SQLite

        lappend rebase [sqlite3changeset_apply_v2 db $c xConflict]
      }
    }
    #if {$tn=="2.1.4"} { puts [changeset_to_list $rebase] ; breakpoint }
    #puts [changeset_to_list [lindex $rebase 0]] ; breakpoint
    #puts [llength $rebase]
  

    sqlite3rebaser_create R
    foreach r $rebase {

      R configure $r
    }
    set c1r [R rebase $c1]
    R delete
    #if {$tn=="2.1.4"} { puts [changeset_to_list $c1r] }
  
    sqlite3changeset_apply_v2 db2 $c1r xConflictAbort

** The buffer that the argument points to contains a serialized SQL value.
** Return the number of bytes of space occupied by the value (including
** the type byte).
*/
static int sessionSerialLen(u8 *a){
  int e = *a;
  int n;
  if( e==0 || e==0xFF ) return 1;
  if( e==SQLITE_NULL ) return 1;
  if( e==SQLITE_INTEGER || e==SQLITE_FLOAT ) return 9;
  return sessionVarintGet(&a[1], &n) + 1 + n;
}

/*
** Based on the primary key values stored in change aRecord, calculate a

  int op2,                        /* Second change operation */
  int bIndirect,                  /* True if second change is indirect */
  u8 *aRec,                       /* Second change record */
  int nRec,                       /* Number of bytes in aRec */
  SessionChange **ppNew           /* OUT: Merged change */
){
  SessionChange *pNew = 0;
  int rc = SQLITE_OK;

  if( !pExist ){
    pNew = (SessionChange *)sqlite3_malloc(sizeof(SessionChange) + nRec);
    if( !pNew ){
      return SQLITE_NOMEM;
    }
    memset(pNew, 0, sizeof(SessionChange));
    pNew->op = op2;
    pNew->bIndirect = bIndirect;

    pNew->aRecord = (u8*)&pNew[1];
    if( bIndirect==0 || bRebase==0 ){
      pNew->nRecord = nRec;
      memcpy(pNew->aRecord, aRec, nRec);
    }else{
      int i;
      u8 *pIn = aRec;
      u8 *pOut = pNew->aRecord;
      for(i=0; i<pTab->nCol; i++){
        int nIn = sessionSerialLen(pIn);
        if( *pIn==0 ){
          *pOut++ = 0;
        }else if( pTab->abPK[i]==0 ){
          *pOut++ = 0xFF;
        }else{
          memcpy(pOut, pIn, nIn);
          pOut += nIn;
        }
        pIn += nIn;
      }
      pNew->nRecord = pOut - pNew->aRecord;
    }
  }else if( bRebase ){
    if( pExist->op==SQLITE_DELETE && pExist->bIndirect ){
      *ppNew = pExist;
    }else{
      int nByte = nRec + pExist->nRecord + sizeof(SessionChange);
      pNew = (SessionChange*)sqlite3_malloc(nByte);
      if( pNew==0 ){
        rc = SQLITE_NOMEM;
      }else{
        int i;
        u8 *a1 = pExist->aRecord;
        u8 *a2 = aRec;
        u8 *pOut;

        memset(pNew, 0, nByte);
        pNew->bIndirect = bIndirect || pExist->bIndirect;
        pNew->op = op2;
        pOut = pNew->aRecord = (u8*)&pNew[1];


        for(i=0; i<pTab->nCol; i++){
          int n1 = sessionSerialLen(a1);
          int n2 = sessionSerialLen(a2);
          if( *a1==0xFF || *a2==0xFF ){
            *pOut++ = 0xFF;
          }else if( *a2==0 ){
            memcpy(pOut, a1, n1);
            pOut += n1;
          }else{
            memcpy(pOut, a2, n2);
            pOut += n2;
          }
          a1 += n1;
          a2 += n2;
        }
        pNew->nRecord = pOut - pNew->aRecord;
      }
      sqlite3_free(pExist);
    }
  }else{
    int op1 = pExist->op;

    /* 
    **   op1=INSERT, op2=INSERT      ->      Unsupported. Discard op2.
    **   op1=INSERT, op2=UPDATE      ->      INSERT.
    **   op1=INSERT, op2=DELETE      ->      (none)

        pNew->nRecord = (int)(aCsr - pNew->aRecord);
      }
      sqlite3_free(pExist);
    }
  }

  *ppNew = pNew;
  return rc;
}

/*
** Add all changes in the changeset traversed by the iterator passed as
** the first argument to the changegroup hash tables.
*/
static int sessionChangesetToHash(

          memcpy(pOut, a2, nn2);
          pOut += nn2;
        }else{
          memcpy(pOut, a1, nn1);
          pOut += nn1;
        }
      }else{
        if( *a1==0 || *a1==0xFF ){
          memcpy(pOut, a2, nn2);
          pOut += nn2;
        }else{
          memcpy(pOut, a1, nn1);
          pOut += nn1;
        }
      }
      a1 += nn1;
      a2 += nn2;
    }

    pBuf->nBuf = pOut-pBuf->aBuf;
    assert( pBuf->nBuf<=pBuf->nAlloc );
  }
}

static void sessionAppendPartialUpdate(
  SessionBuffer *pBuf,            /* Append record here */
  sqlite3_changeset_iter *pIter,  /* Iterator pointed at local change */
  u8 *aRec, int nRec,             /* Local change */
  u8 *aChange, int nChange,       /* Record to rebase against */
  int *pRc                        /* IN/OUT: Return Code */
){
  sessionBufferGrow(pBuf, 2+nRec+nChange, pRc);
  if( *pRc==SQLITE_OK ){
    int bData = 0;
    u8 *pOut = &pBuf->aBuf[pBuf->nBuf];
    int i;
    u8 *a1 = aRec;
    u8 *a2 = aChange;

    *pOut++ = SQLITE_UPDATE;
    *pOut++ = pIter->bIndirect;
    for(i=0; i<pIter->nCol; i++){
      int n1 = sessionSerialLen(a1);
      int n2 = sessionSerialLen(a2);
      if( pIter->abPK[i] || a2[0]==0 ){
        if( !pIter->abPK[i] ) bData = 1;
        memcpy(pOut, a1, n1);
        pOut += n1;
      }else if( a2[0]!=0xFF ){
        bData = 1;
        memcpy(pOut, a2, n2);
        pOut += n2;
      }else{
        *pOut++ = '\0';
      }
      a1 += n1;
      a2 += n2;
    }
    if( bData ){
      a2 = aChange;
      for(i=0; i<pIter->nCol; i++){
        int n1 = sessionSerialLen(a1);
        int n2 = sessionSerialLen(a2);
        if( pIter->abPK[i] || a2[0]!=0xFF ){
          memcpy(pOut, a1, n1);
          pOut += n1;
        }else{
          *pOut++ = '\0';
        }
        a1 += n1;
        a2 += n2;
      }
      pBuf->nBuf = (pOut - pBuf->aBuf);
    }
  }
}


static int sessionRebase(
  sqlite3_rebaser *p,             /* Rebaser hash table */
  sqlite3_changeset_iter *pIter,  /* Input data */
  int (*xOutput)(void *pOut, const void *pData, int nData),
  void *pOut,                     /* Context for xOutput callback */
  int *pnOut,                     /* OUT: Number of bytes in output changeset */

              sessionAppendByte(&sOut, pIter->bIndirect, &rc);
              sessionAppendRecordMerge(&sOut, pIter->nCol, 1,
                  pCsr, nRec-(pCsr-aRec), 
                  pChange->aRecord, pChange->nRecord, &rc
              );
            }
          }else{










            sessionAppendPartialUpdate(&sOut, pIter,
                aRec, nRec, pChange->aRecord, pChange->nRecord, &rc
            );

          }
          break;

        default:
          assert( pIter->op==SQLITE_DELETE );
          bDone = 1;
          if( pChange->op==SQLITE_INSERT ){

**   changeset. Or, if the conflict resolution was REPLACE, add
**   nothing to the rebased changeset.
**
** <dt>Local DELETE<dd>
**   This may conflict with a remote UPDATE or DELETE. In both cases the
**   only possible resolution is OMIT. If the remote operation was a
**   DELETE, then add no change to the rebased changeset. If the remote
**   operation was an UPDATE, then the old.* fields of change are updated
**   to reflect the new.* values in the UPDATE.
**
** <dt>Local UPDATE<dd>
**   This may conflict with a remote UPDATE or DELETE. If it conflicts
**   with a DELETE, and the conflict resolution was OMIT, then the update
**   is changed into an INSERT. Any undefined values in the new.* record
**   from the update change are filled in using the old.* values from
**   the conflicting DELETE. Or, if the conflict resolution was REPLACE,
**   the UPDATE change is simply omitted from the rebased changeset.
**
**   If conflict is with a remote UPDATE and the resolution is OMIT, then
**   the old.* values are rebased using the new.* values in the remote
**   change. Or, if the resolution is REPLACE, then the change is copied
**   into the rebased changeset with updates to columns also updated by
**   the conflicting remote UPDATE removed. If this means no columns would 
**   be updated, the change is omitted.
** </dl>
**
** A local change may be rebased against multiple remote changes 
** simultaneously. If a single key is modified by multiple remote 
** changesets, they are combined as follows before the local changeset
** is rebased:
**
** <ul>
**    <li> If there has been one or more REPLACE resolutions on a
**         key, it is rebased according to a REPLACE.
**
**    <li> If there have been no REPLACE resolutions on a key, then
**         the local changeset is rebased according to the most recent
**         of the OMIT resolutions.
** </ul>
**
** Note that conflict resolutions from multiple remote changesets are 
** combined on a per-field basis, not per-row. This means that in the 
** case of multiple remote UPDATE operations, some fields of a single 
** local change may be rebased for REPLACE while others are rebased for 
** OMIT.
*/
typedef struct sqlite3_rebaser sqlite3_rebaser;

/* Create a new rebaser object */
int sqlite3rebaser_create(sqlite3_rebaser **ppNew);

/* Call this one or more times to configure a rebaser */