postgres provider: cancel running geometry type query

src/providers/postgres/qgscolumntypethread.cpp

@@ -34,6 +34,7 @@ void QgsGeomColumnTypeThread::addGeometryColumn( QgsPostgresLayerProperty layerP
 
 void QgsGeomColumnTypeThread::stop()
 {
+  mConn->cancel();
   mStopped = true;
 }
 
@@ -50,7 +51,8 @@ void QgsGeomColumnTypeThread::run()
     {
       mConn->retrieveLayerTypes( layerProperty, mUseEstimatedMetadata );
     }
-    else
+
+    if ( mStopped )
     {
       layerProperty.type = "";
       layerProperty.srid = "";

src/providers/postgres/qgspgsourceselect.cpp

@@ -361,6 +361,7 @@ QgsPgSourceSelect::~QgsPgSourceSelect()
   {
     mColumnTypeThread->stop();
     mColumnTypeThread->wait();
+    finishList();
   }
 
   QSettings settings;

src/providers/postgres/qgspostgresconn.cpp

@@ -1425,3 +1425,23 @@ void QgsPostgresConn::deleteConnection( QString theConnName )
   settings.remove( key + "/save" );
   settings.remove( key );
 }
+
+bool QgsPostgresConn::cancel()
+{
+  PGcancel *c = ::PQgetCancel( mConn );
+  if ( !c )
+  {
+    QgsMessageLog::logMessage( tr( "Query could not be canceled [%1]" ).arg( tr( "PQgetCancel failed" ) ),
+                               tr( "PostGIS" ) );
+    return false;
+  }
+
+  char errbuf[256];
+  int res = ::PQcancel( c, errbuf, sizeof errbuf );
+  ::PQfreeCancel( c );
+
+  if ( !res )
+    QgsMessageLog::logMessage( tr( "Query could not be canceled [%1]" ).arg( errbuf ), tr( "PostGIS" ) );
+
+  return res == 0;
+}

src/providers/postgres/qgspostgresconn.h

@@ -133,6 +133,9 @@ class QgsPostgresConn : public QObject
     PGresult *PQprepare( QString stmtName, QString query, int nParams, const Oid *paramTypes );
     PGresult *PQexecPrepared( QString stmtName, const QStringList &params );
 
+    // cancel running query
+    bool cancel();
+
     /** Double quote a PostgreSQL identifier for placement in a SQL string.
      */
     static QString quotedIdentifier( QString ident, bool isGeography = false );