opcode: OpenEphemeral P1 P2 * P4 *
................................................................................
          break;
        }
        /* If we reach this point, then the P3 value must be a floating
        ** point number. */
        assert( (pIn3->flags & MEM_Real)!=0 );

        if( iKey==SMALLEST_INT64 && (pIn3->r<(double)iKey || pIn3->r>0) ){
          /* The P3 value is too large in magnitude to be expressed as an
          ** integer. */
          res = 1;
          if( pIn3->r<0 ){
            if( oc==OP_SeekGt || oc==OP_SeekGe ){
              rc = sqlite3BtreeFirst(pC->pCursor, &res);
              if( rc!=SQLITE_OK ) goto abort_due_to_error;
            }
................................................................................
        res = sqlite3BtreeEof(pC->pCursor);
      }
    }
    assert( pOp->p2>0 );
    if( res ){
      pc = pOp->p2 - 1;
    }
  }else{
    /* This happens when attempting to open the sqlite3_master table
    ** for read access returns SQLITE_EMPTY. In this case always
    ** take the jump (since there are no records in the table).
    */
    assert( pC->pseudoTable==0 );
    pc = pOp->p2 - 1;
  }
  break;
}

/* Opcode: Seek P1 P2 * * *
**
................................................................................
  int i;
  VdbeCursor *pC;

  i = pOp->p1;
  assert( i>=0 && i<p->nCursor );
  pC = p->apCsr[i];
  assert( pC!=0 );
  if( ALWAYS(pC->pCursor!=0) ){
    assert( pC->isTable );
    pC->nullRow = 0;
    pC->movetoTarget = sqlite3VdbeIntValue(pIn2);
    pC->rowidIsValid = 0;
    pC->deferredMoveto = 1;
  }
  break;
................................................................................
** to P2.  If an entry does existing, fall through.  The cursor is left
** pointing to the entry that matches.
**
** See also: Found, NotExists, IsUnique
*/
case OP_NotFound:       /* jump, in3 */
case OP_Found: {        /* jump, in3 */

  int alreadyExists;
  VdbeCursor *pC;
  int res;
  UnpackedRecord *pIdxKey;
  char aTempRec[ROUND8(sizeof(UnpackedRecord)) + sizeof(Mem)*3 + 7];


  alreadyExists = 0;
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  if( ALWAYS(pC->pCursor!=0) ){

    assert( pC->isTable==0 );
    assert( pIn3->flags & MEM_Blob );
    pIdxKey = sqlite3VdbeRecordUnpack(pC->pKeyInfo, pIn3->n, pIn3->z,
                                      aTempRec, sizeof(aTempRec));
    if( pIdxKey==0 ){
      goto no_mem;
................................................................................
** operation assumes the key is an integer and that P1 is a table whereas
** NotFound assumes key is a blob constructed from MakeRecord and
** P1 is an index.
**
** See also: Found, NotFound, IsUnique
*/
case OP_NotExists: {        /* jump, in3 */

  VdbeCursor *pC;
  BtCursor *pCrsr;
  int res;
  u64 iKey;

  assert( pIn3->flags & MEM_Int );
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->isTable );
  pCrsr = pC->pCursor;
  if( pCrsr!=0 ){
    res = 0;


    iKey = pIn3->u.i;
    rc = sqlite3BtreeMovetoUnpacked(pCrsr, 0, iKey, 0, &res);
    pC->lastRowid = pIn3->u.i;
    pC->rowidIsValid = res==0 ?1:0;
    pC->nullRow = 0;
    pC->cacheStatus = CACHE_STALE;
    pC->deferredMoveto = 0;
    if( res!=0 ){
      pc = pOp->p2 - 1;
      assert( pC->rowidIsValid==0 );
    }
    pC->seekResult = res;
  }else{
    /* This happens when an attempt to open a read cursor on the 
    ** sqlite_master table returns SQLITE_EMPTY.
    */
    assert( !pC->pseudoTable );
    assert( pC->isTable );
    pc = pOp->p2 - 1;
    assert( pC->rowidIsValid==0 );
    pC->seekResult = 0;
  }
  break;
}
................................................................................
** generated record number.  No new record numbers are allowed to be less
** than this value.  When this value reaches its maximum, a SQLITE_FULL
** error is generated.  The P3 register is updated with the generated
** record number.  This P3 mechanism is used to help implement the
** AUTOINCREMENT feature.
*/
case OP_NewRowid: {           /* out2-prerelease */
  i64 v;                 /* The new rowid */

  VdbeCursor *pC;        /* Cursor of table to get the new rowid */
  int res;               /* Result of an sqlite3BtreeLast() */
  int cnt;               /* Counter to limit the number of searches */
  Mem *pMem;             /* Register holding largest rowid for AUTOINCREMENT */





  v = 0;
  res = 0;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  if( NEVER(pC->pCursor==0) ){
    /* The zero initialization above is all that is needed */
  }else{
    /* The next rowid or record number (different terms for the same
    ** thing) is obtained in a two-step algorithm.
    **
    ** First we attempt to find the largest existing rowid and add one
    ** to that.  But if the largest existing rowid is already the maximum
    ** positive integer, we have to fall through to the second
    ** probabilistic algorithm
    **
    ** The second algorithm is to select a rowid at random and see if
    ** it already exists in the table.  If it does not exist, we have
    ** succeeded.  If the random rowid does exist, we select a new one
    ** and try again, up to 100 times.


















    */
    assert( pC->isTable );
    cnt = 0;








#ifdef SQLITE_32BIT_ROWID
#   define MAX_ROWID 0x7fffffff
#else
    /* Some compilers complain about constants of the form 0x7fffffffffffffff.
    ** Others complain about 0x7ffffffffffffffffLL.  The following macro seems
    ** to provide the constant while making all compilers happy.
................................................................................
        if( rc!=SQLITE_OK ){
          goto abort_due_to_error;
        }
        if( res ){
          v = 1;
        }else{
          sqlite3BtreeKeySize(pC->pCursor, &v);

          if( v==MAX_ROWID ){
            pC->useRandomRowid = 1;
          }else{
            v++;
          }
        }
      }
................................................................................
        pMem->u.i = v;
      }
#endif

      sqlite3BtreeSetCachedRowid(pC->pCursor, v<MAX_ROWID ? v+1 : 0);
    }
    if( pC->useRandomRowid ){
      assert( pOp->p3==0 );  /* We cannot be in random rowid mode if this is
                             ** an AUTOINCREMENT table. */
      v = db->priorNewRowid;
      cnt = 0;
      do{
        if( cnt==0 && (v&0xffffff)==v ){
          v++;
        }else{
          sqlite3_randomness(sizeof(v), &v);
          if( cnt<5 ) v &= 0xffffff;
        }


        rc = sqlite3BtreeMovetoUnpacked(pC->pCursor, 0, (u64)v, 0, &res);
        cnt++;
      }while( cnt<100 && rc==SQLITE_OK && res==0 );
      db->priorNewRowid = v;
      if( rc==SQLITE_OK && res==0 ){
        rc = SQLITE_FULL;
        goto abort_due_to_error;
      }
    }
    pC->rowidIsValid = 0;
    pC->deferredMoveto = 0;
    pC->cacheStatus = CACHE_STALE;
................................................................................
  assert( pC!=0 );
  assert( pC->pCursor!=0 || pC->pseudoTable );
  assert( pKey->flags & MEM_Int );
  assert( pC->isTable );
  REGISTER_TRACE(pOp->p2, pData);
  REGISTER_TRACE(pOp->p3, pKey);

  iKey = pKey->u.i;
  if( pOp->p5 & OPFLAG_NCHANGE ) p->nChange++;
  if( pOp->p5 & OPFLAG_LASTROWID ) db->lastRowid = pKey->u.i;
  if( pData->flags & MEM_Null ){
    pData->z = 0;
    pData->n = 0;
  }else{
    assert( pData->flags & (MEM_Blob|MEM_Str) );
................................................................................
  assert( pC!=0 );
  if( pC->nullRow ){
    /* Do nothing so that reg[P2] remains NULL */
    break;
  }else if( pC->deferredMoveto ){
    v = pC->movetoTarget;
  }else if( pC->pseudoTable ){
    v = pC->iKey;
#ifndef SQLITE_OMIT_VIRTUALTABLE
  }else if( pC->pVtabCursor ){
    pVtab = pC->pVtabCursor->pVtab;
    pModule = pVtab->pModule;
    assert( pModule->xRowid );
    if( sqlite3SafetyOff(db) ) goto abort_due_to_misuse;
    rc = pModule->xRowid(pC->pVtabCursor, &v);
................................................................................
    rc = sqlite3VdbeCursorMoveto(pC);
    if( rc ) goto abort_due_to_error;
    if( pC->rowidIsValid ){
      v = pC->lastRowid;
    }else{
      assert( pC->pCursor!=0 );
      sqlite3BtreeKeySize(pC->pCursor, &v);

    }
  }
  pOut->u.i = v;
  MemSetTypeFlag(pOut, MEM_Int);
  break;
}

*************************************************************************
** 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 1.172 2009/06/19 14:06:03 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.
*/
#define keyToInt(X)   (X)
#define intToKey(X)   (X)


/*
** SQL is translated into a sequence of instructions to be
** executed by a virtual machine.  Each instruction is an instance
** of the following structure.
*/
typedef struct VdbeOp Op;

*************************************************************************
** 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 1.173 2009/06/22 00:55:31 drh Exp $
*/
#ifndef _VDBEINT_H_
#define _VDBEINT_H_









/*
** SQL is translated into a sequence of instructions to be
** executed by a virtual machine.  Each instruction is an instance
** of the following structure.
*/
typedef struct VdbeOp Op;

**
*************************************************************************
** 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 1.461 2009/06/19 00:33:32 drh Exp $
*/
#include "sqliteInt.h"
#include "vdbeInt.h"



/*
................................................................................
    int res, rc;
#ifdef SQLITE_TEST
    extern int sqlite3_search_count;
#endif
    assert( p->isTable );
    rc = sqlite3BtreeMovetoUnpacked(p->pCursor, 0, p->movetoTarget, 0, &res);
    if( rc ) return rc;
    p->lastRowid = keyToInt(p->movetoTarget);
    p->rowidIsValid = ALWAYS(res==0) ?1:0;
    if( NEVER(res<0) ){
      rc = sqlite3BtreeNext(p->pCursor, &res);
      if( rc ) return rc;
    }
#ifdef SQLITE_TEST
    sqlite3_search_count++;

**
*************************************************************************
** 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 1.462 2009/06/22 00:55:31 drh Exp $
*/
#include "sqliteInt.h"
#include "vdbeInt.h"



/*
................................................................................
    int res, rc;
#ifdef SQLITE_TEST
    extern int sqlite3_search_count;
#endif
    assert( p->isTable );
    rc = sqlite3BtreeMovetoUnpacked(p->pCursor, 0, p->movetoTarget, 0, &res);
    if( rc ) return rc;
    p->lastRowid = p->movetoTarget;
    p->rowidIsValid = ALWAYS(res==0) ?1:0;
    if( NEVER(res<0) ){
      rc = sqlite3BtreeNext(p->pCursor, &res);
      if( rc ) return rc;
    }
#ifdef SQLITE_TEST
    sqlite3_search_count++;