Unique.cc

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/*
 * Copyright (C) 2007-2015 Hypertable, Inc.
 *
 * This file is part of Hypertable.
 *
 * Hypertable is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 3
 * of the License, or any later version.
 *
 * Hypertable is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#include <Common/Compat.h>

#include "Unique.h"

#include <Hypertable/Lib/Schema.h>
#include <Hypertable/Lib/TableMutator.h>
#include <Hypertable/Lib/TableScanner.h>

namespace Hypertable { namespace HyperAppHelper {

void 
create_cell_unique(const TablePtr &table, const KeySpec &key,
                String &guid)
{
  ColumnFamilySpec *cf_spec;

  // check the schema - if TIME_ORDER is not descending then this function
  // will not work
  cf_spec=table->schema()->get_column_family(key.column_family);
  if (!cf_spec)
    HT_THROW(Error::FAILED_EXPECTATION, 
            "Unknown column family");
  if (!cf_spec->get_option_time_order_desc())
    HT_THROW(Error::BAD_SCAN_SPEC, 
            "Column family is not chronological (use TIME_ORDER DESC)");

  // if the cell has no value: assign a new guid
  if (guid.empty())
    guid=generate_guid();

  // now insert the cell with a regular mutator
  {
    TableMutatorPtr mutator( table->create_mutator() );
    mutator->set(key, guid);
    mutator->flush();
  }

  // and check if it was really inserted or if another client was faster
  {
    ScanSpecBuilder ssb;
    ssb.add_row((const char *)key.row);
    ssb.add_column(key.column_family);
    ssb.set_cell_limit(1);
    TableScannerPtr scanner( table->create_scanner(ssb.get()) );
    Cell c;
    if (!scanner->next(c)) {
      HT_THROW(Error::FAILED_EXPECTATION, 
               "Inserted GUID was not found");
    }
    if (c.value_len!=guid.size() || memcmp(c.value, guid.c_str(), c.value_len)) {
      HT_THROW(Error::ALREADY_EXISTS, 
               "The inserted cell already exists and is not unique");
    }
  }
}

}} // namespace HyperAppHelper, HyperTable