view PostgreSQL/Plugins/PostgreSQLStorageArea.cpp @ 134:cc3dc759c989

Added an advisory lock to avoid race conditions during database setup
author Sebastien Jodogne <s.jodogne@gmail.com>
date Wed, 08 May 2019 20:21:13 +0200
parents 714c5d2bee76
children 3266785d5627
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/**
 * Orthanc - A Lightweight, RESTful DICOM Store
 * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
 * Department, University Hospital of Liege, Belgium
 * Copyright (C) 2017-2019 Osimis S.A., Belgium
 *
 * This program is free software: you can redistribute it and/or
 * modify it under the terms of the GNU Affero General Public License
 * as published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * This program 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
 * Affero General Public License for more details.
 * 
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 **/


#include "PostgreSQLStorageArea.h"

#include "../../Framework/PostgreSQL/PostgreSQLTransaction.h"

#include <Plugins/Samples/Common/OrthancPluginCppWrapper.h>
#include <Core/Logging.h>


namespace OrthancDatabases
{
  IDatabase* PostgreSQLStorageArea::OpenInternal()
  {
    std::auto_ptr<PostgreSQLDatabase> db(new PostgreSQLDatabase(parameters_));

    db->Open();

    if (parameters_.HasLock())
    {
      db->AdvisoryLock(43 /* some arbitrary constant */);
    }

    /**
     * Try and acquire a transient advisory lock to protect the setup
     * of the database, because concurrent statements like "CREATE
     * TABLE" are not protected by transactions.
     * https://groups.google.com/d/msg/orthanc-users/yV3LSTh_TjI/h3PRApJFBAAJ
     **/
    PostgreSQLDatabase::TransientAdvisoryLock lock(*db, 44 /* some arbitrary constant */);

    if (clearAll_)
    {
      db->ClearAll();
    }

    {
      PostgreSQLTransaction t(*db);

      if (!db->DoesTableExist("StorageArea"))
      {
        db->Execute("CREATE TABLE IF NOT EXISTS StorageArea("
                    "uuid VARCHAR NOT NULL PRIMARY KEY,"
                    "content OID NOT NULL,"
                    "type INTEGER NOT NULL)");

        // Automatically remove the large objects associated with the table
        db->Execute("CREATE OR REPLACE RULE StorageAreaDelete AS ON DELETE "
                    "TO StorageArea DO SELECT lo_unlink(old.content);");
      }

      t.Commit();
    }

    return db.release();
  }


  PostgreSQLStorageArea::PostgreSQLStorageArea(const PostgreSQLParameters& parameters) :
    StorageBackend(new Factory(*this)),
    parameters_(parameters),
    clearAll_(false)
  {
  }
}