diff --git a/python/core/qgsvectordataprovider.sip.in b/python/core/qgsvectordataprovider.sip.in
index b5ba3bffd73..1927eafbf84 100644
--- a/python/core/qgsvectordataprovider.sip.in
+++ b/python/core/qgsvectordataprovider.sip.in
@@ -233,6 +233,13 @@ Providers with the FastTruncate capability will use an optimised method to trunc
 %End
 
     virtual bool cancel();
+%Docstring
+Cancels the pending query.
+
+:return: true if the pending query has been interrupted, false otherwise
+
+.. versionadded:: 3.2
+%End
 
     virtual bool addAttributes( const QList<QgsField> &attributes );
 %Docstring
diff --git a/python/core/qgsvirtuallayerdefinition.sip.in b/python/core/qgsvirtuallayerdefinition.sip.in
index a3a8ff5c644..d38c42e8125 100644
--- a/python/core/qgsvirtuallayerdefinition.sip.in
+++ b/python/core/qgsvirtuallayerdefinition.sip.in
@@ -151,7 +151,23 @@ Set the name of the field with unique identifiers
 %End
 
     void setPostpone( bool postpone );
+%Docstring
+Sets the postpone mode. If ``postpone`` is true, then the loading is
+delayed until an explicit reloading of the layer.
+
+:param postpone: True to delay the loading, false otherwise
+
+.. versionadded:: 3.2
+%End
+
     bool postpone() const;
+%Docstring
+Returns the postpone mode.
+
+:return: True if the loading is delayed, false otherwise.
+
+.. versionadded:: 3.2
+%End
 
     QString geometryField() const;
 %Docstring
diff --git a/python/core/qgsvirtuallayertask.sip b/python/core/qgsvirtuallayertask.sip
index efabcba28eb..c1189b815eb 100644
--- a/python/core/qgsvirtuallayertask.sip
+++ b/python/core/qgsvirtuallayertask.sip
@@ -13,9 +13,10 @@ class QgsVirtualLayerTask : QgsTask
 {
 %Docstring
 
-Initializes a virtual layer in a separated task.
+Initializes a virtual layer with postpone mode activated and reloads the
+data in a separated thread.
 
-.. versionadded:: 3.0
+.. versionadded:: 3.2
 %End
 
 %TypeHeaderCode
@@ -24,16 +25,35 @@ Initializes a virtual layer in a separated task.
   public:
 
     QgsVirtualLayerTask( const QgsVirtualLayerDefinition &definition );
+%Docstring
+Constructor.
+
+:param definition: The definition to use for initializing the virtual layer
+%End
 
     QgsVectorLayer *layer();
+%Docstring
+Returns the underlying virtual layer.
+%End
 
     QgsVirtualLayerDefinition definition() const;
+%Docstring
+Returns the virtual layer definition.
+%End
 
     virtual bool run();
 
+%Docstring
+Reloads the data.
+
+:return: True if the virtual layer is valid, false otherwise.
+%End
 
     virtual void cancel();
 
+%Docstring
+Cancels the pending query and the parent task.
+%End
 
 };
 
diff --git a/src/core/qgsvectordataprovider.h b/src/core/qgsvectordataprovider.h
index a30df6ddb48..4f272e55c26 100644
--- a/src/core/qgsvectordataprovider.h
+++ b/src/core/qgsvectordataprovider.h
@@ -249,6 +249,11 @@ class CORE_EXPORT QgsVectorDataProvider : public QgsDataProvider, public QgsFeat
      */
     virtual bool truncate();
 
+    /**
+     * Cancels the pending query.
+     * \returns true if the pending query has been interrupted, false otherwise
+     * \since QGIS 3.2
+     */
     virtual bool cancel();
 
     /**
diff --git a/src/core/qgsvirtuallayerdefinition.h b/src/core/qgsvirtuallayerdefinition.h
index 0bdf4f8f042..fb8e2cdcf17 100644
--- a/src/core/qgsvirtuallayerdefinition.h
+++ b/src/core/qgsvirtuallayerdefinition.h
@@ -131,7 +131,19 @@ class CORE_EXPORT QgsVirtualLayerDefinition
     //! Set the name of the field with unique identifiers
     void setUid( const QString &uid ) { mUid = uid; }
 
+    /**
+     * Sets the postpone mode. If \a postpone is true, then the loading is
+     * delayed until an explicit reloading of the layer.
+     * \param postpone True to delay the loading, false otherwise
+     * \since QGIS 3.2
+     */
     void setPostpone( bool postpone ) { mPostpone = postpone; }
+
+    /**
+     * Returns the postpone mode.
+     * \returns True if the loading is delayed, false otherwise.
+     * \since QGIS 3.2
+     */
     bool postpone() const { return mPostpone; }
 
     //! Get the name of the geometry field. Empty if no geometry field
diff --git a/src/core/qgsvirtuallayertask.h b/src/core/qgsvirtuallayertask.h
index 790f40f03a2..ac1b644eb47 100644
--- a/src/core/qgsvirtuallayertask.h
+++ b/src/core/qgsvirtuallayertask.h
@@ -25,9 +25,10 @@
 /**
  * \ingroup core
  *
- * Initializes a virtual layer in a separated task.
+ * Initializes a virtual layer with postpone mode activated and reloads the
+ * data in a separated thread.
  *
- * \since QGIS 3.0
+ * \since QGIS 3.2
  */
 class CORE_EXPORT QgsVirtualLayerTask : public QgsTask
 {
@@ -35,14 +36,31 @@ class CORE_EXPORT QgsVirtualLayerTask : public QgsTask
 
   public:
 
+    /**
+     * Constructor.
+     * \param definition The definition to use for initializing the virtual layer
+     */
     QgsVirtualLayerTask( const QgsVirtualLayerDefinition &definition );
 
+    /**
+     * Returns the underlying virtual layer.
+     */
     QgsVectorLayer *layer();
 
+    /**
+     * Returns the virtual layer definition.
+     */
     QgsVirtualLayerDefinition definition() const;
 
+    /**
+     * Reloads the data.
+     * \returns True if the virtual layer is valid, false otherwise.
+     */
     bool run() override;
 
+    /**
+     * Cancels the pending query and the parent task.
+     */
     void cancel() override;
 
   private:
diff --git a/src/providers/virtual/qgsvirtuallayerprovider.h b/src/providers/virtual/qgsvirtuallayerprovider.h
index 9fe22c40c38..52d7cbb969f 100644
--- a/src/providers/virtual/qgsvirtuallayerprovider.h
+++ b/src/providers/virtual/qgsvirtuallayerprovider.h
@@ -53,8 +53,17 @@ class QgsVirtualLayerProvider: public QgsVectorDataProvider
     QString description() const override;
     QgsAttributeList pkAttributeIndexes() const override;
     QSet<QgsMapLayerDependency> dependencies() const override;
+
+    /**
+     * Interrupts the pending query.
+     * \since QGIS 3.2
+     */
     bool cancel() override;
 
+    /**
+     * Reloads the underlying data.
+     * \since QGIS 3.2
+     */
     void reloadData() override;
 
   private: