Add async model for virtual layers

python/core/core_auto.sip

@@ -126,6 +126,7 @@
 %Include qgsvectorlayerundocommand.sip
 %Include qgsvectorlayerundopassthroughcommand.sip
 %Include qgsvectorlayerutils.sip
+%Include qgsvirtuallayertask.sip
 %Include qgsvirtuallayerdefinition.sip
 %Include qgsvirtuallayerdefinitionutils.sip
 %Include qgsmapthemecollection.sip

python/core/qgsvectordataprovider.sip.in

@@ -50,6 +50,7 @@ of feature and attribute information from a spatial datasource.
       FastTruncate,
       ReadLayerMetadata,
       WriteLayerMetadata,
+      CancelSupport,
     };
 
     typedef QFlags<QgsVectorDataProvider::Capability> Capabilities;
@@ -231,6 +232,8 @@ Providers with the FastTruncate capability will use an optimised method to trunc
 .. seealso:: :py:func:`deleteFeatures`
 %End
 
+    virtual bool cancel();
+
     virtual bool addAttributes( const QList<QgsField> &attributes );
 %Docstring
 Adds new ``attributes`` to the provider. Returns true in case of success and false in case of failure.

python/core/qgsvirtuallayerdefinition.sip.in

@@ -150,6 +150,9 @@ Get the name of the field with unique identifiers
 Set the name of the field with unique identifiers
 %End
 
+    void setPostpone( bool postpone );
+    bool postpone() const;
+
     QString geometryField() const;
 %Docstring
 Get the name of the geometry field. Empty if no geometry field

python/core/qgsvirtuallayertask.sip

@@ -0,0 +1,46 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsvirtuallayertask.h                                       *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+class QgsVirtualLayerTask : QgsTask
+{
+%Docstring
+
+Initializes a virtual layer in a separated task.
+
+.. versionadded:: 3.0
+%End
+
+%TypeHeaderCode
+#include "qgsvirtuallayertask.h"
+%End
+  public:
+
+    QgsVirtualLayerTask( const QgsVirtualLayerDefinition &definition );
+
+    QgsVectorLayer *layer();
+
+    QgsVirtualLayerDefinition definition() const;
+
+    virtual bool run();
+
+
+    virtual void cancel();
+
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsvirtuallayertask.h                                       *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

python/plugins/db_manager/db_plugins/vlayers/data_model.py

@@ -19,14 +19,14 @@
  ***************************************************************************/
 """
 
-from ..data_model import TableDataModel, BaseTableModel
+from ..data_model import TableDataModel, BaseTableModel, SqlResultModelAsync
 
 from .connector import VLayerRegistry, getQueryGeometryName
 from .plugin import LVectorTable
-from ..plugin import DbError
+from ..plugin import DbError, BaseError
 
 from qgis.PyQt.QtCore import QTime, QTemporaryFile
-from qgis.core import QgsVectorLayer, QgsWkbTypes, QgsVirtualLayerDefinition
+from qgis.core import QgsVectorLayer, QgsWkbTypes, QgsVirtualLayerDefinition, QgsVirtualLayerTask, QgsTask
 
 
 class LTableDataModel(TableDataModel):
@@ -63,40 +63,88 @@ def rowCount(self, index=None):
         return 0
 
 
-class LSqlResultModel(BaseTableModel):
-    # BaseTableModel
+class LSqlResultModelTask(QgsTask):
+
+    def __init__(self, subtask, db):
+        QgsTask.__init__(self)
+        self.subtask = subtask
+        self.db = db
+        self.model = None
+
+    def run(self):
+        try:
+            path = self.subtask.definition().filePath()
+            sql = self.subtask.definition().query()
+            self.model = LSqlResultModel(self.db, sql, None, self.subtask.layer(), path)
+        except Exception as e:
+            self.error = BaseError(str(e))
+            return False
+        return True
+
+    def cancelQuery(self):
+        self.subtask.cancel()
+        self.cancel()
+
+
+class LSqlResultModelAsync(SqlResultModelAsync):
 
     def __init__(self, db, sql, parent=None):
-        # create a virtual layer with non-geometry results
-        t = QTime()
-        t.start()
+        SqlResultModelAsync.__init__(self, db, sql, parent)
 
         tf = QTemporaryFile()
         tf.open()
-        tmp = tf.fileName()
+        path = tf.fileName()
         tf.close()
 
         df = QgsVirtualLayerDefinition()
-        df.setFilePath(tmp)
-        df.setQuery(sql)
-        p = QgsVectorLayer(df.toString(), "vv", "virtual")
-        self._secs = t.elapsed() / 1000.0
-
-        if not p.isValid():
-            data = []
-            header = []
-            raise DbError(p.dataProvider().error().summary(), sql)
+        df.setFilePath(path)
+        df.setQuery(self.sql)
+
+        self.subtask = QgsVirtualLayerTask(df)
+        self.task = LSqlResultModelTask(self.subtask, db)
+        self.task.addSubTask(self.subtask, [], QgsTask.ParentDependsOnSubTask)
+        self.task.taskCompleted.connect(self.modelDone)
+        self.task.taskTerminated.connect(self.modelDone)
+
+    def modelDone(self):
+        self.status = self.task.status
+        self.model = self.task.model
+        self.done.emit()
+
+
+class LSqlResultModel(BaseTableModel):
+
+    def __init__(self, db, sql, parent=None, layer=None, path=None):
+        t = QTime()
+        t.start()
+
+        if not layer:
+            tf = QTemporaryFile()
+            tf.open()
+            path = tf.fileName()
+            tf.close()
+
+            df = QgsVirtualLayerDefinition()
+            df.setFilePath(path)
+            df.setQuery(sql)
+            layer = QgsVectorLayer(df.toString(), "vv", "virtual")
+            self._secs = t.elapsed() / 1000.0
+
+        data = []
+        header = []
+
+        if not layer.isValid():
+            raise DbError(layer.dataProvider().error().summary(), sql)
         else:
-            header = [f.name() for f in p.fields()]
+            header = [f.name() for f in layer.fields()]
             has_geometry = False
-            if p.geometryType() != QgsWkbTypes.NullGeometry:
-                gn = getQueryGeometryName(tmp)
+            if layer.geometryType() != QgsWkbTypes.NullGeometry:
+                gn = getQueryGeometryName(path)
                 if gn:
                     has_geometry = True
                     header += [gn]
 
-            data = []
-            for f in p.getFeatures():
+            for f in layer.getFeatures():
                 a = f.attributes()
                 if has_geometry:
                     if f.hasGeometry():

python/plugins/db_manager/db_plugins/vlayers/plugin.py

@@ -98,6 +98,10 @@ def sqlResultModel(self, sql, parent):
         from .data_model import LSqlResultModel
         return LSqlResultModel(self, sql, parent)
 
+    def sqlResultModelAsync(self, sql, parent):
+        from .data_model import LSqlResultModelAsync
+        return LSqlResultModelAsync(self, sql, parent)
+
     def toSqlLayer(self, sql, geomCol, uniqueCol, layerName="QueryLayer", layerType=None, avoidSelectById=False, _filter=""):
         df = QgsVirtualLayerDefinition()
         df.setQuery(sql)

python/plugins/db_manager/dlg_cancel_task_query.py

@@ -61,6 +61,5 @@ def show(self):
         super(QDialog, self).show()
 
     def hide(self):
-        self.cancelStatus = False
         self.mGif.stop()
         super(QDialog, self).hide()

python/plugins/db_manager/dlg_sql_window.py

@@ -187,24 +187,25 @@ def executeSqlCanceled(self):
     def executeSqlCompleted(self):
         self.dlg_cancel_task.hide()
 
-        if self.modelAsync.task.status() == QgsTask.Complete:
-            model = self.modelAsync.model
-            cols = []
-            quotedCols = []
-
-            self.viewResult.setModel(model)
-            self.lblResult.setText(self.tr("{0} rows, {1:.1f} seconds").format(model.affectedRows(), model.secs()))
-            cols = self.viewResult.model().columnNames()
-            for col in cols:
-                quotedCols.append(self.db.connector.quoteId(col))
+        with OverrideCursor(Qt.WaitCursor):
+            if self.modelAsync.task.status() == QgsTask.Complete:
+                model = self.modelAsync.model
+                cols = []
+                quotedCols = []
+
+                self.viewResult.setModel(model)
+                self.lblResult.setText(self.tr("{0} rows, {1:.1f} seconds").format(model.affectedRows(), model.secs()))
+                cols = self.viewResult.model().columnNames()
+                for col in cols:
+                    quotedCols.append(self.db.connector.quoteId(col))
 
-            self.setColumnCombos(cols, quotedCols)
-            self.update()
-        elif not self.dlg_cancel_task.cancelStatus:
-            DlgDbError.showError(self.modelAsync.error, self)
-            self.uniqueModel.clear()
-            self.geomCombo.clear()
-            pass
+                self.setColumnCombos(cols, quotedCols)
+                self.update()
+            elif not self.dlg_cancel_task.cancelStatus:
+                DlgDbError.showError(self.modelAsync.error, self)
+                self.uniqueModel.clear()
+                self.geomCombo.clear()
+                pass
 
     def executeSql(self):
 

src/core/CMakeLists.txt

@@ -297,6 +297,7 @@ SET(QGIS_CORE_SRCS
   qgsvectorfilewriter.cpp
   qgsvectorfilewritertask.cpp
   qgsvectorlayer.cpp
+  qgsvirtuallayertask.cpp
   qgsvectorlayerfeaturecounter.cpp
   qgsvectorlayercache.cpp
   qgsvectorlayerdiagramprovider.cpp
@@ -635,6 +636,7 @@ SET(QGIS_CORE_MOC_HDRS
   qgsvectorlayereditbuffer.h
   qgsvectorlayereditpassthrough.h
   qgsvectorlayer.h
+  qgsvirtuallayertask.h
   qgsvectorlayerexporter.h
   qgsvectorlayerfeaturecounter.h
   qgsvectorlayerjoinbuffer.h

src/core/qgsvectordataprovider.cpp

@@ -804,6 +804,11 @@ QTextCodec *QgsVectorDataProvider::textEncoding() const
   return mEncoding;
 }
 
+bool QgsVectorDataProvider::cancel()
+{
+  return false;
+}
+
 QStringList QgsVectorDataProvider::sEncodings;
 
 QList<QgsRelation> QgsVectorDataProvider::discoverRelations( const QgsVectorLayer *, const QList<QgsVectorLayer *> & ) const

src/core/qgsvectordataprovider.h

@@ -90,6 +90,7 @@ class CORE_EXPORT QgsVectorDataProvider : public QgsDataProvider, public QgsFeat
       FastTruncate = 1 << 20, //!< Supports fast truncation of the layer (removing all features). Since QGIS 3.0
       ReadLayerMetadata = 1 << 21, //!< Provider can read layer metadata from data store. Since QGIS 3.0. See QgsDataProvider::layerMetadata()
       WriteLayerMetadata = 1 << 22, //!< Provider can write layer metadata to the data store. Since QGIS 3.0. See QgsDataProvider::writeLayerMetadata()
+      CancelSupport = 1 << 23, //!< Supports interruption of pending queries from a separated thread. Since QGIS 3.0
     };
 
     Q_DECLARE_FLAGS( Capabilities, Capability )
@@ -248,6 +249,8 @@ class CORE_EXPORT QgsVectorDataProvider : public QgsDataProvider, public QgsFeat
      */
     virtual bool truncate();
 
+    virtual bool cancel();
+
     /**
      * Adds new \a attributes to the provider. Returns true in case of success and false in case of failure.
      * If attributes are added using this method then QgsVectorLayer::updateFields() must be called

src/core/qgsvirtuallayerdefinition.cpp

@@ -157,6 +157,10 @@ QgsVirtualLayerDefinition QgsVirtualLayerDefinition::fromUrl( const QUrl &url )
         }
       }
     }
+    else if ( key == QLatin1String( "postpone" ) )
+    {
+      def.setPostpone( true );
+    }
   }
   def.setFields( fields );
 
@@ -209,6 +213,11 @@ QUrl QgsVirtualLayerDefinition::toUrl() const
       url.addQueryItem( QStringLiteral( "field" ), f.name() + ":text" );
   }
 
+  if ( postpone() )
+  {
+    url.addQueryItem( QStringLiteral( "postpone" ), QLatin1String( "" ) );
+  }
+
   return url;
 }
 

src/core/qgsvirtuallayerdefinition.h

@@ -131,6 +131,9 @@ class CORE_EXPORT QgsVirtualLayerDefinition
     //! Set the name of the field with unique identifiers
     void setUid( const QString &uid ) { mUid = uid; }
 
+    void setPostpone( bool postpone ) { mPostpone = postpone; }
+    bool postpone() const { return mPostpone; }
+
     //! Get the name of the geometry field. Empty if no geometry field
     QString geometryField() const { return mGeometryField; }
     //! Set the name of the geometry field
@@ -174,6 +177,7 @@ class CORE_EXPORT QgsVirtualLayerDefinition
     QString mGeometryField;
     QString mFilePath;
     QgsFields mFields;
+    bool mPostpone = false;
     QgsWkbTypes::Type mGeometryWkbType = QgsWkbTypes::Unknown;
     long mGeometrySrid = 0;
 };