qgsqueryresultwidget.cpp

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/***************************************************************************
  qgsqueryresultwidget.cpp - QgsQueryResultWidget
 
 ---------------------
 begin                : 14.1.2021
 copyright            : (C) 2021 by Alessandro Pasotti
 email                : elpaso at itopen dot it
 ***************************************************************************
 *                                                                         *
 *   This program 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 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
#include "qgsqueryresultwidget.h"
#include "qgsabstractdatabaseproviderconnection.h"
#include "qgsexpressionutils.h"
#include "qgscodeeditorsql.h"
#include "qgsmessagelog.h"
#include "qgsquerybuilder.h"
#include "qgsvectorlayer.h"
#include "qgsapplication.h"
#include "qgsgui.h"
#include "qgshistoryproviderregistry.h"
#include "qgshistoryentry.h"
#include "qgsproviderregistry.h"
#include "qgsprovidermetadata.h"
 
#include <QClipboard>
#include <QShortcut>
 
QgsQueryResultWidget::QgsQueryResultWidget( QWidget *parent, QgsAbstractDatabaseProviderConnection *connection )
  : QWidget( parent )
{
  setupUi( this );
 
  // Unsure :/
  // mSqlEditor->setLineNumbersVisible( true );
 
  mQueryResultsTableView->hide();
  mQueryResultsTableView->setItemDelegate( new QgsQueryResultItemDelegate( mQueryResultsTableView ) );
  mQueryResultsTableView->setContextMenuPolicy( Qt::CustomContextMenu );
  connect( mQueryResultsTableView, &QTableView::customContextMenuRequested, this, &QgsQueryResultWidget::showCellContextMenu );
 
  mProgressBar->hide();
 
  connect( mExecuteButton, &QPushButton::pressed, this, &QgsQueryResultWidget::executeQuery );
  connect( mClearButton, &QPushButton::pressed, this, [ = ]
  {
    mSqlEditor->setText( QString() );
  } );
  connect( mLoadLayerPushButton, &QPushButton::pressed, this, [ = ]
  {
    if ( mConnection )
    {
      emit createSqlVectorLayer( mConnection->providerKey(), mConnection->uri(), sqlVectorLayerOptions() );
    }
  }
         );
  connect( mSqlEditor, &QgsCodeEditorSQL::textChanged, this, &QgsQueryResultWidget::updateButtons );
  connect( mFilterToolButton, &QToolButton::pressed, this, [ = ]
  {
    if ( mConnection )
    {
      try
      {
        std::unique_ptr<QgsVectorLayer> vlayer { mConnection->createSqlVectorLayer( sqlVectorLayerOptions() ) };
        QgsQueryBuilder builder{ vlayer.get() };
        if ( builder.exec() == QDialog::Accepted )
        {
          mFilterLineEdit->setText( builder.sql() );
        }
      }
      catch ( const QgsProviderConnectionException &ex )
      {
        mMessageBar->pushCritical( tr( "Error opening filter dialog" ), tr( "There was an error while preparing SQL filter dialog: %1." ).arg( ex.what() ) );
      }
    }
  } );
 
 
  mStatusLabel->hide();
  mSqlErrorText->hide();
 
  mLoadAsNewLayerGroupBox->setCollapsed( true );
 
  connect( mLoadAsNewLayerGroupBox, &QgsCollapsibleGroupBox::collapsedStateChanged, this, [ = ]( bool collapsed )
  {
    if ( ! collapsed )
    {
      // Configure the load layer interface
      const bool showPkConfig { connection &&connection->sqlLayerDefinitionCapabilities().testFlag( Qgis::SqlLayerDefinitionCapability::PrimaryKeys )};
      mPkColumnsCheckBox->setVisible( showPkConfig );
      mPkColumnsComboBox->setVisible( showPkConfig );
 
      const bool showGeometryColumnConfig {connection &&connection->sqlLayerDefinitionCapabilities().testFlag( Qgis::SqlLayerDefinitionCapability::GeometryColumn )};
      mGeometryColumnCheckBox->setVisible( showGeometryColumnConfig );
      mGeometryColumnComboBox->setVisible( showGeometryColumnConfig );
 
      const bool showFilterConfig { connection &&connection->sqlLayerDefinitionCapabilities().testFlag( Qgis::SqlLayerDefinitionCapability::SubsetStringFilter ) };
      mFilterLabel->setVisible( showFilterConfig );
      mFilterToolButton->setVisible( showFilterConfig );
      mFilterLineEdit->setVisible( showFilterConfig );
 
      const bool showDisableSelectAtId{ connection &&connection->sqlLayerDefinitionCapabilities().testFlag( Qgis::SqlLayerDefinitionCapability::UnstableFeatureIds ) };
      mAvoidSelectingAsFeatureIdCheckBox->setVisible( showDisableSelectAtId );
 
    }
  } );
 
  QShortcut *copySelection = new QShortcut( QKeySequence::Copy, mQueryResultsTableView );
  connect( copySelection, &QShortcut::activated, this, &QgsQueryResultWidget::copySelection );
 
  setConnection( connection );
}
 
QgsQueryResultWidget::~QgsQueryResultWidget()
{
  cancelApiFetcher();
  cancelRunningQuery();
}
 
void QgsQueryResultWidget::setSqlVectorLayerOptions( const QgsAbstractDatabaseProviderConnection::SqlVectorLayerOptions &options )
{
  mSqlVectorLayerOptions = options;
  if ( ! options.sql.isEmpty() )
  {
    setQuery( options.sql );
  }
  mAvoidSelectingAsFeatureIdCheckBox->setChecked( options.disableSelectAtId );
  mPkColumnsCheckBox->setChecked( ! options.primaryKeyColumns.isEmpty() );
  mPkColumnsComboBox->setCheckedItems( {} );
  if ( ! options.primaryKeyColumns.isEmpty() )
  {
    mPkColumnsComboBox->setCheckedItems( options.primaryKeyColumns );
  }
  mGeometryColumnCheckBox->setChecked( ! options.geometryColumn.isEmpty() );
  mGeometryColumnComboBox->clear();
  if ( ! options.geometryColumn.isEmpty() )
  {
    mGeometryColumnComboBox->setCurrentText( options.geometryColumn );
  }
  mFilterLineEdit->setText( options.filter );
  mLayerNameLineEdit->setText( options.layerName );
}
 
void QgsQueryResultWidget::setWidgetMode( QueryWidgetMode widgetMode )
{
  mQueryWidgetMode = widgetMode;
  switch ( widgetMode )
  {
    case QueryWidgetMode::SqlQueryMode:
      mLoadAsNewLayerGroupBox->setTitle( tr( "Load as New Layer" ) );
      mLoadLayerPushButton->setText( tr( "Load Layer" ) );
      mLoadAsNewLayerGroupBox->setCollapsed( true );
      break;
    case QueryWidgetMode::QueryLayerUpdateMode:
      mLoadAsNewLayerGroupBox->setTitle( tr( "Update Query Layer" ) );
      mLoadLayerPushButton->setText( tr( "Update Layer" ) );
      mLoadAsNewLayerGroupBox->setCollapsed( false );
      break;
  }
}
 
void QgsQueryResultWidget::executeQuery()
{
  mQueryResultsTableView->hide();
  mSqlErrorText->hide();
  mFirstRowFetched = false;
 
  cancelRunningQuery();
  if ( mConnection )
  {
    const QString sql { mSqlEditor->text( ) };
 
    bool ok = false;
    mCurrentHistoryEntryId = QgsGui::historyProviderRegistry()->addEntry( QStringLiteral( "dbquery" ),
                             QVariantMap
    {
      { QStringLiteral( "query" ), sql },
      { QStringLiteral( "provider" ), mConnection->providerKey() },
      { QStringLiteral( "connection" ), mConnection->uri() },
    },
    ok );
 
    mWasCanceled = false;
    mFeedback = std::make_unique<QgsFeedback>();
    mStopButton->setEnabled( true );
    mStatusLabel->show();
    mStatusLabel->setText( tr( "Executing query…" ) );
    mProgressBar->show();
    mProgressBar->setRange( 0, 0 );
    mSqlErrorMessage.clear();
 
    connect( mStopButton, &QPushButton::pressed, mFeedback.get(), [ = ]
    {
      mStatusLabel->setText( tr( "Stopped" ) );
      mFeedback->cancel();
      mProgressBar->hide();
      mWasCanceled = true;
    } );
 
    // Create model when result is ready
    connect( &mQueryResultWatcher, &QFutureWatcher<QgsAbstractDatabaseProviderConnection::QueryResult>::finished, this, &QgsQueryResultWidget::startFetching, Qt::ConnectionType::UniqueConnection );
 
    QFuture<QgsAbstractDatabaseProviderConnection::QueryResult> future = QtConcurrent::run( [ = ]() -> QgsAbstractDatabaseProviderConnection::QueryResult
    {
      try
      {
        return mConnection->execSql( sql, mFeedback.get() );
      }
      catch ( QgsProviderConnectionException &ex )
      {
        mSqlErrorMessage = ex.what();
        return QgsAbstractDatabaseProviderConnection::QueryResult();
      }
    } );
    mQueryResultWatcher.setFuture( future );
  }
  else
  {
    showError( tr( "Connection error" ), tr( "Cannot execute query: connection to the database is not available." ) );
  }
}
 
void QgsQueryResultWidget::updateButtons()
{
  mFilterLineEdit->setEnabled( mFirstRowFetched );
  mFilterToolButton->setEnabled( mFirstRowFetched );
  mExecuteButton->setEnabled( ! mSqlEditor->text().isEmpty() );
  mLoadAsNewLayerGroupBox->setVisible( mConnection && mConnection->capabilities().testFlag( QgsAbstractDatabaseProviderConnection::Capability::SqlLayers ) );
  mLoadAsNewLayerGroupBox->setEnabled(
    mSqlErrorMessage.isEmpty() &&
    mFirstRowFetched
  );
}
 
void QgsQueryResultWidget::showCellContextMenu( QPoint point )
{
  const QModelIndex modelIndex = mQueryResultsTableView->indexAt( point );
  if ( modelIndex.isValid() )
  {
    QMenu *menu = new QMenu();
    menu->setAttribute( Qt::WA_DeleteOnClose );
 
    menu->addAction( QgsApplication::getThemeIcon( "mActionEditCopy.svg" ), tr( "Copy" ), this, [ = ]
    {
      copySelection();
    }, QKeySequence::Copy );
 
    menu->exec( mQueryResultsTableView->viewport()->mapToGlobal( point ) );
  }
}
 
void QgsQueryResultWidget::copySelection()
{
  const QModelIndexList selection = mQueryResultsTableView->selectionModel()->selectedIndexes();
  if ( selection.empty() )
    return;
 
  int minRow = -1;
  int maxRow = -1;
  int minCol = -1;
  int maxCol = -1;
  for ( const QModelIndex &index : selection )
  {
    if ( minRow == -1 || index.row() < minRow )
      minRow = index.row();
    if ( maxRow == -1 || index.row() > maxRow )
      maxRow = index.row();
    if ( minCol == -1 || index.column() < minCol )
      minCol = index.column();
    if ( maxCol == -1 || index.column() > maxCol )
      maxCol = index.column();
  }
 
  if ( minRow == maxRow && minCol == maxCol )
  {
    // copy only one cell
    const QString text = mModel->data( selection.at( 0 ), Qt::DisplayRole ).toString();
    QApplication::clipboard()->setText( text );
  }
  else
  {
    copyResults( minRow, maxRow, minCol, maxCol );
  }
}
 
void QgsQueryResultWidget::updateSqlLayerColumns( )
{
  // Precondition
  Q_ASSERT( mModel );
 
  mFilterToolButton->setEnabled( true );
  mFilterLineEdit->setEnabled( true );
  mPkColumnsComboBox->clear();
  mGeometryColumnComboBox->clear();
  const bool hasPkInformation { ! mSqlVectorLayerOptions.primaryKeyColumns.isEmpty() };
  const bool hasGeomColInformation { ! mSqlVectorLayerOptions.geometryColumn.isEmpty() };
  static const QStringList geomColCandidates { QStringLiteral( "geom" ), QStringLiteral( "geometry" ),  QStringLiteral( "the_geom" ) };
  const QStringList constCols { mModel->columns() };
  for ( const QString &c : constCols )
  {
    const bool pkCheckedState = hasPkInformation ? mSqlVectorLayerOptions.primaryKeyColumns.contains( c ) : c.contains( QStringLiteral( "id" ), Qt::CaseSensitivity::CaseInsensitive );
    // Only check first match
    mPkColumnsComboBox->addItemWithCheckState( c, pkCheckedState && mPkColumnsComboBox->checkedItems().isEmpty() ? Qt::CheckState::Checked : Qt::CheckState::Unchecked );
    mGeometryColumnComboBox->addItem( c );
    if ( ! hasGeomColInformation && geomColCandidates.contains( c, Qt::CaseSensitivity::CaseInsensitive ) )
    {
      mGeometryColumnComboBox->setCurrentText( c );
    }
  }
  mPkColumnsCheckBox->setChecked( hasPkInformation );
  mGeometryColumnCheckBox->setChecked( hasGeomColInformation );
  if ( hasGeomColInformation )
  {
    mGeometryColumnComboBox->setCurrentText( mSqlVectorLayerOptions.geometryColumn );
  }
}
 
void QgsQueryResultWidget::cancelRunningQuery()
{
  // Cancel other threads
  if ( mFeedback )
  {
    mFeedback->cancel();
  }
 
  // ... and wait
  if ( mQueryResultWatcher.isRunning() )
  {
    mQueryResultWatcher.waitForFinished();
  }
}
 
void QgsQueryResultWidget::cancelApiFetcher()
{
  if ( mApiFetcher )
  {
    mApiFetcher->stopFetching();
    // apiFetcher and apiFetcherWorkerThread will be deleted when the thread fetchingFinished signal is emitted
  }
}
 
void QgsQueryResultWidget::startFetching()
{
  if ( ! mWasCanceled )
  {
    if ( ! mSqlErrorMessage.isEmpty() )
    {
      showError( tr( "SQL error" ), mSqlErrorMessage, true );
    }
    else
    {
      if ( mQueryResultWatcher.result().rowCount() != static_cast<long long>( Qgis::FeatureCountState::UnknownCount ) )
      {
        mStatusLabel->setText( QStringLiteral( "Query executed successfully (%1 rows, %2 ms)" )
                               .arg( QLocale().toString( mQueryResultWatcher.result().rowCount() ),
                                     QLocale().toString( mQueryResultWatcher.result().queryExecutionTime() ) ) );
      }
      else
      {
        mStatusLabel->setText( QStringLiteral( "Query executed successfully (%1 s)" ).arg( QLocale().toString( mQueryResultWatcher.result().queryExecutionTime() ) ) );
      }
      mProgressBar->hide();
      mModel = std::make_unique<QgsQueryResultModel>( mQueryResultWatcher.result() );
      connect( mFeedback.get(), &QgsFeedback::canceled, mModel.get(), [ = ]
      {
        mModel->cancel();
        mWasCanceled = true;
      } );
 
      connect( mModel.get(), &QgsQueryResultModel::fetchMoreRows, this, [ = ]( long long maxRows )
      {
        mFetchedRowsBatchCount = 0;
        mProgressBar->setRange( 0, maxRows );
        mProgressBar->show();
      } );
 
      connect( mModel.get(), &QgsQueryResultModel::rowsInserted, this, [ = ]( const QModelIndex &, int first, int last )
      {
        if ( ! mFirstRowFetched )
        {
          emit firstResultBatchFetched();
          mFirstRowFetched = true;
          mQueryResultsTableView->show();
          updateButtons();
          updateSqlLayerColumns( );
          mActualRowCount = mModel->queryResult().rowCount();
        }
        mStatusLabel->setText( tr( "Fetched rows: %1/%2 %3 %4 ms" )
                               .arg( QLocale().toString( mModel->rowCount( mModel->index( -1, -1 ) ) ),
                                     mActualRowCount != -1 ? QLocale().toString( mActualRowCount ) : tr( "unknown" ),
                                     mWasCanceled ? tr( "(stopped)" ) : QString(),
                                     QLocale().toString( mQueryResultWatcher.result().queryExecutionTime() ) ) );
        mFetchedRowsBatchCount += last - first + 1;
        mProgressBar->setValue( mFetchedRowsBatchCount );
      } );
 
      mQueryResultsTableView->setModel( mModel.get() );
      mQueryResultsTableView->show();
 
      connect( mModel.get(), &QgsQueryResultModel::fetchingComplete, mStopButton, [ = ]
      {
        bool ok = false;
        const QgsHistoryEntry currentHistoryEntry = QgsGui::historyProviderRegistry()->entry( mCurrentHistoryEntryId, ok );
        QVariantMap entryDetails = currentHistoryEntry.entry;
        entryDetails.insert( QStringLiteral( "rows" ), mActualRowCount );
        entryDetails.insert( QStringLiteral( "time" ), mQueryResultWatcher.result().queryExecutionTime() );
 
        QgsGui::historyProviderRegistry()->updateEntry( mCurrentHistoryEntryId,
            entryDetails );
        mProgressBar->hide();
        mStopButton->setEnabled( false );
      } );
    }
  }
  else
  {
    mStatusLabel->setText( tr( "SQL command aborted" ) );
    mProgressBar->hide();
  }
}
 
void QgsQueryResultWidget::showError( const QString &title, const QString &message, bool isSqlError )
{
  mStatusLabel->show();
  mStatusLabel->setText( tr( "An error occurred while executing the query" ) );
  mProgressBar->hide();
  mQueryResultsTableView->hide();
  if ( isSqlError )
  {
    mSqlErrorText->show();
    mSqlErrorText->setText( message );
  }
  else
  {
    mMessageBar->pushCritical( title, message );
  }
}
 
void QgsQueryResultWidget::tokensReady( const QStringList &tokens )
{
  mSqlEditor->setExtraKeywords( mSqlEditor->extraKeywords() + tokens );
  mSqlErrorText->setExtraKeywords( mSqlErrorText->extraKeywords() + tokens );
}
 
void QgsQueryResultWidget::copyResults()
{
  const int rowCount = mModel->rowCount( QModelIndex() );
  const int columnCount = mModel->columnCount( QModelIndex() );
  copyResults( 0, rowCount - 1, 0, columnCount - 1 );
}
 
void QgsQueryResultWidget::copyResults( int fromRow, int toRow, int fromColumn, int toColumn )
{
  QStringList rowStrings;
  QStringList columnStrings;
 
  const int rowCount = mModel->rowCount( QModelIndex() );
  const int columnCount = mModel->columnCount( QModelIndex() );
 
  toRow = std::min( toRow, rowCount - 1 );
  toColumn = std::min( toColumn, columnCount - 1 );
 
  rowStrings.reserve( toRow - fromRow );
 
  // add titles first
  for ( int col = fromColumn; col <= toColumn; col++ )
  {
    columnStrings += mModel->headerData( col, Qt::Horizontal, Qt::DisplayRole ).toString();
  }
  rowStrings += columnStrings.join( QLatin1Char( '\t' ) );
  columnStrings.clear();
 
  for ( int row = fromRow; row <= toRow; row++ )
  {
    for ( int col = fromColumn; col <= toColumn; col++ )
    {
      columnStrings += mModel->data( mModel->index( row, col ), Qt::DisplayRole ).toString();
    }
    rowStrings += columnStrings.join( QLatin1Char( '\t' ) );
    columnStrings.clear();
  }
 
  if ( !rowStrings.isEmpty() )
  {
    const QString text = rowStrings.join( QLatin1Char( '\n' ) );
    QString html = QStringLiteral( "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 Transitional//EN\"><html><head><meta http-equiv=\"content-type\" content=\"text/html; charset=utf-8\"/></head><body><table border=\"1\"><tr><td>%1</td></tr></table></body></html>" ).arg( text );
    html.replace( QLatin1String( "\t" ), QLatin1String( "</td><td>" ) ).replace( QLatin1String( "\n" ), QLatin1String( "</td></tr><tr><td>" ) );
 
    QMimeData *mdata = new QMimeData();
    mdata->setData( QStringLiteral( "text/html" ), html.toUtf8() );
    if ( !text.isEmpty() )
    {
      mdata->setText( text );
    }
    // Transfers ownership to the clipboard object
#ifdef Q_OS_LINUX
    QApplication::clipboard()->setMimeData( mdata, QClipboard::Selection );
#endif
    QApplication::clipboard()->setMimeData( mdata, QClipboard::Clipboard );
  }
}
 
QgsAbstractDatabaseProviderConnection::SqlVectorLayerOptions QgsQueryResultWidget::sqlVectorLayerOptions() const
{
  mSqlVectorLayerOptions.sql = mSqlEditor->text();
  mSqlVectorLayerOptions.filter = mFilterLineEdit->text();
  mSqlVectorLayerOptions.primaryKeyColumns = mPkColumnsComboBox->checkedItems();
  mSqlVectorLayerOptions.geometryColumn = mGeometryColumnComboBox->currentText();
  mSqlVectorLayerOptions.layerName = mLayerNameLineEdit->text();
  mSqlVectorLayerOptions.disableSelectAtId = mAvoidSelectingAsFeatureIdCheckBox->isChecked();
  QgsAbstractDatabaseProviderConnection::SqlVectorLayerOptions options { mSqlVectorLayerOptions };
  // Override if not used
  if ( ! mPkColumnsCheckBox->isChecked() )
  {
    options.primaryKeyColumns.clear();
  }
  if ( ! mGeometryColumnCheckBox->isChecked() )
  {
    options.geometryColumn.clear();
  }
  return options;
}
 
void QgsQueryResultWidget::setConnection( QgsAbstractDatabaseProviderConnection *connection )
{
  mConnection.reset( connection );
 
  cancelApiFetcher();
 
  if ( connection )
  {
 
    // Add provider specific APIs
    const QMultiMap<Qgis::SqlKeywordCategory, QStringList> keywordsDict { connection->sqlDictionary() };
    QStringList keywords;
    for ( auto it = keywordsDict.constBegin(); it != keywordsDict.constEnd(); it++ )
    {
      keywords.append( it.value() );
    }
 
    // Add static keywords from provider
    mSqlEditor->setExtraKeywords( keywords );
    mSqlErrorText->setExtraKeywords( keywords );
 
    // Add dynamic keywords in a separate thread
    QThread *apiFetcherWorkerThread = new QThread();
    QgsConnectionsApiFetcher *apiFetcher = new QgsConnectionsApiFetcher( mConnection->uri(), mConnection->providerKey() );
    apiFetcher->moveToThread( apiFetcherWorkerThread );
    connect( apiFetcherWorkerThread, &QThread::started, apiFetcher, &QgsConnectionsApiFetcher::fetchTokens );
    connect( apiFetcher, &QgsConnectionsApiFetcher::tokensReady, this, &QgsQueryResultWidget::tokensReady );
    connect( apiFetcher, &QgsConnectionsApiFetcher::fetchingFinished, apiFetcherWorkerThread, [apiFetcher, apiFetcherWorkerThread]
    {
      apiFetcherWorkerThread->quit();
      apiFetcherWorkerThread->wait();
      apiFetcherWorkerThread->deleteLater();
      apiFetcher->deleteLater();
    } );
 
    mApiFetcher = apiFetcher;
    apiFetcherWorkerThread->start();
  }
 
  updateButtons();
 
}
 
void QgsQueryResultWidget::setQuery( const QString &sql )
{
  mSqlEditor->setText( sql );
}
 
void QgsQueryResultWidget::notify( const QString &title, const QString &text, Qgis::MessageLevel level )
{
  mMessageBar->pushMessage( title, text, level );
}
 
 
 
void QgsConnectionsApiFetcher::fetchTokens()
{
  if ( mStopFetching )
  {
    emit fetchingFinished();
    return;
  }
 
 
  QgsProviderMetadata *md = QgsProviderRegistry::instance()->providerMetadata( mProviderKey );
  if ( !md )
  {
    emit fetchingFinished();
    return;
  }
  std::unique_ptr< QgsAbstractDatabaseProviderConnection > connection( static_cast<QgsAbstractDatabaseProviderConnection *>( md->createConnection( mUri, {} ) ) );
  if ( ! mStopFetching && connection )
  {
    mFeedback = std::make_unique< QgsFeedback >();
    QStringList schemas;
    if ( connection->capabilities().testFlag( QgsAbstractDatabaseProviderConnection::Capability::Schemas ) )
    {
      try
      {
        schemas = connection->schemas();
        emit tokensReady( schemas );
      }
      catch ( QgsProviderConnectionException &ex )
      {
        QgsMessageLog::logMessage( tr( "Error retrieving schemas: %1" ).arg( ex.what() ), QStringLiteral( "QGIS" ), Qgis::MessageLevel::Warning );
      }
    }
    else
    {
      schemas.push_back( QString() );  // Fake empty schema for DBs not supporting it
    }
 
    for ( const auto &schema : std::as_const( schemas ) )
    {
 
      if ( mStopFetching )
      {
        connection.reset();
        emit fetchingFinished();
        return;
      }
 
      QStringList tableNames;
      try
      {
        const QList<QgsAbstractDatabaseProviderConnection::TableProperty> tables = connection->tables( schema, QgsAbstractDatabaseProviderConnection::TableFlags(), mFeedback.get() );
        for ( const QgsAbstractDatabaseProviderConnection::TableProperty &table : std::as_const( tables ) )
        {
          if ( mStopFetching )
          {
            connection.reset();
            emit fetchingFinished();
            return;
          }
          tableNames.push_back( table.tableName() );
        }
        emit tokensReady( tableNames );
      }
      catch ( QgsProviderConnectionException &ex )
      {
        QgsMessageLog::logMessage( tr( "Error retrieving tables: %1" ).arg( ex.what() ), QStringLiteral( "QGIS" ), Qgis::MessageLevel::Warning );
      }
 
      // Get fields
      for ( const auto &table : std::as_const( tableNames ) )
      {
 
        if ( mStopFetching )
        {
          connection.reset();
          emit fetchingFinished();
          return;
        }
 
        QStringList fieldNames;
        try
        {
          const QgsFields fields( connection->fields( schema, table, mFeedback.get() ) );
          if ( mStopFetching )
          {
            connection.reset();
            emit fetchingFinished();
            return;
          }
 
          for ( const auto &field : std::as_const( fields ) )
          {
            fieldNames.push_back( field.name() );
            if ( mStopFetching )
            {
              connection.reset();
              emit fetchingFinished();
              return;
            }
          }
          emit tokensReady( fieldNames );
        }
        catch ( QgsProviderConnectionException &ex )
        {
          QgsMessageLog::logMessage( tr( "Error retrieving fields for table %1: %2" ).arg( table, ex.what() ), QStringLiteral( "QGIS" ), Qgis::MessageLevel::Warning );
        }
      }
    }
  }
 
  connection.reset();
  emit fetchingFinished();
}
 
void QgsConnectionsApiFetcher::stopFetching()
{
  mStopFetching = 1;
  if ( mFeedback )
    mFeedback->cancel();
}
 
QgsQueryResultItemDelegate::QgsQueryResultItemDelegate( QObject *parent )
  : QStyledItemDelegate( parent )
{
}
 
QString QgsQueryResultItemDelegate::displayText( const QVariant &value, const QLocale &locale ) const
{
  Q_UNUSED( locale )
  QString result { QgsExpressionUtils::toLocalizedString( value ) };
  // Show no more than 255 characters
  if ( result.length() > 255 )
  {
    result.truncate( 255 );
    result.append( QStringLiteral( "…" ) );
  }
  return result;
}