CTK/Libs/DICOM/Core/ctkDICOMDatabase.cpp

/*=========================================================================

  Library:   CTK

  Copyright (c) Kitware Inc.

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0.txt

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.

=========================================================================*/

#include <stdexcept>

// Qt includes
#include <QDate>
#include <QDebug>
#include <QDirIterator>
#include <QFile>
#include <QFileInfo>
#include <QFileSystemWatcher>
#include <QMutexLocker>
#include <QSet>
#include <QSqlError>
#include <QSqlQuery>
#include <QSqlRecord>
#include <QStringList>
#include <QVariant>

// ctkDICOM includes
#include "ctkDICOMDatabase.h"
#include "ctkDICOMAbstractThumbnailGenerator.h"
#include "ctkDICOMDataset.h"

#include "ctkLogger.h"

// DCMTK includes
#include <dcmtk/dcmdata/dcfilefo.h>
#include <dcmtk/dcmdata/dcfilefo.h>
#include <dcmtk/dcmdata/dcdeftag.h>
#include <dcmtk/dcmdata/dcdatset.h>
#include <dcmtk/ofstd/ofcond.h>
#include <dcmtk/ofstd/ofstring.h>
#include <dcmtk/ofstd/ofstd.h>        /* for class OFStandard */
#include <dcmtk/dcmdata/dcddirif.h>   /* for class DicomDirInterface */
#include <dcmimage.h>

#include <dcmtk/dcmjpeg/djdecode.h>  /* for dcmjpeg decoders */
#include <dcmtk/dcmjpeg/djencode.h>  /* for dcmjpeg encoders */
#include <dcmtk/dcmdata/dcrledrg.h>  /* for DcmRLEDecoderRegistration */
#include <dcmtk/dcmdata/dcrleerg.h>  /* for DcmRLEEncoderRegistration */

//------------------------------------------------------------------------------
static ctkLogger logger("org.commontk.dicom.DICOMDatabase" );
//------------------------------------------------------------------------------

// Flag for tag cache to avoid repeated serarches for
// tags that do no exist.
static QString TagNotInInstance("__TAG_NOT_IN_INSTANCE__");

//------------------------------------------------------------------------------
class ctkDICOMDatabasePrivate
{
  Q_DECLARE_PUBLIC(ctkDICOMDatabase);
protected:
  ctkDICOMDatabase* const q_ptr;

public:
  ctkDICOMDatabasePrivate(ctkDICOMDatabase&);
  ~ctkDICOMDatabasePrivate();
  void init(QString databaseFile);
  void registerCompressionLibraries();
  bool executeScript(const QString script);
  ///
  /// \brief runs a query and prints debug output of status
  ///
  bool loggedExec(QSqlQuery& query);
  bool loggedExec(QSqlQuery& query, const QString& queryString);
  bool LoggedExecVerbose;

  ///
  /// \brief group several inserts into a single transaction
  ///
  void beginTransaction();
  void endTransaction();

  // dataset must be set always
  // filePath has to be set if this is an import of an actual file
  void insert ( const ctkDICOMDataset& ctkDataset, const QString& filePath, bool storeFile = true, bool generateThumbnail = true);

  ///
  /// copy the complete list of files to an extra table
  ///
  void createBackupFileList();

  ///
  /// remove the extra table containing the backup
  ///
  void removeBackupFileList();


  ///
  /// get all Filename values from table
  QStringList filenames(QString table);

  /// Name of the database file (i.e. for SQLITE the sqlite file)
  QString      DatabaseFileName;
  QString      LastError;
  QSqlDatabase Database;
  QMap<QString, QString> LoadedHeader;

  ctkDICOMAbstractThumbnailGenerator* thumbnailGenerator;

  /// these are for optimizing the import of image sequences
  /// since most information are identical for all slices
  QString LastPatientID;
  QString LastPatientsName;
  QString LastPatientsBirthDate;
  QString LastStudyInstanceUID;
  QString LastSeriesInstanceUID;
  int LastPatientUID;

  /// resets the variables to new inserts won't be fooled by leftover values
  void resetLastInsertedValues();

  /// parallel accesses are not allowed
  /// - http://qt-project.org/doc/qt-4.8/threads-modules.html#threads-and-the-sql-module
  QMutex databaseAccessMutex;

  /// tagCache table has been checked to exist
  bool TagCacheVerified;
  /// tag cache has independent database to avoid locking issue
  /// with other access to the database which need to be
  /// reading while the tag cache is writing
  QSqlDatabase TagCacheDatabase;
  QString TagCacheDatabaseFilename;
  QStringList TagsToPrecache;
  void precacheTags( const QString sopInstanceUID );

  int insertPatient(const ctkDICOMDataset& ctkDataset);
  void insertStudy(const ctkDICOMDataset& ctkDataset, int dbPatientID);
  void insertSeries( const ctkDICOMDataset& ctkDataset, QString studyInstanceUID);
};

//------------------------------------------------------------------------------
// ctkDICOMDatabasePrivate methods

//------------------------------------------------------------------------------
ctkDICOMDatabasePrivate::ctkDICOMDatabasePrivate(ctkDICOMDatabase& o): q_ptr(&o)
{
  this->thumbnailGenerator = NULL;
  this->LoggedExecVerbose = false;
  this->TagCacheVerified = false;
  this->resetLastInsertedValues();
}

//------------------------------------------------------------------------------
void ctkDICOMDatabasePrivate::resetLastInsertedValues()
{
  this->LastPatientID = QString("");
  this->LastPatientsName = QString("");
  this->LastPatientsBirthDate = QString("");
  this->LastStudyInstanceUID = QString("");
  this->LastSeriesInstanceUID = QString("");
  this->LastPatientUID = -1;
}

//------------------------------------------------------------------------------
void ctkDICOMDatabasePrivate::init(QString databaseFilename)
{
  Q_Q(ctkDICOMDatabase);

  q->openDatabase(databaseFilename);

}

//------------------------------------------------------------------------------
void ctkDICOMDatabasePrivate::registerCompressionLibraries(){
  logger.debug("Register compression libraries");
  // Register the JPEG libraries in case we need them
  //   (registration only happens once, so it's okay to call repeatedly)
  // register global JPEG decompression codecs
  DJDecoderRegistration::registerCodecs();
  // register global JPEG compression codecs
  DJEncoderRegistration::registerCodecs();
  // register RLE compression codec
  DcmRLEEncoderRegistration::registerCodecs();
  // register RLE decompression codec
  DcmRLEDecoderRegistration::registerCodecs();
}

//------------------------------------------------------------------------------
ctkDICOMDatabasePrivate::~ctkDICOMDatabasePrivate()
{
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabasePrivate::loggedExec(QSqlQuery& query)
{
  return (loggedExec(query, QString("")));
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabasePrivate::loggedExec(QSqlQuery& query, const QString& queryString)
{
  QMutexLocker lock(&(this->databaseAccessMutex));

  bool success;
  if (queryString.compare(""))
    {
      success = query.exec(queryString);
    }
  else
    {
      success = query.exec();
    }
  if (!success)
    {
      QSqlError sqlError = query.lastError();
      logger.debug( "SQL failed\n Bad SQL: " + query.lastQuery());
      logger.debug( "Error text: " + sqlError.text());
    }
  else
    {
      if (LoggedExecVerbose)
      {
      logger.debug( "SQL worked!\n SQL: " + query.lastQuery());
      }
    }
  return (success);
}

//------------------------------------------------------------------------------
void ctkDICOMDatabasePrivate::beginTransaction()
{
  Q_Q(ctkDICOMDatabase);
  QMutexLocker lock(&(this->databaseAccessMutex));

  QSqlQuery transaction( this->Database );
  transaction.prepare( "BEGIN TRANSACTION" );
  transaction.exec();
}

//------------------------------------------------------------------------------
void ctkDICOMDatabasePrivate::endTransaction()
{
  Q_Q(ctkDICOMDatabase);
  QMutexLocker lock(&(this->databaseAccessMutex));

  QSqlQuery transaction( this->Database );
  transaction.prepare( "END TRANSACTION" );
  transaction.exec();
}

//------------------------------------------------------------------------------
void ctkDICOMDatabasePrivate::createBackupFileList()
{
  QSqlQuery query(this->Database);
  loggedExec(query, "CREATE TABLE IF NOT EXISTS main.Filenames_backup (Filename TEXT PRIMARY KEY NOT NULL )" );
  loggedExec(query, "INSERT INTO Filenames_backup SELECT Filename FROM Images;" );
}

//------------------------------------------------------------------------------
void ctkDICOMDatabasePrivate::removeBackupFileList()
{
  QSqlQuery query(this->Database);
  loggedExec(query, "DROP TABLE main.Filenames_backup; " );
}



//------------------------------------------------------------------------------
void ctkDICOMDatabase::openDatabase(const QString databaseFile, const QString& connectionName )
{
  Q_D(ctkDICOMDatabase);
  d->DatabaseFileName = databaseFile;
  d->Database = QSqlDatabase::addDatabase("QSQLITE", connectionName);
  d->Database.setDatabaseName(databaseFile);
  if ( ! (d->Database.open()) )
    {
      d->LastError = d->Database.lastError().text();
      return;
    }
  if ( d->Database.tables().empty() )
    {
      if (!initializeDatabase())
        {
          d->LastError = QString("Unable to initialize DICOM database!");
          return;
        }
    }
  d->resetLastInsertedValues();

  if (!isInMemory())
    {
      QFileSystemWatcher* watcher = new QFileSystemWatcher(QStringList(databaseFile),this);
      connect(watcher, SIGNAL(fileChanged(QString)),this, SIGNAL (databaseChanged()) );
    }

  //Disable synchronous writing to make modifications faster
  {
  QMutexLocker lock(&(d->databaseAccessMutex));
  QSqlQuery pragmaSyncQuery(d->Database);
  pragmaSyncQuery.exec("PRAGMA synchronous = OFF");
  pragmaSyncQuery.finish();
  }

  // set up the tag cache for use later
  QFileInfo fileInfo(d->DatabaseFileName);
  d->TagCacheDatabaseFilename = QString( fileInfo.dir().path() + "/ctkDICOMTagCache.sql" );
  d->TagCacheVerified = false;
  if ( !this->tagCacheExists() )
    {
    this->initializeTagCache();
    }
}



//------------------------------------------------------------------------------
// ctkDICOMDatabase methods

//------------------------------------------------------------------------------
ctkDICOMDatabase::ctkDICOMDatabase(QString databaseFile)
  : d_ptr(new ctkDICOMDatabasePrivate(*this))
{
  Q_D(ctkDICOMDatabase);
  d->registerCompressionLibraries();
  d->init(databaseFile);
}

ctkDICOMDatabase::ctkDICOMDatabase(QObject* parent)
  : d_ptr(new ctkDICOMDatabasePrivate(*this))
{
  Q_UNUSED(parent);
  Q_D(ctkDICOMDatabase);
  d->registerCompressionLibraries();
}

//------------------------------------------------------------------------------
ctkDICOMDatabase::~ctkDICOMDatabase()
{
}

//----------------------------------------------------------------------------

//------------------------------------------------------------------------------
const QString ctkDICOMDatabase::lastError() const {
  Q_D(const ctkDICOMDatabase);
  return d->LastError;
}

//------------------------------------------------------------------------------
const QString ctkDICOMDatabase::databaseFilename() const {
  Q_D(const ctkDICOMDatabase);
  return d->DatabaseFileName;
}

//------------------------------------------------------------------------------
const QString ctkDICOMDatabase::databaseDirectory() const {
  QString databaseFile = databaseFilename();
  if (!QFileInfo(databaseFile).isAbsolute())
    {
      databaseFile.prepend(QDir::currentPath() + "/");
    }
  return QFileInfo ( databaseFile ).absoluteDir().path();
}

//------------------------------------------------------------------------------
const QSqlDatabase& ctkDICOMDatabase::database() const {
  Q_D(const ctkDICOMDatabase);
  return d->Database;
}

//------------------------------------------------------------------------------
void ctkDICOMDatabase::setThumbnailGenerator(ctkDICOMAbstractThumbnailGenerator *generator){
  Q_D(ctkDICOMDatabase);
  d->thumbnailGenerator = generator;
}

//------------------------------------------------------------------------------
ctkDICOMAbstractThumbnailGenerator* ctkDICOMDatabase::thumbnailGenerator(){
  Q_D(const ctkDICOMDatabase);
  return d->thumbnailGenerator;
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabasePrivate::executeScript(const QString script) {
  QMutexLocker lock(&(this->databaseAccessMutex));
  QFile scriptFile(script);
  scriptFile.open(QIODevice::ReadOnly);
  if  ( !scriptFile.isOpen() )
    {
      qDebug() << "Script file " << script << " could not be opened!\n";
      return false;
    }

  QString sqlCommands( QTextStream(&scriptFile).readAll() );
  sqlCommands.replace( '\n', ' ' );
  sqlCommands.remove( '\r' );
  sqlCommands.replace("; ", ";\n");

  QStringList sqlCommandsLines = sqlCommands.split('\n');

  QSqlQuery query(Database);

  for (QStringList::iterator it = sqlCommandsLines.begin(); it != sqlCommandsLines.end()-1; ++it)
    {
      if (! (*it).startsWith("--") )
        {
          qDebug() << *it << "\n";
          query.exec(*it);
          if (query.lastError().type())
            {
              qDebug() << "There was an error during execution of the statement: " << (*it);
              qDebug() << "Error message: " << query.lastError().text();
              return false;
            }
        }
    }
  return true;
}

//------------------------------------------------------------------------------
QStringList ctkDICOMDatabasePrivate::filenames(QString table)
{
  /// get all filenames from the database
  QSqlQuery allFilesQuery(this->Database);
  QStringList allFileNames;
  loggedExec(allFilesQuery,QString("SELECT Filename from %1 ;").arg(table) );

  while (allFilesQuery.next())
  {
    allFileNames << allFilesQuery.value(0).toString();
  }
  return allFileNames;
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::initializeDatabase(const char* sqlFileName)
{
  Q_D(ctkDICOMDatabase);

  d->resetLastInsertedValues();

  // remove any existing schema info - this handles the case where an
  // old schema should be loaded for testing.
  QSqlQuery dropSchemaInfo(d->Database);
  d->loggedExec( dropSchemaInfo, QString("DROP TABLE IF EXISTS 'SchemaInfo';") );
  return d->executeScript(sqlFileName);
}

//------------------------------------------------------------------------------
QString ctkDICOMDatabase::schemaVersionLoaded()
{
  Q_D(ctkDICOMDatabase);
  /// look for the version info in the database
  QSqlQuery versionQuery(d->Database);
  if ( !d->loggedExec( versionQuery, QString("SELECT Version from SchemaInfo;") ) )
    {
    return QString("");
    }

  if (versionQuery.next())
    {
    return versionQuery.value(0).toString();
    }

  return QString("");
}

//------------------------------------------------------------------------------
QString ctkDICOMDatabase::schemaVersion()
{
  // When changing schema version:
  // * make sure this matches the Version value in the
  //   SchemaInfo table defined in Resources/dicom-schema.sql
  // * make sure the 'Images' contains a 'Filename' column
  //   so that the ctkDICOMDatabasePrivate::filenames method
  //   still works.
  //
  return QString("0.5.3");
};

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::updateSchemaIfNeeded(const char* schemaFile)
{
  if ( schemaVersionLoaded() != schemaVersion() )
    {
    return this->updateSchema(schemaFile);
    }
  else
    {
    emit schemaUpdateStarted(0);
    emit schemaUpdated();
    return false;
    }
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::updateSchema(const char* schemaFile)
{
  // backup filelist
  // reinit with the new schema
  // reinsert everything

  Q_D(ctkDICOMDatabase);
  d->createBackupFileList();

  d->resetLastInsertedValues();
  this->initializeDatabase(schemaFile);

  QStringList allFiles = d->filenames("Filenames_backup");
  emit schemaUpdateStarted(allFiles.length());

  int progressValue = 0;
  foreach(QString file, allFiles)
  {
    emit schemaUpdateProgress(progressValue);
    emit schemaUpdateProgress(file);

    // TODO: use QFuture
    this->insert(file,false,false,true);

    progressValue++;
  }
  // TODO: check better that everything is ok
  d->removeBackupFileList();
  emit schemaUpdated();
  return true;

}


//------------------------------------------------------------------------------
void ctkDICOMDatabase::closeDatabase()
{
  Q_D(ctkDICOMDatabase);
  d->Database.close();
  d->TagCacheDatabase.close();
}

//
// Patient/study/series convenience methods
//

//------------------------------------------------------------------------------
QStringList ctkDICOMDatabase::patients()
{
  Q_D(ctkDICOMDatabase);
  QMutexLocker lock(&(d->databaseAccessMutex));
  QSqlQuery query(d->Database);
  query.prepare ( "SELECT UID FROM Patients" );
  query.exec();
  QStringList result;
  while (query.next())
    {
      result << query.value(0).toString();
    }
  return( result );
}

//------------------------------------------------------------------------------
QStringList ctkDICOMDatabase::studiesForPatient(QString dbPatientID)
{
  Q_D(ctkDICOMDatabase);
  QMutexLocker lock(&(d->databaseAccessMutex));
  QSqlQuery query(d->Database);
  query.prepare ( "SELECT StudyInstanceUID FROM Studies WHERE PatientsUID = ?" );
  query.bindValue ( 0, dbPatientID );
  query.exec();
  QStringList result;
  while (query.next())
    {
      result << query.value(0).toString();
    }
  return( result );
}

//------------------------------------------------------------------------------
QStringList ctkDICOMDatabase::seriesForStudy(QString studyUID)
{
  Q_D(ctkDICOMDatabase);
  QMutexLocker lock(&(d->databaseAccessMutex));
  QSqlQuery query(d->Database);
  query.prepare ( "SELECT SeriesInstanceUID FROM Series WHERE StudyInstanceUID=?");
  query.bindValue ( 0, studyUID );
  query.exec();
  QStringList result;
  while (query.next())
    {
      result << query.value(0).toString();
    }
  return( result );
}

//------------------------------------------------------------------------------
QStringList ctkDICOMDatabase::filesForSeries(QString seriesUID)
{
  Q_D(ctkDICOMDatabase);
  QMutexLocker lock(&(d->databaseAccessMutex));
  QSqlQuery query(d->Database);
  query.prepare ( "SELECT Filename FROM Images WHERE SeriesInstanceUID=?");
  query.bindValue ( 0, seriesUID );
  query.exec();
  QStringList result;
  while (query.next())
    {
      result << query.value(0).toString();
    }
  return( result );
}

//------------------------------------------------------------------------------
QString ctkDICOMDatabase::fileForInstance(QString sopInstanceUID)
{
  Q_D(ctkDICOMDatabase);
  QMutexLocker lock(&(d->databaseAccessMutex));
  QSqlQuery query(d->Database);
  query.prepare ( "SELECT Filename FROM Images WHERE SOPInstanceUID=?");
  query.bindValue ( 0, sopInstanceUID );
  query.exec();
  QString result;
  if (query.next())
    {
    result = query.value(0).toString();
    }
  return( result );
}

//------------------------------------------------------------------------------
QString ctkDICOMDatabase::instanceForFile(QString fileName)
{
  Q_D(ctkDICOMDatabase);
  QMutexLocker lock(&(d->databaseAccessMutex));
  QSqlQuery query(d->Database);
  query.prepare ( "SELECT SOPInstanceUID FROM Images WHERE Filename=?");
  query.bindValue ( 0, fileName );
  query.exec();
  QString result;
  if (query.next())
    {
    result = query.value(0).toString();
    }
  return( result );
}

//------------------------------------------------------------------------------
QDateTime ctkDICOMDatabase::insertDateTimeForInstance(QString sopInstanceUID)
{
  Q_D(ctkDICOMDatabase);
  QMutexLocker lock(&(d->databaseAccessMutex));
  QSqlQuery query(d->Database);
  query.prepare ( "SELECT InsertTimestamp FROM Images WHERE SOPInstanceUID=?");
  query.bindValue ( 0, sopInstanceUID );
  query.exec();
  QDateTime result;
  if (query.next())
    {
    result = QDateTime::fromString(query.value(0).toString(), Qt::ISODate);
    }
  return( result );
}


//
// instance header methods
//

//------------------------------------------------------------------------------
QStringList ctkDICOMDatabase::allFiles()
{
  Q_D(ctkDICOMDatabase);
  return d->filenames("Images");
}

//------------------------------------------------------------------------------
void ctkDICOMDatabase::loadInstanceHeader (QString sopInstanceUID)
{
  Q_D(ctkDICOMDatabase);
  QSqlQuery query(d->Database);
  query.prepare ( "SELECT Filename FROM Images WHERE SOPInstanceUID=?");
  query.bindValue ( 0, sopInstanceUID );
  query.exec();
  if (query.next())
    {
      QString fileName = query.value(0).toString();
      this->loadFileHeader(fileName);
    }
  return;
}

//------------------------------------------------------------------------------
void ctkDICOMDatabase::loadFileHeader (QString fileName)
{
  Q_D(ctkDICOMDatabase);
  d->LoadedHeader.clear();
  DcmFileFormat fileFormat;
  OFCondition status = fileFormat.loadFile(fileName.toLatin1().data());
  if (status.good())
    {
      DcmDataset *dataset = fileFormat.getDataset();
      DcmStack stack;
      while (dataset->nextObject(stack, true) == EC_Normal)
        {
          DcmObject *dO = stack.top();
          if (dO)
            {
              QString tag = QString("%1,%2").arg(
                    dO->getGTag(),4,16,QLatin1Char('0')).arg(
                    dO->getETag(),4,16,QLatin1Char('0'));
              std::ostringstream s;
              dO->print(s);
              d->LoadedHeader[tag] = QString(s.str().c_str());
            }
        }
    }
  return;
}

//------------------------------------------------------------------------------
QStringList ctkDICOMDatabase::headerKeys ()
{
  Q_D(ctkDICOMDatabase);
  return (d->LoadedHeader.keys());
}

//------------------------------------------------------------------------------
QString ctkDICOMDatabase::headerValue (QString key)
{
  Q_D(ctkDICOMDatabase);
  return (d->LoadedHeader[key]);
}

//
// instanceValue and fileValue methods
//

//------------------------------------------------------------------------------
QString ctkDICOMDatabase::instanceValue(QString sopInstanceUID, QString tag)
{
  QString value = this->cachedTag(sopInstanceUID, tag);
  if (value == TagNotInInstance)
    {
    return "";
    }
  if (value != "")
    {
    return value;
    }
  unsigned short group, element;
  this->tagToGroupElement(tag, group, element);
  return( this->instanceValue(sopInstanceUID, group, element) );
}

//------------------------------------------------------------------------------
QString ctkDICOMDatabase::instanceValue(const QString sopInstanceUID, const unsigned short group, const unsigned short element)
{
  QString tag = this->groupElementToTag(group,element);
  QString value = this->cachedTag(sopInstanceUID, tag);
  if (value == TagNotInInstance)
    {
    return "";
    }
  if (value != "")
    {
    return value;
    }
  QString filePath = this->fileForInstance(sopInstanceUID);
  if (filePath != "" )
    {
    value = this->fileValue(filePath, group, element);
    return( value );
    }
  else
    {
    return ("");
    }
}


//------------------------------------------------------------------------------
QString ctkDICOMDatabase::fileValue(const QString fileName, QString tag)
{
  unsigned short group, element;
  this->tagToGroupElement(tag, group, element);
  QString sopInstanceUID = this->instanceForFile(fileName);
  QString value = this->cachedTag(sopInstanceUID, tag);
  if (value == TagNotInInstance)
    {
    return "";
    }
  if (value != "")
    {
    return value;
    }
  return( this->fileValue(fileName, group, element) );
}

//------------------------------------------------------------------------------
QString ctkDICOMDatabase::fileValue(const QString fileName, const unsigned short group, const unsigned short element)
{
  // here is where the real lookup happens
  // - first we check the tagCache to see if the value exists for this instance tag
  // If not,
  // - for now we create a ctkDICOMDataset and extract the value from there
  // - then we convert to the appropriate type of string
  //
  //As an optimization we could consider
  // - check if we are currently looking at the dataset for this fileName
  // - if so, are we looking for a group/element that is past the last one
  //   accessed
  //   -- if so, keep looking for the requested group/element
  //   -- if not, start again from the begining

  QString tag = this->groupElementToTag(group, element);
  QString sopInstanceUID = this->instanceForFile(fileName);
  QString value = this->cachedTag(sopInstanceUID, tag);
  if (value == TagNotInInstance)
    {
    return "";
    }
  if (value != "")
    {
    return value;
    }

  ctkDICOMDataset dataset;
  dataset.InitializeFromFile(fileName);

  DcmTagKey tagKey(group, element);

  value = dataset.GetAllElementValuesAsString(tagKey);
  this->cacheTag(sopInstanceUID, tag, value);
  return( value );
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::tagToGroupElement(const QString tag, unsigned short& group, unsigned short& element)
{
  QStringList groupElement = tag.split(",");
  bool groupOK, elementOK;
  if (groupElement.length() != 2)
    {
    return false;
    }
  group = groupElement[0].toUInt(&groupOK, 16);
  element = groupElement[1].toUInt(&elementOK, 16);

  return( groupOK && elementOK );
}

//------------------------------------------------------------------------------
QString ctkDICOMDatabase::groupElementToTag(const unsigned short& group, const unsigned short& element)
{
  return QString("%1,%2").arg(group,4,16,QLatin1Char('0')).arg(element,4,16,QLatin1Char('0'));
}

//
// methods related to insert
//

//------------------------------------------------------------------------------
void ctkDICOMDatabase::insert( DcmDataset *dataset, bool storeFile, bool generateThumbnail)
{
  if (!dataset)
    {
      return;
    }
  ctkDICOMDataset ctkDataset;
  ctkDataset.InitializeFromDataset(dataset, false /* do not take ownership */);
  this->insert(ctkDataset,storeFile,generateThumbnail);
}
void ctkDICOMDatabase::insert( const ctkDICOMDataset& ctkDataset, bool storeFile, bool generateThumbnail)
{
  Q_D(ctkDICOMDatabase);
  d->insert(ctkDataset, QString(), storeFile, generateThumbnail);
}


//------------------------------------------------------------------------------
void ctkDICOMDatabase::insert ( const QString& filePath, bool storeFile, bool generateThumbnail, bool createHierarchy, const QString& destinationDirectoryName)
{
  Q_D(ctkDICOMDatabase);
  Q_UNUSED(createHierarchy);
  Q_UNUSED(destinationDirectoryName);

  /// first we check if the file is already in the database
  if (fileExistsAndUpToDate(filePath))
    {
      logger.debug( "File " + filePath + " already added.");
      return;
    }

  logger.debug( "Processing " + filePath );

  std::string filename = filePath.toStdString();

  DcmFileFormat fileformat;
  ctkDICOMDataset ctkDataset;

  ctkDataset.InitializeFromFile(filePath);
  if ( ctkDataset.IsInitialized() )
    {
      d->insert( ctkDataset, filePath, storeFile, generateThumbnail );
    }
  else
    {
      logger.warn(QString("Could not read DICOM file:") + filePath);
    }
}

//------------------------------------------------------------------------------
int ctkDICOMDatabasePrivate::insertPatient(const ctkDICOMDataset& ctkDataset)
{
  int dbPatientID;

  // Check if patient is already present in the db
  // TODO: maybe add birthdate check for extra safety
  QString patientID(ctkDataset.GetElementAsString(DCM_PatientID) );
  QString patientsName(ctkDataset.GetElementAsString(DCM_PatientName) );
  QString patientsBirthDate(ctkDataset.GetElementAsString(DCM_PatientBirthDate) );

  QSqlQuery checkPatientExistsQuery(Database);
  checkPatientExistsQuery.prepare ( "SELECT * FROM Patients WHERE PatientID = ? AND PatientsName = ?" );
  checkPatientExistsQuery.bindValue ( 0, patientID );
  checkPatientExistsQuery.bindValue ( 1, patientsName );
  loggedExec(checkPatientExistsQuery);

  if (checkPatientExistsQuery.next())
    {
      // we found him
      dbPatientID = checkPatientExistsQuery.value(checkPatientExistsQuery.record().indexOf("UID")).toInt();
      qDebug() << "Found patient in the database as UId: " << dbPatientID;
    }
  else
    {
      // Insert it

      QString patientsBirthTime(ctkDataset.GetElementAsString(DCM_PatientBirthTime) );
      QString patientsSex(ctkDataset.GetElementAsString(DCM_PatientSex) );
      QString patientsAge(ctkDataset.GetElementAsString(DCM_PatientAge) );
      QString patientComments(ctkDataset.GetElementAsString(DCM_PatientComments) );

      QSqlQuery insertPatientStatement ( Database );
      insertPatientStatement.prepare ( "INSERT INTO Patients ('UID', 'PatientsName', 'PatientID', 'PatientsBirthDate', 'PatientsBirthTime', 'PatientsSex', 'PatientsAge', 'PatientsComments' ) values ( NULL, ?, ?, ?, ?, ?, ?, ? )" );
      insertPatientStatement.bindValue ( 0, patientsName );
      insertPatientStatement.bindValue ( 1, patientID );
      insertPatientStatement.bindValue ( 2, QDate::fromString ( patientsBirthDate, "yyyyMMdd" ) );
      insertPatientStatement.bindValue ( 3, patientsBirthTime );
      insertPatientStatement.bindValue ( 4, patientsSex );
      // TODO: shift patient's age to study,
      // since this is not a patient level attribute in images
      // insertPatientStatement.bindValue ( 5, patientsAge );
      insertPatientStatement.bindValue ( 6, patientComments );
      loggedExec(insertPatientStatement);
      dbPatientID = insertPatientStatement.lastInsertId().toInt();
      logger.debug ( "New patient inserted: " + QString().setNum ( dbPatientID ) );
      qDebug() << "New patient inserted as : " << dbPatientID;
    }
    return dbPatientID;
}

//------------------------------------------------------------------------------
void ctkDICOMDatabasePrivate::insertStudy(const ctkDICOMDataset& ctkDataset, int dbPatientID)
{
  QMutexLocker lock(&(this->databaseAccessMutex));
  QString studyInstanceUID(ctkDataset.GetElementAsString(DCM_StudyInstanceUID) );
  QSqlQuery checkStudyExistsQuery (Database);
  checkStudyExistsQuery.prepare ( "SELECT * FROM Studies WHERE StudyInstanceUID = ?" );
  checkStudyExistsQuery.bindValue ( 0, studyInstanceUID );
  checkStudyExistsQuery.exec();
  if(!checkStudyExistsQuery.next())
    {
      qDebug() << "Need to insert new study: " << studyInstanceUID;

      QString studyID(ctkDataset.GetElementAsString(DCM_StudyID) );
      QString studyDate(ctkDataset.GetElementAsString(DCM_StudyDate) );
      QString studyTime(ctkDataset.GetElementAsString(DCM_StudyTime) );
      QString accessionNumber(ctkDataset.GetElementAsString(DCM_AccessionNumber) );
      QString modalitiesInStudy(ctkDataset.GetElementAsString(DCM_ModalitiesInStudy) );
      QString institutionName(ctkDataset.GetElementAsString(DCM_InstitutionName) );
      QString performingPhysiciansName(ctkDataset.GetElementAsString(DCM_PerformingPhysicianName) );
      QString referringPhysician(ctkDataset.GetElementAsString(DCM_ReferringPhysicianName) );
      QString studyDescription(ctkDataset.GetElementAsString(DCM_StudyDescription) );

      QSqlQuery insertStudyStatement ( Database );
      insertStudyStatement.prepare ( "INSERT INTO Studies ( 'StudyInstanceUID', 'PatientsUID', 'StudyID', 'StudyDate', 'StudyTime', 'AccessionNumber', 'ModalitiesInStudy', 'InstitutionName', 'ReferringPhysician', 'PerformingPhysiciansName', 'StudyDescription' ) VALUES ( ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ? )" );
      insertStudyStatement.bindValue ( 0, studyInstanceUID );
      insertStudyStatement.bindValue ( 1, dbPatientID );
      insertStudyStatement.bindValue ( 2, studyID );
      insertStudyStatement.bindValue ( 3, QDate::fromString ( studyDate, "yyyyMMdd" ) );
      insertStudyStatement.bindValue ( 4, studyTime );
      insertStudyStatement.bindValue ( 5, accessionNumber );
      insertStudyStatement.bindValue ( 6, modalitiesInStudy );
      insertStudyStatement.bindValue ( 7, institutionName );
      insertStudyStatement.bindValue ( 8, referringPhysician );
      insertStudyStatement.bindValue ( 9, performingPhysiciansName );
      insertStudyStatement.bindValue ( 10, studyDescription );
      if ( !insertStudyStatement.exec() )
        {
          logger.error ( "Error executing statament: " + insertStudyStatement.lastQuery() + " Error: " + insertStudyStatement.lastError().text() );
        }
      else
        {
          LastStudyInstanceUID = studyInstanceUID;
        }
    }
  else
    {
    qDebug() << "Used existing study: " << studyInstanceUID;
    }
}

//------------------------------------------------------------------------------
void ctkDICOMDatabasePrivate::insertSeries(const ctkDICOMDataset& ctkDataset, QString studyInstanceUID)
{
  QMutexLocker lock(&(this->databaseAccessMutex));
  QString seriesInstanceUID(ctkDataset.GetElementAsString(DCM_SeriesInstanceUID) );
  QSqlQuery checkSeriesExistsQuery (Database);
  checkSeriesExistsQuery.prepare ( "SELECT * FROM Series WHERE SeriesInstanceUID = ?" );
  checkSeriesExistsQuery.bindValue ( 0, seriesInstanceUID );
  logger.warn ( "Statement: " + checkSeriesExistsQuery.lastQuery() );
  checkSeriesExistsQuery.exec();
  if(!checkSeriesExistsQuery.next())
    {
      qDebug() << "Need to insert new series: " << seriesInstanceUID;

      QString seriesDate(ctkDataset.GetElementAsString(DCM_SeriesDate) );
      QString seriesTime(ctkDataset.GetElementAsString(DCM_SeriesTime) );
      QString seriesDescription(ctkDataset.GetElementAsString(DCM_SeriesDescription) );
      QString modality(ctkDataset.GetElementAsString(DCM_Modality) );
      QString bodyPartExamined(ctkDataset.GetElementAsString(DCM_BodyPartExamined) );
      QString frameOfReferenceUID(ctkDataset.GetElementAsString(DCM_FrameOfReferenceUID) );
      QString contrastAgent(ctkDataset.GetElementAsString(DCM_ContrastBolusAgent) );
      QString scanningSequence(ctkDataset.GetElementAsString(DCM_ScanningSequence) );
      long seriesNumber(ctkDataset.GetElementAsInteger(DCM_SeriesNumber) );
      long acquisitionNumber(ctkDataset.GetElementAsInteger(DCM_AcquisitionNumber) );
      long echoNumber(ctkDataset.GetElementAsInteger(DCM_EchoNumbers) );
      long temporalPosition(ctkDataset.GetElementAsInteger(DCM_TemporalPositionIdentifier) );

      QSqlQuery insertSeriesStatement ( Database );
      insertSeriesStatement.prepare ( "INSERT INTO Series ( 'SeriesInstanceUID', 'StudyInstanceUID', 'SeriesNumber', 'SeriesDate', 'SeriesTime', 'SeriesDescription', 'Modality', 'BodyPartExamined', 'FrameOfReferenceUID', 'AcquisitionNumber', 'ContrastAgent', 'ScanningSequence', 'EchoNumber', 'TemporalPosition' ) VALUES ( ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ? )" );
      insertSeriesStatement.bindValue ( 0, seriesInstanceUID );
      insertSeriesStatement.bindValue ( 1, studyInstanceUID );
      insertSeriesStatement.bindValue ( 2, static_cast<int>(seriesNumber) );
      insertSeriesStatement.bindValue ( 3, QDate::fromString ( seriesDate, "yyyyMMdd" ) );
      insertSeriesStatement.bindValue ( 4, seriesTime );
      insertSeriesStatement.bindValue ( 5, seriesDescription );
      insertSeriesStatement.bindValue ( 6, modality );
      insertSeriesStatement.bindValue ( 7, bodyPartExamined );
      insertSeriesStatement.bindValue ( 8, frameOfReferenceUID );
      insertSeriesStatement.bindValue ( 9, static_cast<int>(acquisitionNumber) );
      insertSeriesStatement.bindValue ( 10, contrastAgent );
      insertSeriesStatement.bindValue ( 11, scanningSequence );
      insertSeriesStatement.bindValue ( 12, static_cast<int>(echoNumber) );
      insertSeriesStatement.bindValue ( 13, static_cast<int>(temporalPosition) );
      if ( !insertSeriesStatement.exec() )
        {
          logger.error ( "Error executing statament: "
                         + insertSeriesStatement.lastQuery()
                         + " Error: " + insertSeriesStatement.lastError().text() );
          LastSeriesInstanceUID = "";
        }
      else
        {
          LastSeriesInstanceUID = seriesInstanceUID;
        }
    }
  else
    {
    qDebug() << "Used existing series: " << seriesInstanceUID;
    }
}

//------------------------------------------------------------------------------
void ctkDICOMDatabase::setTagsToPrecache( const QStringList tags)
{
  Q_D(ctkDICOMDatabase);
  d->TagsToPrecache = tags;
}

//------------------------------------------------------------------------------
const QStringList ctkDICOMDatabase::tagsToPrecache()
{
  Q_D(ctkDICOMDatabase);
  return d->TagsToPrecache;
}

//------------------------------------------------------------------------------
void ctkDICOMDatabasePrivate::precacheTags( const QString sopInstanceUID )
{
  Q_Q(ctkDICOMDatabase);

  ctkDICOMDataset dataset;
  QString fileName = q->fileForInstance(sopInstanceUID);
  dataset.InitializeFromFile(fileName);

  QSqlQuery transaction( this->TagCacheDatabase );
  transaction.prepare( "BEGIN TRANSACTION" );
  this->loggedExec(transaction);

  foreach (const QString &tag, this->TagsToPrecache)
    {
    unsigned short group, element;
    q->tagToGroupElement(tag, group, element);
    DcmTagKey tagKey(group, element);
    QString value = dataset.GetAllElementValuesAsString(tagKey);
    q->cacheTag(sopInstanceUID, tag, value);
    }

  transaction.prepare( "END TRANSACTION" );
  this->loggedExec(transaction);
}

//------------------------------------------------------------------------------
void ctkDICOMDatabasePrivate::insert( const ctkDICOMDataset& ctkDataset, const QString& filePath, bool storeFile, bool generateThumbnail)
{
  Q_Q(ctkDICOMDatabase);

  // this is the method that all other insert signatures end up calling
  // after they have pre-parsed their arguments
 
  // Check to see if the file has already been loaded
  // TODO:
  // It could make sense to actually remove the dataset and re-add it. This needs the remove
  // method we still have to write.
  //
  //
  
  this->beginTransaction();

  QString sopInstanceUID ( ctkDataset.GetElementAsString(DCM_SOPInstanceUID) );

  QSqlQuery fileExists ( Database );
  fileExists.prepare("SELECT InsertTimestamp,Filename FROM Images WHERE SOPInstanceUID == :sopInstanceUID");
  fileExists.bindValue(":sopInstanceUID",sopInstanceUID);
  {
  QMutexLocker lock(&(this->databaseAccessMutex));
  bool success = fileExists.exec();
  if (!success)
    {
      logger.error("SQLITE ERROR: " + fileExists.lastError().driverText());
      this->endTransaction();
      return;
    }
  }

  QString databaseFilename(fileExists.value(1).toString());
  QDateTime fileLastModified(QFileInfo(databaseFilename).lastModified());
  QDateTime databaseInsertTimestamp(QDateTime::fromString(fileExists.value(0).toString(),Qt::ISODate));

  qDebug() << "inserting filePath: " << filePath;
  if (databaseFilename == "")
    {
      qDebug() << "database filename for " << sopInstanceUID << " is empty - we should insert on top of it";
    }
  else
    {
      QMutexLocker lock(&(this->databaseAccessMutex));
      qDebug() << "database filename for " << sopInstanceUID << " is: " << databaseFilename;
      qDebug() << "modified date is: " << fileLastModified;
      qDebug() << "db insert date is: " << databaseInsertTimestamp;
      if ( fileExists.next() && fileLastModified < databaseInsertTimestamp )
        {
          logger.debug ( "File " + databaseFilename + " already added" );
          this->endTransaction();
          return;
        }
    }

  //If the following fields can not be evaluated, cancel evaluation of the DICOM file
  QString patientsName(ctkDataset.GetElementAsString(DCM_PatientName) );
  QString studyInstanceUID(ctkDataset.GetElementAsString(DCM_StudyInstanceUID) );
  QString seriesInstanceUID(ctkDataset.GetElementAsString(DCM_SeriesInstanceUID) );
  QString patientID(ctkDataset.GetElementAsString(DCM_PatientID) );
  if ( patientID.isEmpty() && !studyInstanceUID.isEmpty() )
  { // Use study instance uid as patient id if patient id is empty - can happen on anonymized datasets
    // see: http://www.na-mic.org/Bug/view.php?id=2040
    logger.warn("Patient ID is empty, using studyInstanceUID as patient ID");
    patientID = studyInstanceUID;
  }
  if ( patientsName.isEmpty() && !patientID.isEmpty() )
    { // Use patient id as name if name is empty - can happen on anonymized datasets
      // see: http://www.na-mic.org/Bug/view.php?id=1643
      patientsName = patientID;
    }
  if ( patientsName.isEmpty() || studyInstanceUID.isEmpty() || patientID.isEmpty() )
    {
      logger.error("Dataset is missing necessary information (patient name, study instance UID, or patient ID)!");
      this->endTransaction();
      return;
    }

  // store the file if the database is not in memomry
  // TODO: if we are called from insert(file) we
  // have to do something else
  //
  QString filename = filePath;
  if ( storeFile && !q->isInMemory() && !seriesInstanceUID.isEmpty() )
    {
      // QString studySeriesDirectory = studyInstanceUID + "/" + seriesInstanceUID;
      QString destinationDirectoryName = q->databaseDirectory() + "/dicom/";
      QDir destinationDir(destinationDirectoryName);
      filename = destinationDirectoryName +
          studyInstanceUID + "/" +
          seriesInstanceUID + "/" +
          sopInstanceUID;

      destinationDir.mkpath(studyInstanceUID + "/" +
                            seriesInstanceUID);

      if(filePath.isEmpty())
        {
          logger.debug ( "Saving file: " + filename );

          if ( !ctkDataset.SaveToFile( filename) )
            {
              logger.error ( "Error saving file: " + filename );
              this->endTransaction();
              return;
            }
        }
      else
        {
          // we're inserting an existing file

          QFile currentFile( filePath );
          currentFile.copy(filename);
          logger.debug( "Copy file from: " + filePath );
          logger.debug( "Copy file to  : " + filename );
        }
    }

  //The dbPatientID  is a unique number within the database,
  //generated by the sqlite autoincrement
  //The patientID  is the (non-unique) DICOM patient id
  int dbPatientID = LastPatientUID;

  if ( patientID != "" && patientsName != "" )
    {
      //Speed up: Check if patient is the same as in last file;
      // very probable, as all images belonging to a study have the same patient
      QString patientsBirthDate(ctkDataset.GetElementAsString(DCM_PatientBirthDate) );
      if ( LastPatientID != patientID
           || LastPatientsBirthDate != patientsBirthDate
           || LastPatientsName != patientsName )
        {  QString seriesInstanceUID(ctkDataset.GetElementAsString(DCM_SeriesInstanceUID) );

          qDebug() << "This looks like a different patient from last insert: " << patientID;
          // Ok, something is different from last insert, let's insert him if he's not
          // already in the db.

          dbPatientID = insertPatient( ctkDataset );

          /// keep this for the next image
          LastPatientUID = dbPatientID;
          LastPatientID = patientID;
          LastPatientsBirthDate = patientsBirthDate;
          LastPatientsName = patientsName;
        }

      qDebug() << "Going to insert this instance with dbPatientID: " << dbPatientID;

      // Patient is in now. Let's continue with the study

      if ( studyInstanceUID != "" && LastStudyInstanceUID != studyInstanceUID )
        {
          insertStudy(ctkDataset,dbPatientID);
        }

      if ( seriesInstanceUID != "" && seriesInstanceUID != LastSeriesInstanceUID )
        {
          insertSeries(ctkDataset, studyInstanceUID);
        }
      // TODO: what to do with imported files
      //
      if ( !filename.isEmpty() && !seriesInstanceUID.isEmpty() )
        {
          QSqlQuery checkImageExistsQuery (Database);
          checkImageExistsQuery.prepare ( "SELECT * FROM Images WHERE Filename = ?" );
          checkImageExistsQuery.bindValue ( 0, filename );
          checkImageExistsQuery.exec();
          if(!checkImageExistsQuery.next())
            {
              QSqlQuery insertImageStatement ( Database );
              insertImageStatement.prepare ( "INSERT INTO Images ( 'SOPInstanceUID', 'Filename', 'SeriesInstanceUID', 'InsertTimestamp' ) VALUES ( ?, ?, ?, ? )" );
              insertImageStatement.bindValue ( 0, sopInstanceUID );
              insertImageStatement.bindValue ( 1, filename );
              insertImageStatement.bindValue ( 2, seriesInstanceUID );
              insertImageStatement.bindValue ( 3, QDateTime::currentDateTime() );
              insertImageStatement.exec();

              // insert was needed, so cache any application-requested tags
              this->precacheTags(sopInstanceUID);
            }
        }

      if( generateThumbnail && thumbnailGenerator && !seriesInstanceUID.isEmpty() )
        {
          QString studySeriesDirectory = studyInstanceUID + "/" + seriesInstanceUID;
          //Create thumbnail here
          QString thumbnailPath = q->databaseDirectory() +
              "/thumbs/" + studyInstanceUID + "/" + seriesInstanceUID
              + "/" + sopInstanceUID + ".png";
          QFileInfo thumbnailInfo(thumbnailPath);
          if( !(thumbnailInfo.exists()
                && (thumbnailInfo.lastModified() > QFileInfo(filename).lastModified())))
            {
              QDir(q->databaseDirectory() + "/thumbs/").mkpath(studySeriesDirectory);
              DicomImage dcmImage(QDir::toNativeSeparators(filename).toAscii());
              thumbnailGenerator->generateThumbnail(&dcmImage, thumbnailPath);
            }
        }

      if (q->isInMemory())
        {
          emit q->databaseChanged();
        }
    }
  else
    {
    qDebug() << "No patient name or no patient id - not inserting!";
    }

  this->endTransaction();
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::fileExistsAndUpToDate(const QString& filePath)
{
  Q_D(ctkDICOMDatabase);
  bool result(false);

  QSqlQuery check_filename_query(database());
  check_filename_query.prepare("SELECT InsertTimestamp FROM Images WHERE Filename == ?");
  check_filename_query.bindValue(0,filePath);
  d->loggedExec(check_filename_query);
  if (
      check_filename_query.next() &&
      QFileInfo(filePath).lastModified() < QDateTime::fromString(check_filename_query.value(0).toString(),Qt::ISODate)
      )
    {
      result = true;
    }
  check_filename_query.finish();
  return result;
}


//------------------------------------------------------------------------------
bool ctkDICOMDatabase::isOpen() const
{
  Q_D(const ctkDICOMDatabase);
  return d->Database.isOpen();
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::isInMemory() const
{
  Q_D(const ctkDICOMDatabase);
  return d->DatabaseFileName == ":memory:";
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::removeSeries(const QString& seriesInstanceUID)
{
  Q_D(ctkDICOMDatabase);
  QMutexLocker lock(&(d->databaseAccessMutex));

  // get all images from series
  QSqlQuery fileExists ( d->Database );
  fileExists.prepare("SELECT Filename, SOPInstanceUID, StudyInstanceUID FROM Images,Series WHERE Series.SeriesInstanceUID = Images.SeriesInstanceUID AND Images.SeriesInstanceUID = :seriesID");
  fileExists.bindValue(":seriesID",seriesInstanceUID);
  bool success = fileExists.exec();
  if (!success)
    {
      logger.error("SQLITE ERROR: " + fileExists.lastError().driverText());
      return false;
    }

  QList< QPair<QString,QString> > removeList;
  while ( fileExists.next() )
    {
      QString dbFilePath = fileExists.value(fileExists.record().indexOf("Filename")).toString();
      QString sopInstanceUID = fileExists.value(fileExists.record().indexOf("SOPInstanceUID")).toString();
      QString studyInstanceUID = fileExists.value(fileExists.record().indexOf("StudyInstanceUID")).toString();
      QString internalFilePath = studyInstanceUID + "/" + seriesInstanceUID + "/" + sopInstanceUID;
      removeList << qMakePair(dbFilePath,internalFilePath);
    }

  QSqlQuery fileRemove ( d->Database );
  fileRemove.prepare("DELETE FROM Images WHERE SeriesInstanceUID == :seriesID");
  fileRemove.bindValue(":seriesID",seriesInstanceUID);
  logger.debug("SQLITE: removing seriesInstanceUID " + seriesInstanceUID);
  success = fileRemove.exec();
  if (!success)
    {
      logger.error("SQLITE ERROR: could not remove seriesInstanceUID " + seriesInstanceUID);
      logger.error("SQLITE ERROR: " + fileRemove.lastError().driverText());
    }

  QPair<QString,QString> fileToRemove;
  foreach (fileToRemove, removeList)
    {
      QString dbFilePath = fileToRemove.first;
      QString thumbnailToRemove = databaseDirectory() + "/thumbs/" + fileToRemove.second + ".png";

      // check that the file is below our internal storage
      if (dbFilePath.startsWith( databaseDirectory() + "/dicom/"))
        {
          if (!dbFilePath.endsWith(fileToRemove.second))
            {
              logger.error("Database inconsistency detected during delete!");
              continue;
            }
          if (QFile( dbFilePath ).remove())
            {
              logger.debug("Removed file " + dbFilePath );
            }
          else
            {
              logger.warn("Failed to remove file " + dbFilePath );
            }
        }
      if (QFile( thumbnailToRemove ).remove())
        {
          logger.debug("Removed thumbnail " + thumbnailToRemove);
        }
      else
        {
          logger.warn("Failed to remove thumbnail " + thumbnailToRemove);
        }
    }

  this->cleanup();

  d->resetLastInsertedValues();

  return true;
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::cleanup()
{
  Q_D(ctkDICOMDatabase);
  QMutexLocker lock(&(d->databaseAccessMutex));
  QSqlQuery seriesCleanup ( d->Database );
  seriesCleanup.exec("DELETE FROM Series WHERE ( SELECT COUNT(*) FROM Images WHERE Images.SeriesInstanceUID = Series.SeriesInstanceUID ) = 0;");
  seriesCleanup.exec("DELETE FROM Studies WHERE ( SELECT COUNT(*) FROM Series WHERE Series.StudyInstanceUID = Studies.StudyInstanceUID ) = 0;");
  seriesCleanup.exec("DELETE FROM Patients WHERE ( SELECT COUNT(*) FROM Studies WHERE Studies.PatientsUID = Patients.UID ) = 0;");
  return true;
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::removeStudy(const QString& studyInstanceUID)
{
  Q_D(ctkDICOMDatabase);
  QMutexLocker lock(&(d->databaseAccessMutex));

  QSqlQuery seriesForStudy( d->Database );
  seriesForStudy.prepare("SELECT SeriesInstanceUID FROM Series WHERE StudyInstanceUID = :studyID");
  seriesForStudy.bindValue(":studyID", studyInstanceUID);
  bool success = seriesForStudy.exec();
  if (!success)
    {
      logger.error("SQLITE ERROR: " + seriesForStudy.lastError().driverText());
      return false;
    }
  bool result = true;
  while ( seriesForStudy.next() )
    {
      QString seriesInstanceUID = seriesForStudy.value(seriesForStudy.record().indexOf("SeriesInstanceUID")).toString();
      if ( ! this->removeSeries(seriesInstanceUID) )
        {
          result = false;
        }
    }
  d->resetLastInsertedValues();
  return result;
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::removePatient(const QString& patientID)
{
  Q_D(ctkDICOMDatabase);
  QMutexLocker lock(&(d->databaseAccessMutex));

  QSqlQuery studiesForPatient( d->Database );
  studiesForPatient.prepare("SELECT StudyInstanceUID FROM Studies WHERE PatientsUID = :patientsID");
  studiesForPatient.bindValue(":patientsID", patientID);
  bool success = studiesForPatient.exec();
  if (!success)
    {
      logger.error("SQLITE ERROR: " + studiesForPatient.lastError().driverText());
      return false;
    }
  bool result = true;
  while ( studiesForPatient.next() )
    {
      QString studyInstanceUID = studiesForPatient.value(studiesForPatient.record().indexOf("StudyInstanceUID")).toString();
      if ( ! this->removeStudy(studyInstanceUID) )
        {
          result = false;
        }
    }
  d->resetLastInsertedValues();
  return result;
}

///
/// Code related to the tagCache
///

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::tagCacheExists()
{
  Q_D(ctkDICOMDatabase);

  if (d->TagCacheVerified)
    {
    return true;
    }

  // try to open the database if it's not already open
  if ( !(d->TagCacheDatabase.isOpen()) )
    {
    QMutexLocker lock(&(d->databaseAccessMutex));
    qDebug() << "TagCacheDatabase not open\n";
    d->TagCacheDatabase = QSqlDatabase::addDatabase("QSQLITE", d->Database.connectionName() + "TagCache");
    d->TagCacheDatabase.setDatabaseName(d->TagCacheDatabaseFilename);
    if ( !(d->TagCacheDatabase.open()) )
      {
      qDebug() << "TagCacheDatabase would not open!\n";
      qDebug() << "TagCacheDatabaseFilename is: " << d->TagCacheDatabaseFilename << "\n";
      return false;
      }

    //Disable synchronous writing to make modifications faster
    QSqlQuery pragmaSyncQuery(d->TagCacheDatabase);
    pragmaSyncQuery.exec("PRAGMA synchronous = OFF");
    pragmaSyncQuery.finish();

    }

  // check that the table exists
  QSqlQuery cacheExists( d->TagCacheDatabase );
  cacheExists.prepare("SELECT * FROM TagCache LIMIT 1");
  bool success = d->loggedExec(cacheExists);
  if (success)
    {
    qDebug() << "TagCacheDatabase verified!\n";
    d->TagCacheVerified = true;
    return true;
    }
  qDebug() << "TagCacheDatabase NOT verified based on table check!\n";
  return false;
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::initializeTagCache()
{
  Q_D(ctkDICOMDatabase);

  // First, drop any existing table
  if ( this->tagCacheExists() )
    {
    qDebug() << "TagCacheDatabase drop existing table\n";
    QSqlQuery dropCacheTable( d->TagCacheDatabase );
    dropCacheTable.prepare( "DROP TABLE TagCache" );
    d->loggedExec(dropCacheTable);
    }

  // now create a table
  qDebug() << "TagCacheDatabase adding table\n";
  QSqlQuery createCacheTable( d->TagCacheDatabase );
  createCacheTable.prepare(
    "CREATE TABLE TagCache (SOPInstanceUID, Tag, Value, PRIMARY KEY (SOPInstanceUID, Tag))" );
  bool success = d->loggedExec(createCacheTable);
  if (success)
    {
    d->TagCacheVerified = true;
    return true;
    }
  return false;
}

//------------------------------------------------------------------------------
QString ctkDICOMDatabase::cachedTag(const QString sopInstanceUID, const QString tag)
{
  Q_D(ctkDICOMDatabase);
  if ( !this->tagCacheExists() )
    {
    if ( !this->initializeTagCache() )
      {
      return( "" );
      }
    }
  QSqlQuery selectValue( d->TagCacheDatabase );
  selectValue.prepare( "SELECT Value FROM TagCache WHERE SOPInstanceUID = :sopInstanceUID AND Tag = :tag" );
  selectValue.bindValue(":sopInstanceUID",sopInstanceUID);
  selectValue.bindValue(":tag",tag);
  d->loggedExec(selectValue);
  QString result("");
  if (selectValue.next())
    {
    result = selectValue.value(0).toString();
    }
  return( result );
}

//------------------------------------------------------------------------------
bool ctkDICOMDatabase::cacheTag(const QString sopInstanceUID, const QString tag, const QString value)
{
  Q_D(ctkDICOMDatabase);
  if ( !this->tagCacheExists() )
    {
    if ( !this->initializeTagCache() )
      {
      return false;
      }
    }
  QString valueToInsert(value);
  if (valueToInsert == "")
    {
    valueToInsert = TagNotInInstance;
    }
  QSqlQuery insertTag( d->TagCacheDatabase );
  insertTag.prepare( "INSERT OR REPLACE INTO TagCache VALUES(:sopInstanceUID, :tag, :value)" );
  insertTag.bindValue(":sopInstanceUID",sopInstanceUID);
  insertTag.bindValue(":tag",tag);
  insertTag.bindValue(":value",valueToInsert);
  return d->loggedExec(insertTag);
}