SQLite

  if( *pRc==SQLITE_OK ){
    SessionBuffer buf2 = {0, 0, 0};
    int bNoop = 1;
    int i;
    u8 *pCsr = p->aRecord;
    sessionAppendByte(pBuf, SQLITE_UPDATE, pRc);
    for(i=0; i<sqlite3_column_count(pStmt); i++){
      int bChanged = 0;
      int nAdvance;
      int eType = *pCsr;
      switch( eType ){
        case SQLITE_NULL:
          nAdvance = 1;
          if( sqlite3_column_type(pStmt, i)!=SQLITE_NULL ){
            bChanged = 1;
          }
          break;

        case SQLITE_FLOAT:
        case SQLITE_INTEGER: {
          nAdvance = 9;
          if( eType==sqlite3_column_type(pStmt, i) ){
            sqlite3_int64 iVal = sessionGetI64(&pCsr[1]);
            if( eType==SQLITE_INTEGER ){
              if( iVal==sqlite3_column_int64(pStmt, i) ) break;
            }else{
              double dVal;
              memcpy(&dVal, &iVal, 8);
              if( dVal==sqlite3_column_double(pStmt, i) ) break;
            }
          }
          bChanged = 1;
          break;
        }

        case SQLITE_TEXT:
        case SQLITE_BLOB: {
          int nByte;
          int nHdr = 1 + sessionVarintGet(&pCsr[1], &nByte);
          nAdvance = nHdr + nByte;
          if( eType==sqlite3_column_type(pStmt, i) 
           && nByte==sqlite3_column_bytes(pStmt, i) 
           && 0==memcmp(&pCsr[nHdr], sqlite3_column_blob(pStmt, i), nByte)
          ){
            break;
          }
          bChanged = 1;
        }
      }



      if( bChanged || abPK[i] ){

        sessionAppendBlob(pBuf, pCsr, nAdvance, pRc);

      }else{
        sessionAppendByte(pBuf, 0, pRc);
      }

      if( bChanged ){
        sessionAppendCol(&buf2, pStmt, i, pRc);
        bNoop = 0;
      }else{
        sessionAppendByte(&buf2, 0, pRc);
      }

      pCsr += nAdvance;
    }

    if( bNoop ){
      pBuf->nBuf -= (1 + sqlite3_column_count(pStmt));
    }else{
      sessionAppendBlob(pBuf, buf2.aBuf, buf2.nBuf, pRc);

    if( rc==SQLITE_OK ){
      rc = sqlite3_prepare_v2(db, (char *)buf.aBuf, buf.nBuf, ppStmt, 0);
    }
    sqlite3_free(buf.aBuf);
  }
  return rc;
}

static int sessionConstraintConflict(
  sqlite3 *db,                    /* Database handle */
  sqlite3_changeset_iter *pIter,  /* Changeset iterator */
  u8 *abPK,                       /* Primary key flags array */
  sqlite3_stmt *pSelect,          /* SELECT statement from sessionSelectRow() */
  int(*xConflict)(void *, int, sqlite3_changeset_iter*),
  void *pCtx
){
  int res;
  int rc;
  int i;
  int nCol;
  int op;
  const char *zDummy;

  sqlite3changeset_op(pIter, &zDummy, &nCol, &op);
  assert( op==SQLITE_UPDATE || op==SQLITE_INSERT );

  /* Bind the new.* PRIMARY KEY values to the SELECT statement. */
  for(i=0; i<nCol; i++){
    if( abPK[i] ){
      sqlite3_value *pVal;
      if( op==SQLITE_UPDATE ) rc = sqlite3changeset_old(pIter, i, &pVal);
      else                    rc = sqlite3changeset_new(pIter, i, &pVal);
      if( rc!=SQLITE_OK ) return rc;
      sqlite3_bind_value(pSelect, i+1, pVal);
    }
  }

  if( SQLITE_ROW==sqlite3_step(pSelect) ){
    /* There exists another row with the new.* primary key. */
    pIter->pConflict = pSelect;
    res = xConflict(pCtx, SQLITE_CHANGESET_CONFLICT, pIter);
    pIter->pConflict = 0;
    sqlite3_reset(pSelect);
  }else{
    /* No other row with the new.* primary key. */
    rc = sqlite3_reset(pSelect);
    if( rc==SQLITE_OK ){
      res = xConflict(pCtx, SQLITE_CHANGESET_CONSTRAINT, pIter);
    }
  }

  return rc;
}

int sqlite3changeset_apply(
  sqlite3 *db,
  int nChangeset,
  void *pChangeset,
  int(*xConflict)(
    void *pCtx,                   /* Copy of fifth arg to _apply() */

  sqlite3_stmt *pDelete = 0;      /* DELETE statement */
  sqlite3_stmt *pUpdate = 0;      /* DELETE statement */
  sqlite3_stmt *pInsert = 0;      /* INSERT statement */
  sqlite3_stmt *pSelect = 0;      /* SELECT statement */

  rc = sqlite3_exec(db, "SAVEPOINT changeset_apply", 0, 0, 0);
  if( rc!=SQLITE_OK ) return rc;

  sqlite3changeset_start(&pIter, nChangeset, pChangeset);
  while( SQLITE_ROW==sqlite3changeset_next(pIter) ){
    int op;
    const char *zThis;
    sqlite3changeset_op(pIter, &zThis, &nCol, &op);
    if( zTab==0 || sqlite3_strnicmp(zThis, zTab, nTab+1) ){
      sqlite3_free(azCol);
      rc = sessionTableInfo(db, zThis, nCol, &zTab, &azCol, &abPK);
      nTab = strlen(zTab);

      sqlite3_finalize(pDelete);
      sqlite3_finalize(pUpdate);
      sqlite3_finalize(pInsert);
      sqlite3_finalize(pSelect);
      pSelect = pUpdate = pInsert = pDelete = 0;

      if( (rc = sessionSelectRow(db, zTab, nCol, azCol, abPK, &pSelect))
       || (rc = sessionUpdateRow(db, zTab, nCol, azCol, abPK, &pUpdate))
       || (rc = sessionDeleteRow(db, zTab, nCol, azCol, abPK, &pDelete))
      ){
        break;
      }
    }

    if( op==SQLITE_DELETE ){
      int res;
      int i;
      rc = sessionDeleteRow(db, zTab, nCol, azCol, abPK, &pDelete);
      for(i=0; rc==SQLITE_OK && i<nCol; i++){

        rc = sqlite3changeset_old(pIter, i, &pOld);
        if( rc==SQLITE_OK ){
          rc = sqlite3changeset_new(pIter, i, &pNew);
        }
        if( rc==SQLITE_OK ){
          if( pOld ) sqlite3_bind_value(pUpdate, i*3+1, pOld);
          sqlite3_bind_int(pUpdate, i*3+2, !!pNew);
          if( pNew ) sqlite3_bind_value(pUpdate, i*3+3, pNew);
        }
      }
      if( rc==SQLITE_OK ) rc = sqlite3_bind_int(pUpdate, nCol*3+1, 0);
      if( rc!=SQLITE_OK ) break;

      sqlite3_step(pUpdate);
      rc = sqlite3_reset(pUpdate);

        }else{
          rc = sqlite3_reset(pSelect);
          if( rc==SQLITE_OK ){
            res = xConflict(pCtx, SQLITE_CHANGESET_NOTFOUND, pIter);
          }
        }
      }else if( rc==SQLITE_CONSTRAINT ){
        /* This may be a CONSTRAINT or CONFLICT error. It is a CONFLICT if
        ** the only problem is a duplicate PRIMARY KEY, or a CONSTRAINT 
        ** otherwise. */
        int bPKChange = 0;

        /* Check if the PK has been modified. */
        rc = SQLITE_OK;
        for(i=0; i<nCol && rc==SQLITE_OK; i++){
          if( abPK[i] ){
            sqlite3_value *pNew;
            rc = sqlite3changeset_new(pIter, i, &pNew);
            if( rc==SQLITE_OK && pNew ){
              bPKChange = 1;
              break;
            }
          }
        }

        if( bPKChange ){
          /* See if there exists a row with a duplicate primary key. */
          rc = sessionConstraintConflict(
              db, pIter, abPK, pSelect, xConflict, pCtx
          );
        }else{
          res = xConflict(pCtx, SQLITE_CHANGESET_CONSTRAINT, pIter);
        }
      }

    }else{
      int i;
      assert( op==SQLITE_INSERT );
      if( pInsert==0 ){
        SessionBuffer buf = {0, 0, 0};

        }
      }
      if( rc!=SQLITE_OK ) break;

      sqlite3_step(pInsert);
      rc = sqlite3_reset(pInsert);
      if( rc==SQLITE_CONSTRAINT && xConflict ){

        rc = sessionConstraintConflict(













              db, pIter, abPK, pSelect, xConflict, pCtx
        );






      }
    }
  }
  rc2 = sqlite3changeset_finalize(pIter);
  if( rc==SQLITE_DONE ) rc = rc2;

  if( rc==SQLITE_OK ){

# Test UPDATE changesets.
#
do_execsql_test 3.3.1 {
  CREATE TABLE t4(a, b, c, PRIMARY KEY(b, c));
  INSERT INTO t4 VALUES(1, 2, 3);
  INSERT INTO t4 VALUES(4, 5, 6);
  INSERT INTO t4 VALUES(7, 8, 9);
  INSERT INTO t4 VALUES(10, 11, 12);
}
do_db2_test 3.3.2 {
  CREATE TABLE t4(a NOT NULL, b, c, PRIMARY KEY(b, c));
  INSERT INTO t4 VALUES(0, 2, 3);
  INSERT INTO t4 VALUES(4, 5, 7);
  INSERT INTO t4 VALUES(7, 8, 9);
  INSERT INTO t4 VALUES(10, 11, 12);
}

do_conflict_test 3.3.3 -tables t4 -sql {
  UPDATE t4 SET a = -1 WHERE b = 2;
  UPDATE t4 SET a = -1 WHERE b = 5;
  UPDATE t4 SET a = NULL WHERE c = 9;
  UPDATE t4 SET a = 'x' WHERE b = 11;
} -conflicts {
  {UPDATE t4 DATA {i 1 i 2 i 3} {i -1 {} {} {} {}} {i 0 i 2 i 3}}
  {UPDATE t4 NOTFOUND {i 4 i 5 i 6} {i -1 {} {} {} {}}}
  {UPDATE t4 CONSTRAINT {i 7 i 8 i 9} {n {} {} {} {} {}}}
}

do_db2_test     3.3.4 { SELECT * FROM t4 } {0 2 3 4 5 7 7 8 9 x 11 12}
do_execsql_test 3.3.5 { SELECT * FROM t4 } {-1 2 3 -1 5 6 {} 8 9 x 11 12}



catch { db2 close }
finish_test